The Hurricane Season in August Look Out You Must

8 08 2020

Dale C. S. Destin |

August is the second most busy month of the hurricane season, behind September. We in Antigua and Barbuda and the rest of the Caribbean have been impacted by tropical cyclones (TCs) – tropical depressions and named storms (tropical storms or hurricanes), many times in August. Hence, “look out you must” act to become hurricane strong.

Storms and hurricanes for August – 1851 to 2019. The 1899 Ciriaco Hurricane highlighted

The Atlantic Basin, including the Caribbean, averages in August: 3 to 4 named storms, including 2 hurricanes and 1 major hurricane – Category 3 intensity or more, based on the current climatological standard normal period, 1981-2010. The month sees a Category 5 hurricane every 7-8 years; the last one was Dorian of last year. Note that we credit TCs to the month in which they were formed.

Super Category 5 Hurricane Dorian in the northern Bahamas – Sep 1, 2019

The last hurricane to impact Antigua and Barbuda, in August, was Hurricane Earl of 2010. The centre of the hurricane passed within 40 km (25 mi) and 89 km (55 mi) north of Barbuda and Antigua respectively. At the time of impacting the islands, Earl was a Category 2 hurricane with maximum sustained winds of 169 km/h (105 mph). 

Category 2 Hurricane Earl with eye just northwest of Anguilla – August 30, 2010

Barbuda likely got close to the maximum impact from Earl. At the V. C. Bird International Airport in Antigua, maximum winds measured were 82 km/h (51 mph) gusting to 105 km/h (65 mph). The damage to both islands amounted to around US$13 million, and there was one fatality.

Earl also caused damage to the rest of the Leeward Islands, the Virgin Islands, Puerto Rico, the East Coast of the United States and Canada. The system caused a total of 8 fatalities and around US$45 million in damage.

The probability of Antigua and Barbuda being impacted by a storm or hurricane, in August, is around 18 percent, based on the current base period of 1981-2010. The probability increases to 38 percent for the active period being experienced by the Atlantic since 1995. This means that we have been impacted by a storm or hurricane every 2 to 3 years since the mid-1990s.

August Hurricane Climatology
The zones of origin and tracks of storms in August during the hurricane season

The probability of us being impacted by a hurricane, in August, is around 6 percent based on 1981-2010 data and around 11 percent for the current active period. This means that we are affected by a hurricane, in August, every nine years.

Antigua and Barbuda have been affected by 22 tropical storms and 18 hurricanes, in august, dating back to 1851. Our most powerful August hurricane was a Category 4 system nicknamed the San Ciriaco Hurricane of 1899. This is the longest-lived Atlantic hurricane on record – 28 days.

Since 1851, the Eastern Caribbean (EC) has been affected by 99 named storms; 37 were hurricanes and 10 were major hurricanes.

Storms to have pass through the Eastern Caribbean in August – 1851 to 2019

The last hurricane to impact the Caribbean in August was Dorian of 2019. It passed through the Windward Islands as a tropical storm, then turned north-northwest and brushed Antigua and most of the Leeward Islands. Dorian became a hurricane over the Virgin Islands. After leaving the Caribbean, it intensified into the second strongest Atlantic hurricane, tied with the Labour Day Hurricane of 1935 and (Wild) Gilbert of 1988, then literally flattened the northern Bahamas, over a three day period, in which it moved at a “snail’s pace”. It left in its wake 84 fatalities, 245 missing and US$4.6 billion. Dorian became the strongest hurricane, on record, to form in August.

Hurricane Dorian with centre near St. Croix, US Virgin Islands – August 30, 2019

The probability of at least a storm or hurricane impacting the EC annually, in August, is 41 percent; the probability of a hurricane is 15 percent and the probability of a major hurricane is 6 percent. It means that the EC is impacted by a storm or hurricane, in August, every 2-3 years; a hurricane every 6-7 years and a major hurricane every 16-17 years.

The probability of a storm or hurricane across the western Caribbean is around 33 percent. For the central Caribbean, this probability is around 26 percent.

August has produced 392 named storms of which 247 were hurricanes, 120 were major hurricanes and 14 were Category 5 hurricanes, based on NOAA. We note that there are likely storms that were missed prior to the Satellite era – prior to the mid-1960s. For climate period – 1981 to 2010, there have been 101 named storms of which 51 were hurricanes and 26 major hurricanes.

August has trice had a maximum of 8 named storms in a given year – 2012, 2011 and 2004. On two occasions, there were 3 hurricanes – 1966 and 1916. Further, on four occasions there were three major hurricanes – 1969, 1933, 1893 and 1886.

Like July, above normal tropical cyclone activity in August normally signals a busy hurricane season. What will this August bring? We can’t be sure, but the forecast is for an above normal to hyperactive season. Whatever it brings, let’s be prepared! Be hurricane strong!

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July Stand By 2020 Hurricane Summary

1 08 2020

Dale C. S. Destin|

July stand by turned out to be a historic month. This July tied with July 2005 for the greatest number of Atlantic named storms – five, for the month, on record dating back to 1851. It was also the first time since 1996 Antigua and Barbuda experienced sustained storm-force winds.

Tropical cyclone tracks through July 30 courtesy the Weather Channel

The month produced five named storms: Edouard, Fay, Gonzalo, Hanna and Isaias. Hanna and Isaias went on to become Category 1 hurricanes. This is over 450% the usual number of storms for July or 4.5 times the average. Further, the two hurricanes represent 400% the average amount.

We are just one-third the way through the 2020 hurricane season; however, we have seen more storms than what was observed in 80 full seasons. Further, the nine named storms, for the year thus far, are more than or equal to the total storms for 92 individual seasons – more than half of all previous 169 seasons, on record. An average season produces 12 named storms, 6 hurricanes and 3 major hurricanes.

Nine storms down, 8 to 19 more are forecast; the list is likely to be exhausted.

All the storms in July were the earliest in their positions, on record. Thus, Edouard, Fay, Gonzalo, Hanna and Isaias were the earliest 5th, 6th, 7th, 8th and 9th named storms, on record, respectively. In other words, there has never been this many storms, this early, in the hurricane season. On average, the season through July 31, produces ONLY two named storms, a hurricane every other year and a major hurricane every 5 years.

The 2020 season, thus far, has nearly 5 times the average number of storm, nearly four times the average number of hurricanes and over twice the average amount of ACE.

Gonzalo – 21 to 25 July, is one of two storms that impacted the Caribbean. The other storm was Isaias, which formed July 30, went on to become a hurricane and continues at present across the Bahamas and threatening the East Coast of the United States. Gonzalo caused minimal impacts to the southern Caribbean. Meanwhile the impacts from Isaias are ongoing and are expected to be extensive.

Isaias caused sustained storm-force winds across Antigua and Barbuda while it was still Potential Tropical Cyclone (PTC) Nine. In Antigua, peak winds of 69 km/h (43 mph) were recorded at the V.C. Bird international Airport, on July 29, at 07:09 UTC (3:09 am local time). Peak gusts of 82 km/h (51 mph) was recorded at the Sir Vivian Richards Stadium.

Over in Barbuda, PTC caused peak winds 63 km/h (39 mph), which were observed at the Hannah Thomas Hospital, July 29, at 09:54 UTC (5:54 am local time). It also produced peak gusts of 74 km/h (46 mph). The last time Antigua and Barbuda had sustained storm-force winds was 24 years ago from Hurricane Bertha.

PTC Nine also produced 25 to 75 mm (1 to 3 in) of rain, in 36 hours, resulting in minor flooding.

Potential Tropical Cyclone Nine moving across the Caribbean Jul 29, 2020. Antigua and Barbuda circled in yellow

Fay – 9 to 11 July, was the most deadly and destructive of the July storms. It killed six persons and caused US$400 million in damage across Southeastern and Northeastern United States and Eastern Canada.

Hanna – 23 to 27 July, was the second most deadly and destructive. It killed 5 persons and caused over US$395 million in damage. It impacted Hispaniola, Cuba, the Gulf Coast of the United States and Mexico.

Edouard – 4 to 6 July, was the weakest and least impacting of the storms. It affected Bermuda and the British Isles.

While writing this blog, Tropical Depression Ten formed near the coast of Africa. It is forecast to become a storm but not expected to impact any landmass.

Recall that July averages one named storm per year, a hurricane every other year and a major hurricane every 6 to 7 years. Compared to the numbers above for this year, this July was momentous, almost unprecedented.  

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Updated Hurricane Season Forecast – July Stand By 2020

13 07 2020

Dale C. S. Destin|

My “July stand by” updated forecast for the 2020 Atlantic Hurricane Season is out, and it continues to call for an above normal season, which is likely to be hyperactive – well above normal.

My forecast calls for 23 named storms (up 2), including Arthur, Bertha, Cristobal and Dolly, with 9 becoming hurricanes (unchanged) and 5 becoming major hurricanes (unchanged). The accumulated cyclone energy (ACE) index is forecast to be 200 (down 2). Further, there is a 70% confidence of

  • 17 to 28 named storms;
  • 6 to 13 becoming hurricanes;
  • 3 to 7 becoming major hurricanes and
  • 122 to 283 ACE.

If the forecast materialises, the ACE would be top 10 of all times. And if we use the ACE as an indicator of destructive potential, as some do, it means that the season’s destructive potential would also be top 10 of all times.

To date, the season has produced an ACE of 7.8, twice the usual amount for January through July 13. A normal season produces 106 ACE. Also, there have been six named storms to date, five time the average of 1.2. So, it has been a record busy season. Never before in history have we seen this many Atlantic tropical storms this early in the year.

The main reasons for the above normal forecast are:

  1. the continuation of a warmer than usual tropical North Atlantic (TNA) and
  2. a developing La Niña.

The greater the likelihood of these two things happening at the same time – August to October, the greater the chances for an above normal season.

There is one thing that may mitigate these developing near perfect conditions for tropical cyclone formation – more than usual Saharan Dust, streaming across the area. If this were to continue, the forecast numbers would be lower. Unfortunately, we have no skill in forecasting the dust beyond a week; hence, we do not know if the dust will continue beyond July and into the peak of the season – August to October.

Compared to my forecast, most other forecasts continue to call for an above normal season. However, compared with most other forecasts, my forecast is calling for a much more active season – 32% more, on average.

Accumulated Cyclone Energy (ACE) based on 15 forecasting entities, including 268Weather.

Clearly, we have no control over the numbers for the season. But notwithstanding the forecast, you should always prepare the same each season, as it only takes one hurricane to ruin your year and or life.

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Drought Deepens…Relief Uncertain

9 07 2020

Dale Destin|

The paltry rainfall for the last three months for Antigua, has caused the meteorological drought to plunge from moderate to severe levels. The rainfall for April-June (AMJ) amounted to only 82.6 mm (3.25 in). This is the sixth driest AMJ on record, dating back to 1928. Further, the rainfall for AMJ represents only meagre 32 percent of the normal total of 274.6 mm (10.81 in). 

Potworks Dam in the background, going on three months, without a drop of its billion-gallon-water capacity. (“Normal” corrected for units Jul 14, 2020)

Other droughts have also tumbled with the meteotological drought, which is considered the mother of them all. These others are at moderate or worse intensity.

The rainfall for June was below normal for the third month in a row. The rainfall of 45.7 mm (1.80 in) was only 66 percent of the normal total for the month of 69.3 mm (2.73 in).

Although drier than normal, it was wetter than the last two Junes combined and more than the last two months combined. This is an indication of just how dry those months were.

Recall that we had very happy first-quarter rainfall. The first three months of the year was wetter than normal. However, since then, things have gone south. Rainfall for the year, thus far, for the dry season – Jan to June, stands at below normal.

The dry season rainfall of 320 mm (12.6 in) amounts to just 74 percent of the normal total of 434.3 mm (17.1 in). It is the driest three-month period since June-August 2018.

The woefully low rainfall since March looks to be mainly due to higher than normal pressure at the lower levels of the atmosphere. This unusual arrangement of pressure resulted in, more often than usual, sinking air, which inhibited warm rising air needed for cloud formation and rainfall.  A record amount of Saharan Dust during June would have also played a huge role in stifling rainfall.

Low level pessure anomaly across the Caribbean Basin and parts of the North Atlantic – April 1 to June 30, 2020. Higher that usual low level pressure inhibits the water cycle and hence, rainfall.
High-level Omega anomaly across the Caribbean Basin and parts of the North Atlantic – April 1 to June 30, 2020. Positive values indicate sinking motion, which is bad for rainfall.

Relief from the drought weather is becoming uncertain. The forecast for July-September (JAS) is for a 45 percent chance of above normal rainfall. This means that rainfall required to bring us out of drought is unlikely.

Looking beyond JAS, my latest forecast calls for less than 40 percent chance of above normal rainfall for the rest of the year, the wet season – July to December. This means that near or below normal rainfall is more likely than drought busting rainfall.  

Considering the whole year, 2020 will most likely be drier than usual. My latest projection is for a 50 percent chance of below normal rainfall, 30 percent chance of the usual rainfall and 20 percent chance of the year getting more than usual rainfall.

How dry it is projected to be? At this time, Antigua’s most likely rainfall for 2020 is 1026 mm (40.4 mm) with a 70 percent confidence that it will fall in the range of 760 to 1349 mm (30 to 53 in). Normally, the island gets 1207 mm (47.5 in).

Projected rainfall for Antigua in inches. There is a 20% chance of it being above normal (A 20%), 30% chance of it being near normal (N 30%) and 50% chance of it being below normal (B 50%). Background pic courtesy Karen Corbin of the Humane Society.

The parched weather was not restricted to Antigua and Barbuda. Much of the rest of the region have been suffering the same fate. There are a few exceptions, most notably is Cuba.

May was a record dry month for Anguilla and St. Thomas. Parts of the Dominican Republic and Belize saw record low rainfall for April. Severe or worse droughts are being experienced in many islands, including Aruba, Barbados, Martinique and St. Lucia.

Rainfall anomaly across the Caribbean Basin – January 7 to July 4, 2020 based on CPC CMORPH

Large scale atmospheric and ocean conditions continue to trend in the direction that would usually cause relief across the Caribbean Basin, including Antigua and Barbuda. However, models continue to not be very enthusiastic about forecasting significant rainfall for much of the region.

The favourable conditions for rainfall for our area are: warmer than usual tropical North Atlantic and cooling of the central to eastern equatorial Pacific i.e. a developing La Nina. Once these two things happen together, we invariably get good rainfall. However, what we can’t predict beyond a week, could negate the positive conditions – Saharan Dust, the x-factor. If it does not let up, it will suppress rainfall and wipe out any optimism in the forecasts for drought-stopping rain.

From all that have been examined, the drought is unlikely to end for the foreseeable future and if it were to, it would only be temporary. This is not to say that we won’t see more rainfall in the second half of the year than the first. We will; however, it is unlikely to end the drought.

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The Hurricane Season in July Stand By

5 07 2020

Dale C. S. Destin|

Unlike June, we have been impacted by tropical cyclones – tropical depressions, tropical storms or hurricanes, in July. Hence, as the 1898 poem by R. Inwards said “stand by” for news of storms that may be coming our way. Notwithstanding, July is still a relatively slow month for tropical cyclone activity.

The last hurricane to impact Antigua and Barbuda, in July, was Hurricane Bertha of 1996. Bertha hit while we were still recovering from one of our busiest hurricane seasons in modern times – 1995, the year of Hurricanes Luis (Category 4) and Marilyn and Tropical Storm Iris.  

139 named storms for July with Hurricane Bertha of 1996 highlighted

The centre of Bertha passed just south of Barbuda, likely causing the island to experience all its 137 km/h (85 mph) winds it was packing, at the time. Passing north of Antigua, the system caused peak sustained winds of only 63 km/h (39 mph). Damage to Antigua was minimal but unclear for Barbuda. Regardless of the damage, the psychological trauma would have been extreme for many, coming 10 months after the horror of Luis.

Bertha also caused damage across the rest of the Leeward Islands, the Virgin Islands, Puerto Rico, the East Coast of the United States and Canada. The system also caused a total of 12 fatalities and at least US$330 million in damage.

Category 3 Hurricane Bertha – July 9, 1996

The probability of us (Antigua and Barbuda) being impacted by a named strom – a tropical storm or hurricane, in July is around 3 percent for all seasons and around 5 percent during the active period being experienced by the Atlantic since 1995. This means that we are impacted by a named storm every 33 years, on average.

The probability of us being impacted by a hurricane is the same as indicated above for named storms. In our history, there have been six named storms of which one was a hurricane – Bertha.

July is also a relatively slow month for tropical cyclone activity, across the Eastern Caribbean. The region has seen 22 named storms, 6 of which were hurricanes and 1 major hurricane – Category 3 Hurricane Emily of 2005, the strongest to pass through the islands in July.

Storms to have pass through the Eastern Caribbean – 1851 to 2019

Emily is also the last hurricane to impact the Caribbean in July. It passed just north of Tobago, then the centre passed over the southern tip of Grenada. It then travelled west-northwest across the Caribbean Sea, brushing Jamaica as a Category 5 hurricane before slamming into the Yucatan as a Category 4 hurricane.

Satellite image of Category 5 Hurricane Emily south of Jamaica – 16 July, 2005
The track of Category 5 Hurricane Emily – July, 2005

It left death and or damage and destruction in its wake stretching from Trinidad to Texas. One person was killed in Grenada and Honduras, five in Jamaica, Haiti and Mexico, amounting to a total of 17 fatalities. Total damage from Emily was over US$1 billion, with the Caribbean accounting for over US$200 million.

The probability of a hurricane impacting the Eastern Caribbean annually, in July, is 6%. This means that the region gets a hurricane every 16 years, on average. With the last hurricane occurring in 2005, we are one year short of being due one, in July. The probability for a hurricane in July, across the central and western Caribbean is a little higher – 10%.

The zones of origin and tracks of storms in July during the hurricane season

Overall, July averages one named storm per year, a hurricane every other year and a major hurricane every 6 to 7 years. The last named storm and hurricane was Barry of 2019; the last major hurricane was Bertha of 2008 and the last Category 5 hurricane was Emily of 2005.

Based on record since 1851, July has produced 139 named storms of which 66 became hurricanes and 12 became major hurricanes. We note that there are likely storms that were missed prior to the Satellite era – prior to the mid-1960s. For the current standard climate period – 1981 to 2010, there have been 33 named storms, with 16 becoming hurricanes and 5 becoming major hurricanes.

July has had a maximum of 5 named storms in a given year – 2005. On two occasions, there have been 3 hurricanes – 1966 and 1916. Further, on two occasions there were two major hurricanes – 2005 and 1926.

The strongest hurricane on record – Hurricane Allen of 1980, formed on July 31. It slammed Barbados on August 3, with Category 3 winds and Martinique, St. Lucia and St. Vincent, with Category 4 winds. It then reached Category 5 in the Eastern Caribbean Sea before pummelling parts of the Dominica Republic, Haiti, Jamaica and Cuba, on August 6. Allen then reach maximum strength of 306 km/h (190 mph) near the western tip of Cuba, on August 7. Earlier on that day, it severely impacted parts of the Cayman Islands.

Category 5 Hurricane Allen of 1980 – the strongest Atlantic hurricane on record

It goes without saying that Allen left a long trail of death and or damage and destruction from Barbados to Texas. Some damage was catastrophic, for example, St Lucia had 6 fatalities and over US$230 million in damage. Deaths from Allen totalled 269 and damage over US$1.5 billion.

Unlike May and June, above normal tropical cyclone activity in July normally signals a busy hurricane season. What will this July bring? We can’t be sure, but the forecast is for an above normal season. Whatever it brings, let’s be prepared! Be hurricane strong!

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June Too Soon 2020 Hurricane Summary

1 07 2020

Dale C. S. Destin|

June too soon is over, one month down and five more to go for the Atlantic hurricane season. This June had two named storms – Tropical Storms Cristobal and Dolly, the most since 2017. Only four seasons have seen more named storms in June – 1968, 1936, 1909 and 1886.

2020 Tropical Cyclone Tracks Through June 30

Tropical Storm Cristobal became the third named storm for the year – June 1 to 10. It also became the earliest third named storm on record – previous was Tropical Storm Collin of 2016.

Clouds from Tropical Storm Cristobal covering much of Mexico and Central America

Interestingly, Cristobal formed from the remnants of Tropical Storm Amanda. Amanda was the first named storm of the East Pacific hurricane season. It formed on May 30, just south of Guatemala and west El Salvador and moved onshore that area May 31, then rapidly dissipated the same day. That was the end of Amanda but the start of Cristobal.

Together, Tropical Storms Amanda and Cristobal, left a trail of destruction and death caused mainly by torrential rainfall, amounting to up to 1016 mm (40 in), in some areas. The trail runs from Central America to Canada, passing through eastern Mexico, central United States and Canada.

Dolly – June 22 to 24, was a “sheep of a storm”. It formed over the Atlantic, hundreds of miles east of New York and travelled parallel to the east coasts of the United States and Canada, never making landfall.

Upon formation, Dolly became the third earliest fourth named storm in a year, on record. Only Tropical Storm Debby of 2012 and Tropical Storm Danielle of 2016, were earlier. Dolly also became the farthest north forming Atlantic tropical storm, on record, before July 1.

Four down, 13 to 22 more are forecast

Recall that there is a storm in June every other year; one hurricane every 8 years and a major hurricane every 50 years, on average. The month has now gone six years without a hurricane and 54 years without a major hurricane. A good “drought” to have, right?

Recall also the we (Antigua and Barbuda) has never had a storm in June, so the happy streak continues. This is also true for most islands of the Caribbean east of Cuba.

The season is certainly off to a busy record tying start. Thus far, there have been four named storms – Tropical Storms Arthur, Bertha, Cristobal and Dolly. This year ties with 2012 and 1954 for the most named storms by July 1.

Although it was an active June, it may have been more active, if not for record levels of Saharan Dust traversing the tropical North Atlantic, the Caribbean and especially the Western Caribbean and the Gulf of Mexico, the main development regions during June. It was certainly a dust event for the ages.  

Saharan Dust as seen by Goes 16 Satellite at mid day June 23, 2020

So, it’s 30 days down and 152 more to go for the 2020 Atlantic hurricane season. Attention now turns to July stand by. Be prepared, be hurricane strong!

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Saharan Dust to Reduce Air Quality to Unhealthy Levels

20 06 2020

Dale C. S. Destin|

A fresh surge of Saharan Dust is set to reduce the air quality across much of the Caribbean to unhealthy levels on Sunday. The Dust brings with it the potential for wide-reaching health implications from itchy eyes and runny nose to even death.

The presence of particulate matters 2.5 and 10, in the Saharan Dust surge, makes it potentially deadly for sensitive groups people. This includes persons with respiratory or heart disease, the elderly and children.

The unhealthy air quality levels increase the likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly.

People who are especially sensitive to the Dust should restrict outdoor activity. Also, keep windows and doors closed, as much as possible, and wear a face mask, rated to filter out PM 2.5, when going outside. Already, we are wearing masks to mitigate COVID-19, these masks are also helpful in mitigating against the health impacts of the Dust.

The caution is for mostly sensitive people. However, there is the potential for the air quality to be worse than forecast and impact everyone in the general population, resulting in increased respiratory illnesses.

The health concerns from the dust is not limited to the impacts of particulate matters. This Saharan Dust is also said to contain bacterial and fungal spores, which can also sicken persons.

Of perhaps even graver concern to health professionals is the chemical content of the Dust. It has been tested positive for such pesticides as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals, which are known to very harmful to human health.

Research has also shown that the Dust is also harmful to the health of other creatures. It is harmful to coral reefs by way of the pathogens it contains. The dust is also credited for algae blooms or “red time”, resulting in fish kills and the death of other marine life.

The Saharan Dust is ever-present across the Caribbean but not at constant levels. It gets to us via the prevailing easterly winds, which places the Caribbean downwind from the Sahara Desert. The Dust generally peaks in June and is lowest in December.

Sahara Desert - the Source of the Dust
Sahara Desert – the Source of the Dust

This episode of the Saharan Dust will peak on Sunday at unhealthy levels. However, at present, it is moderate and will return to moderate levels on Monday and continue this way through much of the upcoming week.

Air quality index, as measured at various sites across the Eastern Caribbean Sat afternoon, 20 June 2020
Air quality index, as measured at various sites across the Eastern Caribbean Sun morning, 21 June 2020

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The Hurricane Season in June Too Soon

14 06 2020

Dale C. S. Destin|

We, Antigua and Barbuda, have never had a tropical cyclone – tropical depression, tropical storm or hurricane, in June (knock wood). The same is true for much of the Caribbean east of Cuba.

All 107 Named Storms for June 1851-2019, based on data from NOAA

There has only been one hurricane to impact the Eastern Caribbean in June – Unnamed Category 1 Hurricane of 1933, also called the Trinidad Hurricane. It was a deadly hurricane – killing 13 people in Trinidad, 22 in Cuba and killing, at least, 35 people in total across Trinidad, Venezuela, Jamaica and Cuba. It also caused deaths and destruction across Mexico.

The hurricane season in June for the Caribbean – 1851 to 2019

June averages one named storm (tropical storm or hurricane) every other year; one hurricane every 8 years and a major hurricane – Category 3 or higher intensity, every 50 years, on average. It is the least active month of the hurricane season.

Before this year, the last storm in June was Cindy in 2017; the last hurricane was Arthur of 2014 and the last major hurricane was Alma in 1966.

Given the current season, it may be said that Cristobal, of this June, was overdue by a year; the next June hurricane is due around 2022 and the next June major hurricane is overdue by about 3 years. Will this be the year for what would be the fourth major hurricane for the month? Unfortunately, there are no tools available currently to answer this question.

Interestingly, over the relatively reliable data period of 1966-2019, there is no significant difference in the average number of hurricanes in June for above and below normal seasons. A hurricane forms in June around every five above normal seasons and every four below normal seasons. The mentioned period has no hurricanes in June for normal seasons.

There have been three major hurricanes in June based on record dating back to 1851; however, over the period 1966 to 2019, there has only been one major hurricane – Alma of 1966.

Category 3 Hurricane Alma of 1966 – the most powerful Atlantic June Cyclone along with Hurricane Audrey of 1957

So, what is the probability of a hurricane this June, given an above normal season? It’s around 19 percent. What is the probability for a major hurricane? About 5 percent. For all seasons considered for 1966-2019, the probability of a hurricane and major hurricane is 17 and 2 percent respectively. No significant difference between an above and below normal season.

The zones of origin and tracks of storms in June during the hurricane season

Based on record for 1851 to 2019, there have been, in June, 107 named storms of which 37 became hurricanes and 3 reached major hurricane status – Category 3 intensity or higher. For more reliable data, the period 1966 to 2019 have seen, in June, 37 named storms, 7 becoming hurricanes and no major hurricane. For the current standard climate or base period of 1981-2010, there have been 21 named storms, 4 hurricanes and no major hurricanes.

It turns out that like May, storms in June say nothing about the overall activity for the season i.e. whether it will be above, near or below normal.  

Using the current climate period 1981-2010, if storms are going to form in June, they will mostly do so during the first or last 10 days of the month. Over 80 percent of all storms in June, for the current climate period, forms between June 1-10 or June 20-30.

June on 5 occasions had a maximum of three named storms in a given season – 1968, 1959, 1936, 1909 and 1886. On one occasion it had three hurricanes, 3 Category 2s – 1886. Note: these ALL occurred outside the climate change era. This year could make six years since there was a hurricane forming in the month.

Recall that the forecast is for this hurricane season to be above or well above normal. And notwithstanding what happens in June or any other month, it only takes one hurricane to ruin your year or life. Thus, you need to be prepared as best as possible for every hurricane season.

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Updated Hurricane Season Forecast – June Too Soon 2020

10 06 2020

Dale C. S. Destin|

My “June too soon” updated forecast for the 2020 Atlantic Hurricane Season is out, and it continues to call for an above normal season, which is likely to be hyperactive – well above normal.

The forecast predicts an accumulated cyclone energy (ACE) index of 202 (up 13 over the previous forecast), 21 named storms (up 2 to include Arthur and Bertha), 9 hurricanes (unchanged) and 5 major hurricanes (up 1).

To give a clearer picture of the forecast and the uncertianties, there is a 70% confidence of

  • 17 to 26 named storms;
  • 6 to 13 becoming hurricanes;
  • 2 to 7 becoming major hurricanes – Category 3 and higher and
  • 122 to 289 ACE.

If the forecast materialises, the ACE would be top 10 of all times. And if we use the ACE as an indicator of destructive potential, as some do, it means that the season’s destructive potential would also be top 10 of all times.

The main reasons for the above normal forecast are:

  1. the likely continuation of a warmer than usual tropical North Atlantic (TNA) and
  2. the potential for a cooler than normal eastern equatorial Pacific i.e. La Niña.

The greater the likelihood of these two things happening at the same time – August to October , the greater the chances for an above normal season.

TNA Index – very positive since about February 2020, indicative of warmer than usual sea surface temperatures across the region

According to other forecasts surveyed, the consensus is for an ACE of 151 (up 5), 17 named storms (unchanged), 9 hurricanes (up 1) and 4 major hurricanes (unchanged). These numbers represent an above normal season.

Accumulated Cyclone Energy (ACE) based on 15 forecasting entities, including 268Weather.

Compared to my forecast, most other forecasts are also calling for an above normal season. However, compared with most other forecasts, my forecast is calling for a much more active season – 34% more.

Clearly, we have no control over the numbers for the season. But notwithstanding the forecast, you should always prepare the same each season, as it only takes one hurricane to ruin your year and or life.

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Driest April-May for Over 80 Years

6 06 2020

Dale C. S. Destin|

The combined rainfall total for April and May is near record-breaking low levels for Antigua. The total for this Apr-May: 36.8 mm (1.45 in), is the second lowest on record, dating back to 1928. Only Apr-May 1939, 81 years ago, had less rain – 27.9 mm (1.10 in).

Normally, these months would produce a combined rainfall of 189.2 mm (7.45 in). This means that the rainfall for Apr-May is less than 20% of the normal total, a deficit of over 80%.

Such low precipitation for Apr-May only happens once every 67 years, on average. In other words, there is only a 1.5% chance of this happening per year. Most Antiguans alive today have never witnessed such dryness before, for these months, and are very unlikely to witness it again.

Usually, Apr-May would account for 52% of the rainfall for Jan-May but instead it only accounted for less than 14%. Both April and May had similar extreme deficits. There have been only three other occasions when both months registered less than an inch of rain in the same year – 1973, 1939 and 1928.

It was not long ago that we were enjoying ample rainfall. First quarter rainfall, Jan-Mar, was above normal. However, this wonderful start to the year came to a screeching halt.

The horizontal (flat line) from Apr 1 to May 31 is indicative of the rapid downturn in rainfall as compared to the previous three months.

The difference in rainfall between Jan-Mar and Apr-May is the second greatest on record, indicative of the extremely sharp downturn in precipitation. We went from 237.7 mm (9.36 in) for Jan-Mar to 36.8 mm (1.45 in) for Apr-May, a decline of 200.9 mm (7.91 in). Normally, Jan-Mar and Apr-May produce 176.0 mm (6.93 in) and 189.2 mm (7.45 in) respectively.

Few of us alive today have ever seen this kind of change of rainfall, in Antigua. This kind sharp decline in rainfall from Jan-Mar to Apr-May only happens once every 100 years, on average. Only 1967 has had a greater decline, 240 mm (9.45 in), over the similar month periods.

This Apr-May is also the driest two-month period since May-Jun of 2001. It is also the 12th driest combined consecutive two months on record.

This past April and May were clearly extremely dry, and this dryness was magnified by the preceding wetter than normal first quarter.

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4th Driest May on Record for Antigua

5 06 2020

Dale C. S. Destin|

Potworks Dam, Antigua – June 1, 2020. Currently dry but when full, holds a billion gallons. Pic courtesy Karen Corbin – Humane Society

May 2020 was another very dry month for Antigua. The rainfall total of 20.8 mm (0.82 in) was the lowest since 2001 and the fourth lowest on record dating back to 1928. Only May 2001, 1939 and 1928 have been drier, with May 2001 being the driest with 6.4 mm (0.25 in).

Relative to the normal total for the month of 103.6 mm (4.08 in) only 20% fell; hence, the month had a rainfall deficit of 80%, based on the current base period of 1981-2010.

Such a low rainfall total for May is relatively rare. It happens once every 21 years, on average or has only 4-5% probability of occurring each year.

The rainfall for May is almost “bipolar” – you either get a lot or a little. This makes the rainfall for the month the most unpredictable with the highest variability index of all the months.

The dryness for May was not confined to Antigua. Most of the region from Hispaniola to Trinidad saw, at most, only 25% of the normal rainfall for the month.

The reason for the truant rainfall looks to be due mainly to higher than normal surface pressure and lower than normal relative humidity.  

Rainfall for the year has now fallen to below normal after an excellent start in the first quarter. There are some hopes for the return of seasonal or above seasonal rainfall over the upcoming months. The current forecast is for above normal rainfall for the period June to August.

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Pre-hurricane Season Summary – 2020

1 06 2020

Dale C. S. Destin|

It is June too soon – the Atlantic hurricane season officially starts today. However, it seems like no one remembered to remind the “storm gods” of this fact. Already, we have seen two named storms – Arthur and Bertha, resulting in a very active pre-hurricane season 2020. Only twice on record before, dating back to 1842, that May has produced two named storms – 2012 and 1887.

Arthur formed on May 16, just north of the northern Bahamas. It moved north to near the Outer Banks of North Carolina, then out over the Atlantic and lost its tropical characteristics. It caused tropical storm force winds across a small portion of North Carolina and reached peak sustained winds of 97 kph (60 mph).

Tracks of Tropical Storms Arthur (right) and Bertha (left)

Bertha was a bit of a surprise storm. Formation was not expected due to strong upper-level wind shear. On the morning of 12:50 am, May 27, it was given a 30% chance of formation and by 8:30 am, it was declared a tropical storm with sustained winds of 72 kph (45 mph). It eventually reached peak sustained wind speed of 80 kph (50 mph), before dissipating on May 28. The system caused one death.

In terms of pre-season storms – storms forming between March and May, there have been only four occasions when there were two named storms – 2012, 1951, 1908 and 1887. Of course, I am mindful that before the satellite era – pre mid-1960s, a number of short-lived storms went undetected, resulting in gaps in the record.

On average, there is a storm in May once every 7 to 8 years, based on record for the period 1981-2010, whereas, there is a preseason storm once every 5 years. Most pre-season storms form in May – about 85%, 9% in April and 6% in March.

Preseason storms say nothing about the season they precede, in terms of how active or inactive they will be. However, this season is expected to be active and likely to be hyperactive – well above normal.

We all need to be prepared for the hurricane season regardless of the number of storms and hurricanes being forecast, as it only takes one hurricane to ruin our year or life.

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Tropical Storms in May Mean Nothing

15 05 2020

Dale C. S. Destin |

The first tropical or subtropical storm for the pre-hurricane season is about to form in the Bahamas. Some think that this is a harbinger (sign) for the upcoming hurricane season – June 1 to November 30, but is it?

Tropical disturbance AL90 across the Bahamas with an 80% chance of becoming Tropical Storm Arthur within 48 hours.

To the “naked eyes”, it is understood why some may take a storm forming in May as a sign of bad news for the upcoming hurricane season; however, the numbers don’t agree.

The numbers say that it usually means nothing in terms of the overall activity of the upcoming season. According to NOAA, there have been 29 named storms in May, spread over 27 seasons from 1842 to 2019. Of the 27 seasons, using NOAA’s definitions, nine were above normal (active or hyperactive), 11 were near normal and 7 were below normal (inactive or quiet).

Overall, most seasons with a storm in May, are near normal – 11 times of 27 – 41%. However, from a statistical standpoint, there are no significant differences between above, near or below normal seasons, when there is a storm in May. Hence, a tropical storm forming in the month has no bearing on the activity of the upcoming hurricane season.

Of the 27 seasons with May storms, 9 or 33% was active or above normal; 11 or 41% was normal and 7 or 26% was quiet or inactive

Notwithstanding the above, this hurricane season is expected to be above normal or likely hyperactive – well above normal, see my latest forecast. Clearly, this has nothing to do with the expected formation of Tropical Storm Arthur over the Bahamas.

Further on the tropical cyclone climatology on May, of the 29 named storms to have formed in the month, 5 became hurricanes with none ever becoming a major hurricane. The strongest tropical cyclone of the month occurred in 1863 – a Category 2 unnamed cyclone.

The only Cat 2 May Hurricane on record – Unnamed Hurricane – 1863

On average, there is one storm forming in May every 7-8 years. However, there have been a storm in May of the last 2 years and 6 in the last 10 years. Twice, two storms formed in May of the same season – 2012 and 1887, the most of any. So much for averages, right!

The Eastern Caribbean has never been impacted by a tropical cyclone in May, “knock wood”, based on available record dating back to 1842.

Storms forming in this part of the region in May are not unusual. Of the 29 May storms, 28% have formed or traverse within 300 miles of Nassau, Bahamas.

Unfortunately for the Bahamas, this year they are still recovering from Super Category 5 Hurricane Dorian of September 2019, which levelled much of Northwest Bahamas. You may say that they can’t “catch a break”, as they are about to deal with potentially strong storm-force winds and flooding rainfall, in addition to dealing with the COVID-19 Pandemic.

Possible tracks of what is expected to become Tropical Storm Arthur in 48 hours

May storms mean nothing in terms of the overall activity of the hurricane season; however, they mean a lot with respect to where they impact. Let us be prepared regardless of omens or forecasts for the season – it only takes one hurricane to ruin your year or life.

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May 2020 Updated Hurricane Season Forecast: Hyperactive Season Likely

11 05 2020

Dale C. S. Destin |

Our updated forecast for the 2020 Atlantic Hurricane Season is out, and it calls for higher than normal activity – an above normal season. The forecast predicts an accumulated cyclone energy (ACE) index of 189 (down 6 from the previous forecast), 19 named storms (down 1), 9 hurricanes (unchanged) and 4 major hurricanes (down 1). With these numbers, it is also likely that the season will be hyperactive i.e. well above normal and possibly unusually destructive.

If this forecast, for which there is very high confidence, pans out, this season would be the most active since 2017, in terms of ACE, and the 10th most active on record dating back to 1851.

The season also has the potential to be record breaking in some areas, as there is 70 percent confidence of

  • 14 to 23 named storms;
  • 6 to 12 becoming hurricanes;
  • 2 to 7 becoming major hurricanes and
  • 112 to 276 ACE.

If the higher end of the ranges were to materialise, records would be equalled or broken for the number of major hurricanes and more importantly ACE, which is the universally accepted metric used to classify the overall activity of a hurricane season.

According to other forecasts surveyed, the consensus is for an ACE of 146 (down 3), 17 named storms (up 1), 8 hurricanes (unchanged) and 4 major hurricanes (unchanged) – above normal season. This is generally consistent with my forecast but with less activity. However, regardless of the forecast, you should always prepare the same each season, as it only takes one hurricane to ruin your year and or life.

Accumulated Cyclone Energy (ACE) based on 10 forecasting entities, including 268Weather.

The main reasons for the above normal forecasts are the likely above normal sea surface temperatures across the tropical North Atlantic and a cold-neutral El Niño Southern Oscillation (ENSO) or a weak cold ENSO, i.e. weak La Niña, during the peak of the hurricane season – August to October.

A typical season has 12 named storms, 6 hurricanes, and 3 major hurricanes. Major hurricanes have sustained wind speeds of at least 178 km/h or 111 miles per hour (e.g., Category 3 or higher), according to the Saffir Simpson Hurricane Wind Scale.

Click for pronounciations

With respect to records, the 2005 season has the highest number of named storms and hurricanes – 28 and 15 respectively. The 2005 season also tied with the 1961 season for the highest number of major hurricanes – 7, and the season with the highest ACE – the most active season on record, based on ACE only, is 1933 with 259.

The last Atlantic hurricane season – 2019, was more active than normal and will long be remembered for Super Category 5 Hurricane Dorian’s destruction of the northwest Bahamas. The season had 18 named storms, 6 became hurricanes – winds of at least 119 km/h or 74 miles per hour, and 3 became major hurricanes.

This forecast will be updated monthly until August. The next update will be issued around June 10.

The Atlantic hurricane season begins in days – June 1 and concludes on November 30, be prepared!

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Driest April for Antigua in Over Two Generations

1 05 2020

Dale C. S. Destin|

Not since 1944 has an April been drier for Antigua than April 2020. It was the third driest April on record – the driest in 76 years or well over two generations. The last time April was drier, V. C. Bird Snr was president of the Antigua Trades and Labour Union and World War II was still raging.

Potworks Dam, May 1, 2020. Picture courtesy Karen Corbin – Humane Society

The island average for the month is 16.1 mm (0.63 in). Only April 1944, with 5.9 mm (0.23 in) and 1939, with 8.4 mm (0.33 in), have been drier in nearly 100 years.

The total for the month represents only 19% of the normal total of 85.6 mm (3.37 in) – a deficit of 81%, based on the current climatological standard period of 1981-2010.

Such a low rainfall total is very rare for April. How rare? It has only around a 4% chance of occurring or once every 25 years on average, based on record: 1928-2019. This would suggest that we were around 50 years overdue for such a parched April.

The reason for us going so many years overdue for such a near record low total is likely due to “positive” climate change. Rainfall for April has been on a steady wetting increase, rising from an average of 53.1 mm (2.09 in) for the period 1928-1957 to 80.8 mm (3.18 in) for the period 1990-2019.

So, if you were to segment the data, there is around an 11% chance of getting 16.1 mm during the years 1928-1957, as compared to just a 0.6% chance for the period 1990-2019. In other words, our current climate for April is over 18 times less likely to produce such a low rainfall total as compared to the past climate of 1928-1957.

Now, based on the segmented data, the return period for April’s rainfall of 16.1 mm is once every 9 years on average for the past climate. However, the return period for the same value in the current climate is once every 167 years on average. Hence, most persons alive along with their grand and great grand children are unlikely to see a similar or drier April in Antigua.

Compared to other months, this April is the driest since June 2018. And of all the 1108 months on record dating back to 1928, it ranks as the 23rd driest. This puts it in the top 2% of all time driest months.

Notwithstanding the miniscule rainfall for April, the rainfall for the year, thus far, is near normal.  However, if not for a wetter than normal first quarter, the situation would be much more dire.

The reason for the absentee rainfall for April looks to be due to a switch from a positive North Atlantic Oscillation (NAO) to a negative NAO. This is manifest in the swing from above normal pressure over the subtropical North Atlantic to below normal pressure. This switch or swing resulted in a reduction of moist unstable air flowing across the area and depositing rainfall.

The pressure over our islands also went from neutral, over the period January-March 2020, to above normal for April. Such a configuration of the pressure would usually also inhibit rainfall, which was evident.

April 2020 was a remarkably dry month. One that most of us have never seen and will likely never see again – happily.

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2020 Atlantic Hurricane Season Early Forecast

10 04 2020

Dale C. S. Destin |

My early forecast for the 2020 Atlantic Hurricane Season is out and it calls for above normal activity being likely. It calls for an accumulated cyclone energy (ACE) index of 195, 20 named storms, 9 hurricanes and 5 major hurricanes. With these numbers, it is also likely to be a hyperactive and unusually destructive season.

2020 Atlantic Hurricane Season Forecast

If this forecast pans out, this season would be the most active since 2017, in terms of ACE, and the 10th most active on record dating back to 1851. It would also be the ranked 10th highest season for the number of major hurricanes, 16th for hurricanes and 2nd for named storms.

The season also has the potential to be record breaking, as there is 70 percent confidence of

  • 14 to 25 named storms;
  • 6 to 12 becoming hurricanes;
  • 3 to 8 becoming major hurricanes and
  • 105 to 285 ACE.

If the higher end of the ranges were to materialise, records would be equalled or broken for the number of major hurricanes and more importantly ACE, which is the universally accepted metric used to classify the overall activity of a hurricane season.

According to other forecasts surveyed, the consensus is for an ACE of 149, 16 named storms, 8 hurricanes and 4 major hurricanes – above normal season. This is generally consistent with my forecast but with less activity. However, regardless of the forecast, you should always prepare the same each season, as it only takes one hurricane to ruin your year and or life.

The main reasons for the above normal forecasts are the likely above normal sea surface temperatures across the tropical North Atlantic and a cold-neutral El Niño Southern Oscillation (ENSO) or a weak cold ENSO, i.e. weak La Niña, during the peak of the hurricane season – August to October.

A typical season has 12 named storms, 6 hurricanes, and 3 major hurricanes. Major hurricanes have sustained wind speeds of at least 178 km/h or 111 miles per hour (e.g., Category 3 or higher), according to the Saffir Simpson Hurricane Wind Scale.

With respect to records, the 2005 season has the highest number of named storms and hurricanes – 28 and 15 respectively. The 2005 season also tied with the 1961 season for the highest number of major hurricanes – 7, and the season with the highest ACE – the most active season on record, based on ACE only, is 1933 with 259.

The last Atlantic hurricane season – 2019, was more active than normal and will long be remembered for Super Category 5 Hurricane Dorian’s destruction of the northwest Bahamas. The season had 18 named storms, 6 became hurricanes – winds of at least 119 km/h or 74 miles per hour, and 3 became major hurricanes.

This forecast will be updated monthly until August. The first update will be issued around May 10.

The Atlantic hurricane season begins on June 1 and concludes on November 30 – be prepared!

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Another Bomb Cyclone to Push Impactful Swells to the Caribbean

7 03 2020

Dale C. S. Destin|

Another bomb cyclone is expected to cause another episode of  large and damaging swells across much of the Caribbean Basin. The impactful swells will start to reach the shorelines of the Basin this Sunday. These swells are forecast to reach a few metres and break at higher heights on coastlines.

Visualization of northerly swells forecast to come to the Caribbean from the bomb cyclone

Swells will rise to at least 3 metres (at least 10 feet) across most of the Atlantic waters of the islands. These swells will produce even higher surfs or breaking waves. Surfs could be as much as twice the height of the incoming swells, depending on the bathymetry/topography of the near shore seafloor. The swells and surfs are expected to cause beach closures, as swimming conditions will become quite hazardous. Other impacts include:

  • major beach erosion;
  • flooding of some low-lying coastal roads;
  • disruptions to marine recreation and businesses;
  • disruptions to potable water from desalination;
  • damage to coral reefs and
  • financial losses.

Advisories and warnings will be required for much of the upcoming week. Please be guided by the bulletins coming out of your national weather services.

The event will be cause by an average extratropical cyclone transitioning to a bomb cyclone – a drop of 24 millibars/hectopascals or more in 24 hours or less. This will result in the system developing gale-force or tropical-storm-force winds that will push large waves to the Caribbean.

8 pm local time Friday, 6 March, 2020: Bomb cyclone with centre marked by the X near the red L, just off the coast of New York
Visualization of Bomb Cyclone 6 am UTC Saturday or 2 am local time Saturday, 7 March, 2020: Pressure – shaded areas, isobars – circular fixed lines (1012, 1008, 1004 etc.) and wind direction – lines circling inwards toward the centre of the bomb cyclone
Visualization of Bomb Cyclone 6 am UTC Saturday or 2 am local time Saturday, 7 March, 2020: Wind speed – shaded areas, wind direction – lines circling inwards toward the centre of the bomb cyclone

The cyclone will remain very far away from the area – thousands of miles; however, it will have a significant impact on the region, by way of swells transforming into high surfs on our shores. Associated with these surfs are potentially very powerful and life-threatening rip currents.

The first set of these swells will reach the Bahamas on Sunday; the northeast Caribbean, including Antigua and Barbuda, by Monday and the rest of the Eastern Caribbean by Tuesday. The event will likely last three days from its start time. So, for the northeast Caribbean, its Monday through Thursday.

As usual, the impacts on shorelines will not be the uniformed. The impacts will depend on the depth and the natural shelter of the coastal waters. Northern islands with moderately sloping, shallow, northern and or north-facing shorelines are expected to see the highest swells and surfs, and hence; the greatest impacts.

This event is not expected to be worse than the last notable one which took place in January 2020. Notwithstanding, it will not be your “garden variety” event.

The event will also be felt along the East Coast of the United States. The same powerful cyclone will also cause extreme weather across Ireland, the United Kingdom and northern Europe next week.

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February 2020 to be Among the Wettest on Record

17 02 2020

Dale C. S. Destin

This February is on track to becoming one of the wettest on record for Antigua. Thus far, it is the wettest February, at the V. C. Bird International Airport (VCBIA) since 2005 and the wettest for Antigua since 2004.

It has been the wettest first two weeks of February, at the VCBIA, since 2002. The rainfall total of 55 mm (2.17 in), at the end of February 14, at the Airport, is well above normal – in the top 10 percentile on record dating back to 1962. It is more than twice the average – 25.4 mm (1.0 in), for the same period and the fourth wettest on record. Only three other times February 1-14 has been wetter, at VCBIA: 1997 – 66 mm (2.60 in), 1982 – 59.7 mm (2.35 in) and 2002 – 56.8 mm (2.24 in).

Heavy rainfall days (days with 10 mm – 0.40 in, or more) are fairly rare for February, at the Airport. There was none since 2009; however, already for this Feberuary, there have been three recorded. This ties with 2005, 1991, 1982, 1981 and 1976 February for the most number of heavy rainfall days, at VCBIA. The three heavy rainfall days tie with those of February 2005, 1991, 1982, 1981 and 1976. This record will likely be broken by the end of the month.

There is no daily breakdown of the island-average rainfall; however, based on the fact that the current island-average total of 59.9 mm (2.36 in) is already the most since 2004, and the average for the month is 55.9 mm (2.20 in), it is highly likely that the rainfall for the first two weeks of February was also well above normal for the island.

The cause of our wetter than usual February weather is the positive North Atlantic Oscillation (NAO) index. The NAO is a large-scale seesaw in atmospheric pressure between the subtropical (Atlantic) high and the polar low.

Click here for more

The positive NAO index occurs when the subtropical high is higher (stronger) than usual and the polar low is deeper (lower) than usual. When this happens, it causes the winds across the area to be higher than usual (fresh to strong), which in turn destabilises the lower atmosphere by way of mixing and convergence – resulting in above normal rainfall for Antigua and likely other nearby islands.

When the NAO is above normal, the mean rainfall for Antigua for February is 62.7 mm (2.47 in) plus or minus 11.4 mm (0.45 in). These numbers are based on a 95% confidence interval and a probability value (p-value) of 0.009.

A positive NAO index also has implications for other places. For example, the United Kingdom, Ireland and northern Europe get more and stronger winter storms when the NAO index is positive, which have been happening. Thus far, there have been four named winter storms to significantly impact the area, the last being Storm Dennis.

The NAO index is forecast to remain above normal; hence, wetter than usual conditions are expected to continue. Unfortunately, the NAO index is not predictable beyond two weeks; thus, only short-range forecasting can be done using it as a predictor. Also, for some other months, a positive index is associated with below normal rainfall.

The wettest February for the VCBIA and Antigua, on record dating back to 1928, is 1982 with 110.5 mm (4.35 in) and 130.8 mm (5.15 in) respectively. The wettest February 1-14 at the VCBIA is 1997 with 66 mm (2.60 in).  

The average rainfall totals for February for the VCBIA and Antigua are 44.9 mm (1.77 in) and 55.9 mm (2.20 in) respectively. This February could be among the top three wettest on record.

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Climate Change and Tropical Cyclone Forward Speed

26 01 2020

Dale C.S. Destin|

Many have made tropical cyclones (hurricanes, tropical storms and tropical depressions) the posterchild for climate change with respect to how they are or may be responding to a warming climate. It is a hot topic of debate that researchers are continuously investigating for answers. One of the many questions been asked is, “Are global tropical cyclones moving slower in a warning climate?”  

The track of Hurricane Irma – 2017

A recent research letter, in the Institute of Physics (IOP) Publishing, by Kelvin T.F. Chan, of the School of Atmospheric Sciences, and Guangdong Province Key Laboratory for Climate and Natural Disaster Studies, Sun Yat-sen University, Zhuhai, People’s Republic of China, weighed in, quite forcefully and persuasively, on the above question.

Time series of annual-mean global tropical-cyclone translation speed and their linear trends in periods 1949–2016 (blue) and 1970–2016 (orange).

According to Chan, the short answer to the question is no. Chan successfully show that, with the use of reliable data from 1970 to 2016, there is no significant change in the forward speed of tropical cyclones, notwithstanding the pronounced warning of the globe seen over the last half-century.

Chan’s finding virtually contradicts a 2018 paper present by James P. Kossin of the NOAA National Centers for Environmental Information, Center for Weather and Climate, Madison, WI, USA. Kossin found that there was a 10% slowdown in global tropical-cyclone translation (forward) speed over the past 68 years – 1949 to 2016. His implication was that this was related to anthropogenic climate change.

The IOP letter, by Chan, successfully shows that the findings of Kossin was based on the use of widely accepted spurious data obtained prior to the satellite era – pre 1966. Unanimously accepted, more accurate data since the satellite era – 1970 to 2016, show no significant slowdown of tropical cyclones. Understandably, prior to weather satellites in 1966, accurately tracking tropical cyclones was very difficult to impossible; hence, translation speed data before then are highly unreliable.

This finding of Chan is consistent with the findings of Knutson et al, in a very comprehensive study on the entire subject of climate change and tropical cyclones. According to Knutson, the results for the models “indicate no significant changes, and only 2 of the 10 individual… model projections show a significant change (increase).” He concluded that there was no clear consistent trend in the forward speed of tropical cyclones.

The question of how climate change is or may impact the forward speed of tropical cyclones is very important from a adoptation standpoint. A slower moving tropical cyclone has the potential for more destruction and vice versa. Naturally, the longer a tropical cyclone hangs around a particular populated area, the more the destruction is likely to be via wind, flooding rainfall and storm-surge.

Intuitively, it would be consistent to think that since a warning climate is slowing down the circulation of the tropics, it is also slowing down tropical cyclones, embedded its circulation. However, this is clearly not happening, certainly not based on the data since 1970 to 2016.

Tropical cyclones may be the posterchild for climate change; however, there is no evidence to support any changes in tropical cyclones forward speed, due to the changing climate being forced by humans.  

More broadly, there exist no evidence that there have been any changes in tropical cyclones, due to anthropogenic climate change. However, that is not to say that climate change won’t have an impact on tropical cyclones in the future.  

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Bomb Cyclone to Push Damaging Swells Across the Caribbean

16 01 2020

Dale C.S Destin|

The Caribbean Basin is about to see another round of large and damaging swells reaching its shorelines starting Saturday, from a bomb cyclone. Swells are forecast to exceed 3.5 metres (12 feet) and break at higher heights, as surfs, on coastlines. This is likely to be the biggest swell event since Swellmageddon of March 2018.

Animation of bomb cyclone, east of Canada, with pressure pattern, wind speeds and directions, as forecast by the Global Forecasting System (GFS) Model. Time in UTC

The event will be kicked off by a relatively inconspicuous low-pressure system (LPS), currently over the northeast United States. The LPS will go through explosive development (bombogenesis) over the next 24 hours and become a ginormous and powerful bomb cyclone (extratropical cyclone) over the northwest North Atlantic, with hurricane-force winds.

Although this system will form over 3220 km (2000 miles) away, it will have a significant impact on the region, through its strong winds pushing unusually high waves to our shores. The first set of these swells will reach the Bahamas on Saturday; the northeast Caribbean, including Antigua and Barbuda, on Sunday and the Guianas on Monday. The event will likely last three days from its start time. So, for the northeast Caribbean, its Sunday through Tuesday.

Animation of swells forecast to move across the region from the bomb cyclone, as predicted by the European Centre for Medium-Range Weather Forecasts (ECMWF) wave model (WAM). Time in UTC.

Swells will rise to to in excess of 3.5 metres across most of the Atlantic waters of the islands. There swells will produce even higher surfs or breaking waves. These surfs could be as much as twice the height of the incoming swells, depending on the bathymetry/topography of the near shore seafloor. This is expected to cause beach closures, as swimming conditions will become quite hazardous. Other impacts include:

  • major beach erosion;
  • flooding of some low-lying coastal roads;
  • disruptions to marine recreation and businesses;
  • disruptions to potable water from desalination;
  • damage to coral reefs and
  • Financial losses.

Advisories and warnings will be required for the weekend and or the first half of next week. The event will also be felt along the East Coast of the United States, Canada, Greenland, Iceland, the United Kingdom and Norway. Rowers of the Talisker Whisky Atlantic Challenge will also be negatively impacted, exponentially increasing the challenge of an already very challenging race.

High surf warnings or advisories will be required for coastal areas for much of the Caribbean this weekend and into the middle of next week

The impact on shorelines will not be the same everywhere. Depending on the depth and the natural shelter of the coastal waters, the impact will be different. Moderately sloping, shallow, north and or north-facing shorelines are expected to see the highest swells and surfs.

The bomb cyclone will go from a central pressure of 1004 hectopascals (hpa) (which is the same in millibars) to around 968 hpa in 24 hours and to a minimum of 955 hpa in 48 hours, just east of Newfoundland and Labrador, Canada. This represents an explosive drop of 59 hpa – more than one hpa per hour; thus, meeting the definition of a bomb cyclone – a drop in pressure of an extratropical cyclone of at least 24 hpa in 24 hours or less.

By Saturday, this weather bomb will be packing Category 1, hurricane force winds – 119 to 153 km/h (74 to 95 mph). These are the winds that will, in turn, generate large waves that will traverse the Atlantic and pound the shorelines of the Caribbean, inundating some low-lying coastal areas.

Of course, the hurricane force winds do not even have the remotest of chance of reaching the Islands; however, some of the wind energy, transferred into the seas will reach us in the form of ocean waves – ground swells. As you may know, waves do not transport water; they transport energy, which can de destructive when they break on shorelines.

Animation of wind directions and speeds forecast to impact the region, as predicted by the ECMWF Integrated Forecasting System (IFS) Model. Time in UTC.

Talking about winds, they are expected to surge – getting to the general range of 25 to 45 (16 to 28 mph), across the region again late Saturday and likely continue into Monday. Storm-force gusts to near 65 km/h (40 mph) are expected, especially in showers. Thus, both high wind advisories and small craft warnings are highly possible late Saturday through Monday morning.

Our (Caribbean) weather will also become wet again over the weekend and into midweek. There is a very high chance of occasional brief showers, as the high winds will destabilise the atmosphere via mixing and low-level convergence.

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