Third Wettest July on Record but Droughts Continue

26 08 2020

Dale C.S. Destin|

July was a very wet month for Antigua. It was the wettest month for the year, thus far, by “miles”, the wettest month since May 2019 and the wettest July since 2011 with 177.3 mm (6.98 in) of rainfall. On record, it is the third wettest July dating back to 1928. Notwithstanding the well above normal rainfall, there has been a mixed effect on the droughts started back in April.

Droughts have eased or ended but the drought that matters most – the hydrological drought, continues. A hydrological drought speaks to shortfall on surface or subsurface water supply. In our case, surface catchments, such as Potworks Dam, remain dry or low with ground water levels also remaining low, although improved. Evidence of the continuing hydrological drought can be seen in the continuation of water rationing by Antigua Public Utilities Authority (APUA).

Potworks Dam, our billion gallon water catchment still dry – 24 July, 2020. Picture courtesy Karen Corbin of the Humane Society.

The agricultural and ecological droughts would have, at least, eased significantly or ended, with the bountiful rainfall in July. Meanwhile, the meteorological and socioeconomic droughts have eased to, at least, slight levels.

Normally, we get 100.3 mm (3.95 in) of rain in July. The total of 177.3 mm represents a surplus of 77.0 mm (3.03 in) or 77%. In other words, the rainfall for this July was 177% of normal or average. Only two other times this mark was exceeded, for the month – 2011 and 1963 with 216.7 mm and 224.8 mm (8.53 and 8.85 in) respectively.

The change in our rainfall fortune is linked to warmer than normal sea surface temperatures across the tropical North Atlantic and the transitioning of the Pacific to La Nina conditions.

The very wet July has also brought the rainfall total for the year to near normal. It is unclear what the last four plus months of the year will bring. Models surveyed indicate equal chance of below, near and above normal rainfall for August-December and for 2020.

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Busy Week Ahead for the Caribbean

16 08 2020

Dale C. S. Destin |

Looks like the Caribbean is set for another busy week. There is the potential for two tropical cyclones – tropical depressions, tropical storms or hurricanes, impacting the area.

Tropical Disturbances AL97 (near the Caribbean) and AL96 (near Africa)

It is the start of a new week but the continuation of a record-breaking hurricane season, which could add two more storms to its tally, in days. There are two new disturbances between Africa and the Caribbean, taking aim at the islands.

Satellite picture animation showing the locations of the distrubances

It is uncertain as to whether these disturbances will become tropical cyclones, where they will go and what hazards, they will bring to the area. However, at this time of the year, most disturbances do develop into tropical cyclones, as conditions are generally conducive, like they are currently, bar the dry and dusty Saharan air.

Today, we saw the end of Tropical Storm Josephine, which threatened the area but eventually passed a safe distance north of all the islands.

Tropical Storm Josephine passing by on Saturday afternoon, 15 August, 2020

With Josephine gone, all attention is now on Disturbances AL96 and AL97. They both have a 50 percent chance of formation. And they both have tracks that take them through the Caribbean.

The second of the two systems, AL96, appears to be more of a future threat to the Caribbean, particularly the Leeward Islands. AL97 is perhaps moving too rapidly for much development to take place before reaching the Eastern Caribbean tomorrow; however, it is forecast to slow down in the Caribbean Sea where it will encounter favourable conditions for formation Wednesday.

Most available models have AL97 becoming a tropical storm in 48 hours – Tuesday night/Wednesday
Most available models have AL97 going through the southern Caribbean, at most, as a Tropical Depression

The gold standard of models – the ECMWF IFS or European model is very sweet on AL96. It gives it a relatively high chance of becoming a tropical storm and track towards our “neck of the woods” – the Leeward Islands this upcoming weekend. This week could end similarly to the one just gone – with us under a Tropical Cyclone Alert or worse.

Already for the season, there have been 11 named storms, the most to have ever occurred this early in the year, with the more active half of the hurricane season just getting started. With half of the season to go, only 48 out a total of 169 seasons, dating back to 1851, has seen more storms.

Be prepared! Based on the forecast, the season is likely to produce, at least, nine more named storms, five more hurricanes and three major hurricanes. It is likely to be a very long season.

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Updated Hurricane Season Forecast – August Look Out You Must, 2020

12 08 2020

Dale C. S. Destin |

My “August look out you must” 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 very active/hyperactive – well above normal.

My forecast calls for 26 named storms (up 3), including ArthurBerthaCristobal, Dolly, Edouard, Fay, Gonzalo, Hanna and Isaias, with 10 becoming hurricanes (up 1) and 4 becoming major hurricanes (down 1). The accumulated cyclone energy (ACE) index is forecast to be 218 (up 18). Further, there is a 70% confidence of

  • 20 to 32 named storms;
  • 7 to 15 becoming hurricanes;
  • 3 to 7 becoming major hurricanes and
  • 141 to 305 ACE.

If the forecast materializes, the ACE would be top 8 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 8 of all times.

To date, the season has produced an ACE of 23.1, more than twice the usual amount for January through July. A normal season produces 106 ACE. Also, there have been nine named storms to date, two of which became hurricanes – over five time the average number of hurricanes of 1.9 and four times the usual number of hurricanes of 0.2. 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.

If the forecast materializes, the ACE would be top 8 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 8 of all times.

To date, the season has produced an ACE of 23.1, more than twice the usual amount for January through July. A normal season produces 106 ACE. Also, there have been nine named storms to date, two of which became hurricanes – over five time the average number of hurricanes of 1.9 and four times the usual number of hurricanes of 0.2. 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 the continuation of a much warmer than usual tropical North Atlantic (TNA) and a developing La Niña.

Tropical North Atlantic (TNA) Index – Reds for warmer than usual and blues for the opposite.
Pacific Ocean Niño3.4 – Reds for warmer than usual and blues for the opposite

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 August and deep into the peak of the months – 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 – 34% 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.

This is my last forecast for this hurricane season. My first forecast for the 2021 season will be available around April 10. All the best for the rest of this 2020 season.

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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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