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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Strong Howling Winds to Continue to Impact the Caribbean

11 01 2020

Dale C.S. Destin, updated January 12, 2020 |

Strong howling winds are expected to continue across much of the Caribbean Basin through Tuesday. These huffing and puffing, big bad wolf winds are causing notable socio-economic impacts to the islands.

As the winds go up, so also do the seas; hence, hazardous seas have engulfed the region – from the Bahamas to the Guyanas, including the Caribbean Sea.

The winds have risen to the range of 29 to 52 km/h or (18 to 32 mph) over land and are expected to persist until Tuesday. Further, gusts as high as 80 km/h (50 mph) are possible for some areas. Over the Caribbean Sea, the winds are forecast to be stronger than some places over land. One such area is between Jamaica and Columbia, where sustained winds – 70 km/h (44 mph), are forecast. With respect to land, the highest sustained winds are forecast for the Eastern Caribbean.

The blustery winds will cause the seas to remain very angry with significant wave heights of 2.5 to over 4 metres (8 to 14 feet) and occasionally reaching over 5 metres (18 feet). There is an area between Jamaica and Columbia where the significant wave heights are predicted to be over 5 metres (18 feet), occasionally reaching 7 metres (23 feet).

Over the past 24 hours, above normal swells, from distant strong winds, have added to the hazards across the area. So, not only there are concerns for high winds and hazardous marine conditions in open waters, there is now also a concern for the impact of life-threatening surfs (breaking waves) along, mainly northern and north-facing shorelines; hence, a high surf advisory has or will be required for most islands. Already, a high surf advisory is in effect for much of the Caribbean.

Beachgoers should be extremely cautious; bathe only where lifeguards are present or the sheltered, less affected beaches, mainly to the south. See the bulletins from your national weater service for detail and specific guidance for you local.

Such conditions are very conducive fo rip currents – powerful channels of water flowing quickly away from shore, which occur most often at low spots or breaks in the sandbar and near structures such as groins, jetties and piers. If caught in a rip current, relax and float. Don`t swim against the current. If able, swim in a direction following the shoreline. If unable to escape, face the shore and call or wave for help.

As a result of the weather, more so the strong winds, three cruise ships had to abort berthing at the St. John’s Harbour in Antigua. These, I am informed, were The Anthem of the Seas, Norwegian Dawn and Crown Princess. Ferry service between Antigua and Montserrat has been cancelled until Thursday. The have also been aborted attempts by LIAT to land in Dominica. There are also reports of downed banana and other trees in the Windward Islands and Trinidad and Tobago, and there have been power outage in the British Virgin Islands and Trinidad and Tobago attributed to the strong winds.

Thus far, the highest winds (10-minute sustained and gusts) have been observed at:

  • Grantley Adams International Airport (GAIA), Barbados;
  • George F.L. Charles Airport (GFLCA), St Lucia and
  • Norman Manley International Airport, Jamaica.
The winds by the numbers. One mph = 1.61 km/h. Multiply 10-minute sustaned winds by 1.11 and 1.40 to get 1-minute sustained winds and 3 second gusts respectively. *Harper et al. 2010 is the World Meteorological Organization (WMO) standard.

Looking at the winds by the numbers. Speeds of 39 mph or more are storm-force or gale-force winds, gusts in this case. However, when dealing with tropical cyclones, categorization is based on a maximum 1-minute sustaned wind speed. To convert from 10-minute wind speeds to 1-minute wind speeds, multiply by 1.11. Thus, parts of Barbados, Jamaica and St. Lucia had sustained storm-force windsstorm conditions (35×1.11 = 39 mph or 63 km/h). However, note that there are no tropical cyclones in the area.

Winds blow because of the differential of pressure across the Earth’s surface. The higher the horizontal differential or the higher the pressure gradient, the stronger the winds. The strong winds, over the next several days, will continue to be due to a very steep pressure gradient. The pressure will be that steep largely due to a 1042 millibar high-pressure system moving off the US east coast.

Pressure pattern forecast for 2 am Saturday, January 11, 2020
The ususal pressure pattern across the North Atlantic for January. Note that the usual difference of pressure between Bermuda High and the Caribbean is around 6 to 8 mb.

Immediately above is the usual pressure pattern for the North Atlantic. Note that the usual difference in pressure between the Bermuda High and the Caribbean is around 6 to 8 millibars. However, compare the graphic below to the one above and you will observed that the difference in pressure between the Bermuda High and the Caribbean (at 2 am, Sat, 11 Jan 2020) was 20 to 24 millibars. Thus, the pressure difference and gradient were two to four times higher that usual or 200 to 400% of normal; hence, the very strong winds.

North Atlantiuc surface chart – 2 am, Saturday, 11 January 2020

The highest and most dangerous waves will take place across the waters of the western Caribbean – between Jamaica and Columbia. This area will also experience the strongest winds – 51 to 64 km/h (32 to 40 mph), gale-force/storm-force winds, with gusts in excess of 96 km/h (60 mph).

Advisories and or warnings to mariners have been issued by a number of islands, including Antigua and Barbuda, Puerto Rico and Barbados.

As a small craft operator, if an advisory is issued – inexperienced mariners, especially those operating smaller vessels should avoid navigating in these conditions. If a small craft warning is issued – you should stay in or very near port.

Potential impacts from this hazardous sea event include injuries or loss of life, damage or loss of boats and fishing equipment and disruption to sea transportation. Other possible impacts comprise of:

  • disruptions to sea search and rescue;
  • scarcity of seafood;
  • disruptions to off shore marine recreation and businesses;
  • business and economic losses.

On the other hand, the strong winds could result in further disruptions to transportation and outdoor sporting activities, soil erosion, vehicular accidents and financial losses.

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Potworks Dam Back Online!

23 12 2019

Dale C. S. Destin|

Potworks Dam, Antigua’s largest water catchment, is back online after being offline from around middle of last month, for the fourth time this year. The billion-gallon catchment water levels rose above extraction levels during the rains of late November and early December allowing for it to be reconnected to country’s water lines, to supply potable water.

Ian Lewis, Manager – Antigua Public Utilities Authority (APUA) Water Business Unit

For the year, the Dam first fell below extraction levels back in April but was topped up in late May. It again went below extraction levels in September but was topped up later that month. And again, it fell below extraction levels around mid-November but was partially recharged late November/early December; hence the reason why it is back online.

There is now a slight meteorological drought, which started in October. Based on the latest forecasts, over the upcoming months, it is expected to persist or worsen. Prior to this drought, there was a severe drought from October 2017 to April 2019 – 19 month long.

For the month of November, the catchment area – Bethesda Village, received a little over 100 mm (over 4 in) of rainfall. This is below normal but twice the total for October – 54.9 mm (2.16 in), which is well below normal 150-175 mm (6-7 in). Already, for December, the area has had over 100 mm (over 4 in), which is more than usual.

With Potworks back above extraction levels along with other smaller catchments, water rationing has been terminated, according to the Antigua Public Utility Authority (APUA), the water authority. However, there remains a hydrological drought of, at least, moderate intensity, with no end in sight.

Potworks Dam is less than a quarter full (over three-quarters empty). It has around 200,000 million gallons compared to a capacity of a billion gallons. It has been over five years since it reached capacity; being close to empty or empty has been the norm since 2014.

Potworks Dam – December 4, 2019. Pic courtesy Karen Corbin – Antigua Humane Society

According to APUA, at the usual rate of extraction, the Dam has two to three months of water supply. This means that it will be a part of the country’s water mix until March – the heart of the dry season. Thus, there is not enough surface water to last through the dry season – January to June 2020.

Recharge of catchments is very unlikely during the dry season. This is especially so for this coming dry season, as the outlook is for below normal rainfall being most likely. Hence, Potworks is expected to come offline again by March and will likely remain offline from then until the wetter portion of the wet season – August to November.

Precipitation forecast for January-March 2020, based on 12 global models – 40 to 50% chance of below normal rainfall for Antigua and the rest of the Eastern Caribbean
The outlook shows 45% chance of below normal rainfall for Antigua and the northeast Caribbean for March to May 2020

Given the season and the forecast, a return to water rationing is almost inevitable in about three months, when Potworks Dam is expected to be offline again. Water conservation and efficiency cannot be over encouraged. Let us treat water like the scarce but precious commodity that it is and make every drop count. Think rain!

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Another Windy, Rough and Wet Week Ahead

16 12 2019

Dale C. S. Destin|

Rough Seas – Photo by Getty Images

This is a new week, but similar weather is expected to last week’s – windy and wet with rough seas. Winds are expected to surge over the next 24 hours, resulting in the winds becoming fresh to strong by Monday night. This will in turn cause hazardous seas and wet weather across much of the Caribbean Basin, including Antigua and Barbuda.

The winds and seas will be a threat to the life and property of mainly mariners. Some outdoor activities, on land, could also become dangerous.

By late Monday, the winds will rise to the range of 26 to 42 km/h (16 to 26 mph) with stronger gusts . It is expected that the winds will gusts to near storm-force/gale-force – 63 km/h (39 mph), mainly over open waters, exposed coastal areas and elevated terrains.

Given the expected winds, a high wind advisory may be required, particularly for the areas listed above. If a high wind advisory is issued, residents should secure loose and light outdoor items, which can be blown away, and caution should be taken when driving.

As the winds go, so go the seas – as the winds go up, the seas will go up also and become hazardous. Seas (significant wave height – SWH) are forecast to rise to a range of 2 to 3 metres (7-10 feet) with the potential extreme (10% chance) of reaching over 3.5 metres or 12 feet. Notwithstanding, the potential extreme SWH, seas are expected to occasionally reach near 4 metres (13 feet).  

Recall that seas are given as SWH, which is the average height of the highest 1/3 of the waves. Individual waves may be twice the SWH.

Given the expected height of the seas, particularly wind waves, a small craft warning is expected to go into effect for much of the waters of the Eastern Caribbean Monday night through Thursday morning. An advisory is in effect and one will be in effect after the warning.

Recall that a small craft warning generally means that wind speeds of 38 to 61 km/h (24 to 38 mph) and or seas of 9 feet or greater are expected to produce hazardous wave conditions to small crafts. If or when a warning is issued, small craft operators should stay in or near port and safeguard their vessels.

Impacts possible/likely/expected from hazardous seas include the following:

  • Loss of life;
  • injuries;
  • sea search and rescue disruptions;
  • disruptions to sea transportation;
  • scarcity of sea food;
  • damage or loss of boats and fishing equipment;
  • disruptions to marine recreation and businesses
  • and economic losses. 

Other impacts from the high winds, apart from hazardous seas, include:

  • injuries;
  • soil erosion;
  • localized disruptions of businesses;
  • disruption to outdoor and sporting activities;
  • disruption of transportation (air and especially sea) and
  • vehicular accidents and financial losses.

Wind of this strength could make some outdoor activities uncomfortable, if not outright dangerous. High winds can create dangerous fallen or blowing objects.

The strongest winds and the highest and most dangerous seas will take place on Tuesday. The highest seas will take place in the Atlantic waters of the islands.

The strong winds will be due to a very steep pressure gradient. Think of the pressure gradient like a hill and the wind as a car. The steeper the hill the faster the car will roll down the hill and vice versa. On a weather map, the steepest gradient and strongest winds are where the lines of equal pressure (isobars) are closest.

The higher than usual winds will destabilize the atmosphere, resulting in brief passing showers from time to time. Possible rainfall total for the week across the Eastern Caribbean is 25 to 150 mm (1-6 inches). The highest totals are likely across the southern Caribbean.

Last week, similar type weather took place. The area had fresh to strong winds with gusts in excess of 48 km/h (30 mph). The whole of the Eastern Caribbean had wet weather with some areas experiencing rainfall in excess of 150 mm (6 inches).

Seas will subside from warning to advisory levels by Thusday; however, it is unclear as to when seas will return to safe levels – when no warning, advisory or caution is required.

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The 2019 Atlantic Hurricane Season Summary

30 11 2019

Dale C.S. Destin|

The 2019 Atlantic hurricane season will come to an end midnight tonight. It will long be remembered for Super Category 5 Hurricane Dorian’s destruction of the northwest Bahamas. The season was also an above normal (or active) one, consistent with my initial forecast issued in April and the updates issued May, June, July and August.

2019 Atlantic basin tropical cyclone tracks.

The active year produced 18 named storms, 6 hurricanes, 3 major hurricanes and over 130 Accumulated Cyclone Energy (ACE). Overall, this year ranks 35 out of 169 on record, dating back to 1851, based on the ACE – the internationally accepted metric for determining the activity of hurricane seasons.

Quite interestingly and unprecedentedly, seven named storms lasted only 24 hours or less. The previous record was six in 2005. Notwithstanding, if this were 40 years ago, many of these short-lived storms would have gone undetected; they certainly would have during the pre-satellite era i.e. before 1966.

My forecast

My best performing forecast for the hurricane season – June 1 to November 30, was the one issued in July, which called for an ACE of 127, with a range of 71-198; 13 named storms, with a range of 9-16; 6 hurricanes, with a range of 4-9 and 3 major hurricane (at least Category 3), with a range of 2-5.

Most powerful and destructive hurricane

Dorian was the most powerful hurricane for this season and many other seasons – past and future. It tied with Hurricanes Wilma of 2005, Gilbert of 1988 and the Labour Day Hurricane of 1935 for second for the most powerful hurricane, based on sustained winds – 295 km/h (185 mph). Only Hurricane Allen of 1990 has had higher winds – 305 km/h (190 mph). However, Dorian became the strongest hurricane, with respect to winds, to make landfall in the Atlantic Basin. In other words, no other land mass in this part of the world, apart from Abaco Bahamas, has ever experienced such high sustained winds.

Dorian about to make landfall on Great Abaco Island , Bahamas – Sep 1, 2019

The season caused over USD 12 billion dollars in damage – the lowest since 2014, with Dorian causing at least 8.28 billion dollars. Of the 8.28 billion, 85% (7 billions) was caused in the Bahamas; this represents around 58% of the total damage for the year.

Hurricane Dorian’s destruction in the Bahamas. Picture courtesy Wikipedia

The death toll is at least 98, with at least 61 dead and at least 400 missing in the Bahamas. The total fatalities for 2019 could be the highest since 2017, when it was over 3300.

Rankings

Looking at the year with respect to the number of named storms – 18. This tied with 1969 for the eighth highest number of named storms for a year. It is the highest number of named storms since 2012.

Ranking of hurricane season by tropical storms (TSs). Graphic courtesy Wikipedia.

The 2019 season is the fourth active season in a row, dating back to 2016; however, 2019 was the least active of the period although it had the highest number of named storms. The main difference is that 2019 had fewer hurricanes.

Relative to the normal season of 12 named storms, 6 hurricanes, 3 major hurricanes and 106 ACE, this season had 50% more named storms than normal but the same number of hurricanes and major hurricanes. The ACE was 23% higher than usual. All metrics indicate that the 2019 season was near or above normal.

Other notable records are:

  • Dorian became the strongest hurricane ever recorded outside of the Caribbean and the Gulf of Mexico – the previous record was held by Hurricane Irma of 2017
  • Dorian impacted the Bahamas for 27 hours as a Category 5 hurricane – the longest ever on record for a Category 5 hurricane to impact one location.

Relative to Antigua and Barbuda

Antigua was brushed by Dorian on August 27, with the system passing about 110 miles southwest of the island. During the passage, it caused wind gusts of 44 to 63 km/h (28 to 39 mph).

The impact on the island was minor, as the system was quite disorganised due to it ingesting dry and dusty air from the Sahara Desert and being battered by hostile wind shear.

On average, Antigua and Barbuda gets one named storm passing within 105 nm every other year, one hurricane every three years and a major hurricane every seven years.

Why was the season active?

The season was active because of warmer than normal sea surface temperatures across the Atlantic and below normal wind shear, particularly during the peak of the seas – August to September.

The absence of an El Nino also allowed for a more active season than normal.

Keep following for more on the just ended hurricane season, tropical cyclones and climate change and all things weather and climate. The next hurricane season starts June 1, 2020 – six months from now, let us all be prepared. Our first forecast for the next season will be issued around April 10.

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Destructive Swells to Impact Much of the Atlantic Basin This Week – Including the Caribbean

27 10 2019

Dale C. S. Destin|

A major swell event is forecast to impact much of the Atlantic Basin this week, including Antigua and Barbuda and the rest of the Caribbean, washed by the Atlantic. The swells are expected to cause high surfs and powerful rip currents, which will be a severe threat to life and property, mainly in the surf zone. There is also the increased likelihood of damage due to flooding of some low-lying coastal areas.

Swells Forecast For Friday Nov 1, 2019

Swells reaching the region are expected to rise to over 3 metres (over 10 ft) and locally or occasionally exceeding 3.5 metres (12 ft), coming out of the northeast. These swells will result in dangerous, life-threatening surfs for beachgoers and other users of coastal areas; hence, advisories and or warnings will be required. Some meteorological services have already issued marine alerts on the event – see information coming out of your national meteorological service for the specifics on this event.

Swells heading our way – Antigua and the Caribbean, have spiked to near 14 feet (4 metres). At periods of 10-15 seconds, it takes 8 to 12 hours for swells to reach us from this buoy/weather station. Please note that we may not see 14 ft swells in the area; however, they are expected to, at least, peak over 10 feet, with higher surfs – causing very hazardous, life-threatening conditions at near-shore/coastals areas. 

The swell event started four days ago by hurricane-force winds associated with an enormaous low-pressure area, which contained Hurricane Pablo and a very powerful extra-tropical cyclone. Since then, Pablo has dissipated and the extra-tropical cyclone ahs transitioned to Subtropical Storm Rebekah. Of course, the extreme weather directly associated with the low never had a chance of reaching the Caribbean and Rebekah likewise has no chance of directly impacting the region.

The Enormous Low-Pressure Area Generating the Swells

The swells in and of themselves are not the real concern. The greater concern is the large breaking swells or high surfs that these swells will caused when they reach the shorelines of the region. Such long period swells can result in surfs as high as twice their heights i.e. in excess of 6 metres ( in excess of 20 ft), in some areas.

Puerto Rico’s Met Service is Forecasting Surfs to Exceed 15 Feet (4.5 metres)
High Surf - Fort James, Antigua
Past High Surf – Fort James, Antigua

The eventual heights of the surfs are largely dependent on the bathymetry (shape and depth) of the near shore coastal areas they interact with. Generally, the shallower the near shore areas, the higher the surfs. The greatest impact will be on the north, northeast and east-facing beaches and coastlines.

The event has started across the northeast Caribbean and will reach the southern Caribbean and South America, including the Guyanas by tomorrow – Monday. A second pulse of dangerous swells will reach the Caribbean by late Thursday. These swells are also forecast to reach the east coast of the United States, Canada and as far away as Greenland, Iceland, the United Kingdom, Europe and Africa.

These high surfs will have the potential impact of injuries or loss of life, beach closures and financial losses. Impacts could also include:

  • disruption to potable water from desalination;
  • salt water intrusion;
  • flooding of low-lying coastal roads;
  • beach erosion;
  • disruptions to near shore marine recreation and businesses;
  • damage to coral reefs and
  • disruptions of marine transportation.

These swells and surfs could result in strong rip currents that can carry even the strongest swimmers out to sea. Rip currents are powerful channels of water flowing quickly away from shore, which occur most often at low spots or breaks in the sandbar and near structures such as groins, jetties and piers.

If caught in a rip current, relax and float. Don`t swim against the current. If able, swim in a direction following the shoreline. If unable to escape, face the shore and call or wave for help.

There is also concern for those who visit non-beach coastal areas. High surfs can knock spectators off exposed rocks and jetties. Those who rock fish need to pay attention and not expose themselves to this hazard. Breaking waves may occasionally impact harbours making navigating the harbour channel dangerous.

With this event happening during or near a new moon, coastal flooding and erosion are more likely than usual. Coastal flooding from the sea is largely depended on high tides, onshore wind and swell actions.

The potential impacts listed above are just that – potential/possible impacts. I am not saying that they will all definitely happen, but conditions could result in such and past similar swell events have caused such.

If an high advisory is issued for an area – be extremely cautious; bathe only where lifeguards are present. If a high surf warning is issued – do not enter the water. Relatively safe conditions are likely on the opposite, or in this case, the southern sides of the islands.

Swells and associated surfs will peak across the Caribbean tonight and or Monday and again Thursday and or Friday. The highest swells across the region are likely across the northeast Caribbean – Antigua and Barbuda and the rest of the Leeward Islands.

I will keep you updated on this event via TwitterFacebook and Instagram. Please share this blog, if you found it useful and follow me for more on all things weather and climate.

Editor’s note: This post was originally published Oct 27, 2019 and updated on Oct 31, 2019 to reflect changing conditions.








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