Here We Go Again – It’s Hurricane Season 2017; What’s the Forecast?

2 06 2017

Dale C. S. Destin |

When you live in “Hurricane Alley” like we do, you often don’t want to think about the hurricane season before it starts – it’s too stressful. But you really should, as preparation is key to survival. If you are now preparing for the 2017 Atlantic hurricane season, you are late, but there is still some time left.

What to prepare for – What’s the forecast?

Key to your preparations is to know what to prepare for. From this vantage point, we will most likely have a near normal hurricane season. Normally, the season has 12 named storms (tropical storms and hurricanes), 6 hurricanes and 3 major hurricanes. This year, our ensemble (mean) forecast is for 14 named storms, 7 hurricanes and 3 major hurricanes.

2017JuneHurricaneSeasonForecast1

A better indicator of the activity for the season is the accumulated cyclone energy (ACE) index. This is a measurement of the potential of wind and storm surge destruction of a named storm. Summing together the ACE index of each named storm, provides a more complete picture of activity for a season, outside of just the number of storms. The mean ACE index forecast for this year is 110; the average is 106 (1981-2010).

The latest forecast represents an uptick in the activity for the season. The previous forecast called for a below normal hurricane season – 11 named storms, 6 becoming hurricanes and 3 major hurricanes, with an ACE of 71. This was predicated on the forecast of an El Nino during the heart of the season.

El Nino normally inhibits tropical cyclone (tropical depression, tropical storm and hurricane) activity. However, over the past few months, an El Nino seems less likely, delayed or insignificant, if developed; hence, the uptick in the activity for the season.

Also, contributing to the uptick in the forecast activity for the season is the forecast of warmer than normal sea surface temperatures across the tropical north Atlantic and lighter than normal trade winds. All things relish by tropical cyclones.

2017HurricaneNames

Our forecast is the ensemble (mean) of the forecasts from Klotzbach of Colorado State University, the U.S. National Oceanic and Atmospheric Administration (NOAA), Saunders and Lea of Tropical Storm Risk.com (TSR), the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF), UK Met Office and The Weather Company (TWC).

It must be noted that NOAA is the only group, of the five surveyed, that is forecasting an above normal season.

So, that’s the forecast – what is the probability of Antigua being hit?

The probability of Antigua being hit or brushed by one or more named storm this year is around 63% – up 14% from the average of 49%. The probability of one or more hurricanes is 22% – down 15% from the average of 37%.

These numbers were calculated based ONLY on the likely best similar years (1957, 1969, 1979 and 2006) to the upcoming hurricane season according to Klotzbach. Of these years, we were hit by Tropical Storms Claudette, Frederic and Chris and brushed by Hurricane David.

Notwithstanding, at the end of the day, these numbers don’t mean a whole lot. We could be hit by one or more named storms or none at all. Bottomline – we truly do not know what is going to happen, with any certainty. However, what we do know, with absolute certainty, is that storms and hurricanes form every year, and we could get hit, as we have many times in the past. So, regardless of the probabilities and forecasts, we need to prepare. It only takes one tropical cyclone to set you back for years.

A season can produce many storms, but have little impact, or produce few storms and have one or more hitting Antigua with major impact.

Antigua averages one hurricane every three years and one named storm every two years or every other year.

What happened last season – 2016?

The 2016 season was more active than normal – the first active season since 2012 and the most active since 2010. It spawned 15 named storms, 7 became hurricanes and 3 reached major hurricane status. The strongest hurricane for the season was Matthew, which had peak sustained winds of 258 km/h (160 mph).

Satellite Image of Hurricane Matthew - Sep 30, 2016

Satellite Image of Hurricane Matthew – Sep 30, 2016

Hurricane Matthew also caused the most devastation. In total, up to 600 deaths have been attributed to the system, including over 500 in Haiti, making it one of the deadliest Atlantic hurricanes.

Hurricane Matthew 2016

Rainfall Trail From Hurricane Matthew 2016

The 2016 season is the first year since 2008 that no tropical cyclone hit or brushed Antigua. It was likely the least stressful hurricane season for the island in, at least, eight years.

The 2017 season is forecast to be similar to 2016.

The hurricane season runs from June 1 to November 30.

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November 2016 to April 2017 Climate Outlooks for Antigua and Barbuda

30 11 2016

Dale C. S. Destin |

The November 2016 to April 2017 climate outlooks are now available for Antigua and Barbuda. Our worst meteorological (Met) drought on record ended in September and remains that way. Moderate or worse Met drought is unlikely for the foreseeable future. It is, however, unclear what will happen with respect to rainfall over the next six months as there are equal chances of below, near or above normal rainfall. Meanwhile, warmer than normal mean temperature is likely to continue.

Drought Meter

Drought

The Met and agrometeorological (AgMet) droughts remain ended, notwithstanding near record low rainfall for October. However, the hydrological (Hydro) and socioeconomic (SE) droughts continue at slight levels or worse. The island-average of 46.2 mm (1.82 in) for October 2016 is the fourth lowest on record dating back to, at least, 1928 and the lowest since October 2000.

Projected rainfall for next 6 months

Looking forward – unfortunately there is no decisive information on what can be expected rainfall-wise. There are equal chances of below, near or above normal rainfall for November-January (NDJ), February-April  (FMA) and November-April. Given these and other forecasts, particularly the drought forecast, moderate or worse Met and AgMet droughts are unlikely. Meanwhile, the Hydro and SE droughts are not expected to undergo sustained worsening. The drought watches have been dropped.

The cold phase of El Nino Southern Oscillation (ENSO) – La Nina is evident although an episode cannot yet be declared. Further, the criteria and episode – five overlapping “seasons” of La Nina temperatures is unlikely to be met.

If you are in our part of the world – the Caribbean, a La Nina would be more than welcome. However, it is coming a bit late as the greatest positive impact on our rainfall occurs during the wet season, which will come to a close at the end of December.

Precipitation and temperature

Year-to-date, the rainfall for Antigua is almost one-and-a-half times more than all the rainfall for 2015. Further, it is the wettest January-October since 2013. Notwithstanding, we are still over 5 inches in the “red” relative to the long-term average of 952.8 mm (37.51 in).

Notwithstanding the low rainfall for October, there has been a general up-tick in rainfall since August. It is difficult to say at this time what can be expected to the upcoming months what quantity we will get as we have no climate signal. However, we are unlikely to have below normal rainfall.

It is now almost certain that Antigua will have near normal rainfall for 2016 – 1067 to 1321 mm (42 to 52 in). This is doubled the amount for last year – the driest year on record.

For the period November to April, above normal temperature is likely.

See the following links for the full outlooks: November 2016, November-January 2016, February-April 2017November 2016-April 2017Drought, 2016 Updated Hurricane Season Forecast.

The next set of outlooks will be available by December 7, 2016.





Easter to See More Hazardous Marine Weather Across Most of the Caribbean

26 03 2016

Dale C. S. Destin |

Fresh to strong gusty winds are causing hazardous seas across most of the Caribbean. This is expected to continue beyond Easter Monday (March 28).

Credit UCAR

Hazardous seas; Credit UCAR

Based on observations from met. offices and weather buoys, the winds were in the range of 15 to 22 knots (17-25 mph) with gusts in excess of 32 knots (37 mph).

In some areas, the winds were much stronger. At the Norman Manley International Airport, Jamaica, peak sustained winds of 26 knots (30 mph) were measured. No doubt parts of that island had gusts in excess of 34 knots (39 mph) – the equivalent to gale force or tropical storm force winds.

Weather report

Weather report from Norman Manley Int’l Airport – Mar 25, 2016, 2 pm local time

Winds were strongest across the Caribbean Sea, south of Jamaica. Today, Buoy 42058 measured winds in the range of 21 to 25 knots (24-29 mph) with gusts reaching 32 knots (37 mph).

Buoy data show the Caribbean Sea, especially south of Jamaica, is basically impassable by boat due to tremendously hazardous seas reaching as high as 4 metres (13 feet). Across the waters Eastern Caribbean, seas are near 2.5 metres (8 feet) and building.

Buoy data for March 25, 2016

Buoy data, seas for Mar 22-26, 2016 GMT/UTC

Buoy Data

Buoy data, wind speed Mar 22-26, 2016 GMT/UTC

The strong winds are in response to the high pressure gradient across the region. Winds blow as a result of differential pressure. The greater this differential is i.e. higher the pressure gradient, the stronger the winds and vice versa.

Surface chart depicting high pressure gradient evident by the closeness of the isobars (black lines)

Surface chart depicting high pressure gradient evident by the closeness and high quantity of the isobars (black lines)

As the winds increase, the friction on the underlying sea surface results in building seas or wind-driven waves. The stronger the winds, the higher the wind-driven waves and vice versa.

A further increase in the pressure gradient is forecast over the next 24 hours. Hence, winds and seas are expected to get higher. Thus, marine conditions are expected to become even more treacherous tomorrow.

Seas could exceed 4.5 metres (15 feet) across the waters between Jamaica and Panama. Meanwhile seas and could exceed 2.7 metres (9 feet) mainly on the Atlantic (east) side of Barbuda, Antigua, Guadeloupe, Dominica and Martinique.

Forecast Seas

Forecast Seas (feet), valid 2 pm (1800 UTC), Sat, March 26, 2016

The winds could increase by another 2 to 5 knots (2-6 mph) with gusts in the upper 20s to lower 40s knots ( upper 20s to upper 40s mph).

Forecast Winds

Forecast Winds (knots), valid around 11 am (1500 UTC) Sat, Mar 26, 2016

Forecast Gusts

Forecast Gusts (knots), valid around 11 am Sat, Mar 26, 2016

Clearly, it goes without saying that mariners should not venture far from port and sea-bathers should be extremely careful. As a matter of fact, sea-bathers should avoid the beaches on the northern and eastern sides of the islands. For Hispaniola and Jamaica, beach-goers should also avoid the waters on the southern side of those islands.

The strong winds could also make some outdoor activities very uncomfortable to perform, if not outright dangerous. This is especially true of work at elevations. Please be guided accordingly.

The winds will start to subside on Sunday. However, seas will not return to safe levels until around Wednesday.

Cuba is the only Island being spared by the strong winds and hazardous seas.

We will keep you updated via our social media platform, which includes twitter, facebook, wordpress, instagram, tumblr, and google+. You are invited to follow for all things weather and climate.





The Latest Round of Seasonal Forecasts for Antigua – Mar to Aug 2016

3 03 2016

Dale C. S. Destin |

Our latest round of seasonal forecasts for Antigua is indicating that the current record longest drought will likely continue into the second half of the year. Both the spring and summer rainfall forecasts are calling for below to near normal rainfall.

SeasonalOutlook_Mar-Aug2016.png

The previous round of forecasts had indicated a high chance of the drought easing to slight levels or ending around the middle of the year. However, the latest round of forecasts is backing away from the optimism of significant showers over the period May-July.

Notwithstanding our forecasts for the upcoming seasons, the prospects for drought busting rainfall is still possible. A number of the global models are forecasting above normal rainfall for the mentioned seasons. However, our downscaled forecasts, which we believe have better skill for our region, are predicting drier than normal weather will persist.

Our drought outlook is also in support of the drought continuing beyond the middle of the year. The periods December 2015-May 2016, October 2015 to June 2016 and September 2015 to August 2016 are projected to see moderate to major rainfall deficits.

Temperatures for the upcoming six months are generally expected to be above normal. Hence, this spring and summer are anticipated to be warmer than normal. This could further exacerbate the scarcity of water.

The next round of forecasts, which will cover April to September 2016, will be available by April 3. Hopefully, we will have better news then. All of our outlooks can be found here





A Tropical Wave to Shower the Leeward Islands

21 06 2015

Dale C. S. Destin |tropwaveJun21

A tropical wave is expected to raise our rainfall total over the next 24 hour. It will likely shower the island with 5 to 10 mm (0.20 to 0.40 in) of rain as it traverses the region. It’s possible that rainfall total could reach as high as 25 mm in some places.

forecast_June22

Already, the system has dumped over 25 mm of rain on parts Barbados with more rain in the forecast. The Windward Islands and the rest of the Leeward Islands are also in for some much needed showers, from the tropical wave.

Many of the islands are in the midst of droughts and are thirsty for rainfall. For example: as of the end of May, Antigua only had two more months of surface water remaining, according to Ian Lewis, Water Production Manager of the water authority. Meanwhile, the Government of St. Lucia has declared a “water emergency”.

The wave will also cause a surge in the winds and seas across the Eastern Caribbean. Winds are expected to rise to near 20 knots, mainly over open water and elevated places. Wind gusts to near 28 knots will also take place.

Seas_June 21

In response to the strong winds, the seas will become hazardous with heights reaching 2.4 m (8 ft), especially on the eastern side of the islands.

The winds alone will make some outdoor activities, such as working at heights, uncomfortable if not dangerous.

While the rain is expected to subside by the end of tomorrow (Monday), strong winds and rough seas will continue until Wednesday. Given the situation, mariners should really stay near shore until winds and seas subside to safe levels.

Given the rainfall deficits across much of the region, the possible rainfall totals from the tropical wave are only “drops in the bucket”. However, we are in a very desperate position; hence, we will cheer for every and any shower.





Hold on to Your Hats and Skirts!

31 12 2014

Dale C. S. Destin |

Forecast Wind Speeds - Sun Jan 4, 2015

Forecast Wind Speed – Sun Jan 4, 2015

Hold on to your hats and skirts and batten down the hatches. Strong winds and very rough seas to kick off the new year across Antigua and much of the Caribbean.

The winds will become stronger with peak sustained speed near 25 mph (22 knots) over the weekend across Antigua and Barbuda. The winds will also be very gusty with gusts as high as 37 mph (32 knots) possible, just 2 mph short of storm force.

Forecast Wind Gust - Sun Jan 4, 2015

Forecast Wind Gust – Sun Jan 4, 2015

The strong winds will stirrup very rough seas in our area. Seas could peak as high as 3.6 metres (12 ft) Sunday and continue above 2.4 metres (8 ft) until, at least, the middle of next week. By next Thursday there could be a transition from wind waves to swell waves from a frontal low pressure system.

Forecast Wave Height - Sun Jan 4, 2015

Forecast Wave Height – Sun Jan 4, 2015

The strong winds are in response to the steepening of the pressure gradient across the area. You may recall that winds are the horizontal movement of air. They only occur due to the spatial deferential in atmospheric pressure. The change in pressure across a particular area is called the pressure gradient. The steeper the gradient or greater the pressure difference between two points, the stronger the winds and vice versa.

Warnings are already in effect for hazardous seas that are bound to get much worse. Mariners should consider staying near shore until winds and seas subside, perhaps late next week.

The strong winds could make certain activities uncomfortable, if not dangerous. For example, working at elevation could be dangerous and should be curtailed until the winds return to normal speeds.

The worst conditions will be seen in the western Caribbean Seas, juts north of Columbia. The winds are expected to peak near 44 mph (38 knots) with gusts near 54 mph (47 knots); this is tropical storm strength and under tropical cyclone criteria would require a tropical storm warning. Wave heights will approach 6 metres (20 ft).

This area of storm force winds is pushing large waves outward which will cause most of the Caribbean Sea to be rough for the next several days. Mariners should avoid travelling not only the Atlantic waters of the Caribbean but also the Caribbean Sea, especially the western Caribbean Sea south of Jamaica.

Feel free to share with us your experiences of this strong wind and very rough seas event and follow us on wordpress: anumetservice.wordpress.com twitter: @anumetservice facebook: /anumetservice tumblr: anumetservice.tumblr.com to keep current with weather and climate info.

Happy New Year!





More Drought Quenching Rainfall for Antigua

17 12 2014

Dale C. S. Destin |

Surface chart showing stationary front across northern Caribbean (red & blue)

Surface chart showing stationary front across northern Caribbean (red & blue)

More drought quenching rainfall fell today across Antigua yesterday December 16. A near stationary front (shown below on the surface chart) showered the island with much needed water. At the V. C. Bird International Airport (VCBIA), 10.9 mm of rain was measured, all falling between 2:45 pm and 6:45 pm. However, estimates from weather radar (shown below) indicate that as much as 50 mm may have fallen on northern side of the island. Over in Barbuda, a drenching 150 mm or more fell according to radar estimates. Going by what was actually measured by raingauge, at the VCBIA, the rainfall total now stands at 69.7 mm (2.74 in). This means that the Airport, thus far, has received near normal rainfall for December. However, above normal rainfall, above 91.4 mm (3.6 in) is forecast for the month. Thus, further quenching of the drought is anticipated.

Radar rainfall estimates

Radar rainfall estimates

The front did not just affect Antigua; satellite photo and TRMM data below show the cloud and rainfall signature patterns of the system stretching across much of the northern Caribbean from the Leeward Islands west to Jamaica and parts of Cuba.

 

Satellite picture of the stationary front

Satellite picture of the stationary front

Here are the rainfall totals reported by some of the other affected islands:

  • Robert L. Bradshaw International Airport, St. Kitts – 39 mm
  • Luis Muñoz Marín International Airport, Puerto Rico – 101 mm
  • Sangster International Airport, Jamaica – 38 mm
TRMM rainfall estimates

TRMM rainfall estimates

Rainfall at the VCBIA continues to run above normal for December. Exceeding 100 mm is a real possibility. If this were to happen, it would be the fourth time in the last five years. Continue to think rain.

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