Potential Hurricane Scare Early Next Week

30 08 2016

Dale C.S. Destin |

A weather disturbance coming off West Africa will likely cause a scare to residents of the northeast Caribbean early next week. Two of the more reliable weather models are forecasting this disturbance to become tropical storm or hurricane later this week and track in the direction of the islands.

Tropical Disturbance Moving Off the West Coast of Africa - Aug 29, 2016

Tropical Disturbance Moving Off the West Coast of Africa – Aug 29, 2016

The preliminary forecast track has it moving on a westerly path, in line with the Leeward Islands, which includes Antigua and Barbuda. However, just before reaching the islands, it’s forecast to turn right or north away from the islands, which should spare us its wrath.

ECMWF IFS

ECMWF Integrated Forecast System Showing at least an 80% Chance of a Tropical Cyclone Near the Northeast Caribbean Between Sep 4 and 6

Twenty-one years ago from September 5, 2016, Antigua and Barbuda experienced one of the most powerful hurricanes in its history – Category 4 Hurricane Luis. It brought death and major destruction to the islands. It left in its wake three dead and around US$350 million dollars in damage. It is easily our costliest hurricane in history.

The system that could cause us some stress is not being forecast to be a Luis, God forbid! However, its potential path and timing are reminiscent of Luis. It could be nearest us around September 5, just that this time, it should turn away sooner than Luis did and spare us this time.

The hurricane season runs until November 30. The forecast calls for 15 named storms, 7 hurricanes and 3 major hurricanes. Thus far, there have been seven named storms and three hurricanes, the last one being Gaston. The peak of the hurricane season is around September 10; however, for us, it’s around August 20 and September 3. Become hurricane strong by being prepared!

Follow us via our social media platform and stay updated on the 2016 Atlantic hurricane season. We are available on twitter, facebook, wordpress, instagram, tumblr, and google+. Follow us also for all things weather and climate.





The 2016 Atlantic Hurricane Season Early Forecast

15 04 2016

Dale C. S. Destin |

Early forecasts just issued for the upcoming 2016 Atlantic hurricane season (AHS) indicate a near normal season is most likely. However, relative to the past three years, this season could be much more active.

Ensemble forecast

The ensemble (mean) forecast, based on predictions from Klotzbach of Colorado State University, Saunders and Lea of Tropical Storm Risk.com (TSR) and AccuWeather.com, is for 13 named storms, 6 becoming hurricanes and 3 becoming major hurricanes.

2016_Hurricane_Season_Forecast

A better indicator of the activity for the season is the accumulated cyclone energy (ACE) index which is a measurement of the strength and duration of each tropical cyclone. Summing together the ACE of each cyclone, provides a more complete picture of how active the season is likely to be outside of just the number of storms.

This year, the ensemble forecast calls for an ACE index of 85. If this forecast pans out, the 2016 season would be around 136%, 27% and 35% more active than 2013, 2014 and 2015 respectively.

It must be noted though that there is very low skill in forecasting the AHS (June to November) in April. However, this is the best available forecast for the season, at this time, and can be used as a guide for what is possible. A more skillful forecast will be available around June 1.

End of Atlantic active phase?

Around 1995, the AHS went from a quiet to an active phase. The average annual number of named storms increased from 9 to 15. There is now increasing evidence that we have seen the end of that active phase.

If the active phase has in fact ended, it would mean a reduction in the mean number of tropical cyclones (depressions, tropical storms, hurricanes) across the Atlantic over the next 20 to 30 years. This would translate to an annually reduced probability (chance) of us being impacted by a tropical cyclone between now and around the year 2041.

The x factors

There are at least two climate factors that could cause the hurricane season to be quieter than is currently being predicted. El Nino is ongoing and is virtually synonymous with inactive AHSs. The forecast is for a transition from El Nino to neutral conditions around the middle of the year and possible La Nina around October. However, if El Nino were to persist beyond summer, we would see another quiet hurricane season. On the other hand, La Nina could lead to an active season.

The second potential inhibitor of the 2016 AHS is the transport of cooler-than-normal sea-surface-temperatures (SSTs) into the tropical North Atlantic by ocean currents originating south of Greenland. Reduced SSTs hinder tropical cyclone formation and growth.

Probability of Antigua being hit by a hurricane

According to Klotzbach, the likely best similar years to the upcoming 2016 AHS are 1941, 1973, 1983, 1992, 1998 and 2014. Of these years, we were hit by Hurricane Georges and Tropical Storm Bonnie in 1998 and Tropical Storm Christine in 1973. Thus, based ONLY on similar years, the probability of Antigua being hit this year by one or more named storms is around 39%, while the probability of one or more hurricanes is around 15%.

In general, the probability of Antigua being hit by one or more named storms annually appears to vary according to the phase of the Atlantic. During the quiet phase of 1962 to 1994, the probability of one or more named storms was around 26%, while the probability of one or more hurricanes was around 14%. Meanwhile, for the active phase of 1995 to present, the probability of one or more named storms increased to around 55%, while the probability of one or more hurricanes is around 35%.

Based on the climatological period of 1981-2010, the probability of being hit by one or more named storms is around 41%, while the probability of one or more hurricanes is around 28%.

2015 hurricane season and lessons learnt

The 2015 AHS was quiet; it produced 11 named storms, 4 hurricanes and 2 major hurricanes. The ACE index total was 63, the fourth lowest since 1995. Notwithstanding it being a quiet year, Antigua was affected by Tropical Storms Danny and Erika. Damage was minor; however, closure of the country for around 24-hours, due to threat from Erika, caused an unknown loss of revenue.

Erika serves as a perfect reminder of the fact that flooding is a hazard associated with tropical cyclones. The system caused catastrophic flash floods across parts of Dominica, killing dozens of people. I our part of the world, we tend to focus a bit too much on the wind hazard associated with these systems.

Another lesson learnt was that it only takes one named storm to make it an active or miserable hurricane season for us. Thus, quiet season or not, the same hurricane season preparations are required each year.

Follow us and stay updated on the 2016 AHS via our social media platform, which includes twitter, facebook, wordpress, instagram, tumblr, and google+. Follow us also for all things weather and climate.





Struggling TS Danny

19 08 2015

Dale C. S. Destin |

Recent image of TS Danny

Recent image of TS Danny

Recent images of Tropical Storm (TS) Danny were rather unimpressive in terms of organization (good news for the Caribbean). The system appears to be struggling as dry Saharan air is getting sucked into it. However, strengthening is forecast by the official U.S. National Hurricane Center forecast.

At 11 a.m. this morning, Danny was assessed to have sustained winds of 50 mph about 1400 east of Grenada, in the Windward Islands, and 1435 east-northeast of Antigua, in the Leeward Islands. It was moving west at 12 mph.

Official forecast track

Official forecast track

Danny's track

The models appear to be showing a high degree of certainty with respect to the eventual path of Danny. Almost all the models, I have surveyed, have the system passing over or north of the northeast Caribbean.  This means that Antigua and the rest of the northeast Caribbean could be in the direct line of fire from Danny come Monday.

Danny's intensity guidanceContrastingly, the models are showing considerable uncertainty with the forecast strength of Danny. The official forecast is for it to become a hurricane on Friday. However, the models are split down the middle on the eventual strength of the cyclone with an even chance of it remaining a storm or becoming a hurricane. Becoming a hurricane may become the news worst case scenario.

The models are, however, unanimous on Danny not becoming a Category 2 hurricane, unlike previous forecasts (good news). It could still be of similar strength to Gonzalo, of last year, when it reaches us. There is enough uncertainty to suggest that it may even be a weaker cyclone upon arrival.

The more reliable European Centre for Medium-Range Weather Forecasts (ECMWF) continues to only give Danny a less than 5 percent chance of becoming a hurricane. Further, it gives it a low chance of impacting the islands as a TS. The ECMWF continues to be a source of relatively good news for us.

ECMWF forecast

ECMWF forecast

A hurricane watch will likely come into effect for portions of the northern Eastern Caribbean on Friday followed by a warning Saturday/Sunday. Start or get ready to execute your hurricane plan!

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Early Start to the Atlantic Hurricane Season?

4 05 2015

Dale C. S. Destin |

Notwithstanding the forecast for a quiet Atlantic hurricane season this year, it looks like we will see an early start to the season.

IHG13-22152015124

ECMWF Tropical Cyclone Strike Probability Forecast

ECMWF Tropical Cyclone Strike Probability Forecast

The U.S. National Hurricane Centre is presently indicating a low chance of tropical cyclone (depression, tropical storm or hurricane) formation in the next five days. However, one of the most reliable weather models, ECMWF, is indicating a high chance, up to 70% probability, of a tropical cyclone forming later this week, just north of the Bahamas.

If it forms, it looks likely that it will have an impact of the Carolinas and nearby southeast coastal areas of the United States. At most, they may have to deal with the effects of a strong tropical storm.

Antigua and Barbuda, has not been affected by a preseason storm in over 60 years and that streak is not expected to end this year. Our last preseason system was Hurricane Alice2 in January 1954, which actually formed in December 1953. Most of the rest of the Eastern Caribbean has never had a preseason storm and that is not about to change this year.

The initial disturbance is likely to develop from a cold front currently causing extremely wet weather across portions of the Cayman Islands, Cuba, the Bahamas and south Florida. Already, there has been massive flooding in Cuba causing three deaths and forcing tens of thousands from their homes.

TRMM_Rainfall

TRMM satellite has estimated up to a staggering 300 mm (12 inches) of rain has fallen across parts of Cuba and the rest of the affected area within the past seven days. Another 100 mm (4 inches) is possible over the next three days; hence, more flooding is expected.

It’s relatively rare but not unheard of for tropical storms to form in May. According to AOML, there have been 20 tropical storms in May over the period 1851-2014. This translates to one in every nine-ten years, on average. The last May storms were Alberto and Beryl in 2012.

Preseason tropical cyclones have no known omens for the Atlantic hurricane season. So, whether or not there is an early start, a quiet season is most likely this year, given the existing and expected prevailing atmospheric conditions.

Officially, the Atlantic hurricane season runs from June 1 to November 30.

We will continue to monitor this developing story.





THE ATLANTIC HURRICANE SEASON FORECAST – 2013

3 06 2013

| By Dale C. S. Destin

The Forecast

The general consensus among tropical cyclone experts is for an above normal Atlantic Hurricane Season for 2013. The consensus forecast calls for 16 named storms, 9 hurricanes and 4 major hurricanes. A normal season averages of 12.1 named storms, 6.4 hurricanes and 2.7 major hurricanes (See table 1). The science behind the outlook is rooted in the analysis and prediction of current and future global climate patterns as compared to previous seasons with similar conditions. For this season, the experts are citing a warmer than normal Tropical North Atlantic as the main reason for an above normal season prediction.

AtlanticHurricaneSeasonForecasts2013What does this mean for Antigua and Barbuda?

Although there have been great advancements in the science of tropical cyclone (depression, tropical storm and hurricane), the science has not yet reached the stage where accurate predictions can be made of how many cyclones will form in a given year. Also, the science cannot accurately predict when and where these systems will move or make landfall months in advance. The details of the large-scale weather patterns that direct the path of these cyclones cannot be predicted more than a few days into the future. However, for the current active era (1995 – present), there is around a 39% chance or 4 in 10 chances of one or more hurricanes affecting Antigua (directly or indirectly) this season; this is around 10% above the long term chance.

The 2012 Hurricane Season

The 2012 Atlantic Hurricane Season produced nineteen (19) named storms. Of the nineteen (19) storms, ten (10) became hurricanes and one (1) strengthened to achieve major hurricane status – category three (3) or higher on the Saffir-Simpson Hurricane Wind Scale. The strongest tropical cyclone for the season, in terms of pressure was Hurricane Sandy with peak winds of 110 mph and minimum pressure of 940 mb; however, category 3, Major Hurricane Michael had the highest sustained winds of 115 mph and minimum pressure of 964 mb. Relative to Antigua and Barbuda, Isaac and Rafael brushed Antigua and Barbuda as tropical storms.

A number of records were or nearly broken during the 2012 hurricane season. The season had a hectic start and by June 23 Debby formed and become the earliest 4th named storm on record. Prior to the official start of the hurricane season, June 1, there were two preseason storms – Alberto and Chris – the second time on record two storms form in May in a given year, May 1887 was the only other time. It was also the first time since 1908 two named storms preceded the hurricane season and the third time on record. The most intense hurricane, in terms of lowest central pressure, was Hurricane Sandy; it is also considered the largest known Atlantic hurricane by gale diameter on record. Hurricane Nadine was the fifth longest-lived tropical cyclone on record. In addition, August 2012 was tied with August 2004, September 2002, and September 2010 for most number of named storms in a particular month, at eight.

It Only Takes One

Regardless of the numbers, we should always approach the hurricane season in the same manner each year: be aware and be prepared. The prevention of the loss of life and property from tropical cyclones is a responsibility that should be shared by all. As a reminder, recall our lesson from Hurricane George of 1998: it only takes one hurricane to make it a bad season. Accordingly, the Meteorological Service will play its usual role in alerting the public of any tropical cyclone that may form and threaten Antigua and Barbuda, the Leeward Islands and the British Virgin Islands. We endeavour to provide weather and climate information for the protect life, property, livelihood and the enhancement of the economy. Although the hurricane season officially runs from June 1 through November 30 each year, tropical cyclones can and have occurred outside the season – be prepared!

AnuStorms

PDF Format

References

Accuweather.com, State College, Atlantic Hurricane Season: Three US Landfalls Predicted [online].
Available from: <http://www.accuweather.com/en/weather-news/atlantic-hurricane-forecast-2013/12116274>
[Accessed 3 June, 2013]

Colorado State University, Fort Collins, Extended Range of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2013 [online]. Available from: <http://typhoon.atmos.colostate.edu/Forecasts/2013/june2013/jun2013.pdf> [Accessed 3 June, 2013]

Florida State University, Raleigh, FSU COAP Atlantic Hurricane Season Forecast [online]. Available from:
<http://coaps.fsu.edu/hurricanes> [Accessed 3 June, 2013]

National Oceanic and Atmospheric Administration, Silver Spring, NOAA Predicts Active 2013 Atlantic Hurricane Season [online]. Available from: <http://www.noaanews.noaa.gov/stories2013/20130523_hurricaneoutlook_atlantic.html> [Accessed 28 May, 2013]

North Carolina State University, Raleigh, 2013 Atlantic Tropical Cyclone Outlook [online]. Available from: <http://cfdl.meas.ncsu.edu/research/TCoutlook_2013.html>%5BAccessed 28 May, 2013]

Tropical Storm Risk, London, Pre-Season Forecast for Atlantic Hurricane Activity in 2013 [online]. Available from: <http://www.tropicalstormrisk.com/docs/TSRATLPreSeason2013.pdf>[Accessed 28 May, 2013]

United Kingdom Met Office, Exeter, Seasonal Forecasting of Storms [online]. Available from:
< http://www.metoffice.gov.uk/weather/tropicalcyclone/seasonal/forecasting-method > [Accessed 3 June, 2013]





The Heart of the Hurricane Season

28 08 2012

By Dale C. S. Destin

Every year, persons across the Caribbean, Central America and the US Gulf and Atlantic Coasts pray for this period to pass quickly with out a hit – the heart of the hurricane season, which covers the period August to October (ASO). For the period 1851 to 2011, Antigua has had 93 named storms and 44 hurricane giving and average per year of 0.6 named storm and 0.2 hurricane for ASO. For Antigua, the heart of the hurricane season is August to September, which accounts for 79% (Aug 34%, Sep 45%) of all storms to affect the island. (http://www.antiguamet.com/Climate/climate_anu_cyclonesbyday.html ). This period has had 83 named storms and 41 hurricane for an average per year of 0.5 hurricane and 0.2 hurricane i.e. one storm every other year and one hurricane every five years.

August 21 and September 3 are very peculiar days for Antigua. These are the two peak days for Antigua for the hurricane season with a record of 7 named storms each to have affected the island on those days from 1851 to 2011. September 3 has produced three hurricanes and August 21 has produced four. (http://www.antiguamet.com/Climate/climate_anu_cyclonesbyday.html ) Two notorious tropical cyclones that have struck on August 21 were Category 3 Unnamed Hurricane of 1871 and Category 3 Hurricane Baker of 1950.

On average, ASO has 8 named storms and 5 hurricanes per year. Historically the period has had 1237 named storms of which 806 became hurricanes – 1851 to 2011 – with August contributing 362 named storms and 230 hurricanes; 80% of all storms (Aug  23%, Sep 37%, Oct 20%) form during the period ASO. This year has been no ordinary year contrary to initial forecasts; so far for August, there have been six named storms and three hurricanes, when the month averages two named storms and one hurricane. The record for named storms for August is eight, observed in 2004. The forecast for the overall season has moved from near – below normal to above normal/active season with a consensus of 14 named storms, 6 hurricanes and 3 becoming major hurricanes; already there has been 10 named storms  and 4 hurricanes. (http://www.antiguamet.com/Climate/HURRICANE_SEASON_FORECAST/2012AtlanticHurricaneSeasonForecastAug28.pdf) looks like we will actually see more than 14 when the season ends November 30. Currently, ENSO Positive conditions (El Nino) is trying to squelch of shut down the hurricane season as is the norm; however, the tropical North Atlantic is warming and other factors such as negative North Atlantic Oscillation (NOA) and Arctic Oscillation are in favour of further warming. Of course, there are other factors to consider but these are some of the main drivers of the hurricane season. What do you think will happen? How many more named storms will we see before the season ends?








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