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!

Follow us also on @anumetservice, facebook and tumblr for the latest on the current drought and other weather & climate news.





The Atlantic Hurricane Season Consensus Forecast – Aug 14, 2013

14 08 2013

| Dale C. S. Destin

The general consensus among tropical cyclone experts continues to be for an above normal Atlantic Hurricane Season for 2013. The consensus forecast calls for 17 named storms, 8 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).  Much of 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.

Hurricane Season Outlook

What 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 32% chance or 3 in 10 chances of one or more hurricanes affecting Antigua (directly or indirectly) over the period August – October; this is 4% above the long term chance (1981 – 2010).

The 2013 Hurricane Season

The 2013 Atlantic Hurricane Season, thus far, have produced four (4) named storms. The strongest tropical cyclone for the season has been Tropical Storm Andrea with peak winds of 65 mph and minimum pressure of 992 mb. There has been no hurricane, thus far. Relative to Antigua and Barbuda, Chantal, during it passage through the Eastern Caribbean, spawned a destructive water spout, which impacted Camp Blizzard, Antigua. The hurricane season officially runs from June 1 through November 30 each year; however, tropical cyclones can and have occurred outside the season. The peak of the hurricane season is mid August to late October while the peak of the hurricane season for Antigua is mid August to late September (graph 1).

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 – be prepared!

AnuStorms

Graph 1: Antiguan Tropical Cyclones – distribution of tropical cyclones within 120 statute miles of Antiguan (1851 – 2012)

For more information see the links below or email me at dale_destin@yahoo.com. You are also welcome to follow us via twitter facebook youtube and blog .

PDF

References

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

Colorado State University, Fort Collins, Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2013 [online].
<http://typhoon.atmos.colostate.edu/Forecasts/2013/aug2013/aug2013.pdf>
[Accessed 12 August, 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: Atlantic hurricane season on track to be above-normal [online]. Available from: <http://www.noaanews.noaa.gov/stories2013/20130808_atlantichurricaneupdate.html>
[Accessed 12 Aug, 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, August Forecast Update for Atlantic and U.S. Hurricane Activity in 2013 [online]. Available from: <http://www.tropicalstormrisk.com/docs/TSRATLForecastAug2013.pdf>
[Accessed 12 Aug, 2013]

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








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