Our Inaugural Forecast of the Atlantic Hurricane Season

5 07 2017

Dale C. S. Destin |

We have just released our first inhouse-produced forecast of the Atlantic hurricane season. It calls for an above normal season with 16 named storms, 7 becoming hurricanes and 4 reaching major hurricane status.

The main reasons for the above normal forecast are the warmer than usual tropical North Atlantic and the unlikely development of an El Nino. This season could turn our similar to last year’s and be one of the most active since 2010.

We hope that you find this forecast to be a useful resource in your hurricane season preparations. Please feel free to share you feedback with us as usual.  Click here for the full forecast.

Become hurricane strong!

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The Meaning of the Tropical Cyclone Track Forecast

25 08 2015

Dale C. S. Destin |

Some persons are unhappy with the performance of the Antigua and Barbuda Met Service over the tracking of Tropical Cyclone Danny. One of the main issues is that the forecasts, beyond 24 hours,  had Danny passing over Antigua but instead it passed 60-70 miles south of the island.

So the question is did we, including the U.S. National Hurricane Center get it wrong? The simple answer is no. However, for you to be able to answer the question or make accusations, a better understanding to the meaning for the track forecast is required. I wrote a brief blog on tumblr explaining the inherent errors associated with the forecast; you are invited to have a read.

5yr_ALtkerrdist_sm

From the above graphic: the error for a 12-hour forecast (which takes effect 12 hours from the time issued)  is plus/minus 32 miles, for 24 hours it’s plus/minus 52 miles etc.





The 2015 Hurricane Season Early Forecast

11 04 2015

By Dale C. S. Destin |

Early forecasts just issued for the upcoming 2015 Atlantic hurricane season indicate another quiet season is likely. The forecasts indicate that the 2015 season could be even quieter than 2014 and perhaps be the quietest since the middle of the 20th century.

Early 2015 consensus forecast

The consensus based on forecasts from Klotzbach and Gray of Colorado State University and Saunders and Lea of Tropical Storm Risk.com (TSR) calls for nine named storms, four becoming hurricanes and two becoming major (Category 3 or higher) hurricanes.

EarlyHurricaneSeasonForecast2015

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 snapshot of how active the season is likely to be outside of just the number of storms.

This year, the consensus forecast calls for an ACE index total of 48. If this forecast pans out, the 2015 hurricane season would be quieter than last year’s and the third quietest since 1995, when the hurricane season went from a quiet phase to an active one.

End of Atlantic active phase?

Around 1995, the Atlantic hurricane season went from a quiet phase, when the average annual number of named storms increased from 9 to 15. Questions are now being raised in the tropical cyclone community as to whether we have come to the end of this active phase.

According to Saunders and Lea, “should the…forecast for 2015 verify, it would mean that the ACE index total for 2013-2015 was easily the lowest 3-year total since 1992-1994, and it would imply that the active phase of Atlantic hurricane activity which began in 1995 has likely ended”.

However, before we burst open the bubblies in celebration of fewer hurricanes for the next few decades, it must be stressed that the ability to accurately forecast an upcoming hurricane season from April, over one and a half months before the start of the hurricane season, is very low. The next set of forecasts, with better skill, will by out by June 1.

Factors pointing to a quiet season

Although the April seasonal forecasts are very low skilled, there are two already occurring phenomena present that are notorious for producing quiet Atlantic hurricane seasons. These are El Nino and a positive North Atlantic Oscillation (NAO). These are the main factors cited for the projected quiet season.

Probability of Antigua being hit by a hurricane

The probability of Antigua being hit by a hurricane annually appears to vary depending on the phase of the Atlantic. Based on the period 1981-2010, the climatological probability of being hit by at least one hurricane is around 28%. However, for the Atlantic hurricane season quiet phase – 1962 to 1994, the probability was around 14%. While for the active phase – 1995 to present, the probability increased to around 36%.

Interestingly, based on ENSO record dating back to 1950, we have never been hit by a hurricane during an El Nino episode that has occurred over the whole or part of a hurricane season.

On the other hand, we have been hit by nine hurricanes during 24 La Nina episodes. By Poisson distribution, this equates to around a 31% probability of us getting hit by at least one hurricane during La Nina.

According to Klotzbach and Gray, the likely best similar/analogue years to the upcoming 2015 hurricane season are 1957, 1987, 1991, 1993 and 2014. Of these years, we were only hit in 2014 by Gonzalo. Thus based on similar years, the probability of Antigua being hit this year is about 18%.

Good news and bad news

There is an Antiguan saying: “de same stick that hit the wild goat will also hit the tame one.” El Nino and the positive NAO will likely “hit” the hurricane season, resulting in suppressed activity. However, these same phenomena will likely “hit” our rainfall activity, resulting in suppressed rainfall and continued drought.

2014 hurricane season and lessons learnt

The 2014 hurricane season produced eight named storms, three hurricanes and two major hurricanes. The ACE index total was 66, the fourth lowest since 1995. It was a quiet year for many but not Antigua as we were hit by Hurricane Gonzalo.

Gonzalo serves as a perfect reminder that notwithstanding a quiet season, it only takes one hurricane to make it an active season for us. Hence, quiet season or not, the same preparations are required.

Our next blog on this topic will be on June 2.

Follow us also @anumetservice, facebook and tumblr to keep updated with weather & climate info for the protection of life, property, livelihood & the enhancement of the economy.





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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