October 2016 to March 2017 Climate Outlooks for Antigua and Barbuda

24 10 2016

Dale C. S. Destin |

The October 2016 to March 2017 climate outlooks are now available for Antigua and Barbuda. Our worst meteorological (Met) drought on record has come to an end; however, other droughts continue. It is 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 for October-December and January-March. Meanwhile, warmer than normal night-time temperatures are likely to continue.

Potworks Dam, Aug242016 (L) v. Sep62016 (R)

Potworks Dam, Aug 24 2016 (L) v. Sep 6 2016 (R). Pictures courtesy Karen Corbin – Humane Society. 

Drought

After over three years, the rainfall for September 2016 has brought the Met and agrometeorological (AgMet) droughts to an end. However, it was not enough to end the hydrological (Hydro) and socioeconomic (SE) droughts, which continue at slight levels or worse. The island-average of 213.4 mm (8.40 in) for September 2016 is the most for a September since 1995. Further, it is the wettest of any month since October 2012.

Drought Meter

Looking forward – below to near normal rainfall is likely for October-March. Meanwhile, there are equal chances of below, near or above normal rainfall for both October-December (OND) and January-March (JFM). Given these and other forecasts, there is a moderate chance of the country going back into Met and AgMet droughts, and the Hydro and SE droughts re-intensifying in the medium to long-term. Drought watches are in effect.

Rainfall Projection for Jul-Dec2016

El Nino Southern Oscillation (ENSO) – El Nino, is happily becoming a distant memory. There is now a 65% chance of a cold phase i.e. La Nina developing over the next three months.

If you are in our part of the world – the Caribbean, a La Nina would be more than welcome. Unlike El Nino, La Nina often brings us more than usual rainfall. Given our severe water crisis of the past three years, a La Nina is being prayed for.

Precipitation and temperature

Year-to-date, the rainfall for Antigua is 1.3 times more than all the rainfall for 2015. Further, it is the wettest January-September since 2013. Notwithstanding, we are still over an inch in the “red” relative to the long-term average of 792.5 mm (31.2 in).

The recent up-tick in rainfall seems to have flattened-out. There is no clear signal as to rainfall for the upcoming seasons: OND, JFM and October-March. The best forecast is trending toward near to below normal rainfall for the next six months.

The projected rainfall for 2016 is 757.3 to 1336.8 mm (29.8 to 52.6 in) or near to below normal. This is at least 182.0 mm (7.0 in) more than last year’s total. There is only a slight chance of above normal rainfall for the year.

For the period October to March, above normal temperature is likely. Further, night-time lows are likely to continue above normal through OND resulting in continued uncomfortable warmer than usual nights.  Relatively cooler nights are likely for JFM.

The hurricane season

The 2016 hurricane season will go down as the first active season since 2012. Thus far, the current Atlantic hurricane season has produced 14 named storms, 6 hurricanes and 3 major hurricanes.

The accumulated energy (ACE) index which matters most, has shot up to 119% of the average of 106 in less than a month from less than 50%. More than half of this ACE is due to the strength and duration of Major Hurricanes Matthew and Nicole.

In terms of numbers, the forecast for the season is on point as it called for around 15 named storms, 7 becoming hurricanes and 3 major hurricanes.

Notwithstanding the end of the season drawing near, we have been seriously impacted by tropical cyclones in November, recall Hurricane Lenny of 1999. Thus, we need to remain fully prepared, as it only takes one hurricane to set our life and community back by decades. Be prudent: stay prepared for the worst and hope for the best!

See the following links for the full outlooks: October 2016, October-December 2016, January 2016-March 2017October 2016-March 2017Drought, 2016 Updated Hurricane Season Forecast.

The next set of outlooks will be available by November 5, 2016.





September 2016 to February 2017 Climate Outlooks for Antigua and Barbuda

29 09 2016

Dale C. S. Destin |

The September 2016 to February 2017 climate outlooks are now available for Antigua and Barbuda. Over the long-term (September-February), above to near normal rainfall is expected. However, in the short-term – September to November (SON), below to near normal rainfall is expected. The droughts are more likely than not to remain as is or end over the short-term. Meanwhile, uncomfortably warm temperatures are expected for the upcoming six months, especially during the short-term.

Drought

August 2016 is the wettest since 2011 and the wettest of any month since November 2014. It was a wetter than normal August with an island-average of 130.3 mm (5.13 in). Notwithstanding, it was not wet enough to end the droughts, which have gone past 38 months.

Looking forward – there is a moderate chance (55%) of the droughts either not getting worse or ending during the period SON. Conversely, there is also a moderate chance of the SON period having below normal rainfall. Notwithstanding, over the long run, above to near normal rainfall is expected. Thus, drought watches are in effect instead of warnings.

jun-nov2016_rainfall

The warm phase of El Nino Southern Oscillation (ENSO) – El Nino, came to an end in May. At which time, the chance of a cold phase i.e. La Nina was in excess of 75%. However, as of this month, the probability of La Nina is at 55% and declining.

If you are in our part of the world – the Caribbean, a La Nina would be more than welcome. Unlike El Nino, La Nina often brings us more than usual rainfall. Hence, given our severe water crisis of the past three years, to not have a La Nina as “promised” would be a great disappointment.

The rains over the past weeks have put a huge dent into the droughts. We are experiencing one of our wettest, if not wettest September in over 20 years. There is optimism that a few of the droughts have ended. More will be said on this, after a full assessment, by the middle of October.

Precipitation and temperature

Year-to-date, Antigua, on average, has had more than twice the amount of rainfall than for the same period last year. Notwithstanding, we are still over three inches in the “red” relative to the long-term average for January-August of 647.7 mm (25.50 in).

This up-tick in rainfall has a reasonable chance of continuing over the long-term: September 2016 to February 2017, there is an 80% probability of above to near normal rainfall. However, the projected rainfall for 2016 is 657 to 1218.5 mm (25.9-48.0 in) or below to near normal.

For the seasons SON (autumn) and DJF (winter), there are equal chances of below, near or above normal mean temperatures. However, over the long-term, mean temperatures are likely to be above normal. Higher than usual night-time low temperatures are likely to continue through November, resulting in continued uncomfortable warmer nights.

The hurricane season

We are passed the peak days of the hurricane season for us and for the season overall. However, we are still very much in the most active period of the hurricane season – August to October. Thus far, the 2016 Atlantic hurricane season has produced, 12 named storms, four hurricanes and one major hurricane.

The 12 named storms are 50% more than the average of 8 to date [September 25]. However, the accumulated energy (ACE) index which matters most, is less than 50% of the average of 106. The relatively low ACE is indicative of the fact that the storms have been generally weak.

The forecast is for a near normal season with around 15 named storms, 7 becoming hurricanes and 3 major hurricanes; this includes those already formed.

Notwithstanding the forecast, we need to be fully prepared, as it only takes one hurricane to set our life and community back by decades. Be prudent: prepare for the worst and hope for the best!

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

The next set of outlooks will be available by October 5, 2016.





June to November 2016 Climate Outlooks for Antigua and Barbuda

9 06 2016

Dale C. S. Destin |

The June to November 2016 (summer and autumn) climate outlooks are now available for Antigua and Barbuda. We are optimistic that some droughts will come to an end over this period. Meanwhile, uncomfortably warm temperatures are expected for the upcoming six months. June to November is also the Atlantic hurricane season; it is likely to be the most active since 2012.

Drought

May 2016 was wetter than last year’s; however, it was still a relatively dry May – the second driest in nine years. Hence, the droughts (meteorological, agricultural, hydrological and socioeconomic) continue across Antigua and Barbuda. We are now entering the 36th month of mostly moderate or worse rainfall deficits.

Looking forward – some droughts are likely to ease. At worst, slight meteorological and agricultural droughts will exist at the end of the March-August and December 2015-November 2016 periods. Meanwhile, a moderate drought or worse is possible at the end of the January-September 2016 period.

ProjectedRainfall_Mar-Aug2016

The warm phase of El Nino Southern Oscillation (ENSO) – El Nino, is expected to end in weeks and a transition to the cold phase of ENSO – La Nina, is expected during our wet season – July to December. This is good news for us in that La Nina, unlike El Nino, generally encourages rainfall across our area, mainly during the wet season. This is one of the main reasons why we are optimistic about the possibility of drought ending rainfall over the next six months, if not sooner.

However, there is some caution with our optimism as La Nina is not guaranteed nor are its normal positive impacts on our rainfall. Further, the strength of the La Nina is highly uncertain. A strong La Nina favours more rainfall, whereas a weak one favours less.

Precipitation and temperature

Over the coming three months – June to August (JJA), above to near normal rainfall is expected. This could result in the meteorological and agricultural droughts coming to an end or at worse be at slight levels at the end of the period. Unfortunately, these rains are unlikely to end the more serious hydrological and socioeconomic droughts; these will likely continue at moderate or worse levels.

September to November (SON) is also expected to have above to near normal rainfall. SON is on average our wettest “season”, accounting for nearly 40% of our yearly rainfall. Thus, if this forecast pans out, all droughts would be significantly eased, if not end. This is especially true if the JJA forecast holds true also.

So far, 2016 is about 70% wetter that last year, but it’s still much drier than normal. It is now almost certain that the dry season (January-June) will be drier than usual for the third consecutive year.

The summer heat is likely to be on, as warmer than usual temperatures are forecast for June to August. With high confidence of warmer than usual weather, there is also the potential for extreme temperatures. The heat could be very distressing for many especially since night-time temperatures are likely to be higher than usual. This has negative implications for health especially among older adults, infants and young children.

The hurricane season

Relative to the last three years, we are likely to have the most active Atlantic hurricane season since 2012. Notwithstanding, the forecast is for the season to fall in the near normal range with around 14 named storms, 7 becoming hurricanes and 4 major hurricanes.

MayJuneHurricaneSeasonForecast

Like our wet season, the great determinant of the hurricane season is ENSO. El Nino tends to suppress tropical cyclone (depression, tropical storm, hurricane) activity, while its sister-phenomenon – La Nina, does the opposite. Hence, the eventual activity of the season is largely dependent on the strength of La Nina which is quite uncertain, at this time. Stronger La Ninas tend to favour more active seasons than weaker ones.

For Antigua and Barbuda, the probability of a named storm (tropical storm or hurricane) affecting the islands during an active season is quite high (around 74%) and much higher than during a normal or quiet season, with around 59% and 26% probabilities respectively. Meanwhile, the probability of us being affected by a hurricane during an active season is around 49% as opposed to 18% in a normal one and 10% in a quiet one.

Irrespective the kind of Atlantic hurricane season that occurs, we need to be fully prepared, as it only takes one hurricane to set our life and community back by decades. Prepare for the worst and hope for the best!

See the following links for the full outlooks and more: JuneJune-August, September-NovemberJune-November 2016Drought, 2016 Hurricane Season Forecast.

The next set of outlooks will be available by July 3, 2016.





The Most Active Atlantic Hurricane Season in Four Years Likely

4 06 2016

Dale C. S. Destin |

After a hat-trick of quiet Atlantic hurricane seasons, the latest round of forecasts is pointing to the most active season since 2012. However, notwithstanding the projected increase in activity over recent years, the forecast is for the 2016 hurricane season to be near normal.

Ensemble forecast

Our ensemble (mean) forecast calls for 14 named storms with 7 becoming hurricanes and 4 reaching major hurricane status. This represents an increase over the previous forecast for the season of one named storm and one hurricane.

MayJuneHurricaneSeasonForecast

In the tropical cyclone community, the accumulated cyclone energy (ACE) is the indicator used to determine the activity of a hurricane season. The ACE index is a measurement of the strength and duration of a named storm. Summing together the ACE of each named storm, provides a more comprehensive picture of the activity of the season, aside from just the number of storms.

This year, our ensemble forecast calls for an ACE index of 109, which is near normal. If this forecast pans out, the 2016 season would be around 200%, 63% and 73% more active than 2013, 2014 and 2015 respectively.

The ensemble (mean) forecast is based on predictions 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, the Hurricane Genesis & Outlook (HUGO) Project of Coastal Carolina University and the Institute for Meteorology (INSMET) of Cuba.

Uncertainty

It must be noted though that the skill in forecasting the hurricane season (June to November) in May/June is moderate. However, it is the best available on earth, and it continues to improve.

Apart from the inherent limits to our skill in forecasting the season, this year, there is the huge uncertainty of the eventual strength of La Nina (the coolness of the tropical Pacific Ocean). A strong La Nina could result in a more active season than is forecast, with the converse being true.

Probability of Antigua and Barbuda being hit

According to Klotzbach, the likely best similar years to this hurricane season are 1973, 1978, 1983, 1992 and 2003. Of these years, we were only hit by Tropical Storm Christine of 1973. Thus, based ONLY on similar years, the probability of Antigua being hit this year by one or more named storms is around 18%, while the probability of one or more hurricanes is 0%.

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, which may have come to an end, the probability of one or more named storms increased to around 55%, while the probability of one or more hurricanes is around 35%.

Overall, based on the climatological period of 1981-2010, the probability of being hit by one or more named storms is around 49% (every 2 years on average), while the probability of one or more hurricanes is around 31% (every 3 years on average). Barbuda has similar numbers.

Become hurricane strong

Notwithstanding the forecast, it only takes one hurricane to change your life and community, so the same comprehensive preparations are required every year. Become hurricane strong by taking actions today to become hurricane resilient. This includes:

  • Determining your risk from tropical cyclones;
  • Developing an evacuation plan;
  • Securing an insurance check-up;
  • Assembling disaster supplies;
  • Strengthening your home;
  • Identifying trusted sources of information for a hurricane event and
  • Having your written hurricane plan.

Recall – an ounce of prevention is better than pound of cure!

We will publish an undated ensemble forecast by early August, just before the traditional peak of the hurricane season. This forecast is generally the most skilful; it will have much reduced uncertainty.

2016 Atlantic Tropical Cyclone Names

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.





Is Hurricane Alex a Sign?

18 01 2016

Dale C. S. Destin |

By now you may have heard of Hurricane Alex, the first Atlantic hurricane to form in January since the only other one in 1938, according to HURDAT2. Alex is also only the third hurricane to exist over the Atlantic in January. There was Alice2 which formed late December 1954 and continued over into January 1955.

Hurricane Alex, as seen via a NASA satellite image on Jan. 14, 2016.

Hurricane Alex, as seen by a NASA satellite on January 14, 2016.

I suppose a few of the questions raised in some persons minds by Alex are: what does this mean for the upcoming hurricane season; does a January storm equate to an active or inactive season and was Alex caused by climate change?

Looking back at the three other times tropical cyclones – the generic name for depressions, tropical storms and hurricanes – formed in January for clues, I see none.

In 1978, there were 12 named storms (NS), 5 hurricanes and 2 major hurricanes (MH). In 1951, there were also 12 NS, with 8 becoming hurricanes and 3 MH. In 1938, the record shows that after Hurricane One in January, the eventual totals for the year were 9 NS, 4 hurricanes and 2 MH. Nothing unusual!

Based on El Nino Southern Oscillation data, which go back to 1950, Tropical Storm One of 1951 occurred during a moderate La Nina, whereas the 1978 system occurred during a weak El Nino. Of course, Alex formed in one of the strongest, if not the strongest El Nino on record.

Looking at the preceding hurricane seasons to the four January tropical cyclones, I also see nothing interesting.

In 1977, there were 6 NS, 5 hurricanes and a MH; 1950 had 16 NS, 11 hurricanes and 6 MH and 1937 had 11 NS, 4 hurricanes and a MH.  And of course, in 2015, we had 11 NS, four hurricanes and 2 MH. Except for 1950, the other prior years had near normal number of storms.

Of the three previous years with January tropical cyclones, only one had a second preseason tropical cyclone formed before the official hurricane season – June 1 to Nov 30. This was 1951 with Hurricane Able in May. So, one cannot really say that January storms are a precursor to other preseason ones.

Looking a bit more broadly, there have been, at least, six years with preseason hurricanes (May 1970, May 1951, Jan 1938, March and May 1908, May 1889, May 1863) on record since 1851 prior to Alex. For such small sample sizes, no definite conclusions can be made. However, it may be instructive that these six seasons had near normal number of NS and hurricanes.

Here is what Dr. Rick Knabb – Director of the U.S. National Hurricane Center (NHC) – had to say on the meaning of Alex and preseason tropical cyclone activity:

The activity of a hurricane season is more closely linked to the existing climate during the given season. This climate is very difficult to predict in advance of the season, which is evident by the fact that the best performing hurricane season forecasts are those issued around early August.

In speaking with Phil Klotzbach of Colorado State University via email, he shared the view that, “any tropical cyclone forming in January to be more responding to last year’s climate forcings than anything that would be present in 2016.”

So, Alex can be considered a super late hurricane that may be best credited to the 2015 hurricane season as opposed to being a super early system, which will be credited to the 2016 season.

Then there is the question of climate change, which has nothing to do with Alex. The previous three tropical cyclones forming in January occurred before 1979, pretty much predating climate change as an issue. This shows that January cyclones were more frequent before climate change was a concern.

Although HURDAT2 only has three tropical cyclones on record in January, it is a widely known fact that a number of such cyclones were missed prior to the satellite era and possibly shortly thereafter. This is especially so for those short-lived (lasting less than 48 hours) and forming in a similar area to that of Alex.

Given the advanced weather monitoring enterprise that exists today, we in the meteorological fraternity are pretty confident that no such system has formed in the past 20 years, at least. Thus, it would stand to reason that such January tropical cyclones like Alex are becoming fewer with climate change.

Further, according the IPCC, climate change is likely to cause a reduction in the number of tropical cyclones. Thus, based on our understanding of the science, it would be reasonable to expect that out-of-season tropical cyclones, such as Alex, will become even rarer as the more ideal conditions of the summer months would be required for their formation.

One of the things that climate change will alter, that will lead to fewer storms, is the lapse – the change of temperature with increasing height. It will cause it to decrease, leading to a less unstable, hurricane unfriendly atmosphere. In Alex’s case, the environmental lapse rate was very large contrary to the decreasing trend being caused by climate change.

Tropical cyclones in January and preseason hurricanes in general over the Atlantic are very rare; hence, the sample size is very small. Thus, one cannot be dogmatic about what Hurricane Alex means for the upcoming season. Notwithstanding, I am very confident that Alex is an aberration, virtually a freak hurricane, and means nothing for the upcoming hurricane season. It is also clearly not the fault of climate change, which is making it harder for hurricanes to form. Rather, it is simple natural climate variability.

We invite you to subscribe/follow/like us on twitterfacebookinstagramtumblrflickrgoogle+, and youtube for education and information on all things weather and climate to protect and or enhance life, property, livelihood and the economy. Also, feel free to share with us your feedback and questions!








%d bloggers like this: