August 2016 to January 2017 Climate Outlooks for Antigua and Barbuda

16 08 2016

Dale C.S. Destin |

The August 2016 to January 2017 climate outlooks are now available for Antigua and Barbuda. Over the short, medium and long-term the rainfall is likely to be above to near normal.  Thus, there is a moderate chance of, at least, a temporary end to some droughts over the upcoming six months. Meanwhile, uncomfortably warm temperatures are expected for the upcoming six months. August-October (ASO) is the most active part of the hurricane season and is likely to be the most active since 2012.

Drought

July 2016 was wetter than the last three Julys and wetter than the last two combined; however, it was not wet enough to end the droughts (meteorological, agricultural, hydrological and socioeconomic). We have now entered the 38th month of mostly moderate or worse rainfall deficits; however, since April, the meteorological and agricultural droughts have been at slight levels.

May-Oct2016 Rainfall Outlook

Looking forward – the meteorological and agricultural droughts could ease further or perhaps come to, at least, a temporary end as August has a 60% chance of being wetter than usual, and there is a 40% chance of the ASO period getting above normal rainfall. Over the long run, above  to near normal rainfall is likely. Notwithstanding, drought warnings and watches are in effect for various periods through January 2017.

The warm phase of El Nino Southern Oscillation (ENSO) – El Nino, came to an end in May leaving in its wake significant adverse impacts. There is now around a 60% chance of the cold phase of ENSO i.e. La Nina developing during the last third of the year or the latter half of our wet season. A few months, ago the chance of La Nina was in excess of 75%, so its chance of develop is on the decline; nevertheless, it is still more likely than not.

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, and with the record drought we are still experiencing, water is more precious than gold at the moment.

Unlikely, but a much wetter than normal wet season (July-December) is desperately needed to end our severe multi-year droughts.

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. Nevertheless, we are still over 100 mm (four inches) in the “red” relative to the long-term average of 534.9 mm (21.06 in).

This up-tick in rainfall is likely to generally continue over the long-term – August 2016 to January 2017, there is a 75% 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.

The summer heat is likely to continue through October with the ASO “season” likely to be warmer than usual. With a 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 both night-time and day-time temperatures are likely to be higher than usual. High than usual night-time temperatures are likely to continue through January 2017. This has negative implications for health, especially among older adults, infants and young children.

The hurricane season

Thus far for the 2016 Atlantic hurricane season, there have been five named storms and two hurricanes (Alex and Earl). The number of storms is considered above normal relative to the long-term average of three. However, the ACE, which matters most, is near normal.

Recently issued hurricane season forecasts have reasserted that the 2016 season is likely to be the most active since 2012. Notwithstanding, the forecast is for the season to fall in the near normal range 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: August 2016, August-October 2016, November 2016-January 2017, August 2016-January 2017, Drought, 2016 Updated Hurricane Season Forecast.

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

Correction, August 19, 2016: An earlier version of this article incorrectly stated the rainfall forecast for August 2016 to January 2017. The forecast is for above to near normal rainfall rather than below to near normal.

Advertisements




The Most Active Atlantic Hurricane Season in Four Years Remains Likely

15 08 2016

Dale C. S. Destin |

The latest round of forecasts has reaffirmed that the 2016 Atlantic hurricane season is likely to be the most active since 2012. However, notwithstanding the predicted increase in activity over recent years, the forecast continues to call for a near normal 2016 hurricane season.

Ensemble forecast

Our ensemble (mean) forecast calls for 15 named storms with 7 becoming hurricanes and 3 reaching major hurricane status. This represents a slight difference from the previous forecast, which called for one less named storm but one more major hurricane.

Updated Hurricane Season Forecast

In meteorological community, the accumulated cyclone energy (ACE) index is deemed the best “yard-stick” to measure 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 a season, aside from just the number of storms.

This year, our ensemble forecast calls for an ACE index of 102. This is seven less than the previous forecast ACE but still well within the near normal range. If this forecast pans out, the 2016 season would be around 183%, 52% and 62% more active than 2013, 2014 and 2015 respectively.

The ensemble (mean) forecast is based on predictions from seven organizations: 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), Weather Channel, the Institute for Meteorology (INSMET) of Cuba and Truchelut of WeatherTiger.

The season so far

So far, there have been five named storms: Hurricanes Alex and Earl and Tropical Storms Bonnie, Collin and Danielle. None impacted Antigua and Barbuda, but the disturbance that became Earl brought us some welcome showers. The season officially began June 1 and runs until November 30. However, no one told that to Alex and Bonnie – the former developed in January and the latter in May. With five named storms gone, around 10 more are likely.

Uncertainty

The skill in forecasting the hurricane season in August is quite high – up to 50% better than guessing or using the average activity of a season as the forecast, which would be correct around 33% of the time. This translates to the August forecast being right around 83% of the time.

Notwithstanding the high skill, there is and always will be some level of uncertainty. It is still uncertain as to if and when will La Nina (cooler than usual Pacific Ocean) develop. Also, there are uncertainties regarding it strength, if it does develop. A strong La Nina during August to November could result in an active/above normal season as opposed to a near normal one. NOAA has put the probability of an active season at 35% and the probability of a near normal one at 50%.

Probability of Antigua and Barbuda being hit

According to Klotzbach, the likely best similar years to this hurricane season are 1958, 1959, 1966, 1978, 1992 and 1998. Of these years, six named storms passed within 121 miles of Antigua; of them, there were three hurricanes and one tropical storm that hit the island. Of them, Major Hurricane Georges of 1998 is the most notable. Thus, based ONLY on similar years, probabilistically Antigua has a

  • 63% chance of being affected by one or more named storms (passing within 121 miles), usually it’s 62%;
  • 49% chance of being hit by one or more named storms (passing within 17 to 75 miles), usually it’s 49% and
  • 39% chance of being hit by one or more hurricanes (passing within 17 miles), usually its 31%.

 Barbuda’s numbers, based on five named storms passing within 75 miles:

  • 57% chance of being affected by one or more named storms (normally it’s 52%);
  • 57% chance of being hit by one or more named storms (normally it’s 32%) and
  • 39% chance of being hit by one or more hurricanes (normally it’s 23%).

The hit forecast probabilities for Barbuda are significantly higher than usual. The numbers suggest that Barbuda is more likely than not to be hit by a named storm. The other forecast probabilities are similar to what is usual. However, it must be noted that our usual numbers are generally higher than most places.

Become hurricane strong

Notwithstanding the forecast, active or inactive season, it only takes one hurricane to turn your life upside-down, so the same comprehensive preparations are required to mitigate or reduce the impacts a tropical cyclone. Take actions today and become hurricane strong/resilient. Actions include:

  • 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!

A summary of the hurricane season will be available by December. Follow us via our social media platform and stay updated on the current hurricane season. We are available on twitter, facebook, wordpress, instagram, tumblr, and google+. Follow us also for all things weather and climate.





The 2015 Hurricane Season Forecast

2 06 2015

Dale C. S. Destin |

Recently issued forecasts for the 2015 hurricane season, which starts today, indicate another quiet season is most likely. The latest set of forecasts indicates that this season could be even quieter than 2014 and perhaps be among the quietest since 1981.

The 2015 ensemble forecast

The ensemble or mean forecast is for nine named storms (including Tropical Storm Ana), four becoming hurricanes and one becoming a major (Category 3 or higher) hurricane. On average we get twelve named storms, 6 hurricanes and 3 major hurricanes.

HurricaneSeasonForecast2015

Our ensemble forecast is based on forecasts from Klotzbach and Gray of Colorado State University (CSU), the National Ocean Atmospheric Administration (NOAA), Saunders and Lea of Tropical Storm Risk.com (TSR), the United Kingdom Met Office (UKMET), European Centre for Medium-Range Weather Forecasts (ECMWF), Weather Services International (WSI) and Pen State University (PSU).

A better indicator of the activity for the season is the accumulated cyclone energy (ACE) index which is a measurement that takes into consideration the number, strength and duration of tropical cyclones for the season.

The ACE index ensemble forecast for this season is 52. If this forecast verifies, this hurricane season will be the tenth quietest since 1981 and the third quietest since 1995, when the hurricane season went to an active phase.

Why is a quiet season most likely?

El Nino is expected to be the main cause for a quiet season. Basically all the climate models are forecasting El Nino to persist through the hurricane season and keep atmospheric conditions difficult for tropical cyclone formation across much of the Atlantic. Cooling sea surface temperature across the tropical North Atlantic will also hinder tropical cyclone formation.

However, it is not a 100% certainty that we will have a quiet season. We are still in the time of the year when there is very little skill in predicting El Nino. Therefore, notwithstanding what is being said by the models, there is a slight chance of an above normal season; there is also a slight chance of an even quieter season than forecast; it all depends of the eventual strength of El Nino.

It must also be kept in mind that the May seasonal forecasts only possess modest skill in predicting the eventual hurricane season. The early August forecasts, which show the best skill, are the ones to look forward to next.

New normal?

There is a growing consensus that we may have seen the end of a high-activity/active hurricane season era, which started in 1995, and the start of a new low-activity/quiet one, which could last for the next 20-30 years. Thus, for the next several decades, the quiet activity for the past two years could become the norm.

NOAA has indicated that the “current configuration of [sea surface temperatures] SSTs in the Atlantic Ocean… are suggestive that the [Atlantic Multi-Decadal Oscillation] AMO may no longer be in the warm phase” which is synonymous with a high-activity era.

Meanwhile, TSR has continued to indicate that “should this [there] forecast verify… it would imply that the active phase for Atlantic hurricane activity which began in 1995 has likely ended.”

According to CSU, “[the] twelve-month running average values of the [AMO] index are currently at their lowest levels since 1994, when the AMO was in a negative phase” or when we were in the last low-activity era.

This is good news for Antigua and likely the rest of the Caribbean and the wider Atlantic Basin. The fewer the number of tropical cyclones, the less often we will be impacted by tropical cyclones.

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. The probability of being hit by at least one hurricane is around 28%, based on the period 1981-2010. However, during the last low-activity era – 1962 to 1994, the probability was around 14%. While for the high-activity era – 1995 to 2014, the probability increased to around 36%.

Of some comfort, 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.

According to Klotzbach and Gray, the likely best similar/analogue years to the upcoming 2015 hurricane season are 1957, 1965, 1972, 1982, 1987 and 1997. Of these years, we were only brushed by Erika in 1997. Thus, based on similar years, the probability of Antigua being hit this year is about 15%, a decrease of 3% from the April forecast.

Don’t be caught off guard

The 2014 hurricane season produced eight named storms, six 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 each year for the hurricane season, which runs from June 1 to November 30.

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.








%d bloggers like this: