A Hat-trick of Sub-Twenty Temperatures for most of Antigua and Barbuda

22 01 2017

Dale C. S. Destin |

Last night’s cold weather makes it a hat-trick of sub-twenty temperatures for most of Antigua and Barbuda. This is a fairly rare feat for the country. It has only happened seven other times during January, based on historical data for the Airport. The last time it happened in January was back in 1996 – 20 years ago. The last time it happened for any month was in March 2000.jan2017temperatureWhereas the last hat-trick of sub-twenty temperatures occurred last in January 1996, the coolest such period last took place in 1992. It is also the coolest such period, for all months, last occurred in March 2000. This and the rest of what is said here is an update on the previous blog.

The mean minimum temperature for the past three nights, at the Airport, was 18.5 °C (65.3 °F). This is the eighth coldest for three or more days in a row with sub-twenty temperatures at the Airport. Further, it is the 12 coldest for any three-day sub-twenty spell (overlapping and otherwise).

When we consider such a three-peat of sub-twenty temperatures for all months dating back to 1971, it has only happened 27 previous times.

So far for January, the mean minimum temperature at the Airport of 22.0 °C (72 °F) is below normal. However, up to three days ago, it was bordering on above normal – meaning we were having relatively warm nights for this time of the year. The mean daily temperature is well below normal with a value of 24.7 °C (76.5 °F).

As cold as it has been, it certainly has NOT nearly been cold enough to freeze water. Thus, that picture being circulated suggesting that the cold weather caused a small body of water to freeze in Free Town is a HOAX. For this to happen, we would need to have sub-zero temperatures persisting for days, which will NEVER happen.

There have only being five occasions when sub-twenty degree nights have occurred for more than three consecutive nights. Tonight is likely to be the sixth time this has happened. So far, today has been coldest of the past three days.

After tonight, the weather will warmup to usual temperatures for this time of the year. Then the cold weather will more likely than not return on Wednesday and continue on Thursday. Thereafter, the usual temperatures for this time of the year is expected to prevail for the rest of the month.

Although we are unable to say definitively how cold the country or specific areas have been due scarcity of historical temperature data, it is likely the coldest since 1996. This is based on fact that temperatures across a small homogeneous area like Antigua and Barbuda are highly correlated. And since it is the coldest for the Airport since 1992, it should be likewise for the rest of the islands.

From a quantitative standpoint, the statements above are truest for the Airport and surrounding areas; however, from a qualitative assessment, it is applicable to the rest of the country.

Follow us for all you need to know about this mini-cold spell we are experiencing. We can be followed on twitterfacebookinstagramtumblrflickrgoogle+, and youtube for education and information on all things weather and climate.





How Cold was Antigua and Barbuda Last Night?

20 01 2017

Dale C. S. Destin |

By Caribbean standards, the last two nights were very cold for Antigua and Barbuda. One of the coldest spots on the islands was Free Town, which had a minimum temperature of 13.9 °C (57.0 °F) night before last and 11.6 °C (52.9 °F) last night.

picture2jan212017picturejan202017The 11.6 °C  is now the lowest temperature ever measured by the Met Office. It eclipsed the previous short-lived record of 13.9 °C. However, it is unlikely to be the lowest temperature ever experienced in Free Town or by the country. The lowest ever measured is not the same as the lowest on record or in history.

Unfortunately, apart from the Airport, there were NO reliable temperature sensors elsewhere across the country until a few years ago. There exists very little historical data for Free Town, as the station was only installed last January. The same is true for most of the other stations listed above. Thus, regrettably, I am unable to say definitively just how cold it was in Free Town and most of the other locations.

The only site for which historical data exist is the Airport. The minimum temperature measured at the Airport last night was 18.4 °C (65.1 °F); this is well above the record of 16.1 °C (61.0 °F), measured back in December 1974 and January 1976.

Making some reasonable assumptions and using the Airport’s temperature from last night as a “barometer” for the rest of the country, last night was the coldest January night since 1996 and the 12th coldest dating back to, at least, 1971.

Last night, the minimum temperature range for Antigua and Barbuda was 11.0 to 21.0 °C (52 to 69.8 °F) . The previous night it was 13.0 to 22.0 °C (55.4 to 72 °F). It is possible that a few areas had temperatures slightly below or above this range.

The cold weather last night was due to the time of the year, light winds, mostly clear skies and low moisture levels. Last night was colder than Thursday night mainly because moisture levels were lower. These conditions will continue for the next 24 hours; hence, tonight is expected to be similarly cold. Thereafter, the winds will increase and so will the temperature.

With the few cold nights, some have advanced the notion that we are having a colder than usual January. However, this is not borne out by the data at the Airport, thus far. The mean minimum temperature up to two days ago, at the Airport, for the month was 22.6 °C (72.7 °F), 0.2 °C above the average of 22.4 °C  (72.3 °F).

The cold weather was also experienced across most of the rest of the northeast Caribbean for the second night also. Le Raizet, Guadeloupe had a minimum of 17.6 °C (63.7 °F) night before last and 16.8 °C (62.2 °F) last night, meanwhile Clayton J. Lloyd International Airport in Anguilla had 19.4 °C (66.9 °F) and 20.2 °C (68.4 °F) respectively.

Will it be colder tonight, with some places having sub 10 °C (sub 50 °F)? Follow us via our social media platform:  twitter,  facebook,  instagramtumblrflickrgoogle+, and youtube and stay informed. We would also be happy to hear from you regarding how cold you felt and your experience with the weather generally.





Potentially Record Low October Rainfall for Antigua

29 10 2016

Dale C. S. Destin |

After a very wet September – the wettest since 1995 and the wettest of any month since October 2012, October 2016 is turning out to be a near record dry October across much of Antigua.

top5driestoctobers

Thus far, the rainfall for Antigua and the V. C. Bird International Airport (VCBIA) are 20.6 mm (0.81 in) and 14.3 mm (0.56 in) respectively. These currently rank as driest and third driest respectively on record dating back to 1928.

Interestingly, the anemic rainfall for the month seems largely due to Hurricanes Matthew and Nicole and Invest 99 Disturbance. Matthew brought us some rain toward the end of September. However, once it passed through the Eastern Caribbean it served as a giant sponge in sucking up all of the moisture in the area and only sharing it with those areas it made unwelcome visits on.

Nicole and to a lesser extent Invest 99 did similarly. Since then, wind shear and high pressure systems have made it difficult to rain across our area.

It is not over yet; we could still end up with respectable rainfall for October. In the past, up to 100 mm (4 in) has fallen in the last two days of the month.

La Nina, which is good for rainfall at this time of the year for our region seems on the verge of developing.

Our experimental monthly rainfall forecast, issued for October, indicated that the month was likely to be wetter than normal; this is very unlikely. However, recent weather forecasts from various weather models are optimistic about rainfall for much of next week, some of which are likely for the last day of the October.

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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.





Antigua’s Unenviable Record Worst Drought Continues

25 04 2016

Dale C. S. Destin |

Notwithstanding the significant rainfall of the past week, our unenviable record worst drought continues. However, the rains did bring some much-needed relief, as many residents got their cisterns and other catchments replenished. The precipitation also brought some relief to our farming community and landscape.

No sign of water in Potworks Dam, Antigua, April 22, 2016. Photo courtesy Karen Corbin – President of the Humane Society

No sign of water in Potworks Dam, Bethesda, Antigua; April 22, 2016. Photo courtesy Karen Corbin – President of the Humane Society

Recall that there are, at least, four types of droughts – meteorological, agricultural, hydrological and socioeconomic, which is the worst. Antigua has been in these droughts for around two months shy of three years. Of the mentioned droughts, the rains had the greatest impact on the meteorological and agricultural droughts.

For the week ending April 23, the island-average rainfall for Antigua was 63.3 mm (2.49 in). To have ended at least the meteorological drought, we needed over 100 mm (4 in); much more was need to end the other droughts.

Based on a mixture of rain gauge measurements and radar estimates, the rainfall across the island was quite variable, ranging from 25 mm (1 in) in the west to 152 mm (6 in) in the northeast. Notwithstanding, most areas got 40-100 mm (1.5-4 in).

24-hr Estimated Rainfall, From 8 pm April 17, 2016 to 8 pm April 18, 2016

24-hr Estimated Rainfall: From 8 pm April 17, 2016 to 8 pm April 18, 2016

At the V. C. Bird International Airport (VCBIA), the 42 mm that fell on April 18 makes it the wettest day since October 28, 2014. It was also the wettest April 18 at VCBIA since 1992 and 15th wettest of 1620 April days on record since 1962.

VCBIA also had a near record wet spell for April – six consecutive days with at least 1 mm (0.04 in), second only to the seven recorded in 1970. The six-day (April 17-22) total of 70.4 mm (2.77 in) at VCBIA, is now the fourth wettest for the month. With respect to a week, it’s the wettest for April since 2010 and the wettest for all weeks since October 23-29, 2014.

As of Sunday morning, April 24, the island-average rainfall for Antigua for the month was 80.5 mm (3.17 in). Thus far, this is the wettest April since 2013, when we had 132.1 mm (5.20 in). It is also our fourth wettest month since December 2014. On average, April is the fifth driest month with 85.6 mm (3.37 in).

The wet week was all due to a cold front preceded by an associated trough. Both systems have since been replaced by high pressure.

The wet weather has eased the meteorological drought to slight levels; however, not much has changed regarding the more serious hydrological and socioeconomic droughts. Follow us as we continue to monitor our rainfall closely.





The Worst Drought on Record for Antigua

25 03 2016

Dale C. S. Destin |

Antigua is witnessing the worst drought in recent history, dating back to, at least, 1928. The current drought is now over 32 months in length, similar to the drought of 1964-67. However, to date, the record rainfall deficit of 1143 mm (45 in) caused by the current drought, exceeds that of 1964-67 by 254 mm (10 in) or around 29%.

RainfallDeficitGraphic

While we don’t have observed monthly rainfall totals beyond 1928, we do have annual totals going back to 1871. Based on this record, 2015 is now the driest year in the series. This translates to 2015 rainfall total occurring once per 500 years, on average. Thus, it’s perhaps the most intense drought since the arrival of Christopher Columbus.

Not only the last year has been the driest on record, but so to have the last two years (24 months). Further, the last 32 months – July 2013 to February 2016, is the driest such period on record. We are missing about a year’s worth of rainfall.

Surface water contributes to around 30% of our potable water mix. However, since the drought started, the country has been completely out of surface water twice with an aggregate duration of around 14 months. We were out of surface water April to September 2014 and again from August 2015 to present.

The drought was caused by a number of climate actors not necessarily all acting at the same time. These include mainly an abundance of the dry and dusty Saharan air layer (SAL) from Africa, positive North Atlantic Oscillation (NAO), negative Tropical North Atlantic (TNA) Index and El Nino. It is fairly well established that these phenomena, in the mentioned phases, cause less than normal rainfall across our area with the converse being true.

The drought got kicked off by the SAL along with unpredictably strong vertical wind shear, sinking air and the weakening of the Atlantic Ocean overturning circulation. Happily, this resulted in a failed hurricane season in 2013, but unfortunately it also plunged us into what has become our worst rainfall deficit on record.

Contributing to the persistent drought, the NAO has been predominantly positive over the duration of the drought with only nine of the last 32 months having negative (rain-favoured) values. Meanwhile, the TNA was negative (unfavourable rainfall values) for most of January 2014 to June 2015. In 2015, El Nino developed and reach super (record) strength during the latter half of the year.

Droughts are expensive, and severe droughts are severely expensive. It’s believed that the drought has cost the country hundreds of millions of dollars, directly and indirectly. I will address this matter more in a subsequent blog.

The current drought is anticipated to become the longest on record – a further very unwelcome new record. Initial predictions had the drought easing significantly or ending around mid-year. However, our last set of forecasts has it continuing into the second half of the year.





Record Low Cool Nights for Antigua

4 02 2016

Dale C. S. Destin |

2015 saw the fewest number of cool nights on record across much of Antigua. At the V. C. Bird International Airport (VCBIA), the number of cool nights – nights with the temperature falling to at least 22 °C (71.6 °F) – was the fewest on record in a series dating back to 1971.

CoolNightsAtOrBelow22C

Never before on record have there been so few days with the temperature falling to at least 22 °C. There were only 4% of days of the year when the temperature fell to 22 °C or lower. For an average year, this number is 11%, almost three times what was observed in 2015.

January and December, on average, are among the months with the highest number of cool nights. However, December had a record low number of cool nights – zero, and January had near record low – four.

Cool nights have been significantly declining over the years. The numbers at VCBIA have dropped from around 15% of days per year in the 1970s to around 7% at present.

This significant decline in cool nights is consistent with what is taking place globally, as our climate changes. According to the IPCC, “It is very likely that the number of cold…nights has decreased and the number of warm…nights has increased on the global scale.”

In general, cool places and times of the day are warming at a faster rate than warm places and times. In our case, nights are warming faster than days. Further, most of the warming being experienced across our area is due mainly to the nights warming at a significant rate.

The mean minimum temperature (mean-min-Temp) for 2015, a proxy for the mean night-time temperature, was at a record high level. The mean-min-temp of 24.5 °C tied with that of 2002 and 2001 for the record lowest.

Apart from cool nights trending downwards most likely due to climate change, the record low rainfall in 2015 contributed a lot to so few days with temperature falling through 22 °C. Evaporation is a cooling process and, when it rains, the water that is subsequently evaporated leads to cooling and reduced temperature. More rain did not fall than fell in 2015; hence, very little evaporative cooling.

On the other hand, the number of warm days – days with the temperature increasing to at least 31 °C (87.8 °F) – was fewer than normal. The year had 19% of days with 31 °C or higher temperature compared to the average of 25%.  These warm days are trending upwards but not significantly, at the moment.

Fewer cool nights have negative implications for our economy and ecosystem. The lack of cool or respite from our virtually year-round oppressive heat will likely hit us in the pocket as we burn more and more energy to keep our bodies from overheating. Heat stress is very costly to our health and well-being and that of our vital flora and fauna.

Follow this space as we bring you more highlights of our weather and climate of 2015. We can be followed on twitterfacebookinstagramtumblrflickrgoogle+, and youtube for education and information on all things weather and climate.

 








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