The Fourth Longest Sub-Twenty Cold Spell for Antigua and Barbuda

23 01 2017

Dale C. S. Destin |

Last night’s cold weather makes the current sub-twenty °C (sub 70 °F) cold spell the fourth longest on record at the Airport and most of the rest of Antigua and Barbuda. It tied with February and December of 1973.

With a mean minimum temperature of 18.6 °C (65.5 °F), it is also the second coldest sub-twenty cold spell for the country, on record, lasting more than three consecutive nights. The mean minimum temperature for the past four nights ranged between 11 and 22 °C (71.6 °F) with the vast majority of places experiencing sub-twenty temperatures.

jan2017coldspelltemps

The last time the Airport had a temperature below 18 C was in 2000 – 16 years ago.

We are also looking at the coldest four-night period for January since 1980 – over 35 years ago, and since 2000 for all other months, at least, at the Airport.

Of the eight times we have seen this spell lasting more than three days, it has gone for four days twice and five days thrice, based on data for the Airport.

The record five-day sub-twenty cold spell is shared by March 1997, January 1984 and March 1972. The coldest one is March 1972 with a mean minimum temperature of 18.5 °C (65.3 °F).

So far for January, the mean minimum temperature at the Airport is now 21.9 °C (71.4 °F) – below normal. The mean daily temperature is well below normal with a value of 24.6 °C (76.3 °F).

There is now about a 50/50 chance the record will be tied tonight, as conditions could favour sub-twenty temperatures once again. If it were to happen, this cold spell would likely become the longest as the chances of sub-twenty temperatures are high for Tuesday and Wednesday nights. Usual January temperatures are expected after Wednesday.

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 cold spell and all things weather and climate. We can be followed on twitterfacebookinstagramtumblrflickrgoogle+, and youtube.





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.





Very Hazardous Marine Conditions for Antigua and Barbuda

14 01 2017

Dale C. S. Destin |

 

High Surf

High Surf

The shoreline Antigua and Barbuda and the rest of the northeast Caribbean are getting hammered by high surfs. Additionally, starting today, seas in open waters will become very unfriendly to small craft operators. As a result, the weather authority in Antigua and Barbuda has issued special marine statements on the high surfs and rough seas.

Surfs are building – they are expected to range 8-12 feet (2.4-3.6 m) between today and Monday, affecting mainly northern and eastern coastlines. These high surfs are being generated by a low pressure system located just northeast of the area, which is pushing very large swells to our shores.

There is a high risk of rip currents, especially over the next 24 hours when the surfs are expected to peak. Rip currents are powerful channels of water flowing quickly away from shore, which occur most often at low spots or breaks in the sandbar and in the vicinity of structures such as groins such as jetties and piers.

The winds will become fresh to strongthey will frequently be in excess of 18 mph (16 knots) from today to Wednesday. The winds will peak at around 30 mph (22 knots) with occasional gale-force gusts to the around 39 mph (34 knots) today and Sunday likely.  These winds will primarily take place over open waters, coastal areas on the northern and eastern side of the islands and elevated areas.

windjan142017

windgustsjan142017

The seas will respond to the winds – they will become very rough, rising to as high as 3.6 metres (12 feet) on Saturday night Sunday. Waves will decrease to less than 2.0 metres (6 feet) by Wednesday.

seasjan142017

The cause of the strong winds – this is due to a significantly tight of the pressure gradient (horizontal differential of pressure) across, which will tighten a bit more over the next 24 hours. The relatively tight pressure gradient is in response to a strong high pressure system moving from west to east across the Atlantic from the United States. There are NO tropical cyclone (tropical depression, tropical storm or hurricane) in the area.

Surface Chart

Surface Chart for Saturday 8 am, Showing a Tight Pressure a Tight Gradient as Evident by the Closeness of the Isobar (Pressure Lines)

Precautions – Sea-bathers should avoid the waters, mainly on the northern and eastern sides of the islands until Tuesday. Small craft operators should not venture far from port through Monday.

A high surf warning means that high surf will affect beaches in the advisory area, producing beach erosion and dangerous swimming conditions.

A small craft advisory means that wind speeds of 24-38 mph (21 to 33 kt) and or seas of 7 feet (2.1 m) or greater are expected to produce hazardous wave conditions to small craft. Inexperienced mariners, especially those operating smaller vessels should avoid navigating in these conditions.

The strong winds, especially if frequently gusting to gale force, could also make some outdoor activities very uncomfortable if not hazardous, please be guided accordingly.

Stay updated on the situation by following us via our social media platform:  twitter,  facebook,  instagramtumblrflickrgoogle+, and youtube.





Storm-Force Winds and Hurricane-Like Seas to Impact Antigua and Barbuda This Weekend

17 12 2016

Dale C. S. Destin |

Significant tightening of the pressure gradient across the area is expected to cause strong winds with frequent gusts to storm force strength or gale force. The seas will respond to the strong winds and become very rough.

Surface chart

Surface Chart for Sunday 8 am, Showing a Tight Pressure Gradient As Evident by the Closeness of the Isobars (pressure lines)

The winds – they will generally be in excess of 18 mph (16 kt) from late Saturday night to Monday afternoon. The winds will peak as high as 30 mph (26 kt) with frequent gusts between 38 and 46 mph (33 and 38 kt) Sunday morning to Monday morning.

High Sustained Winds

Sustained Winds

Wind Gusts

Wind Gusts

The seas –  they will respond to the winds and become very rough, rising to as high as 3.9 metres (13 ft) on Sunday night. Waves will rise above six feet by Saturday morning and remain above this height through midweek. Waves of 2.7 to 3.9 metres (9 to 13 ft) will prevail from Saturday night to Wednesday. Waves are expected to fall off rapidly after Wednesday.

Seas

Seas

The cause – as indicated above, it is the substantial tightening or steepening of the pressure gradient.  This is in response to a very strong surface high pressure system moving from west to east across the Atlantic from the United States.  This will NOT be due to any tropical cyclone (tropical depression, tropical storms or hurricane).

Fundamentally, wind blow as a result of pressure differential (pressure gradient). The greater the pressure between point A and point B (pressure gradient) the stronger the winds.

Where – the strong winds will mostly take place over open waters, exposed eastern coastal areas and elevated areas of Antigua and Barbuda. The seas will be roughest in the Atlantic coastal waters east of the islands, as the winds will be generally easterly. Similar conditions are expected across most of the rest of the Eastern Caribbean. However, Antigua and Barbuda could get the worst of it.

Precautions – The Antigua and Barbuda Meteorological Services have issued warnings for sea-bather and small craft operators. The former should avoid the beaches, especially those on the Atlantic or eastern side of the islands, and the latter should not venture far from port, at least, until Thursday.

A small craft warning generally means that wind speeds in excess of 16 knots is causing or expected to cause hazardous sea conditions to small craft within 24 hours. Inexperience mariners, especially those operating smaller vessels should avoid navigating these conditions.

According to the Beaufort Scale, gale-force winds run from 39 to 54 mph (34 to 47 kt). Operating a vessel in gale conditions requires special expertise and specially equipped vessels. It is highly recommended that mariners without the proper experience seek safe harbour prior to the onset of gale conditions.

The strong winds, especially if frequently gusting to gale force, could also make some outdoor activities very uncomfortable if not hazardous, please be guided accordingly.

We will be keeping a close eye on this developing situation and keep you informed via our social media platform: twitterfacebookinstagramtumblrflickrgoogle+, and youtube.





November 2016 to April 2017 Climate Outlooks for Antigua and Barbuda

30 11 2016

Dale C. S. Destin |

The November 2016 to April 2017 climate outlooks are now available for Antigua and Barbuda. Our worst meteorological (Met) drought on record ended in September and remains that way. Moderate or worse Met drought is unlikely for the foreseeable future. It is, however, 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. Meanwhile, warmer than normal mean temperature is likely to continue.

Drought Meter

Drought

The Met and agrometeorological (AgMet) droughts remain ended, notwithstanding near record low rainfall for October. However, the hydrological (Hydro) and socioeconomic (SE) droughts continue at slight levels or worse. The island-average of 46.2 mm (1.82 in) for October 2016 is the fourth lowest on record dating back to, at least, 1928 and the lowest since October 2000.

Projected rainfall for next 6 months

Looking forward – unfortunately there is no decisive information on what can be expected rainfall-wise. There are equal chances of below, near or above normal rainfall for November-January (NDJ), February-April  (FMA) and November-April. Given these and other forecasts, particularly the drought forecast, moderate or worse Met and AgMet droughts are unlikely. Meanwhile, the Hydro and SE droughts are not expected to undergo sustained worsening. The drought watches have been dropped.

The cold phase of El Nino Southern Oscillation (ENSO) – La Nina is evident although an episode cannot yet be declared. Further, the criteria and episode – five overlapping “seasons” of La Nina temperatures is unlikely to be met.

If you are in our part of the world – the Caribbean, a La Nina would be more than welcome. However, it is coming a bit late as the greatest positive impact on our rainfall occurs during the wet season, which will come to a close at the end of December.

Precipitation and temperature

Year-to-date, the rainfall for Antigua is almost one-and-a-half times more than all the rainfall for 2015. Further, it is the wettest January-October since 2013. Notwithstanding, we are still over 5 inches in the “red” relative to the long-term average of 952.8 mm (37.51 in).

Notwithstanding the low rainfall for October, there has been a general up-tick in rainfall since August. It is difficult to say at this time what can be expected to the upcoming months what quantity we will get as we have no climate signal. However, we are unlikely to have below normal rainfall.

It is now almost certain that Antigua will have near normal rainfall for 2016 – 1067 to 1321 mm (42 to 52 in). This is doubled the amount for last year – the driest year on record.

For the period November to April, above normal temperature is likely.

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

The next set of outlooks will be available by December 7, 2016.





Potential Flooding Rainfall to End the Hurricane Season

28 11 2016

Dale C. S. Destin |

Satellite Image - Past 6 hrs Ending 11:45 UTC or 7:45 Local Time

Satellite Image – Past 6 hrs Ending 11:45 UTC or 7:45 Local Time

A surface low pressure system is expected to form near the northeast Caribbean and cause potential flooding rainfall across much of the Eastern Caribbean through Tuesday. Antigua and Barbuda is expected to see peak totals today – Monday.

The system could cause 25 to 100 mm (1-4 in) of rainfall, with locally higher amounts, from the Dominican Republic to Trinidad and Tobago. The epicentre of the rainfall is likely to be just south of Antigua or across the northern Windward Islands where the total could max-out above 100 mm (above 4 in).

North American  Mesoscale Forecast System (Model) Rainfall Accumulations - Nov 27-29, 2016

North American Mesoscale (NAM Model) Forecast System Rainfall Accumulations – Nov 27-29, 2016.

 

Globale Forecast System (GFS) Rainfall Accumulations for the Period Nov 27-29, 2016

Global Forecast System (GFS Model) Rainfall Accumulations for the Period Nov 27-29, 2016

With this type of rainfall, minor flooding is expected and moderate or worse flooding is possible. Hence, flash flood watches and warning may be required for a number of other areas over the next 12 to 36 hours.

This may be a fitting end to a very wet start to November. The month had a near record wet start across the Eastern Caribbean. In Antigua, some areas received upward 200 mm (8 in) during the first 10 days of the month. At the V. C. Bird International Airport, the rainfall stood at 143.5 mm (5.7 in) by November 10 – the third most on record dating back to 1928.

Rainfall Anomalies

Rainfall Anomalies for the Period Nov 1-10, 2016

With this type of rainfall, minor flooding is expected and moderate or worse flooding is possible. Hence, flash flood watches and warning may be required for a number of other areas over the next 12 to 36 hours.

This may be a fitting end to a very wet start to November. The month had a near record wet start across the Eastern Caribbean. In Antigua, some areas received upward 200 mm (8 in) during the first 10 days of the month. At the V. C. Bird International Airport, the rainfall stood at 143.5 mm (5.7 in) by November 10 – the third most on record dating back to 1928.

Recall also, that there were deadly floods and landslides across portions of St. Vincent during the early parts of the month.

The forecast rainfall for Monday is not a foregone conclusion but it is quite possible. If it were to materialized, this November would be one of the wettest on record for much of the Eastern Caribbean. In Antigua, it would be the wettest since Hurricane Lenny’s deluge of 1999 and be among the top 10 wettest Novembers of all time.

After the low, very cool northerly winds are expected to blow across the region. These will likely cause our coolest weather for the season and since February. Night-time temperatures could fall to below 19 °C (66 °F) Monday, Tuesday and Wednesday nights.

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