Record Breaking Dry Year for Antigua

28 01 2016

Dale C. S. Destin |

2015 will go down in meteorological history as the driest year on record for Antigua in nearly 150 years. The island-average rainfall was a paltry 574.5 mm (22.62 in), the lowest in a series from, at least, 1871. 2015 has shattered the previous record driest year – 1983 – by some distance, when we had 681.5 mm (26.83 in).

RainfallAccu

Never before on record has a year’s rainfall deficit or the rain that did not fall (rain-not-fall) was greater than the rain that did fall (rainfall). So the rain-not-fall, 628.6 mm(24.75 in), was greater than the rainfall – 574.5 mm. Of course, the rainfall deficit is the difference between what we got and what we usually get.

Avgvs2015Rain

Looking at the deficit another way, the rain-not-fall is roughly equivalent to the rainfall we would normally get from the first seven months of a year.

Such a dry year, as 2015, is extremely rare. It happens only once every 500 years on average. That translates to a 0.2% chance of a given year getting so little rainfall. It is quite possible that the last time it was this dry Christopher Columbus was still sailing the Caribbean.

If we were still in the pre-desalination-era, it would not be a stretch to say that the Antigua and Barbuda’s economy would have collapsed due to lack of sufficient potable water. As has been the case for months now, over 90% of potable water is coming from the ocean via desalination.

Interestingly, no month had record low rainfall. So, the record low rainfall for 2015 came about due to persistent low rainfall throughout most of the year. Five of the 12 months not only had below normal, but well below normal rainfall. Further, all months had below normal rainfall except September and November, which had near normal rainfall.

MonthlyRain

Most areas of the country had record or near record low number of wet days – WDs – (days with at least one mm) for the year. At the V. C. Bird International Airport (VCBIA), there were 97 WDs, the third lowest behind 2001 with 94 and 1983 with 93. However, the total rainfall from WDs of 495.8 mm (19.52 in) was at a record low for 2015. Normally, WDs yield around 1019.3 mm (40.13 in).

Heavy rainfall days – HRDs –  (days with at least 10 mm) was also at record low numbers at many places during 2015. At the VCBIA, they were at a record low total of 12, tying 1983 and 1973. Normally, there are 26 HRDs annually. Meanwhile, the rainfall total from HRDs of 217.1 mm (8.55 in) was the second lowest behind 207.4 (8.16 in) measured in 1983. Usually, it’s around 665.5 mm (26.20 in).

The dismal rainfall for the year was due largely to two factors. Firstly, dry and dusty air from the Sahara Desert which hampered rainfall mainly during the first half of the year. Secondly, a record strong El Nino, which suppressed rainfall mainly over the latter half of 2015.

Follow us on twitterfacebookinstagramtumblrflickrgoogle+, and youtube as we provide you with further analyses of the historic rainfall year for Antigua. We will also provide you with observed and forecast rainfall totals for 2016, as we keep close eyes on our climate.





January 2016 Newsletter

27 01 2016

Dale C. S. Destin |

Our January 2016 newsletter is now available. In it you will find the latest on our weather and climate and forecasts for the next six months.

The notable events of the past three months include the fact that the drought has re-intensified, October to December has been the 9th driest on record and December was among the warmest.

Impacts from the drought include empty surface catchments, households without pipe-borne water for weeks and insufficient water to properly support agriculture and livestock. Over 90% of potable water comes from the sea via the very expensive means of desalination.

For the period January-March, below to near  normal rainfall is anticipated; thus, the continuation of drought and related challenges. However, above to near normal rainfall is forecast for April-June; hence, the drought is forecast to ease or come to an end.

For more, please see our newsletter here: ABMS Climate Section (CliSec) Newsletter





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.

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Growing Concerns for the Atlantic Challenge Rowers

11 01 2016

Dale C. S. Destin |

Concerns are growing for Team Wadadli (or Team Antigua) and the rest of the rowers participating in the Talisker Whisky Atlantic Challenge. Marine conditions are expected to become extremely unfavourable, if not exceptionally dangerous for the seafarers.

Tweet of concern

Tweet of concern

By now, you may have heard of the very powerful extratropical low pressure system that could transition into the first tropical cyclone (generic term for tropical depressions, tropical storms and hurricanes) over the Atlantic in January since 1978.

Extratropical cyclone with centre marked by X, next to the red L. 0600 UTC, Jan 11, 2016 Surface Chart

Extratropical cyclone with centre marked by X, next to the red L. 0600 UTC, Jan 11, 2016 Surface Chart

Transition or not, the low/tropical cyclone is expected to generate across the paths of many of the rowers, ginormous seas, possibly reaching six metres (20 feet) and sustained storm force winds (greater than 34 knots/39 mph). Such severe marine conditions will easily cause boats to capsize and be injurious the occupants, if not worse.

Wave Height (ft), Valid Tue, Jan 11, 2016, Issued Jan 11 at 6 AM AST

Wave Height (ft), Valid Tue, Jan 11, 2016, Issued Jan 11 at 6 AM AST. The box at the top right indicates the seas Team Wadadli and many others could face tomorrow.

Wind Speed (kt), Valid Tue, Jan 11, 2016, Issued Jan 11 at 6 AM AST

Wind Speed (kt), Valid Tue, Jan 11, 2016, Issued Jan 11 at 6 AM AST. The box at the top right indicates the winds Team Wadadli and many other could face tomorrow.

Additionally, unfriendly winds and currents will stop, if not push rowers backwards, towards the starting point instead of the finish line – Antigua. Initially, the unfavourable winds will come from the south, then the west and then north over the next few days in the vicinity of the racers.

Last night, Team Wadadli was forced to “drop” its sea anchor as they were being push towards the bad weather by southerly winds. They also reported that the seas were building. It is not clear how long they will stay in “anchorage”. However, this strategy (of which there are very few) may not be the best for the situation.

tweet from team wadadli

Note that a sea-anchor also known as a drift anchor does not stop a boat from moving, it just slows and stabilizes it in heavy weather. The Race Tracker shows that Team Wadadli, as of 8 am this morning, was still moving towards the bad weather at 1.4 knots (1.6 mph), perhaps on a collision course with what could become Tropical Storm Alex, which is also moving towards them.

Tracker showing the locations and progress of the boats as of 8 am this morning

Tracker showing the locations and progress of the boats as of 8 am this morning

The Tracker also showed many, if not all of the boats were in a similar situation.

If Team Wadadli remains drift anchored, instead of finding away to get out of the southerly flow (drifting from south to north), they could find themselves in a lot of trouble along with many of their competitors.

By my projections, in the next 24 hours, Team Wadadli, could find itself well northeast of its current position, heading out over the North Atlantic, in seas over 4.5 metres (15 feet) and winds greater than 28 knots (32 mph). Of even greater concern is that they could get caught up in the southwesterly winds (winds blowing from the southwest) and move northeast with the bad weather for several days.

Other teams, especially those that are east of longitude 35 degrees west, could suffer a similar fate.

I don’t know what’s the organizer’s criteria for the race to be suspended or cancelled but conditions must be getting pretty close to meeting them.

The low/tropical cyclone will severely affect this year’s edition of the Talisker Whisky Atlantic Challenge. If the rowers were up for a challenge, the upcoming days will fulfil their desire. Let’s hope they come out of it in flying colours with a heck of a story to tell.

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A Rare January Atlantic Hurricane?

8 01 2016

Dale C. S. Destin |

The fourth ever January tropical cyclone (generic name for depressions, tropical storms and hurricanes) could form in the next five days. Weather models have been indicating, with varying degrees of confidence, that a powerful extratropical cyclone centred near Bermuda could transition into a tropical cyclone.

Extratropical cyclone with centre marked by X, next to the red L. 1200 UTC, Jan 8, 2016

Extratropical cyclone, centre marked by X next to the red L. 1200 UTC, Jan 8, 2016 Surface Chart

How often does this happen? This has happened only three other times over the past 165 years, the last being 1978. On average, the probability of a tropical depression, tropical storm or hurricane developing in January is around 2%. This means that it happens once in about every 50 Januarys/years.

What’s the situation? Already, the extratropical cyclone has winds of 57 knots (65 mph). The winds are of similar strength to a strong tropical storm. However, it lacks tropical characteristics such as a warm core, organized deep convection and strong winds close to its centre of circulation – all features required for it to be classified as a tropical storm or hurricane.

Satellite image of the extratropical cyclone that could transition to tropical cyclone

Satellite image of the extratropical cyclone that could transition into a tropical storm or hurricane

What are the chances of a tropical cyclone this January? Currently, the United States National Hurricane Center (NHC) has given the system a 30% chance of developing into a subtropical or tropical cyclone in the next five days. However, the usually very reliable ECMWF model has the chance greater than 90% for the 48 hours starting from 8 am, Saturday, January 9, 2016.

ECMWF model forecast, valid 8 am Sat, Jan 9 to 8 am Mon, Jan 11, 2016

ECMWF model forecast, valid 8 am Sat, Jan 9 to 8 am Mon, Jan 11, 2016

Will it impact the Caribbean? Whether or not the system develops into a tropical cyclone, it is not expected to have a direct impact on Antigua and the rest of the Caribbean. The centre and storm/hurricane force winds will stay well away from our islands. Notwithstanding, the cyclone will push large battering swells to our shores, making for hazardous marine conditions, especially for sea bathers.

Wave height (ft). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wave height (ft). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wind speed (knots). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wind speed (knots). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Where else will it affect? The cyclone will likely make life extremely difficult and dangerous for Team Wadadli and the rest of the rowers taking part in the Atlantic Challenge. In addition to it generating large northerly swells across the preferred path of the race, it is expected to cause strong southerly, westerly and northerly winds during next week.

Swells are expected to reach Africa and Europe during the upcoming week as the system moves east over the eastern North Atlantic.

Where has it affected? Today it caused storm force winds of 43 knots (50 mph) and rain across Bermuda. It has and still is generating very hazardous seas around this island also. Swells from the system have reached the United States east coast and the Bahamas.

What are the other Atlantic January Tropical cyclones? According to NHC’s database – HURDATA2, which dates back to 1851, the three times that there have been tropical cyclones in January are:

None affected any land mass directly.

Has the Caribbean ever receive a direct impact in January? Incidentally, Antigua and the northeast Caribbean were once struck by a Hurricane in January. This happened with Hurricane Alice, which actually formed on December 30, 1954 and crossed over into January 1955, impacting the islands during the first week of the year.

If the extratropical storm does develop into a tropical cyclone it would be called Alex. We will be keeping an eye on this once in a half a century event.





Cheerful Seas Ahead for Atlantic Challenger

4 01 2016

Dale C. S. Destin |

Good news for rowers taking part in the Talisker Whisky Atlantic Challenge, racing to Antigua and Barbuda.  After angry seas for most of the last 15 days, since the challenge started, cheerful marine conditions are expected to greet the challengers after midweek.

The daredevil rowers, including Team Wadadli (Antigua) are currently experiencing fresh to strong winds of 17 to 23 knots (20-26 mph) with wind gusts as high as 30 knots (35 mph). Seas are very rough with heights of 2.4 to 3 metres (8 to 10 feet).

Wave Height (m), Valid Mon, Jan 4, 2016, Issued Jan 4 at 6 AM AST

Wave Height (m), Valid Mon, Jan 4, 2016, Issued Jan 4 at 6 AM AST

The current marine conditions are extremely dangerous. For such conditions in coastal waters, warnings would be in effect and small craft operators, such as these rowers, would be told not to venture far from port. However, I guess, therein lies part of the challenge.

The race was set to start on December 16 but was delayed by hazardous marine conditions to December 20.

Although not very reliable beyond a week, wind wave models are forecasting relatively comfortable sea conditions from around January 7 to January 19. After the middle of this week, the winds will generally stay under 16 knots (18 mph) and seas less than 1.8 metres (6 feet). Until then, the racers will continue to be battered by angry waves.

Wave Height (m), Valid Thu, Jan 7, 2016, Issued Jan 4 at 7 AM AST

Wave Height (m), Valid Thu, Jan 7, 2016, Issued Jan 4 at 7 AM AST

The Talisker Whisky Atlantic Challenge dates back to 1997. Initially, it was a bi-annual event but it‘s set to become annual confrontation of the Atlantic. It rows-off from the Canary Islands and ends, as of 2005, at the Historic Nelson’s Dockyard, English Harbour, Antigua and Barbuda. It covers a journey of around 4.7 million metres (2930 statute miles).

The Progress of the Rowers as of 8 am AST. Team Wadadli's Position is Marked in Plum with a bold White Outline

The Progress of the Rowers as of 8 am AST. Team Wadadli’s Position is Marked in Plum with a bold White Outline

For the first time a team from Antigua and Barbuda is taking part in the race. The team can be followed here on facebook. They are currently in 11th place; however, the focus for them is on the challenge of completing such a race.

Boats should start to arrive in Antigua at in the next 17 days, or so, to hundreds of welcoming Antiguans along with the seafarers families and friends.

Let’s hope the weather after Wednesday give them much cheers until they reach our shores.








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