Early Forecasts for 2018 Atlantic Hurricane Season

11 04 2018

Dale C. S. Destin|

Our early season forecast for the 2018 Atlantic Hurricane Season calls for above normal activity. The prediction is for an accumulated energy (ACE) index of 135, 15 named storms, 7 hurricanes and 4 major hurricanes.

Apr2018HurrucaneSeasonForecast

A typical season has 12 named storms, 6 hurricanes, and 3 major hurricanes. Major hurricanes have sustained wind speeds of at least 178 km/h or 111 miles per hour (e.g., Category 3 or higher), based on the Saffir Simpson Hurricane Wind Scale.

The 2017 Atlantic hurricane season was one of the most destructive for the Caribbean; several islands were almost totalled. Barbuda, one half of the twin island state of Antigua and Barbuda was left uninhabitable for a while. Ten of last year’s 17 named storms reached hurricane strength—meaning they had sustained winds of at least 119 km/h or 74 miles per hour—and six of the 10 hurricanes were major ones.

If this forecast pans out, 2018 would be the second most active since 2010; second to last year’s season.

The Atlantic hurricane season begins on June 1 and concludes on November 30.

We will be updating our 2018 forecast by June 10.

According to other forecasts surveyed, the consensus is for an ACE of 105, 14 named storms, 6 hurricanes and 3 major hurricanes. Thus, our forecast is generally calling for higher activity than most; however, regardless of the forecast, you should always prepare well each season, as it only takes one hurricane to ruin your year.

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2nd Wettest February In Years, Yet Less Than Usual Rainfall

1 04 2018

Dale C. S. Destin|

February 2018 was the second wettest since 2011, yet the rainfall total for the month was below the usual.  The island-average total was 35.8 mm (1.41 in); however, the usual amount for the month is 55.9 mm (2.20 in). Clearly, with only 64% of February’s rains falling, there was no positive impact on the drought situation being experienced.

Slight Meteorological Drought

Rainfall in inches for the past 24 months. Multiply by 25.4 to get mm. For records, the year given marks the start of the period.

The three-month period – December to February, upon which the assessment of the current intensity of the drought is based, had 198.6 mm (7.82 in). This puts the meteorological droughts at slight. However, with Potworks Dam about to go totally dry and the vegetation of the Island struggling, there is little doubt that other droughts are at moderate levels or worse. Of course, and thankfully, the full impact of the droughts is being masked by the presence of the desalination plants.

Drought Level is Slight

Based on the last set of rainfall outlooks, the news is not good for rainfall. Overall, below normal rainfall is most likely for the six-month period March to August. Thus, there is every reason to believe that the droughts will worsen. Even if the rainfall total turns out to be near average, it will not be enough, especially with respect to the hydrological drought, as the monthly evaporation rates significantly exceeds rainfall totals for most of the upcoming months. The chance of the droughts ending is slight – less than 30%.

Recall that the current drought started in October 2017 with the intensity at serious levels. On average, serious meteorological droughts last for close to a year, but not continuously at serious intensity. We have just passed the six-month mark in the drought. Will it go another six months? Unfortunately, the answer looks more like yes than no.

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March to August 2018 Climate Outlook for Antigua and Barbuda

30 03 2018

Dale C. S. Destin |

Antigua and Barbuda remains in, at least, a meteorological drought. The latest round of climate outlooks suggest that it is most likely to worsen, over the coming three to six months. Signs of the dry weather is becoming quite evident, with Potworks Dam transitioning from a water catchment to a temporary sesonal desert. Drought is occurring and drought watch and warning are in effect for the medium to long-term.

Potworks Dam, Antigua; Mar 13, 2018; Almost Totally Dry. Image courtesy Karen Corbin of the Humane Society

Potworks Dam, Antigua, Mar 13, 2018; Almost Totally Dry. Image courtesy Karen Corbin of the Humane Society. At its max, it holds a billion gallons of water.

Rainfall and drought

Last month, we indicated that the drought was unlikely to worsen or could come to an end in the next three months. This months, the climate indicators are indicating that the drought will mostly worsen and continue for the next six months, at least.

ProjectedRainfall_Dec 2017-May2018

Based on the latest round of forecasts, we will likely be facing more than a meteorological drought. Other droughts that could be on the way, if not already with us, are agrometeorological, Hydrological, socioeconomic and ecological droughts.

For the medium term: at the end of the nine-month period ending June 2018, a drought watch is in effect, as a moderate drought or worse is possible for Antigua. Meanwhile, for the long-term: 12-month period ending August 2018, a drought warning is in effect, as a moderate drought or worse will most likely be occurring. It is possible this period could experience serious drought.

Temperature

Temperatures, including maximum and minimum, were generally near normal or the usual for the December-February (DJF) period, based on the climate period 2001-2015.

Looking down the road over the period March to May– above to near normal mean maximum temperature is likely. Otherwise, equal chances of  below, near or above normal mean temperature and mean minimum temperature. In other words, the current climate signals do point in any given direction as to what is likely to happen with these temperatures.

For the period June to August, the mean and maximum temperature are expected to be above to near normal or warmer than usual to usual. Meanwhile, temperature is equal chance of below, near or above normal mean minimum temperature.

El Nino Southern Oscillation

The cold phase of El Nino Southern Oscillation (ENSO) – La Nina is evident; however, it will be short-live, as already, it has started to transition back to ENSO-neutral conditions. The transition to the neutral phase is expected to conclude by the end of May, with a 55 percent confidence.

In our part of the world – the Caribbean, a moderate or strong La Nina is almost always welcome, particularly in the summer when it has a usual positive impact on rainfall. The opposite – El Nino, has a negative impact. Fortunately or unfortunately, outside the wet season – July to December, ENSO has little or no effect on our rainfall.

La Nina is also welcome from a temperature standpoint, as it usually bring welcome cooler than normal weather. The reverse is true.

Tropical North Atlantic

Over the past three months, the tropical North Atlantic sea surface temperatures (TNA-SSTs) has gone from warmer than usual to colder than usual. However, overall, for the period November-January, TNA-SSTs were warmer than usual. For the upcoming March-May period, TNA-SSTs will likely be at the usual or cooler than usual for this time of the year. Historically, these temperatures seems not associated with any particular rainfall total for March to May.

Regarding temperature, higher that normal TNA-SSTs are associated with higher than usual temperatures for Antigua and vise-versa.

Both ENSO and TNA-SSTs are pointing toward near to below normal temperatures for Antigua. This is interesting, drought conditions are expected to continue and drought normally comes with warmer than normal weather. Current trend seems consistent with ENSO and TNA-SSTs signals.

See the following links for the full outlooks: CariCOF Newsletter – summary and outlooks for the regionprecipitation outlooks and temperature outlooks.





Another Swell Event to Impact Antigua and the Northern Caribbean

27 03 2018

Dale C. S. Destin |

A powerful low-pressure system is pushing long period swells of moderate heights across the Atlantic that will reach the northern Caribbean, including Antigua and Barbuda. The swells will start to arrive tonight across the Bahamas, tomorrow morning across Hispaniola and Puerto Rico and Wednesday afternoon across the Leeward Islands, including Antigua and Barbuda.

Fort James Beach During the Last Swell Event - Swellmageddon

Fort James Beach During the Last Swell Event – Swellmageddon – 1st Week of March 2018

This swells even will come no where close to the last one in size and duration. The swell waves will be moderate – 2 to 3 metres across the northeast Caribbean and larger for the islands to the west. However, high surfs will pummel our shorelines with heights of  4.5 metres or 15 feet, getting higher as you go west through the islands.

SwellsMar272018

Such high swells and surfs will produce an elevated threat to life and property in the surf zone. The high surfs that will result in beach closures as swimming conditions will become extremely dangerous for beachgoers.

The event will likely cause major beach erosion; possibly flooding of low-lying coastal roads; disruptions to marine recreation and businesses; financial losses and damage to coral reefs.

Although relatively small, this swell episode may also cause disruptions to potable water from desalination as turbulent seas could increase the turbidity of the water above safe levels for the desalting plants.

A high surf warning has been issued by the Met Office for Antigua and the rest of the northeast Caribbean. Other Offices are expected to issue warnings for as far west as the Bahamas and extending south to the northern Windward Islands. Swells could exceed 5 m (17 ft) across the Bahamas.

The impact on shorelines will not be the same everywhere. Depending on the depth, size, shape and the natural shelter of the coastal waters, the impact will be different. Shallow north-facing shorelines are expected to see the highest swells and surfs; especiall for Barbuda and the more northerly islands.

In open waters, the swells will be virtually harmless to small craft operators as they will be long-period, gentle waves.

Again, this is no “swellmageddon”; however, there will be impacts and associated financial losses.

Keep following us for all things weather and climate.





Hurricane Irma Got Relegated

17 03 2018

Dale C. S. Destin |

Hurricane Irma was relegated from being tied for the second strongest Atlantic hurricane, in terms of wind speed, to being tied for being the third strongest. This is according to the final report on the system issued last week by the U.S. National Hurricane Center (USNHC). The USNHC, in its post-mortem report, lowered Irma’s maximum sustained winds from 185 mph to 180 mph.

VIIRS SATELLITE IMAGE OF HURRICANE IRMA WHEN IT WAS AT ITS PEAK INTENSITY AND MADE LANDFALL ON BARBUDA AT 0535 UTC 6 SEPTEMBER.

VIIRS Satellite Image of  Hurricane Irma When it was at its Peak Intensity and Made Landfall on Barbuda at 0535 UTC (1:35 am) 6 September, 2017.

The downgrade of Irma, by 5 knots (5.75 mph), is relatively negligible; however, from the record book standpoint, it is notable. And looking at the raw data, the USNHC may have still been generous with the peak winds of 180 mph – it could have been lowered further.

There are some other notable things gleamed from the report that I would like to share. A report I would recommend persons to read.

Recall that many persons blamed Irma on climate change, something that I and others continue to debunk? It turned out that Irma’s strength had very little to do with warm sea surface temperatures – the link that is being made to climate change, and more to do with low wind shear and available atmospheric moisture, according to the USNHC report – not climate change.

USNHC has confirmed what we already recognized – Irma was a very small hurricane. Her hurricane force winds extended only 24 km (15 miles) from the centre. On average, the hurricane force winds from a hurricane extends out 64 km (40 miles). Her small size saved Antigua from similar type destruction to what occurred in 1995 from Hurricane Luis.

Along parts of the track of Irma, the effect of the winds on the sea was reminiscent of a tsunami. For example, in Puerto Piloto, the sea retreated offshore by up to 12 metres (39 feet) due to the force of the southerly winds on the eastern side of Irma’s circulation. No doubt similar would have happened for parts of Barbuda and elsewhere.

Irma's Storm-Surge as Recroded by Our Station at River Road, Codrington, Barbuda

Irma’s Storm-Surge as Recorded by Our Tide Station at River Road, Codrington, Barbuda

For Barbuda, the was a tsunami-like surge of 2.5 metres (9.3 feet) measured by our tide gauge at River Road, Codrington, which is on the southern side of the island. It is likely that the surge generated by on the north side was higher. These surges inundated significant portions of Codrington and the island as a whole, which is very flat. At least half of the island lies within 25 feet of mean sea level. The Codrington Lagoon remains breached from the massive surges and waves created by Irma.

In addition to the tsunami-like surge, there were monster waves as high as 8 metres (26 feet) caused by Irma. Such large waves on top of the high surge would have caused seawater to inundate areas well inland, causing serious erosion and saltwater intrusion into aquifers and agricultural lands.

Also confirmed was the fact that the ECMWF was by far the best performing model with respect to the track forecast. However, all the models were left wanting with respect to the forecast of intensity.

In weeks we will have the first set of forecast for the upcoming hurricane season, stay tuned for those.

Don’t forget to take our weather survey, which will help us to better communicate the weather to you: Weather Survey.

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Windmageddon To Produce Swellmageddon Across The Caribbean

3 03 2018

Dale C. S. Destin |

A gigantic low-pressure system, nicknamed windmageddon due to widespread damage and power outages it caused across the Northeast United States, is about to cause swellmageddon. Swellmageddon because the low-pressure area will cause enormous, dangerous and destructive sea swells that will wreak havoc on the shorelines of Antigua and much of the Caribbean.

High Surfs

Large Breaking Swells (High Surfs)

Large and dangerous battering swells, peaking in excess of 4 m (13 ft), are expected to pommel our shoreline starting Sunday and continuing until Friday. This is expected to be the worse swell event thus far for the winter season.

Swellmageddon

Such high swells will produce even higher surfs that will result in beach closures as swimming conditions will become extremely dangerous for beachgoers.

Swellmageddon will likely cause major beach erosion; flooding of low lying coastal roads; disruptions to marine recreation and businesses; financial losses and damage to coral reefs.

This major swell event may also cause disruptions to potable water from desalination as turbulent seas could increase the turbidity of the water above safe levels for the desalting plants.

A high surf warning is expected to be issued by the Met Office for Antigua and the rest of the northeast Caribbean. Other Offices are expected to issue warnings for as far west as the Bahamas and extending south to the Windward islands. Swells could exceed 5 m (17 ft) across the Bahamas.

The impact on shorelines will not be the same everywhere. Depending on the depth and the natural shelter of the coastal waters the impact will be different. Shallow north-facing shorelines are expected to see the highest swells and surfs.

In open waters, the swells from swellmageddon will be virtually harmless to small craft operators as they will be long-period waves with gentle gradients.

Windmageddon will not cause any destructive winds across us, far from, but it will cause them to come from some very unusual directions for this part of the world. They are going to becoming from the south, west and north at times over the next several days before return the usual direction of east next weekend.

Keep following us for more on the weathermageddons and for everything weather and climate.





Drought Eased A Bit For Antigua

2 03 2018

Dale C. S. Destin |

Near normal rainfall for January has eased the drought across Antigua from serious to moderate levels. The island-average rainfall for January was 62.5 mm (2.46 in), 91% of the usual total.

The three-month period – November to January, upon which the assessment of the intensity of the drought is based, had 211.6 mm (8.33 in). It is the second driest such period since 2000 and the 13th driest on record dating back to 1928.

Based on the last set of rainfall outlooks, the news is not good for rainfall. Below to near normal rainfall is expected for the period March to May. Thus, there is every reason to believe that the droughts will worsen or remain the same. There is only a slight chance of them ending over the above mentioned period.

Recall that the current drought started in October 2017 with the intensity at serious levels. On average, serious meteorological droughts last for close to a year, but not continuously at serious intensity.

While we can only speak definitively to meteorological droughts, there is little doubt that we are also experiencing agricultural, hydrological and perhaps socioeconomical droughts. These are likely to become more noticeable in the incoming months; however, the full impact will continue to be masked by the presence of desalination plants.

Potworks Dam Feb 13, 2018, Courtesy Karen Corbin - Humane Society

Potworks Dam Feb 13, 2018, Courtesy Karen Corbin – Humane Society

Potworks Dam, the country’s largest catchment with a capacity of around a billion gallons of water, continues to show signs of drying up. Around the middle of February, the water level had fallen to about a quarter or less. It could be totally dry in couple months.

Keep following us for more on this developing story and things weather and climate.








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