Climate Change Played No Part in the 2013-2016 Antigua Drought

17 10 2018

Dale C. S. Destin |

A recently published paper by Herrera et al. has shown that climate change was not a factor in the 2013-2016 Antigua Drought.

The 2013-2016 drought was the worst for Antigua on record, dating back to 1928. Further, the year 2015 was the driest on record dating back to, at least, 1871 or over 145 years. It was a year without a wet season.

DroughtsOfAtLeastOneYear_Thru2016

Water was a huge problem during 2013-2016, many households were without pipe-borne water for days, weeks and even multiple months at a time. The drought was not only meteorological but socioeconomic – the worst kind of drought. The drought is believed to have contributed to the downfall of the then government.

The drought was not limited to Antigua – it was felt all across the region and was deemed one of the worst Pan-Caribbean droughts ever.

The paper by Herrera et al. answered the million question that was raised by many back then – did climate change cause or play a part in our worst drought on record. Some, without a scintilla of evidence, did answer the question in the affirmative. But clearly, science is not what you believe, but what you can prove. And the researchers were able to definitively answer the question, with proof, that climate change neither caused or contributed to the drought.

The Herrera et al. paper titled, Exacerbation of the 2013-2016 Pan-Caribbean Drought by Anthropogenic Warning, showed that not only did climate change not play a part in the Antigua drought – it did not impact the drought across the rest of the Eastern Caribbean. Further, the vast majority of the rest of the drought across the Caribbean was not affected by climate change. The exception is Cuba and to a much lesser extent small parts of Jamaica, Hispaniola and Puerto Rico.

 

Climate Change Contribution (%) to the Drought Severity Across the Caribbean. Hatching (Black Lines) Corresponds to Those Areas Which had a Climate Change Contribution.

Climate Change Contribution (%) to the Drought Severity Across the Caribbean. Hatchings (Black Marks) Highlight Those Areas Which had a Climate Change Contribution.

Notwithstanding the above findings, interestingly, when the Caribbean is viewed as a whole, the authors of the paper found that climate change played a 15 to 17% role in the severity of the Pan-Caribbean drought, forced, of course, mainly by Cuba.

Climate change contributed to the severity of the drought in Cuba was 32%. Without Cuba being a part of this study, the conclusion for the Caribbean, taken as a whole, would be the opposite – climate change played no role in the 2013-2016 drought.

The take-away from the paper is that while climate change had an impact on the drought in Cuba and very small parts of the rest of the Greater Antilles, the rest of the Caribbean cannot credit any part of the drought on climate change.

Although climate change had no part in the drought of 2013-2016 across much of the Caribbean, this is not to say that future drought will not be impacted. The long-term forecast by the Intergovernmental Panel on Climate Change (IPCC) out to the 2100 is for the region to get warmer and drier.

The overall forecast is for climate change to likely cause an increase in the severity and or duration of drought on a regional to global scale. The new report issued by the IPCC on October 8, 2018 offers no update to this position.

Herrera et al. findings strongly suggest that climate model projected climate change drying in the Caribbean is already underway in the larger islands. This has major implications for the many millions of people in those islands and eventually the rest of us in the smaller islands.

Climate change did not affect the drought in Antigua, but it did affect our regional neighbours – the Greater Antilles. It stands to reason that it is only a matter of time before climate change contributes to increasing the severity of droughts elsewhere in the region, including our island.

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Leslie to Cause a Mini Swellmageddon Across the Caribbean

28 09 2018

Dale C. S. Destin |

Ex-Tropical Storm Leslie is about to cause a mini Swellmageddon across much the Caribbean, after the passage of Kirk. The system is expected to be a major swell-maker, which will become very evident in 24 hours; hence, Swimming conditions at many beaches will become very hazardous.

Fort James Beach During Swellmageddon – Mar 2018

Fort James Beach During Swellmageddon – Mar 2018

Currently, Leslie is not a tropical cyclone. It transitioned into an extratropical cyclone, a few days ago. However, it has not gone any place. The cyclone is forecast to be resurrected. She will strengthen, return to tropical cyclone status in the next 48 hours and eventually become the sixth hurricane for the season.

The hurricane-force winds, to be produced by the cyclone, will never reach us, but they will push, dangerous and damaging sea swells to our shorelines, particularly the Atlantic-facing ones.

Swell height at a NOAA buoy located about 370 NNE of Antigua

Swell Heights at a NOAA Buoy Located About 370 NNE of Antigua

Swells are forecast to steeply climb to 3 metres (10 feet) on Saturday. These large and dangerous battering swells are expected to pummel our shorelines over the upcoming weekend before subsiding to safe levels by mid next week.

Swells Forecast by ECWMF

Swells (colour coded) and Pressure (lines in ATM/Torr) Forecast by the ECMWF WAM 11km Model for Sat Sep 28, 2018

Recall the swell event I dubbed Swellmageddon earlier this year – March 4-7, 2018. It was a swell episode of epic proportion – almost unheard of in the Caribbean. This upcoming swell episode is not expected to be as severe, but it won’t be your garden-variety event either.

The large swells will produce even higher breaking swells or surfs, which could be as much as twice the height of the swells. This means that surfs are expected to range between 3 and 6 metres (10 to 20 feet) this weekend, depending on the bathymetry/topography of the near shore seafloor. This is expected to cause some beach closures, as swimming conditions will become very dangerous for beachgoers, by tomorrow.

This mini Swellmageddon will likely, among other things, also cause:

  • major beach erosion;
  • flooding of some low-lying coastal roads;
  • disruptions to marine recreation and businesses;
  • disruptions to potable water from desalination;
  • damage to coral reefs and
  • Financial losses.

Advisories have already been issued by a few of the region’s national meteorological services. More advisories and or warnings are expected to be issued over the upcoming days. This event will be felt as far west as the Bahamas and as far south as Guyana, Brazil and beyond. The event will also be felt along the East Coast of the United States, Canada and perhaps, as far away as, West Africa.

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. Surfs could rise to as high as 6 metres (20 feet), at some locations.

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

There is no chance of any of the destructive winds, from the cyclone at the centre of this significant swell event, reaching the Caribbean. Normal seasonal winds will prevail.

Keep following us for more on this significant swell event and for everything weather and climate. Actual images of the high surfs will be posted on facebook.com/anumetservice and twitter.com/anumetservice.





9th Driest July on Record for Antigua, Droughts Continue

26 08 2018

Dale C. S. Destin |

July 2018 was the ninth driest on record for Antigua dating back to 1928. The last time we had a drier July was 2015, when we recorded our driest year in, at least, 145 years.

July2018

The total rainfall for the month of 39.6 mm (1.56 in) was a meagre 39% of what normally falls – 100.3 mm (3.95 in). Hence, there was a painful 61% rainfall deficit for the month.

From_mod_to_severe_droughtThis was also the third driest July or the third driest start to the wet season since 1977. Only 2015 and 2014 Julys were drier, with 33.3 mm (1.31 in) and 19.3 mm (0.76 in) respectively, in recent times.

The last three-month period – May to July, upon which the assessment of the current intensity of the drought is based, was severely dry. In that time, only 96.3 mm (3.79 in) of rain fell. This is the fourth driest such period on record and the second driest since 1977.

Cumulatively, May, June and July normally yield 273.1 mm (10.75 in) of rain; however, a massive 65% of it did not fall. This means that we are now in a severe meteorological drought, the worst category on our scale. Other droughts are believed to be at similar severity. Recall that there are, at least, five types of droughts.

RainfallForPast24Months_July2018

Rainfall (in) for the past 2 yrs. All periods showing well below or below normal rainfall.

So, overall, we are now in a severe drought that is currently at severe intensity. Last month, it was assessed to be a serious drought that was at moderate intensity. Recall that the overall description of the drought is based on the worst intensity achieved since it started; however, over time, the intensity will fluctuate.

Potworks Dam, with a billion-gallon capacity, has been totally dry for a few months now. The vegetation of the Island continues to struggle badly – grass has ceased growing in some locations. Many fields are bare, with some having large and dangerous cracks. Some animals are said to have perished due to insufficient food and water. These are indicative of the fact that the droughts, not just meteorological, are at severe levels.

Potworks_Dam_Aug22018

Potworks Dam – August 2, 2018. Picture courtesy Karen Corbin – Humane Society

Happily, the full brunt of the droughts continues to be held at bay by the presence of the desalination plants, which are virtually the only source for potable water in the country. Notwithstanding, many impacts are starting to break through. Potable water is being rationed, places have been left without water for days to weeks, at a time, notwithstanding a schedule issued by APUA – the water authority, to provide water to everyone, at least, three times per week.

The ten-month period – October 2017 to July 2018, the duration of the drought thus far, is deemed severely dry. The total for the last ten months of 504.2 mm (19.85 in) is the third lowest on record and the lowest since 2001. The period normally gets 945.1 mm (37.21 in) – nearly twice the amount that fell.

Based on the last set of rainfall forecasts from regional and especially international sources, the news remains discouraging. Overall, below normal rainfall is likely, if not expected, for the next six months – September 2018 to February 2019. Thus, there is every reason to believe that the droughts will continue and likely worsen. The chance of the droughts ending is, at most 30% or low.

SON_Aug2018

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Sep-Nov 2018

On average, our severe meteorological droughts last for around 16 months, but not continuously at severe intensity. Will this one continue for another six months? Very likely, given the climate signals.

The probability of 2018 being a drier than normal year remains high – 75%. The best forecast for rainfall amount for the year is 872 mm (34.3 in) with a 70% confidence of the amount ranging between 658 mm (25.9 in) and 1130 mm (44.5 in). Normally, we get 1206.5 mm (47.5 in) annually.

If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend, or sharing it on Twitter or Facebook.

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Updated Hurricane Season Forecast: Near Normal Season Most Likely

12 08 2018

Dale C. S. Destin |

Good news! Our August updated forecast for the 2018 Atlantic Hurricane Season is now available and it is indicating that a near normal season is most likely this year. The prediction is for an accumulated cyclone energy (ACE) index of 93, 11 named storms, 5 becoming hurricanes and 2 becoming major hurricanes.

Aug2016HSOutlookCorrected

Recall that a typical season has an ACE index of 106, 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.

Recall also that the ACE is the overall predictor of a hurricane season, it is a measure that represent the total number of storms, their intensities and durations.

According to other forecasts surveyed, the latest consensus is for an ACE of 88, 12 named storms, 6 hurricanes and 2 major hurricanes. Thus, our forecast is calling for similar activity; however, regardless of the forecast, you should always prepare well each season, as it only takes one hurricane to ruin your year.

The Atlantic hurricane season started June 1 and will continue until November 30.

If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend or sharing it on Twitter or Facebook.

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Driest June in Over a Generation for Antigua, Droughts Continue

23 07 2018

Dale C. S. Destin |

June 2018 was the driest for Antigua in 33 years – over a generation. With the median age of the Antiguan population being around 31, most Antiguans have never seen a drier June. Not since 1985 has Antigua experienced a drier start to summer.

Potworks_Dam_Jul6_2018

The total rainfall for the month of 12.7 mm (0.50 in) was a parched 18% of what normally falls – 69.3 mm (2.73 in). Thus, there was an excruciating 82% rainfall deficit for the month.

This was the third driest June on record dating back to 1928. Only 1985 and 1974 Junes were drier with 12.4 mm (0.49 in) and 8.1 mm (0.32 in) respectively. The 12.7 mm for this June has a return period of 34 years i.e. such severe dryness for the month only occurs once in every 34 years, on average.

ModerateMetDroughtUnchangedThe last three-month period – April to June, upon which the assessment of the current intensity of the drought is based, had 128.3 mm (5.05 in), only around half of the normal total of 258.6 mm (10.18 in). This puts the meteorological drought current intensity at moderate, unchanged the previous assessment.

Overall, we are in a serious meteorological drought, but currently it is at moderate intensity. The overall description of the drought is based on the worst intensity achieved since it started; however, over time, the intensity will fluctuate.

Potworks Dam, with a billion-gallon capacity, has been totally dry for a couple of months now. The vegetation of the Island is struggling – grass has virtually ceased growing in some locations. Many fields are bare, with some having large cracks. These are indicative of the fact that the droughts not just meteorological, are at moderate levels or worse.

Happily, the full impacts of the droughts continue to be masked by the presence of the desalination plants; however, impacts are starting to break through. Potable water is being rationed, some places have been left without water for many hours to weeks, at a time. There will be a big press conference this morning by APUA – the water authority, to provide answers to the water problem.

The dry season – January to June, had well below normal rainfall. On a scale of 1 to 100, with 100 being best rainfall situation and 1 being the worst, the rainfall was less than a 10. Only 254.3 mm (10.01 in) or 59% of the normal total of 434.6 mm (17.11 in) fell. It was the 10th driest dry season on record dating back to 1928. Only dry season 2015 was drier since 2004.

RainfallForPast24Months_June2018

Rainfall (in) for the past 2 yrs. All periods showing well below or below normal rainfall.

The nine-month period – October 2017 to June 2018, the duration of the drought thus far, is deemed severely dry. This means that the total is in the bottom 5% of the historical data. Such dryness happens around once every 20 years, on average.

The total for the last nine months of 464.6 mm (18.29 in) is the lowest since 2001 and the third lowest on record dating back to 1928. The period normally gets 845.1 mm (33.27 in).

Based on the last set of rainfall outlooks from regional and especially international sources, the news remains bad for rainfall. Below normal rainfall is most likely for the next six months – August 2018 to January 2019. Thus, there is every reason to believe that the droughts will continue and likely worsen. The chance of the droughts ending is at most 20% or slight.

Prob Multi-Model Ensemble Forecast For ASO_Jul2018

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Aug-Oct 2018

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. Will it go for another three months? Yes, it is now almost certain that this drought will last for a year or more.

Our confidence of 2018 being a drier than normal year is growing. It has increased from 60% to 75% confidence. The best forecast for the amount of rain for the year is around 855 mm (33.7 in) with a 70% chance of the amount ranging between 625 mm (24.6 in) and 1139 mm (44.8 in). Normally, we get 1206.5 mm (47.5 in) annually.

Accumulations_June2018
If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend, or sharing it on Twitter or Facebook.

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Updated Hurricane Season Forecast: Near to Above Normal Season is Now Likely

17 07 2018

Dale C. S. Destin |

Good news and bad news: Our July updated forecast for the 2018 Atlantic Hurricane Season is now available and it indicates that the hurricane season will likely be near to above normal. The prediction is for an accumulated cyclone energy (ACE) index of 99, 12 named storms, 5 becoming hurricanes and 3 becoming major hurricanes.

Jul2018HurricaneSeasonOutlook

The good news is that there is a 37 percent chance of there being a near normal season. The bad news is that there is also a 37 percent chance of there being an above normal/active season; hence, the near to above normal forecast for the season.

Recall that during a near normal season, there is a 33% chance of a named storm (tropical storm or hurricane) affecting, i.e. passing within 120 miles of Antigua and Barbuda. By comparison, during an above normal season, the chance soars to 75%.

With respect to hurricanes, the chance of us being affected during a near normal season – 18 percent, more than triples – 59 percent, for an above normal/active season. Further, we have never had a major hurricane during a near normal season. Clearly, an active season is least prefered.

Chance of Anu Being Affected By TS

These new numbers represent a marginal increase above those of the previous forecast. Previously, the forecast called for an ACE of 93, 11 named storms, 5 hurricanes and 2 major hurricanes. If the season turns out to be near normal, it would be due mainly to cooler than normal sea surface temperatures, across the tropical North Atlantic. If it turns out to be active, it would be mainly due to the absence or late development of El Nino.

Recall that the ACE is the overall predictor of a hurricane season, it is a measure that represent the total number of storms, their intensities and durations.

A typical season has an ACE index of 106, 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.

If this forecast pans out, 2018 would be the least active since 2015. Notwithstanding, a season with activity second only to 2017, since 2005, cannot be ruled out.

According to other forecasts surveyed, the latest consensus is for an ACE of 89, 12 named storms, 5 hurricanes and 2 major hurricanes. Thus, our forecast is calling for slightly higher activity; however, regardless of the forecast, you should always prepare well each season, as it only takes one hurricane to ruin your year.

The Atlantic hurricane season started June 1 and will continue until November 30.

We will be updating this forecast by August 10.

If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend, or sharing it on Twitter or Facebook.

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Cooler Than Normal May for Antigua

30 06 2018

Dale Destin |

TempStmntGraphic_BelowNormalNotwithstanding being drier than usual, May was much cooler than normal, based on preliminary data record at the V.C. Bird International Airport (VCBIA), Antigua. The mean temperature of 26.4 °C (79.5 °F) was the lowest at VCBIA since 2012. Only six other Mays have been cooler on record dating back to 1969.

Further, at VCBIA, the mean daily minimum temperature (mean min) of 23.7 °C (74.7 °F), an indicator of night-time temperature, was well below normal. This is the lowest mean min for May since 1975 and only the third lowest on record dating back to 1969.

Additionally, the mean daily maximum temperature (mean max), an indicator of day-time temperature, was cooler than normal. The mean max of 29.3 °C (84.7 °F) tied with that of 2017 for the lowest temperature at VCBIA since 2014.

Looking deeper into the preliminary numbers at VCBIA, there was an above normal number of cold days (4) and cold nights (5). The most number of cold nights since 2008.

Clearly, the numbers indicated above, with respect to temperatures, differs from those recorded elsewhere across the island. We don’t have long enough datasets to speak definitively about temperatures for other areas of Antigua. However, it is believed that the rankings of temperatures are likely to be similar.

So, although other parts of Antigua had lower or higher temperatures, because temperatures are highly correlated, especially in a small island like ours, most if not all places had a cooler than normal May, relative to the given location. On average, some places across Antigua differ by as much as 5 °C (9 °F).

The reason for the cooler than normal temperatures is the same reason for the drought weather being experienced – cooler than normal sea surface temperatures across the tropical North Atlantic (TNA) Ocean. These temperatures are likely to remain cooler than normal for much of the rest of the year.

Tropical North Atlantic  (TNA) Index - Much Cooler Than Normal

Tropical North Atlantic (TNA) Index – a measure of the sea surface temperature between Africa and the Caribbean – much cooler than normal.

Based on record dating back to 1948, this past May was the coolest the TNA has been for the said month since 1989 and the sixth coolest on record.

If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend, or sharing it via social media.

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