Drought-Busting, Lenny-Type Rainfall Impacted Antigua

10 11 2020

Dale C. S. Destin|

A newly formed tropical disturbance caused drought-busting, Lenny-type rainfall across parts of Antigua. The system dumped over 373 mm (over 14 inches) across parts of the country, over the last 24 hours.

Of course, with this extreme rainfall, there was massive flooding in some areas. The impact is unfolding with images of almost submerged and abandoned vehicles, flooded businesses and homes and damaged roads.

This image has an empty alt attribute; its file name is image-10.png
Last Night: Flooding at Woods, St. John’s, Antigua
Today: Same area as above (Woods, St. John’s, Antigua) but after the runoff.

This rainfall event was quite extreme, if not in amount, certainly with respect to intensity. In 24 hours, two-and-a-half times the month’s total rainfall fell, yes 250% November’s average in less than 24 hours, in some places. The islands average rainfall for November is 149.4 mm (5.88 inches).

The maximum 6-hour rainfall was higher than the average for most months. We measured up to 156 mm (6.14 inches) in six-hours. This is more rainfall than we would have had from most tropical cyclones that have impacted the island. The max six-hour rainfall on record at the Airport is 175.2 mm (6.90 inches); the max for November for the same location is 158.7 mm (6.25 inches).

In an hour yesterday, we measured peak rainfall total of 97 mm (3.82 inches), at the University of the West Indies – Five Islands Campus. At the Airport, the record of 56.4 mm (2.22 inches) was broken by the 77.9 mm (3.07 inches) measured between 4 and 5 pm, yesterday.

Drilling down even deeper, there were occasions when the ten-minute rainfall total reached close to 25 mm (1 inch). This is almost unimaginable to think that in a space of 10 minutes, some areas would have had nearly an inch of rainfall.

Putting the rainfall total into further perspective, the one-day-total, for some areas, for this event is higher than the one-day-total from Lenny recorded at the Airport. Lenny’s maximum one-day total was 241 mm (9.49 inches), at the Airport, as compared to over 320 mm (over 12.6 inches) from this event, at Five islands.

More rain is in the forecast with another 100 to 200 mm (4 to 8 inches) possible in the next 72 hours. This means more moderate to major flooding is likely.

Potential impacts include:

  • loss of life and injuries;
  • widespread financial losses;
  • disruption to transportation;
  • soil erosion;
  • disruption of schools;
  • damage to dams, embankment, irrigation and drainage facilities;
  • decrease in storage capacity of reservoir due to high sediment rate;
  • contamination of potable water;
  • crop and animal losses;
  • environmental degradation;
  • disruption to communication and
  • damage to infrastructure. 

Stay alert and prepared. If or when a flash flood warning is issued, it means that, at least, moderate or worse flooding is imminent or occurring in the warned area. Thus, residents in these areas should move to higher ground immediately.

Do not drive your vehicle into areas where the water covers the roadway, as the underlying road may have washed away, magnifying the potential for harm. A flash flood watch means to prepare for the possibility of warning conditions.

Flooding across portions of Bolans, Antigua

Please continue to follow me for more on the hurricane season and all things weather and climate via TwitterFacebook and Instagram. Also, share this blog, if you found it useful.

The Hurricane Season in November

9 11 2020

Dale C. S. Destin|

November hurricanes are almost unheard of for Antigua and Barbuda. I say almost because we have an exception – Hurricane Lenny of 1999. In 169 years of record dating back to 1851, Lenny is our (Antigua and Barbuda and the rest of the Eastern Caribbean) only November hurricane.

This image has an empty alt attribute; its file name is image-9.png
Lenny south of the US Virgin Islands. Credit Wikipedia
The Track of Hurricane Lenny – November 13-23, 1999

Prior to Lenny, we in the Eastern Caribbean, have not had a November named storm (tropical storm or hurricane) since 1896 – over 100 years before Lenny. November named storms amount to eight for the Eastern Caribbean, four of which affect Antigua, with Lenny being the only hurricane on record.

Lenny impacted Puerto Rico, the Virgin Islands, the Leeward Islands, the Windward Islands and even as far away as Colombia. It killed at least 17 people and caused over US$785 million in damage, a lot due to flooding.

The Atlantic Basin, including the Caribbean, averages one November named storm per year, one hurricane every other year and a major hurricane – Category 3 or higher intensity, every 10 years; this is based on the current climatological period of 1981-2010.

To date, no Category 5 hurricane has had its origin in November, based on the record. There was an unnamed Category 5 hurricane in 1932 that formed in October but reach Category 5 status in November; however, storms are credited to the month in which they were formed or originate in.

The probability of Antigua and Barbuda being impacted by a storm or hurricane, in November, is around 3 percent, based on the 1981-2010 base period. This translates to, at least, a storm or hurricane every 33 years, on average. With Lenny being our last hurricane, we are not due another hurricane in November until around the year 2032. The same is true for a major hurricane, in November.

The probability of a storm or hurricane impacting the Eastern Caribbean, in November, is around 6 percent or one every 16-17 years. This increases to around 12 percent or one every 8-9 years for the Central Caribbean and 28 percent or every 3-4 years for the Western Caribbean.

November Hurricane Climatology
The zones of origin and tracks of named tropical cyclones (tropical storms and hurricanes) in November.

The last November hurricane for the Caribbean was Otto of 2016. It formed across the southwest Caribbean Sea and impacted Nicaragua and Costa Rica, then crossed over into the Pacific Ocean. It killed 23 people and caused damage amounting to over US$192 million. It is the last Atlantic tropical cyclone to crossover to the Pacific and only the 14th to have done so.

Infrared satellite loop of Hurricane Otto making landfall as a Category 3 hurricane in Nicaragua on November 24. Credit Wikipedia.

From 1851 to 2019, November has produced a total of 92 named storms of which 56 were hurricanes and 6 were major hurricanes. For the climate period 1981-2010, there have been 20 named storms, 14 hurricane and 3 major hurricanes.

 November 1-10 Tropical Cyclone Genesis Climatology
Click for large image
 November 11-20 Tropical Cyclone Genesis Climatology
Click for large image
 November 21-30 Tropical Cyclone Genesis Climatology
Click for large image

It must always be noted that there are likely named tropical cyclones (tropical storms and hurricanes) that were missed prior to the satellite era – before the mid-1960s.

November 2005, 1961 and 1931 holds the record for the most named storms for the month – three. Further, 2001, 1994 and 1980 holds the record for the month for hurricanes – two. Meanwhile, no November on record has had more than one major hurricane in a year and only six have had a major hurricane – 2016, 2008, 1999, 1985, 1934 and 1912.

What will this November bring? Given that each month of this hurricane season has produced, 1.5 to 2.5 times its average number of named storms and that up to 32 named storms are forecast to the year, with 28 gone, this November could end up producing up to two storms, with one becoming a hurricane.

It is not over yet, but the end is nigh – November 30. Usually, November is a low stress month for hurricanes; however, this is 2020 – stay prepared!

Please continue to follow me for more on the hurricane season and all things weather and climate via TwitterFacebook and Instagram. Also, share this blog, if you found it useful.

October Not Over 2020 Hurricane Summary

2 11 2020

Dale C. S. Destin|

The hurricane season was certainly not over in October. There was a record-tying number of major hurricanes – two, Delta and Epsilon; this represents over 665 percent of average (normal). The number of named storms – five, was 250 percent of average. Further, the number of hurricanes – four, was over 360 percent of average.

October Not Over 2020 Summary. Note, although Eta became a storm in November it is credited to October to which it owes its origin, according to the international standard

October 2020 is only the fifth October on record with two major hurricanes. The last time there were two major hurricanes in October was 2005. The month averages a major hurricane once every three to four years. Previous years with two major hurricanes are 2005, 2001, 1950 and 1894.

It was a very active October. The metric that speaks more completely to the activity of a month or a hurricane season is called the accumulated cyclone energy (ACE) index. Normally, the month produces an ACE index of 14.5 – that was more than doubled for this October – 39.2. Compared with the activity for September, although it was a record-setting month regarding named storms, the ACE index of 63 was only 1.23 the average – 51.4. Hence, October was more active relative to itself than September was.

Using the ACE index metric, this October was more active that 28 previous full hurricane seasons of 169, including the 2013 season, which had 14 named storms but an ACE of 36. Also, the two major hurricanes during the month were more than or equal to 125 full seasons. We would have also seen more or the same number of hurricanes than 71 full seasons, including 2015.

Every named storm in October was earlier than those with the same names that formed during October of the 2005 hurricane season, which is the only other season with more than 20 named storms, on record. The records were broken by as many as 41 days. This may be an omen for this season setting a record for the highest number of named storms.

Thankfully, none of these storms threatened Antigua and Barbuda and the rest of the Eastern Caribbean. The most we got were moderate to large swells from Epsilon along with minimal showers from a few very weak feeder bands. The rest of the Caribbean Islands fared well also with none experiencing storm or hurricane conditions. Delta was a relatively close call for Jamaica, the Cayman Islands and Cuba.

We are through the season, except for one more month, officially – November. Thus far, there have been 28 named storms – the most through October and tied with 2005 for the most on record, for a season. The 2005 record is now expected to be broken. There have also been 11 hurricanes of which 4 were major hurricanes – Category 3 or over.

2020 Atlantic hurricane season summary map.png

Recall that an average season produces 12 named storms, 6 hurricanes and 3 major hurricanes. Thus, this season has produced, thus far, 233 percent of average number of named storms, 183 percent of average number of hurricanes and 133 percent average number of major hurricanes.

Notwithstanding the record number of named storms, the season is very far from being a record active one. Recall that the activity of a season is based on the ACE index. The ACE index, thus far for 2020, is 143.9; this is only 136 percent of the average – 105.5.

This season is not even ranked in the top 20 with respect to ACE. It is currently at 27th and is unlikely to reach the top 10. The ACE index for a season is also a measure of the potential destructiveness of the collective named storms. This means that although 2020 has produced a record number of storms, there are several seasons that were potentially more destructive, including the 2017 season with and ACE index of 223.

Top 20 Most Active Atlantic Hurricane Season. TS – Tropical Storms; HU – Hurricanes; MH – Major Hurricanes. Credit Wikipedia.

The most active season on record, using the ACE index metric, remains 1933, with an index of 259, produced by “just” 20 named storms. This is nine more ACE than the 2005 season, which had eight (40 percent) more named storms.  

Delta – 5 to 11 October, became the record-tying fourth named storm of 2020 to strike Louisiana, as well as the record-breaking 10th named storm to strike the United States. It was a very destructive Category 4 hurricane with 1-minute peak sustained winds of 230 km/h (145 mph). It caused, at least, US$2 billion in damage and killed 6 people. It also affected Jamaica, the Cayman Islands, The Yucatán Peninsula, the Gulf Coast, Southeastern and Northeastern United States.  

Hurricane Delta, Across the Western Caribbean Sea – Oct 6, 2020

Epsilon – 19 to 26 October, impacted Bermuda minimally, passing about 190 to its east. It had peak sustained winds of 185 km/h (115 mph), making it a Category 3 hurricane. Exact damage to date is unknown but it generated moderate to large swells across most Atlantic coastlines of the Caribbean, the Bahamas, the United States and Canada.

Hurricane Epsilon, Passing Northeast of Bermuda, Oct 23, 2020

Zeta – 24 to 30 October, became the record-tying sixth hurricane to make landfall on the United states in one year. It was also the record fifth named storm to make landfall on Louisiana in one year. Zeta had peak 1-minute sustained winds of 175 km/h (110 mph) and caused eight fatalities and over US$13.7 million in damage across Jamaica alone. It also impacted the Cayman Islands, Central America, the Yucatán Peninsula and the Mid-Atlantic United States.  

Hurricane Zeta Across the Western Caribbean Sea – Oct 26, 2020

Eta – 31 October to present, became the record-tying 28th named storm for the year, placing 2020 level with 2005 for highest number of named storms. Eta is currently a Category 1 hurricane with the potential to reach Category 3 intensity. It is an extreme threat to Nicaragua and Honduras with the potential to cause Catastrophic damage.

Hurricane Eta Across the Western Caribbean Seas – Nov 2, 2020

The month also produced Tropical Storm Gamma – 2 to 6 October. Gamma made landfall on the Yucatán Peninsula with peak 1-minute sustained winds of 110 km/h (70 mph), killing 7 with the damage amount presently unknown.  

Please continue to follow me for more on the hurricane season and all things weather and climate via TwitterFacebook and Instagram. Also, share this blog, if you found it useful.

%d bloggers like this: