Pre-hurricane Season Summary – 2020

1 06 2020

Dale C. S. Destin|

It is June too soon – the Atlantic hurricane season officially starts today. However, it seems like no one remembered to remind the “storm gods” of this fact. Already, we have seen two named storms – Arthur and Bertha, resulting in a very active pre-hurricane season 2020. Only twice on record before, dating back to 1842, that May has produced two named storms – 2012 and 1887.

Arthur formed on May 16, just north of the northern Bahamas. It moved north to near the Outer Banks of North Carolina, then out over the Atlantic and lost its tropical characteristics. It caused tropical storm force winds across a small portion of North Carolina and reached peak sustained winds of 97 kph (60 mph).

Tracks of Tropical Storms Arthur (right) and Bertha (left)

Bertha was a bit of a surprise storm. Formation was not expected due to strong upper-level wind shear. On the morning of 12:50 am, May 27, it was given a 30% chance of formation and by 8:30 am, it was declared a tropical storm with sustained winds of 72 kph (45 mph). It eventually reached peak sustained wind speed of 80 kph (50 mph), before dissipating on May 28. The system caused one death.

In terms of pre-season storms – storms forming between March and May, there have been only four occasions when there were two named storms – 2012, 1951, 1908 and 1887. Of course, I am mindful that before the satellite era – pre mid-1960s, a number of short-lived storms went undetected, resulting in gaps in the record.

On average, there is a storm in May once every 7 to 8 years, based on record for the period 1981-2010, whereas, there is a preseason storm once every 5 years. Most pre-season storms form in May – about 85%, 9% in April and 6% in March.

Preseason storms say nothing about the season they precede, in terms of how active or inactive they will be. However, this season is expected to be active and likely to be hyperactive – well above normal.

We all need to be prepared for the hurricane season regardless of the number of storms and hurricanes being forecast, as it only takes one hurricane to ruin our year or life.

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Tropical Storms in May Mean Nothing

15 05 2020

Dale C. S. Destin |

The first tropical or subtropical storm for the pre-hurricane season is about to form in the Bahamas. Some think that this is a harbinger (sign) for the upcoming hurricane season – June 1 to November 30, but is it?

Tropical disturbance AL90 across the Bahamas with an 80% chance of becoming Tropical Storm Arthur within 48 hours.

To the “naked eyes”, it is understood why some may take a storm forming in May as a sign of bad news for the upcoming hurricane season; however, the numbers don’t agree.

The numbers say that it usually means nothing in terms of the overall activity of the upcoming season. According to NOAA, there have been 29 named storms in May, spread over 27 seasons from 1842 to 2019. Of the 27 seasons, using NOAA’s definitions, nine were above normal (active or hyperactive), 11 were near normal and 7 were below normal (inactive or quiet).

Overall, most seasons with a storm in May, are near normal – 11 times of 27 – 41%. However, from a statistical standpoint, there are no significant differences between above, near or below normal seasons, when there is a storm in May. Hence, a tropical storm forming in the month has no bearing on the activity of the upcoming hurricane season.

Of the 27 seasons with May storms, 9 or 33% was active or above normal; 11 or 41% was normal and 7 or 26% was quiet or inactive

Notwithstanding the above, this hurricane season is expected to be above normal or likely hyperactive – well above normal, see my latest forecast. Clearly, this has nothing to do with the expected formation of Tropical Storm Arthur over the Bahamas.

Further on the tropical cyclone climatology on May, of the 29 named storms to have formed in the month, 5 became hurricanes with none ever becoming a major hurricane. The strongest tropical cyclone of the month occurred in 1863 – a Category 2 unnamed cyclone.

The only Cat 2 May Hurricane on record – Unnamed Hurricane – 1863

On average, there is one storm forming in May every 7-8 years. However, there have been a storm in May of the last 2 years and 6 in the last 10 years. Twice, two storms formed in May of the same season – 2012 and 1887, the most of any. So much for averages, right!

The Eastern Caribbean has never been impacted by a tropical cyclone in May, “knock wood”, based on available record dating back to 1842.

Storms forming in this part of the region in May are not unusual. Of the 29 May storms, 28% have formed or traverse within 300 miles of Nassau, Bahamas.

Unfortunately for the Bahamas, this year they are still recovering from Super Category 5 Hurricane Dorian of September 2019, which levelled much of Northwest Bahamas. You may say that they can’t “catch a break”, as they are about to deal with potentially strong storm-force winds and flooding rainfall, in addition to dealing with the COVID-19 Pandemic.

Possible tracks of what is expected to become Tropical Storm Arthur in 48 hours

May storms mean nothing in terms of the overall activity of the hurricane season; however, they mean a lot with respect to where they impact. Let us be prepared regardless of omens or forecasts for the season – it only takes one hurricane to ruin your year or life.

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Record Number of Storms for May 2012…Could Antigua be affected?

29 05 2012

By Dale C. S. Destin

It seems like someone has forgotten to tell the Atlantic the forecast. All forecasts to date are indicating a near normal Atlantic Hurricane Season. The Atlantic Hurricane Season runs from June 1 to November 30. Notwithstanding, the second pre-season storm – Beryl – for May and the year has formed (May 26 to present). This tied with May of 1887 for the most named storms (2) in May for a given year based on record, which goes back to 1851. The other pre-season storm was Alberto – May 19-22. Although Beryl poses no threat to Antigua, many years ago two pre-season hurricanes affected the area.

All forecasts to date for the Atlantic Hurricane season call for 7 to 15 named storms – a near normal season. The near normal forecasts are due primarily to near normal sea surface temperatures across the Equatorial Tropical Pacific Ocean and normal to below normal sea surface temperatures across the North Atlantic Ocean, particularly the Tropical North Atlantic. However, although there have never been two storms in the same year in the month of May, past pre-season storms have not portend anything about the activity of the upcoming season. Of the past five seasons with pre-season storms or hurricanes, two were above normal, two were near normal and one was below normal. Of course we have never seen two tropical storms in may; let’s see how the year turns out.

Although pre-season storms do not happen often, they are not unusual in the Atlantic Basin (Atlantic Ocean, Caribbean Seas and the Gulf of Mexico). The currently define Atlantic Hurricane Season, June 1 – Nov 30, accounts for about 97% of all Atlantic tropical cyclones (storms and hurricanes); of the remaining 3%, 48% occurs in May and the other months account for the rest.  Further, of the pre-season tropical cyclones, 80% occurs in May (See table 1). Off season tropical cyclones are most likely to occur in the Central to Western Atlantic Ocean and most do not make landfall. Of the tropical cyclones that did strike land, most have affected areas surrounding the Caribbean Sea. Cumulatively, these pre-season cyclones have caused the death of hundreds primarily in Hispaniola and Cuba. The strongest pre-season (and post-season) tropical cyclone was Hurricane Able in May 1951.

Antigua has been struck at least twice by pre-season tropical cyclones. The island was impacted by Hurricane Alice2  January 2 – 3, 1955. The system formed on December 30, 1954 and continued until January 6, 1955; this is the only Hurricane and the first of only two tropical cyclones to span two calendar years; the other tropical cyclone was Tropical Storm Zeta of 2005-2006. Previous to 1955, the island was impacted by (Unnamed) Hurricane One of 1908 March 7 – 8. The system formed on March 6 and dissipated March 9. Both hurricanes passed within 75 statute miles northwest of Antigua and also affected most of the rest of the Northeast Caribbean as the travelled from northeast to southwest. Both also dissipated in the Eastern Caribbean Sea near the islands (See Map 1 and 2)

The record shows that at least one tropical cyclone has occurred in every month of the year. Antigua has been affected by tropical cyclones in seven of twelve months of the year – January, March, July, August, September, October and November. For all of us in this part of the world, a certain level of preparedness is required even outside the hurricane season.

Map 1: Partial Plot of the 1954 Atlantic Hurricane Season. Tropical Cyclone Number 11 is Hurricane Alice2, which affected Antigua and the NE Caribbean in early January 1955.

Map 1: Partial Plot of the 1954 Atlantic Hurricane Season. Tropical Cyclone Number 11 is Hurricane Alice2, which affected Antigua and the NE Caribbean in early January 1955. Adapted from wikipedia.com

Map 2: Partial Plot of the 1908 Atlantic Hurricane Season. Tropical cyclone number one is Hurricane One, which affected the NE Caribbean in March 1908.

Map 2: Partial Plot of the 1908 Atlantic Hurricane Season. Tropical cyclone number one is Hurricane One, which affected the NE Caribbean in March 1908. Adapted from wikipedia.com

Total and Average Number of Tropical Storms by Month
(1851-2011)
Month Tropical Storms Hurricanes Antigua
Tropical Storms Hurricanes
Total Average Total Average Total Average Total Average
JANUARY 2 * 1 * 1 * 1 *
FEBRUARY 1 * 1 * 0 * 0 *
MARCH 1 * 1 * 1 * 1 *
APRIL 1 * 0 * 0 * 0 *
MAY 18 0.1 4 * 0 * 0 *
JUNE 82 0.5 32 0.2 0 * 0 *
JULY 113 0.7 54 0.3 6 * 1 *
AUGUST 362 2.2 230 1.4 36 0.2 18 0.1
SEPTEMBER 556 3.5 384 2.4 47 0.3 23 0.1
OCTOBER 319 2.0 192 1.2 10 0.1 3 *
NOVEMBER 87 0.5 58 0.4 4 * 1 *
DECEMBER 17 0.1 6 * 0 * 0 *
YEAR 1559 9.6 964 6.0 105 0.6 48 0.2
Table 1: *Less than 0.05%. The list excludes subtropical storms. Antigua
Storms and Hurricanes are those that passed within 120 statute of the
island. Data (first 4 columns) from http://www.aoml.noaa.gov








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