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REVIEW OF THE PAST HURRICANE SEASON

WORLD METEOROLOGICAL ORGANIZATION
________________
RA IV HURRICANE COMMITTEE
THIRTY-THIRD SESSION
GRAND CAYMAN, CAYMAN ISLANDS
8 TO 12 MARCH 2011

RA IV/HC-XXXIII/Doc. 4.2(9)

(02.III.2011)

______
ITEM 4.2

Original: ENGLISH

REVIEW OF THE PAST HURRICANE SEASON

REPORTs OF hurRIcanes, tropical STORMs,
tropical DISTURBANCes AND

FLOODING ASSOCIATED WITH THESE EVENTS DURING 2010

(Submitted by Barbados)

Even before the official Hurricane Season started, Barbados was experiencing above average rainfall. A look at the rainfall for Barbados, we see that from April the 2010 totals for each month during this period were above the 30yr average. A total of 18.0mm in October represents the highest total for October on record since 1942.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct
2010	25.1	3.6	18.8	85.9	122.2	181.1	303.3	178.3	316.9	457.2
30 YR ave	56.4	40.4	43,4	58.4	58.9	86.1	112.8	148.8	145.0	170.0

During the period in review, there were many rainfall events which accounted for the surplus in rainfall. Most of these events necessitated the issuance of FLOOD WATCHES and WARNINGS.

On June 09^th a passing tropical wave generated heavy showers across the island, thus prompting the issuance of a special weather statement. Showers started during the early morning and continued throughout the day. Total rainfall measured between 6.00am and 6.00 pm was 38.5 mm .Wind gusts of up to 78 KMH at 1228Z and 89 KMH at 1645Z were recorded.
On the 09^th July another Tropical wave interacted with an upper level trough and produced some adverse weather across the island. The department issued a Flood Watch at 12:00 NOON and was terminated at 6:00pm. The 24 hr rainfall total for this event was 23.1 mm and there was a wind gust of 68 KMH was recorded at 1955Z.

On the 29^th July another Tropical wave in combination with the ITCZ also produced some adverse weather across the island. The department issued a Flood Watch at 9:00 am and was terminated at 4:00pm. The 24 hr rainfall total for this event was 23.0 mm and there was a wind gust of 60 KMH recorded at 1647Z and again at 1951Z.

On the 8thSeptember, a Special Weather Bulletin was issued at 4:00 pm after a low level trough moved across the southern part of the Eastern Caribbean. This feature triggered some pockets of moderate to heavy showers. These showers continued during the night and into the early morning of the 9^th. A Flood Warning was issued at 8:30 am on the 9^th and was discontinued at 4:00pm the same day. This feature yielded a total of 158.2mm over the two day period. There was also a wind gust of 50 KMH.
Another special Bulletin was issued at 4:00 pm on the 20^th September as adverse weather associated with a low level trough/T wave affected the island. As this weather persisted, a Flood Warning was issued at 9:15 am on the 21^st. Initially instituted until 4:00pm, the warning was extended until 6:00am on the 22^nd September. . Between 6 pm on the 19^th and 6 pm on the 20^th, a rainfall total of 21.0 mm was recorded. While, the period, 6 pm on the 20^th to 6 pm on the 21st yielded 59.6 mm. For a total of 80.6mm.
As the trend continued, another, a Special Weather Bulletin was issued at 4:30 pm on the 30th September as the combination of a low level trough and a T/wave spread some moderate to heavy showers across the island during the day. On the 1^st November, localized convection developed over the central, western and north western sections of Barbados. A Flash Flood warning was issued at 3:15 pm and terminated at 6:30pm.
The unsettled conditions associated with a broad area of low pressure over the Eastern Caribbean dumped some heavy showers over Barbados on the 3^rd October. A Flood Warning was instituted at 10.00am, initially until 6.00 pm, but was extended until 6:00am on the 4^th October. The Warning was further extended until 4:00pm as moderate to heavy showers spread across the island. Between 6 p.m on the 2nd and 6 pm on the 3rd, a rainfall total of 18.8 mm was recorded. While, the period, 6 pm on the 3rd to 6 pm on the 4th yielded 65.2 mm.
TOMAS
Introduction
“Tomas” was a late season storm which exited the African coast and soon became embedded deep within the I.T.C.Z. It eventually moved west-northwards across the Windward Islands while passing very close to Barbados as a strong tropical storm during the early morning hours of Saturday October 30^th “Tomas” reached Category 2 hurricane status (on the Saffir-Simpson Scale) as it moved across the central Lesser Antilles later that same day.
Synopsis
This system emerged off the coast of Africa as a tropical wave sometime on October 25^th, 2010 with axis along 2°N 31°W to 10°N 24°W. It traveled westward near 17mph on the extreme southern periphery of a deep-layered high pressure ridge. The strength of this ridge forced the wave deep into the I.T.C.Z and by October 26^th, the wave had progressed to near 36°W with an increase in forward speed of between 17 and 22mph. It was embedded in a abroad mid-level cyclonic rotation and the Barbados Meteorological Office was forecasting this system to bring increased shower activity to the island by the upcoming week-end.

The wave reached 44°W by October 27^th and was expected to come under the influence of a trough system as it approached the Lesser Antilles Meanwhile, the surface ridge behind the wave continued to strengthen and this aided in increasing moisture levels in the vicinity of the tropical wave

By October 28^th, the National Hurricane Center in Miami was categorizing the system as a strong tropical wave which was now supporting a 1006mb area of low pressure near 9°N 55°W or a few hundred miles east of the Guyanas.
During the early morning hours of October 29^th, the system which now had an 80% chance of becoming a tropical cyclone, started to move rapidly west-northwest at near 20 mph. This prompted the Barbados Meteorological Office to issue a Special Weather Bulletin at 10:00 a.m. urging residents to monitor the progress of this system since all indications were pointing to further development of this vigorous wave.
On making contact with the National Hurricane Center in Miami at about 2:30 p.m., it was confirmed that a Hurricane Hunter was on its way into the system. Subsequent reports from the aircraft established that it had become the 19^th named storm of the Atlantic Hurricane Season and so “Tomas” was born. As a consequence, the Barbados Met Office released another Bulletin at 3:00p.m alerting the public that it would start to issue Advisories on “Tomas at 5:00p.m
The Barbados Meteorological Office issued the first tropical storm warnings on “Tomas” at 5:00p.m, Friday, October 29^th, 2010 for Barbados and St. Vincent and the Grenadines. At this time the center of “Tomas” was located near 11.1°N 57.5°W or about. 200 miles south-east of Barbados; movement was towards the west-northwest near 17 mph, with maximum sustained winds near 40mph and a minimum central pressure of 998mb. On this track, it was expected to pass approximately 74miles to the south of Barbados during the next 12 to 18 hours
A Special Advisory from the National Hurricane Center was issued at 8.00p.m on October 29^th, indicated that a Reconnaissance aircraft found that winds in “Tomas” had increased to near 60mph. At this time, the storm was located near 11.6°N 57.6°W or about 170 miles south-east of Barbados. It was tracking west-northwest at 15 mph. Further strengthening was anticipated with “Tomas” forecasted to reach hurricane status by late Saturday.
In the 11:00p.m Advisory, “Tomas” had progressed to near 12.2°N 58.4°W or about 100 miles south-east of Barbados Maximum sustained winds had now increased to 65 miles as the system maintained its west-northwestward track. Barbados and St. Vincent and the Grenadines were now placed under a hurricane warning.
Meanwhile, the leading edge of the storm brought squally weather to Barbados with intermittent moderate to heavy showers and occasional gusty winds. Wind-speeds which ranged between 12 and 17mph during the early part of the day on October 29, were now ranging between 35 and 40 mph as the center of “Tomas” moved ever closer to the island..
At 5:00 a.m., Saturday, October 30^th, 2010, the center of Tropical Storm “Tomas” was located near 12.9°N 59.5°W or about 20 miles to the south of Barbados. Weather conditions continued to deteriorate very rapidly with the increasing proximity of “Tomas” to Barbados. Radar imagery and other analyses showed that the center of “Tomas eventually passed just 10 miles to the south of Barbados and this was immediately followed by a shift in wind-direction. Storm-force winds which were generally north-easterly with the approaching “Tomas” had now veered to the south-east and was accompanied by heavy and persistent rains across the island. This activity continued throughout the day and into the night resulting in wide-spread flooding, damage to numerous properties, downed power lines and up-rooted trees here in Barbados.

Meanwhile, the center of “Tomas” was approaching the Windwards and by 8:00 a.m on Saturday, October 30^th was located near 13.1°N 60.1°N or about 70 miles south-east of St. Lucia. Thus, the Barbados Meteorological Office down-graded the Hurricane Warning for Barbados to a tropical Storm Warning at 11:00 a.m. While the threat to Barbados was decreasing, it was increasing for some of our neighbours in the Lesser Antilles since “Tomas” had now strengthened to a Category 1 system on the Saffir-Simpson Scale near location 13.3°N 60.7°W. By 5:00p.m the Storm-Warning was also discontinued for Barbados but heavy rains persisted across the island overnight and into Sunday, October 31^st.

At 6:00p.m (October 30^th) based on a report from St. Lucia, the Hurricane Center in Miami indicated that “Tomas had further strengthened to a Category 2 hurricane with maximum sustained winds of 90mph. The hurricane was then near 13.5° 61.6°W or about 75 miles west-southwest of St. Lucia. It did untold damage to St. Lucia and St. Vincent as it made it way into the Caribbean Sea.

Radar Imagery of T.S “Tomas” from Radar at Castle Grant in St. Joseph

“Tomas” approaching Barbados at about 5:00p.m on Friday, October 29^th 2010

Satellite image (above) on October 30^th /10:15a.m

“Tomas” west of Barbados at 09:30 a.m on Saturday, October 30^th, 2010

Please note the orange/red band which signifies the greatest rainfall intensity which was headed towards St. Lucia.

Track of “Tomas” compliments of Wikipedia

Meteorological Statistics observed at Grantley Adams’ International Airport
Maximum sustained wind: 040/53mph at 03:55a.m on October 30th
Maximum wind-gust: 040/105mph at 04:45a.m on October 30^th
Lowest Pressure 983.0mb at 05:00a.m on October 30^th. This represented a 24 pressure drop of 16.2MB
Total Rainfall: 293.5mm (Oct 29 to 30)
A preliminary assessment indicates that about 1200 houses were damaged as a result of the storm. Many areas in the island were without power and water. However, Barbados is still in the recovery stage. It was estimated that it will cost about $37 million dollars to repair and replace the damaged housing stock.
CHALLENGES
The Barbados Meteorological Services did encounter some challenges during the passage of the storm. W e lost Radar feed to the office and the satellite dish was detached from its main support. However, the office had electrical power and internet access throughout the whole ordeal. Hence, our delivery of service to the people of Barbados was not adversely affected.

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