WORLD METEOROLOGICAL ORGANIZATION
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RAIV/HC-XXXIV/Doc. 4.2(4)
(31.I.2012)
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RA IV HURRICANE COMMITTEE
THIRTY-FOURTH SESSION
ITEM: 4.2
PONTE VEDRA BEACH, FL, USA
11 TO 15 APRIL 2012
Original: ENGLISH
REVIEW OF THE PAST HURRICANE SEASON
Reports of hurricanes, tropical storms,
tropical disturbances and related flooding during 2011
(Submitted by Barbados)
Although rainfall levels in 2011 fell short of those of the previous year by about 8
inches, the total reached 66.18 inches which represents about 18 inches above the normal
and the fifth highest rainfall year total between 1942 and the present. With the exception of
October, each month’s rainfall total was also well above the long-term average. The year
may also be classified as one in which we had a ‘very wet’ dry season: during the period
January to May, the cumulative rainfall was 19.97” which was almost twice the cumulative
average of 10.15” for this period with April alone producing some 5.64 inches or twice the
30-year average for that month. On average, there were four to five more rain days
(>/=1mm) per month than the long-term average.
A number of trough features which were anchored in the vicinity of the island
chain during April and May in particular, had the effect of weakening the Atlantic high
pressure ridge in the first instance. This weakening of the ridge and the resulting light wind
regime along with strong day-time heating and the northward modulation of I.T.C.Z moisture
contributed significantly to the rainfall events which occurred. Some of these resulted in
severe flooding across the island.
“Katia”, “Maria”, “Ophelia” and “Phillipe” were four other systems which formed in
the far eastern Atlantic but maintained a track well to the north-east of the island chain. The
indirect impact on the eastern Caribbean was again a slackening of the pressure gradient
and the resulting localized shower activity which resulted in some flood events across
Barbados.
Two of the four systems which developed over the tropical Atlantic during
September, namely Hurricane Katia and Hurricane Maria had a direct impact on Barbados'
rainfall during the month.
Although Hurricane Katia passed well to the north of the island chain, the
resulting light wind- regime contributed to some localized shower activity across Barbados
RAIV/HC-XXXIV/Doc. 4.2(4), p. 2
between September 1st and 4th, with this activity affecting mostly central and western
districts.
Showers were more widespread with the passage of Maria which was a tropical
storm when it passed just about 120 miles or so to the north of Barbados between
September 9th and 10th.
On the 9th September feeder bands associated with tropical storm “Maria” started
to affect Barbados during the early hours of the morning. Pockets of moderate to heavy
showers, scattered thunderstorms spread across the island during the day. Northern,
eastern and southern districts across the island experienced some flash-flooding. The
Grantley Adams International Airport recorded 68mm of rainfall up to 8 a.m. Most of this
precipitation occurred between the hours of 5.30 and 6.30 a.m. Golden Ridge, in the center
of the island, recorded 19mm during the same period.
On the 10th September – Overcast conditions, heavy showers and thunderstorms
as another feeder band passed across the island. 10.3mm of rainfall was measured at
Grantley Adams, while 4.9mm was recorded at Golden Ridge up to 2 p.m. that afternoon.
By 5 p.m. on the 10th September “Maria” was located near 17.9°N, 62.4°W,
50mls ESE of St. Martin. The system appeared weak and disorganized and hence all
watches and warning were discontinued for the Lesser Antilles.
The Barbados Meteorological office issued a total of ten special weather
Bulletins between the 8th and 9th of September on this system.
A special weather bulletin was also issued from the meteorological office on the
21st September as Barbados monitored tropical storm ‘Ophelia’. However this storm did not
have an impact on Barbados
Another significant rain-spell occurred between September 14th and 18th as a
trough system induced the northward modulation of the ITCZ across the chain. Rainfall in
excess of 80mm was recorded at the three (3) previously mentioned rainfall stations.
Intermittent showers continued to affect the island up to the 24th of September,
but a dry spell ensued thereafter as a weak low to mid-level ridge pattern dominated
conditions over the southern Lesser Antilles. This was in direct contrast to the weather
conditions which obtained over the remainder of the island chain due to a feeder band from
Hurricane Ophelia inducing a westerly wind-flow and some organized convection over the
northern Lesser Antilles.
Total rainfall at the GAIA for September was 191.8mm which is slightly above the
long term average of 176.8mm but well below the September 2010 total of 303.8mm. Golden
Ridge and Lears observed totals of 253.2mm and 264.2mm respectively.
RAIV/HC-XXXIV/Doc. 4.2(4), p. 3
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