[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181157
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 18 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF SENEGAL
NEAR 18N16W TO A 1010 MB LOW NEAR 12N24W TO A SECOND 1009 MB LOW
NEAR 11N35W ENDING NEAR 9N45W WHERE THE ITCZ CONTINUES TO 4N58W.
A CLUSTER OF STRONG CONVECTION IS JUST OFF THE AFRICAN COAST
FROM 12N-14N BETWEEN 17W-19W. SIMILAR ACTIVITY IS NEAR THE
EASTWARD MOST LOW FROM 12N-14N BETWEEN 22W-26W. SCATTERED
MODERATE/STRONG CONVECTION IS NEAR THE WESTWARD MOST LOW FROM
6N-13N BETWEEN 33W-40W...AND FROM 4N-10N BETWEEN 40W-45W.

...DISCUSSION...

GULF OF MEXICO...
MOSTLY FAIR WEATHER IS ACROSS THE GULF OF MEXICO THIS MORNING
WITH LIGHT ANTI-CYCLONIC SURFACE FLOW AROUND HIGH PRESSURE
CENTERED OVER NEW ENGLAND. ALOFT...UPPER RIDGING DOMINATES
EXTENDING FROM CENTRAL MEXICO TO N FLORIDA. DRY AND SUBSIDENT
AIR ACCOMPANIES THE RIDGE WHICH IS HELPING MAINTAIN THE PLEASANT
CONDITIONS. HOWEVER...SOME MOISTURE FROM THE E PACIFIC IS BEING
WRAPPED AROUND THE WRN SIDE OF THE UPPER RIDGE WHICH HAS MADE
ITS WAY TO SRN TEXAS AND THE NW GULF WHERE AN AREA OF
SHOWERS/THUNDERSTORMS HAS POPPED UP ALONG THE TEXAS COAST AND
WITHIN 90 NM OFFSHORE. DOPPLER RADAR ALSO INDICATES SOME
ISOLATED SHOWERS IN THE SE GULF OFF THE COAST OF SW
FLORIDA...AND IN THE FAR SRN BAY OF CAMPECHE. EXPECT LITTLE
CHANGE OVER THE NEXT 24 HOURS BESIDES A SLIGHT INCREASE IN THE
CHANCE OF RAIN OVER THE SE GULF AS AN AREA OF MOISTURE TO THE E
ADVECTS WWD.

CARIBBEAN SEA...
DEEP LAYER MOISTURE CONTINUES TO IMPACT MUCH OF THE CARIBBEAN
WITH THE FIRST AREA SITTING OVER THE WRN HALF OF THE BASIN W OF
79W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 22N
BETWEEN 79W-86W. A SURFACE TROUGH EXTENDS JUST E OF THE YUCATAN
INTO NRN HONDURAS SUPPORTING A FEW ISOLATED SHOWERS IN ITS
VICINITY. STRONG SHOWERS/THUNDERSTORMS ARE ALSO OVER NRN
COLOMBIA AND E OF COSTA RICA/NICARAGUA INFLUENCED BY THE MONSOON
TROUGH THAT EXTENDS ACROSS PANAMA TO NRN COLOMBIA. AN UPPER
LEVEL LOW IS DOMINATING THE ERN CARIBBEAN CENTERED OVER ERN
PUERTO RICO. DRY AIR IS BEING WRAPPED AROUND THE WRN SIDE OF THE
UPPER LOW KEEPING THE CENTRAL CARIBBEAN UNDER MOSTLY FAIR
CONDITIONS EXCEPT FOR A CLUSTER OF SHOWERS/THUNDERSTORMS S OF
HAITI. CLUSTERS HAVE ALSO POPPED UP OVER NRN VENEZUELA AND OVER
THE NRN WINDWARD ISLANDS NEAR A SURFACE TROUGH EXTENDING FROM
THE VIRGIN ISLANDS TO NRN VENEZUELA NEAR 12N66W. MOST OF THE
REMAINING SHOWER/THUNDERSTORM ACTIVITY ASSOCIATED WITH THE UPPER
LOW IS N AND E OF THE ISLANDS. EXPECT MOIST CONDITIONS TO REMAIN
OVER THE WRN CARIBBEAN AND CENTRAL AMERICA. MOISTURE IN THE ERN
CARIBBEAN IS EXPECTED TO DRIFT WWD WHICH SHOULD INCREASE THE
SHOWER ACTIVITY OVER THAT PORTION OF THE BASIN.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH OVER THE ERN SEABOARD IS SUPPORTING A
STATIONARY FRONT WHICH JUST CLIPS THE AREA AND EXTENDS TO NE
FLORIDA NEAR 29N81W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE WITHIN 60 NM SE OF THE FRONT. A SURFACE TROUGH CONTINUES TO
SIT OVER THE CENTRAL BAHAMAS FROM 28N75W TO 23N77W. MOST OF THE
SHOWER ACTIVITY NEAR THE TROUGH HAS DIED OUT WITH ONLY ISOLATED
SHOWERS ALONG THE AXIS. AN UPPER LEVEL LOW SPINNING OVER ERN
PUERTO RICO IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF
28N BETWEEN 60W-65W...AND S OF 22N BETWEEN 65W-70W. SIMILAR
ACTIVITY IS E OF THE LESSER ANTILLES FROM 15N-20N BETWEEN
60W-63W IN THE AREA OF DIFFLUENCE ALOFT AROUND THE ERN SIDE OF
THE UPPER LOW/TROUGH. FARTHER E...A SURFACE TROUGH IS ANALYZED
IN THE TROPICAL ATLC ALONG 43W FROM 14N-20N. A CLUSTER OF STRONG
SHOWERS/THUNDERSTORMS IS OVER THE TROUGH AXIS FROM 16N-19N
BETWEEN 40W-44W. A LOW PRESSURE SYSTEM IS TO THE N SUPPORTED BY
AN UPPER LEVEL LOW NEAR 32N39W. A SURFACE TROUGH ASSOCIATED WITH
THIS SYSTEM EXTENDS FROM 32N37W TO 27N47W. SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ARE N OF 27N BETWEEN 34W-40W.
SURFACE RIDGING COVERS THE FAR ERN ATLC ANCHORED BY A 1030 MB
HIGH NE OF THE AZORES ISLANDS. THE HIGH IS SUPPORTED BY AN UPPER
LEVEL RIDGE CENTERED NEAR 44N22W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON




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