[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU MAR 12 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 6N9W CROSSING THE EQUATOR NEAR
23W TO 4S30W AND INTO NE BRAZIL NEAR 6S35W. SCATTERED MODERATE
ISOLATED STRONG CONVECTION IS FROM 3N-6N BETWEEN 10W-15W.
ISOLATED MODERATE CONVECTION IS S OF 2N BETWEEN 20W-24W.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONTAL BOUNDARY EXTENDS ACROSS SRN GEORGIA AND
ENTERS THE GULF OF MEXICO NEAR PANAMA CITY FLORIDA. THE FRONT
CONTINUES THROUGH THE MISSISSIPPI RIVER DELTA REGION TO 29N93W
WHERE IT TRANSITIONS INTO A SLOWLY EWD MOVING COLD FRONT ALONG
28N96W 24N97W AND INLAND OVER MEXICO NEAR 23N98W. DOPPLER RADAR
AND VISIBLE SATELLITE DATA INDICATE SCATTERED SHOWERS PRIMARILY
NORTH OF THE FRONT WEST OF 88W. THE UPPER SHORTWAVE TROUGH
SUPPORTING THE BOUNDARY CONTINUES TO MOVE OFF TO THE NE AS AN
UPPER RIDGE IS LOCATED ACROSS THE W ATLC AND FLORIDA PENINSULA.
GLOBAL MODELS FORECAST ANOTHER SHORTWAVE TROUGH TO COME INTO
PHASE WITH THE FRONT SAT WHICH MAY PROVIDE SOME SUPPORT TO MAKE
IT PROGRESSIVE ONCE AGAIN. ELSEWHERE...THE PREVIOUSLY MENTIONED
DEEP LAYERED RIDGING CENTERED E OF THE AREA REMAINS IN CONTROL
ACROSS THE ERN AND SW GULF THIS AFTERNOON PROVIDING FAIR
CONDITIONS AND LIGHT TO MODERATE E-SE SFC WINDS.

CARIBBEAN SEA...
HIGH PRESSURE CENTERED A COUPLE HUNDRED NM W OF BERMUDA IS
GENERATING MODERATE TO FRESH TRADES ACROSS THE CARIBBEAN.
SURFACE OBS AND AN EARLIER QSCAT PASS SUGGEST THAT THE STRONGEST
FLOW...20-25 KT...IS OVER THE S/CENTRAL CARIBBEAN WITH WINDS
REACHING 30 KT NEAR THE COAST OF COLOMBIA BETWEEN 73W-77W.
TYPICAL PATCHES OF LOW-LEVEL CLOUDS AND ISOLATED SHOWERS ARE
SCATTERED ACROSS THE BASIN. MOST NOTABLY NE WINDS ARE USHERING
IN THESE SHOWERS ACROSS THE NE CARIBBEAN N OF 15N E OF 70W.
IN THE MID AND UPPER LEVELS...STRONG SUBSIDENCE PREVAILS OVER
THE ENTIRE BASIN WITH A LARGE CONFLUENCE ZONE OVER THE ERN
CARIBBEAN. LITTLE CHANGE IN THE LARGE SCALE WEATHER PATTERN IS
ANTICIPATED OVER THE NEXT DAY OR SO.

ATLANTIC OCEAN...
AN OCCLUDED 1000 MB LOW PRESSURE SYSTEM IS CENTERED NEAR 31N45W
AND CONTINUES TO MOVE ESE AT 15 KT. THE ATTENDANT WEAKENING COLD
FRONT EXTENDS FROM THE TRIPLE POINT NEAR 34N40W SWD ALONG 30N40W
20N48W THEN AS A SURFACE TROUGH TO 17N60W. SCATTERED SHOWERS ARE
WITHIN 60 NM E OF THE FRONT N OF 24N. A SECONDARY SURFACE TROUGH
IS ANALYZED FROM JUST E OF THE LOW CENTER NEAR 30N43W SW TO
21N51W. INSTABILITY NEAR THE LOW CENTER AND ALONG THE TROUGH IS
TRIGGERING SCATTERED SHOWERS WITHIN 30 NM EITHER SIDE OF THE
TROUGH. WINDS TO GALE FORCE ARE BLOWING WITHIN THE COLD SECTOR
DUE TO THE TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND A SURFACE
RIDGE OVER THE W ATLC. GLOBAL MODELS SHOW THIS FEATURE TRACKING
ESE AND WEAKENING OVER THE NEXT COUPLE OF DAYS AS IT CUTS OFF
FROM THE PROGRESSIVE FLOW. IN THE DEEP TROPICS...STRONG WLY FLOW
ALOFT ON THE N SIDE OF A BROAD UPPER-LEVEL RIDGE IS TRANSPORTING
MID-HIGH LEVEL CLOUDINESS FROM THE LESSER ANTILLES TO W AFRICA.
DIFFLUENCE ALOFT ON THE S SIDE OF THIS RIDGE IS ENHANCING
CONVECTION WITHIN THE ITCZ E OF 20W.

$$
HUFFMAN




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