[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI FEB 27 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 5N8W CROSSING THE EQUATOR NEAR
16W EXTENDING TO 2S25W EQ40W INTO NE BRAZIL NEAR 2S49W.
SCATTERED MODERATE CONVECTION IS FROM THE EQUATOR TO 5N BETWEEN
43W-50W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THIS
CONVECTIVE ACTIVITY. SCATTERED MODERATE CONVECTION IS ALSO NOTED
ALONG LINE FROM 5N13W TO 4N16W.

...DISCUSSION...

GULF OF MEXICO...
GENERALLY FAIR WEATHER PERSISTS EARLY THIS AFTERNOON ACROSS MUCH
OF THE GULF REGION...WHERE NWLY FLOW ALOFT IS SUPPORTING
ATMOSPHERIC SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS.
HOWEVER...SOME UPPER LEVEL MOISTURE IS STREAMING SOUTHEASTWARD
ACROSS PORTIONS OF THE N AND CENTRAL GULF. THE SUBSIDENCE IS
ALSO BEING SUPPORTED BY A SURFACE RIDGE EXTENDING SWWD FROM THE
W ATLC ACROSS THE E GULF INTO THE YUCATAN PENINSULA. ACROSS
PORTIONS OF THE W GULF...SE TO S SURFACE WINDS OF 20 TO 25 KT
ARE PRESENT AROUND THE SURFACE RIDGE. A DEEP LAYERED TROUGH IS
ACROSS THE CENTRAL AND SOUTHERN PLAINS OF THE CONUS. THE
ATTENDANT STRONG COLD FRONT WILL APPROACH THE TEXAS COAST LATE
TONIGHT AND EXTEND FROM THE FLORIDA PANHANDLE TO NEAR TAMPICO
MEXICO SAT EVENING...AND FROM TAMPA BAY TO THE YUCATAN PENINSULA
EARLY SUN. IN THE WAKE OF THE COLD FRONT...INCREASED NORTHERLY
WINDS ARE FORECAST TO OCCUR OVER THE GULF...WITH GALE CONDITIONS
EXPECTED SATURDAY NIGHT AND SUNDAY OVER PORTIONS OF THE SW GULF.
ALSO...A RELATIVELY COOLER AND DRIER AIR MASS WILL FOLLOW THE
FRONT BRINGING ANOTHER ROUND OF COLDER TEMPERATURES ACROSS SOUTH
FLORIDA...PARTICULARLY MONDAY AND TUESDAY MORNINGS.

CARIBBEAN SEA...
A DEEP LAYERED TROUGH OVER THE CENTRAL ATLC IS ASSOCIATED WITH A
STATIONARY FRONT THAT EXTENDS FROM THE WINDWARD PASSAGE NEAR
29N74W NORTHEASTWARD TO NEAR 30N52W. AT THIS POINT...THE FRONT
CONTINUES AS A COLD FRONT OVER THE CENTRAL ATLC. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF THIS FRONT. GENERALLY FAIR WEATHER CONDITIONS ARE
OCCURRING ACROSS MUCH OF THE CARIBBEAN REGION...WHERE CONFLUENCE
IN W-SW FLOW ALOFT IS PRESENT. AS USUAL...SHALLOW MOISTURE
EMBEDDED IN THE TRADE WIND FLOW IS MOVING ACROSS THE BASIN
PRODUCING ISOLATED TO SCATTERED PASSING SHOWERS. THE GREATEST
CONCENTRATION OF THESE SHOWERS IS NOTED JUST N OF THE ABC
ISLANDS. ALSO...SOME HIGH CLOUDS ARE OBSERVED ACROSS THE REGION
ASSOCIATED WITH A JET STREAM BRANCH WITH CORE WINDS OF 70-90 KT
WHICH EXTENDS FROM JAMAICA AND THE WINDWARD PASSAGE ENE OVER THE
WEST-CENTRAL ATLC.

ATLANTIC OCEAN...
AS PREVIOUSLY MENTIONED...A STATIONARY FRONT STRETCHES FROM THE
WINDWARD PASSAGE NORTHEASTWARD TO NEAR 30N52W. TO THE W OF THIS
FRONT...FAIR WEATHER CONDITIONS PREVAIL THANKS TO 1036 MB SFC
HIGH LOCATED NEAR 42N51W. A RIDGE EXTENDS FROM THIS HIGH SWWD
ACROSS THE W ATLC INTO FLORIDA AND THE EASTERN GULF. THIS RIDGE
ALSO ENVELOPS MOST OF CUBA AND THE NW CARIBBEAN. SE OF THE
STATIONARY FRONT...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS
SUPPORTING FAIR WEATHER CONDITIONS. A DEEP LAYERED TROUGH
DOMINATES THE E ATLC AND EXTENDS FROM AN UPPER-LEVEL LOW
SITUATED JUST EAST OF THE MADEIRA ISLANDS NEAR 32N15W TO THE
CAPE VERDE ISLANDS. A JET-STREAM BRANCH WITH MAXIMUM WINDS OF 90
KT ROUNDS THE BASE OF THIS TROUGH WHICH IS SUPPORTING A PAIR OF
1012 MB SFC LOWS. ONE IS NEAR 29N19W...THE OTHER IS NEAR 25N18W.
THE FIRST ONE IS BETTER DEFINED ON VIS SATELLITE PHOTOS...AND AN
EARLIER QSCAT PASS. HOWEVER...BOTH SFC LOWS ARE EXPECTED TO
DISSIPATE IN ABOUT 24 HOURS OR SO AS THE UPPER-LEVEL TROUGH
MOVES EWD INLAND OVER AFRICA. LOW LEVEL CONVERGENCE AND
ATMOSPHERIC INSTABILITY IN THE VICINITY OF THE SURFACE LOWS AND
THE ASSOCIATED SURFACE TROUGHS ARE HELPING TO INDUCE ISOLATED TO
SCATTERED SHOWERS N OF 25N E OF 21W. AN UPPER LEVEL RIDGE COVERS
THE REMAINDER OF THE TROPICAL ATLC ENHANCING THE CONVECTION
ASSOCIATED WITH THE ITCZ.

$$
GR/AC



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