[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE FEB 17 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.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 6N10W 2N20W 1N30W CROSSING THE
EQUATOR AT 39W...AND INTO NE BRAZIL NEAR 3S47W. SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 140 NM N OF
AXIS BETWEEN 28W-34W. SIMILAR CONVECTION IS FOUND WITHIN 70 NM
EITHER SIDE OF AXIS BETWEEN 34W-45W...AND WITHIN 100NM NE OF
LINE FROM 1S45W TO EQ51W.

...DISCUSSION...

GULF OF MEXICO...
A 1029 MB HIGH OVER THE CAROLINAS EXTENDS A RIDGE OVER THE SE
CONUS AND THE ENTIRE GULF OF MEXICO PRODUCING MOSTLY FAIR
WEATHER. SCATTERED COLD AIR STRATOCUMULUS CLOUDS ARE STILL NOTED
PARTICULARLY OVER THE WESTERN HALF OF THE GULF WHERE A SE-S
RETURN FLOW HAS ALREADY ESTABLISHED. THESE WINDS ARE EXPECTED TO
INCREASE TO 20-25 KT THIS AFTERNOON. THE HIGH PRES WILL MOVE SE
TOWARDS THE W ATLC IN ABOUT 24 HOURS ALLOWING THE NEXT COLD
FRONT TO ENTER THE NW PORTION OF THE GULF WED AFTERNOON. THE
FRONT IS FORECAST TO PUSH ACROSS THE ENTIRE GULF ON THU FOLLOWED
BY MODERATE TO STRONG N-NE WINDS. IN THE UPPER LEVELS...A RIDGE
ANCHORED ON A HIGH OVER EPAC REGION NEAR 6N93W COVERS MEXICO AND
MOST OF THE GULF REGION PRODUCING STRONG NW FLOW...AND ALSO
MODERATE TO STRONG SUBSIDENCE SOUTH OF 24N...INCLUDING SE MEXICO
AND THE YUCATAN PENINSULA.

CARIBBEAN SEA...
AS OF 1500 UTC...THE TAIL END OF A COLD FRONT IS OVER THE
WINDWARD PASSAGE/NW HAITI WITH BROKEN LOW CLOUDS AND ISOLATED
SHOWERS. THIS FRONT WILL SWEEP SE AND GRADUALLY DISSIPATE AS IT
CROSSES HISPANIOLA TONIGHT AND WED. LATEST VIS SATELLITE IMAGERY
INDICATES THAT THE FRONTAL BOUNDARY IS ALREADY AFFECTING THE NW
PORTION OF DOMINICAN REPUBLIC WITH NW WINDS AND SOME SHOWER
ACTIVITY. HIGH PRES BEHIND THE COLD FRONT...CENTERED OVER THE
CAROLINAS...COVERS CUBA AND THE NW CARIBBEAN. N-NE WINDS AROUND
THE SOUTHERN PERIPHERY OF THIS HIGH ARE TRANSPORTING COLD AIR
STRATOCUMULUS CLOUDS FROM THE W ATLC INTO CUBA AND THE NW
CARIBBEAN. FURTHER E...A SURFACE TROUGH REMAINS OVER THE EASTERN
CARIBBEAN WITH AXIS ALONG 67W/68W SOUTH OF 17S. THIS TROUGH IS
GENERATING A LARGE ARE OF LOW/MID CLOUDS WITH SOME SHOWER
ACTIVITY OVER THE ABC ISLANDS. LINES OF CLOUDS EMBEDDED IN THE
NE TRADE WIND FLOW ARE NOTED AHEAD OF THIS SFC TROUGH OVER THE
CENTRAL AND SW CARIBBEAN. THE TRADE WINDS WILL START TO INCREASE
LATE TODAY ACROSS THE BASIN AS HIGH PRES OVER THE CAROLINAS
MOVES SE ACROSS THE W ATLC TIGHTENING THE PRESSURE GRADIENT OVER
THE CARIBBEAN. IN THE UPPER LEVELS...A RIDGE/TROUGH/RIDGE
PATTERN COVERS THE ENTIRE BASIN AND CENTRAL AMERICA WITH STRONG
SUBSIDENCE OVER THE W AND CENTRAL CARIBBEAN.

ATLANTIC OCEAN...
A VERY STRONG EXTRATROPICAL CYCLONE WITH HURRICANE FORCE WINDS
ON THE WESTERN SEMICIRCLE IS SPINNING OVER THE W-CENTRAL
ATLANTIC OCEAN NEAR 36N60W. THE ATTENDANT COLD FRONT ENTERS THE
FORECAST AREA NEAR 32N56W THEN CONTINUES SW TO THE WINDWARD
PASSAGE/NW HAITI. A WELL DEFINED BAND OF LOW/MID CLOUDS WITH
EMBEDDED SHOWERS...CURRENTLY AFFECTING HISPANIOLA...IS RELATED
TO THE FRONT. TIGHT PRES GRADIENT BETWEEN THIS STRONG SFC LOW
AND THE HIGH PRES OVER THE CAROLINAS IS PRODUCING A WIDE SWATH
OF STRONG NLY WINDS OF 30 TO 40 KT OVER THE DISCUSSION AREA...
MAINLY N OF 27N AND WEST OF 65W. AS A RESULT...A GALE WARNING IS
IN EFFECT FOR THAT AREA. THE REMAINDER OF THE ATLANTIC IS UNDER
THE INFLUENCE OF A RIDGE ANCHORED ON A HIGH LOCATED WELL N OF
REGION. THIS SYSTEM IS GENERATING MOSTLY FAIR WEATHER...AND
MODERATE TO FRESH TRADE WINDS ACROSS THE TROPICS. ALOFT...AN
AMPLIFIED TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE ATLANTIC
OCEAN. A DEEP LAYERED TROUGH OVER THE W ATLC SUPPORTS THE ABOVE
MENTIONED COLD FRONT. A RIDGE EXTENDS OVER THE CENTRAL ATLC TO
BEYOND THE AZORES ISLANDS. E OF THE RIDGE...THERE IS ANOTHER
DEEP LAYERED TROUGH STRETCHING FROM THE MADEIRA ISLANDS TO THE
CAPE VERDE ISLANDS. W-NW UPPER-LEVEL FLOW COVERS THE DEEP
TROPICS.

$$
GR





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