[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210541
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT MAR 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 3N20W CROSSING THE EQUATOR
ALONG 30W EXTENDING TO 1S40W INTO NE BRAZIL NEAR 2S45W. ISOLATED
MODERATE CONVECTION IS WITHIN 50 NM EITHER SIDE OF AXIS BETWEEN
30W AND 42W.

...DISCUSSION...

GULF OF MEXICO...
HIGH PRES CENTERED OVER THE NE CONUS EXTENDS A RIDGE ACROSS THE
EASTERN U.S. AND THE GULF OF MEXICO WHERE A 1020 MB HIGH IS ALSO
ANALYZED NEAR 23N96W. THERE ARE MOSTLY CLEAR SKIES OVER THE GULF
WATERS...EXCEPT FOR A FEW BROKEN CLOUDS AND ISOLATED SHOWERS
NEAR 24N ASSOCIATED WITH A SMALL REGION OF WEAK INSTABILITY.
SIMILAR CLOUDINESS IS NOTED OVER THE YUCATAN PENINSULA AND
COASTAL WATERS. A WEAKENING COLD FRONT IS CURRENTLY MOVING
ACROSS CENTRAL FLORIDA REACHING THE LAKE OKEECHOBEE AREA. THE
MOSAIC DOPPLER RADAR FROM THE SE U.S. SHOWS ISOLATED SHOWERS
ALONG THE FRONTAL BOUNDARY WHILE SCATTERED SHOWERS ARE NOTED
JUST OFFSHORE THE EAST COAST OF FLORIDA AND ALSO ACROSS THE
STRAITS OF FLORIDA. THE FRONT IS EXPECTED TO MOVE ACROSS SOUTH
FLORIDA THIS AFTERNOON PRODUCING SCATTERED FAST MOVING SHOWERS
AND INCREASING NE WINDS. A QSCAT PASS FROM AROUND 2330 UTC
SHOWED NE WINDS OF 20 TO 25 KT BEHIND THE FRONT OVER THE FAR W
ATLC. IN THE UPPER LEVELS...A WEAK UPPER LEVEL TROUGH OVER THE
CENTRAL GULF IS DROPPING SE INTO THE E GULF...DOWNSTREAM OF AN
AMPLIFYING UPPER RIDGE ALONG 100W. MODERATE TO STRONG
SUBSIDENCE/DRY AIR ALOFT COVERS THE GULF W OF 90W...MAINLY
BEHIND THE TROUGH AXIS.

CARIBBEAN SEA...
AN EARLIER QSCAT PASS AND SFC DATA INDICATED PREDOMINATELY NE TO
E WINDS OVER THE BASIN...WITH WINDS OF 20 KT ALONG THE COLOMBIAN
COAST...DECREASING TO 5-10 KT IN THE NW CARIBBEAN SEA. TYPICAL
PATCHES OF LOW LEVEL CLOUDS WITH EMBEDDED LIGHT TO MODERATE
SHOWERS ARE OBSERVED ACROSS THE AREA PARTICULARLY JUST OFFSHORE
THE COAST OF COLOMBIA...AS CYCLONIC TURNING AROUND THE LOW OVER
COLOMBIA NEAR 9N75W HAS CREATED CONVERGENT FLOW IN THE AREA. THE
TRADE WINDS ARE ALSO ADVECTING LOW LEVEL MOISTURE ACROSS WESTERN
PANAMA AND COSTA RICA. AT THE UPPER LEVELS...WATER VAPOR IMAGERY
INDICATES SUBSIDENCE ACROSS THE CARIBBEAN. SUBTROPICAL JET
STREAK IS OVER THE YUCATAN PENINSULA TO CUBA WITH CORE SPEEDS
OF 80-90 KT. THIS IN COMBINATION WITH LIFT AHEAD OF AN UPPER
LEVEL TROUGH SWEEPING SE OVER THE GULF IS CAUSING BROKEN HIGH
CLOUDS OVER THE NW CARIBBEAN AND THE STRAITS OF FLORIDA. A SFC
TROUGH IS OVER THE WINDWARD PASSAGE. LOW LEVEL CONVERGENCE NEAR
THE TROUGH AXIS IS SUPPORTING PATCHES OF LOW LEVEL CLOUDS OVER
EASTERN CUBA AND HISPANIOLA.

ATLANTIC OCEAN...
STRONG QUASI-STATIONARY LOW PRESSURE IS CURRENTLY WELL N OF THE
DISCUSSION AREA NEAR 37N41W. A COLD FRONT EXTENDS INTO THE AREA
FROM THE LOW TO 32N36W TO 24N45W THEN CONTINUES AS A STATIONARY
FRONT TO 24N60W...AND AS A WARM FRONT TO A 1012 MB LOW NEAR
26N69W. A LOW PRES TROUGH EXTENDS SW FROM THE LOW TO THE
WINDWARD PASSAGE. SCATTERED MODERATE ISOLATED STRONG CONVECTION
IS NOTED WITHIN 80 NM AHEAD OF THE TROUGH N OF 22N. THIS
CONVECTION IS PART OF A MUCH LARGER AREA OF MULTILAYERED CLOUDS
WITH EMBEDDED SHOWERS WHICH COVERED THE AREA N OF 22N BETWEEN
60W AND 70W. WIDELY SCATTERED LOW TOPPED SHOWERS ARE OCCURRING
WITHIN 60 NM EITHER SIDE OF THE COLD FRONT...AND WITHIN 90 NM N
OF THE STATIONARY FRONT. THE LOW PRESSURE IS FORECAST TO MOVE NE
AND AWAY FROM THE FORECAST AREA TO NEAR 33N58W BY 24 HOURS.
ELSEWHERE...A 1023 MB HIGH PRESSURE N OF THE AREA NEAR 36N55W IS
CURRENTLY EXTENDING A RIDGE INTO THE REGION BEHIND THE COLD
FRONT. OTHERWISE...MAINLY CLEAR SKIES WITH A FEW AREA OF BROKEN
CLOUDS DOMINATE THE WEATHER OVER THE REMAINDER OF THE ATLC. AT
THE UPPER LEVELS...A TROUGH/RIDGE/TROUGH/RIDGE PATTERN DOMINATES
THE ENTIRE AREA. A BROAD AREA OF STRONG SUBSIDENCE IS NOTED OVER
THE OCEAN WITHIN THE RIDGE GENERALLY FROM 15N TO 23N BETWEEN 30W
AND 65W. MOSTLY ZONAL FLOW IS FOUND ACROSS THE DEEP TROPICS.

$$
GR







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