[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED MAY 13 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.

...TROPICAL WAVES...
THE FIRST ANALYZED TROPICAL WAVE OF 2009 HAS BEEN ADDED TO THE
13/1200 UTC MAP ALONG 17W/18W MOVING W NEAR 15 KT. RECENT
TIME-HEIGHT ANALYSES FROM BAMAKO INDICATE MEAN SFC-650 MB WINDS
VEERED FROM NE TO SE IN CONJUNCTION WITH AN ORGANIZED AREA OF
DEEP MOIST CONVECTION THAT MOVED OFF THE AFRICAN COAST DURING
THE LAST DAY. THIS WIND SHIFT AT BAMAKO OCCURRED ON MAY 12 2009.
TIME-HEIGHT ANALYSES FROM BAMAKO ALSO INDICATE LOW-TO-MID LEVEL
MOISTURE MAXIMIZED AFTER THE PASSAGE OF THE TROPICAL WAVE.
ALSO...THE WAVE COINCIDES WITH A WESTWARD-MOVING DEEP LAYER
MOISTURE MAXIMUM AS INDICATED IN THE MIMIC TPW PRODUCT FROM
CIMSS. METSAT-9 VISIBLE SATELLITE IMAGERY INDICATES CONTINUED
LOW-LEVEL CYCLONIC TURNING...THOUGH RECENT QUIKSCAT IMAGERY
INDICATES THAT CURVATURE VORTICITY HAS DIMINISHED NEAR THE WAVE
AS IT BECOMES ABSORBED IN STRONGER NORTHERLY FLOW. DESPITE THE
TEMPORARY LOSS IN CURVATURE VORTICITY AT THE SURFACE...REGIONAL
VARIATIONS IN WIND SPEED AT THE SURFACE ARE MAINTAINING POSITIVE
SURFACE VORTICITY NEAR THE WAVE. MUCH OF THE CONVECTION
ASSOCIATED WITH THE WAVE HAS DIMINISHED...WITH SCATTERED
MODERATE CONVECTION FROM 1N-7N BETWEEN 14W-22W.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 4N19W 1N26W 1N38W CROSSING THE
EQUATOR NEAR 46W EXTENDING TO NE BRAZIL NEAR 1S50W. SCATTERED
MODERATE CONVECTION IS S OF 3N BETWEEN 8W-10W AND S OF 3N
BETWEEN 22W-29W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER RIDGE OVER THE WRN GULF IS ADVECTING SOME TROPICAL
MOISTURE FROM THE PACIFIC INTO THE REGION W OF 90W. THIS
MOISTURE IS MAINLY IN THE FORM OF MID-HIGH LEVEL
CLOUDINESS...THOUGH THERE COULD BE SOME EMBEDDED ISOLATED
SHOWERS. SCATTERED SHOWERS ARE MOVING THROUGH THE STRAITS OF
FLORIDA AND FAR SE GULF DRIVEN BY MOIST E/SE LOW-LEVEL FLOW.
ELSEWHERE...MAINLY FAIR WEATHER DOMINATES THE AREA. BUOY/SHIP
OBS AND SCATTEROMETER DATA SHOWS THE STRONGEST WINDS OVER THE
WRN WATERS...SE 15-20 KT...DUE TO THE TIGHTENED PRESSURE
GRADIENT BETWEEN HIGH PRES OVER NEW ENGLAND AND BROAD TROUGHING
OVER THE S CENTRAL CONUS/MEXICO.

CARIBBEAN SEA...
BROAD RIDGING ALOFT COVERS THE SE HALF OF THE CARIBBEAN. UPPER
LEVEL DIFFLUENCE BETWEEN THE RIDGE AND A TROUGH OVER THE NW
CARIBBEAN AND EPAC IS SUPPORTING SCATTERED SHOWERS AND TSTMS
ACROSS THE SW CARIBBEAN S OF 11N INCLUDING ADJACENT PORTIONS OF
PANAMA AND COSTA RICA. HOWEVER...SUBSTANTIALLY MORE CONVECTIVE
ACTIVITY IS FOUND OVER THE NEARBY E PAC WATERS S OF PANAMA AND
COSTA RICA...WHERE LOW-LEVEL CONVERGENCE ALONG THE ITCZ IS AN
ENHANCING FACTOR. MEANWHILE...SURFACE HIGH PRESSURE N OF THE
CARIBBEAN SEA IS RESULTING IN FRESH E TRADE WINDS. THESE FRESH E
TRADE WINDS ARE FORECAST TO PERSIST THROUGH THE WEEK. THE
STRONGEST WINDS ARE FOUND NEAR THE COAST OF COLOMBIA...WHERE A
13/1200 UTC QUIKSCAT PASS SHOWS NE TO E 20-25 KT WINDS. POCKETS
OF LOW LEVEL MOISTURE AND ISOLATED SHOWERS ARE BEING ADVECTED
W ACROSS THE CARIBBEAN...WITH THE GREATEST CONCENTRATION
OF THESE SHOWERS WITHIN 90 NM EITHER SIDE OF A SURFACE TROUGH
OVER THE NE CARIBBEAN THAT EXTENDS FROM S HISPANIOLA NEAR 18N71W
ACROSS THE N CARIBBEAN TO 16N71W. SURFACE OBSERVATIONS CONTINUE
TO INDICATE A WEAK CYCLONIC WIND SHIFT IN THE VICINITY OF THIS
TROUGH. ACROSS THE NW HALF OF THE CARIBBEAN...DEEP LAYER DRY AIR
IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. DURING THE
NEXT FEW DAYS...THE TRADE WINDS WILL GRADUALLY DIMINISH AS THE
SURFACE HIGH OVER THE CENTRAL ATLC MOVES NE AND A BROAD SURFACE
TROUGH DEVELOPS OVER THE GULF OF MEXICO THIS WEEKEND.

ATLANTIC OCEAN...
A SURFACE RIDGE ASSOCIATED WITH A 1029 MB SURFACE HIGH OVER THE
CENTRAL ATLC NEAR 33N36W IS AFFECTING MUCH OF THE ATLC PORTION
OF THE DISCUSSION AREA. SUBSIDENCE ASSOCIATED WITH THE SURFACE
RIDGE IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS ACROSS
MUCH OF THE ATLC PORTION OF THE DISCUSSION AREA. HOWEVER...
POCKETS OF LOW LEVEL MOISTURE WITH ISOLATED SHOWERS ARE MOVING W
ACROSS PORTIONS OF THE SW NORTH ATLC. THE GREATEST CONCENTRATION
OF THESE SHOWERS IS LOCATED WITHIN 90 NM EITHER SIDE OF A
SURFACE TROUGH THAT EXTENDS FROM 22N68W TO N HISPANIOLA NEAR
20N70W. THIS TROUGH WILL CONTINUE MOVING W NEAR 15 KT AS IT
AFFECTS THE GREATER ANTILLES DURING THE NEXT FEW DAYS.
ALSO...ATMOSPHERIC LIFT ASSOCIATED WITH A MID/UPPER-LEVEL TROUGH
OVER THE W ATLC IS SUPPORTING A COLD FRONT FROM 32N60W TO 30N72W
WITH A STATIONARY FRONT EXTENDING FROM 30N72W TO A 1020 MB
SURFACE LOW NEAR 30N75W. WINDS OF 20-25 KT ARE WITHIN 90 NM IN
THE N SEMICIRCLE OF THE LOW WITH NE TO E WINDS TO 20 KT N OF THE
FRONT AS THE LOW TRACKS NW TOWARD THE SURFACE RIDGE AXIS. LOW
LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND ISOLATED
TSTMS ALONG AND WITHIN 90 NM EITHER SIDE OF THE FRONTS. ACROSS
THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT WITH AN AXIS
EXTENDING FROM 13N16W TO 2N48W WITH AN UPPER HIGH CENTERED NEAR
9N27W. ASSOCIATED UPPER LEVEL DIVERGENCE IS ENHANCING ITCZ
CONVECTION.

$$
COHEN/CANGIALOSI





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