[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121730
TWDAT

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

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N21W 1N32W CROSSING THE
EQUATOR NEAR 41W EXTENDING TO NE BRAZIL NEAR 1S48W. SCATTERED
MODERATE CONVECTION IS FROM 5N-7N BETWEEN 14W-17W...FROM 3N-5N
BETWEEN 19W-23W...AND FROM 1N-3N BETWEEN 34W-36W. RECENT
SATELLITE IMAGERY DEPICTS ENHANCED CYCLONIC VORTICITY IN THE
VICINITY OF THE EASTERNMOST AREA OF THIS CONVECTIVE ACTIVITY...
WHICH LIKELY IS ASSOCIATED WITH A TROPICAL WAVE.

...DISCUSSION...

GULF OF MEXICO...
WEAK COLD AIR ADVECTION W OF A WEAK SURFACE LOW OVER CENTRAL
FLORIDA HAS FORCED A WEAKENING COLD FRONT TO SURGE S FROM
SARASOTA FLORIDA TO NEAR MOBILE ALABAMA. VISIBLE SATELLITE
IMAGERY AND RADAR TRENDS DEPICT THIS FEATURE WELL...BUT IT IS
BECOMING INCREASINGLY DIFFUSE. A QUIKSCAT PASS AROUND 11/1130
UTC SHOWS N TO NE 10-15 KT WINDS NE OF THE FRONT. THIS LOW IS
LIKELY BEING DRIVEN BY A WEAK MID/UPPER-LEVEL TROUGH TRAILING SW
FROM THE W ATLC. THIS UPPER FORCING IS ALSO PRODUCING SCATTERED
SHOWERS AND ISOLATED TSTMS OVER THE FAR NE WATERS. E TO SE FLOW
AND MAINLY FAIR WEATHER EXISTS ACROSS THE REMAINDER OF THE
REGION ON THE S/SW PERIPHERY OF SFC HIGH PRES OVER THE OHIO
VALLEY AND NWLY FLOW ALOFT.

CARIBBEAN SEA...
BROAD RIDGING ALOFT COVERS THE SOUTHWESTERN TWO-THIRDS OF THE
CARIBBEAN...WITH UPPER LEVEL DIFFLUENCE BETWEEN THE CARIBBEAN
RIDGE...AND A TROUGH OVER THE NW CARIBBEAN AND EPAC...SUPPORTING
SCATTERED SHOWERS AND TSTMS ACROSS THE SW CARIBBEAN S OF
12N 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 NE TO E 20-25 KT WINDS
ARE OCCURRING. POCKETS OF LOW LEVEL MOISTURE AND ISOLATED
SHOWERS ARE BEING ADVECTED WESTWARD 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
15N63W TO E OF PUERTO RICO NEAR 18N64W. SURFACE OBSERVATIONS
CONTINUE TO INDICATE A WEAK CYCLONIC WIND SHIFT IN THE VICINITY
OF THIS TROUGH. ACROSS THE NORTHWESTERN ONE-THIRD OF THE
CARIBBEAN...DEEP LAYER DRY AIR IS RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS.

ATLANTIC OCEAN...
A SURFACE RIDGE ASSOCIATED WITH A PAIR OF 1026 MB SURFACE HIGHS
OVER THE CENTRAL ATLC IS AFFECTING MUCH OF THE ATLC PORTION OF
THE DISCUSSION AREA. SUBSIDENCE ASSOCIATED WITH THE SURFACE
RIDGE ARE 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 OF THESE
SHOWERS IS LOCATED WITHIN 90 NM EITHER SIDE OF A RATHER
DISORGANIZED SURFACE TROUGH THAT EXTENDS FROM 20N64W TO 18N64W.
THIS TROUGH IS MOVING W NEAR 15 KT AND WILL LIKELY CONTINUE TO
LOSE ITS ORGANIZATION WHILE THE ASSOCIATED SHOWER ACTIVITY
DECREASES IN AREAL COVERAGE. ALSO...ATMOSPHERIC LIFT ASSOCIATED
WITH A MID/UPPER-LEVEL VORTICITY MAXIMUM OVER THE W ATLC IS
SUPPORTING A COLD FRONT FROM 31N75W TO A 1016 MB SURFACE LOW
NEAR 30N79W TO THE E FLORIDA PENINSULA NEAR 28N81W. NE WINDS TO
20 KT ARE PRESENT N OF THE FRONT...AND WILL LIKELY INCREASE
ACROSS THE N SEMICIRCLE OF THE LOW DURING THE NEXT DAY AS IT
TRACKS NW TOWARD THE SURFACE RIDGE AXIS. LOW LEVEL CONVERGENCE
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG
AND WITHIN 90 NM SE OF THE COLD FRONT. ACROSS THE TROPICAL
ATLC...AN UPPER LEVEL RIDGE IS PRESENT WITH AN AXIS EXTENDING
FROM 12N14W TO 2N48W WITH AN UPPER HIGH CENTERED NEAR 4N35W.
ASSOCIATED UPPER LEVEL DIVERGENCE IS ENHANCING ITCZ CONVECTION.

$$
COHEN/CANGIALOSI


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