[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 122336
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUN 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 57W/58W S OF 14N MOVING W 10-15 KT. THIS
WAVE COINCIDES WITHIN A RELATIVELY HIGHLY-AMPLIFIED MAXIMUM IN DEEP
LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. RECENT VISIBLE SATELLITE IMAGERY ALSO INDICATES THAT THIS
WAVE IS EMBEDDED WITHIN A BROAD INVERTED-V SIGNATURE IN THE LOW
LEVEL CLOUD PATTERN. SATELLITE-DERIVED WIND DATA INDICATE CYCLONIC
CURVATURE IN THE LOW LEVEL FLOW ACROSS THIS WAVE. SCATTERED MODERATE
CONVECTION IS FROM 7N-12N BETWEEN 51W-58W.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N13W 7N23W 4N34W 2N44W 1N51W.
SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 10W-13W.
NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM 5N-10N BETWEEN
14W-21W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-8N
BETWEEN 22W-27W.

...DISCUSSION...

GULF OF MEXICO...
DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTH-NORTHWESTERLY FLOW COVER
MUCH OF THE GULF REGION...WHERE GENERALLY FAIR WEATHER IS PRESENT.
THE SUBSIDENCE IS SUPPORTING A 1016 MB SURFACE HIGH OVER THE CENTRAL
GULF NEAR 27N87W. THIS SURFACE HIGH IS FORECAST TO REMAIN NEARLY
STATIONARY DURING THE NEXT DAY. WINDS ARE GENERALLY VARIABLE AT 10
KT OR LESS ACROSS MUCH OF THE MIDDLE AND E GULF...WHILE SE WINDS OF
15 TO 20 KT ARE PRESENT ACROSS PORTIONS OF THE W GULF IN RESPONSE TO
A BROAD SURFACE TROUGH OVER MEXICO AND THE SOUTHERN PLAINS OF THE
UNITED STATES. LITTLE CHANGE IN THIS OVERALL PATTERN IS EXPECTED
DURING THE NEXT FEW DAYS.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS PRESENT ACROSS THE W CARIBBEAN WITH AN AXIS
EXTENDING FROM AN UPPER LOW OVER W CUBA NEAR 23N81W TO 16N82W.
ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER LOW AND UPPER
TROUGH IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE NW
CARIBBEAN N OF 16N BETWEEN 76W-84W INCLUDING PORTIONS OF JAMAICA AND
CUBA...WITH SCATTERED SHOWERS AND THUNDERSTORMS ACROSS
PANAMA...COSTA RICA...S NICARAGUA...AND NEARBY COASTAL WATERS. THIS
ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR A SURFACE
TROUGH EXTENDING FROM 12N81W TO 21N83W. THE ASCAT PASS AROUND
12/1500 UTC CONFIRMS CYCLONIC CURVATURE IN THE LOW LEVEL WINDS
ACROSS THE TROUGH. THIS SURFACE TROUGH IS FORECAST TO MOVE SLOWLY
WESTWARD AND BE LOCATED OVER EASTERN MEXICO AND NORTHERN CENTRAL
AMERICA MONDAY. ADDITIONALLY...STRONG UPPER LEVEL DIFFLUENCE IN
MOIST SOUTHWESTERLY FLOW ALOFT E OF THE AFOREMENTIONED UPPER LEVEL
TROUGH AXIS IS SUPPORTING NUMEROUS SHOWERS AND THUNDERSTORMS OVER
THE CENTRAL CARIBBEAN FROM 14N-18N BETWEEN 71W-75W. FARTHER E...THE
PRESSURE GRADIENT S OF A SURFACE RIDGE ACROSS THE CENTRAL ATLC IS
SUPPORTING E TO SE WINDS TO 15 TO 20 KT ACROSS MUCH OF THE E
CARIBBEAN...WHERE DEEP LAYER DRY AIR IS INHIBITING DEEP CONVECTION.
HOWEVER...THE TROPICAL WAVE ALONG 57W/58W IS FORECAST TO MOVE
WESTWARD ACROSS THE CARIBBEAN DURING THE NEXT FEW DAYS...REACHING
NEAR 80W ON WEDNESDAY. INCREASED MOISTURE ASSOCIATED WITH THIS WAVE
IS EXPECTED OVER THE LESSER ANTILLES DURING THE NEXT DAY.

ATLANTIC OCEAN...
UPPER LEVEL DIFFLUENCE IN MOIST SOUTH-SOUTHWESTERLY FLOW ALOFT
ACROSS THE SW NORTH ATLC IS OCCURRING E OF AN UPPER LOW NE OF THE
BAHAMAS NEAR 26N75W. THIS IS PROVIDING THE SUPPORT FOR SCATTERED
SHOWERS AND THUNDERSTORMS FROM 22N-29N BETWEEN 66W AND 79W INCLUDING
PORTIONS OF THE BAHAMAS. THIS ACTIVITY IS ALSO BEING SUPPORTED BY
LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM 29N67W TO
27N71W. ADDITIONALLY...UPPER LEVEL DIFFLUENCE IN MOIST EASTERLY FLOW
ALOFT E OF AN UPPER LEVEL SHORTWAVE TROUGH IS SUPPORTING NUMEROUS
SHOWERS FROM 23N-27N BETWEEN 54W-59W. FARTHER TO THE W...SUBSIDENCE
IN DRY NORTHERLY FLOW ALOFT IS SUPPORTING GENERALLY FAIR WEATHER
ACROSS WESTERN PORTIONS OF THE SW NORTH ATLC. ACROSS THE CENTRAL AND
E ATLC...GENERALLY FAIR WEATHER IS PRESENT WHERE SUBSIDENCE IS
OCCURRING NEAR A BROAD SURFACE RIDGE. THIS SURFACE RIDGE IS ANCHORED
BY A 1024 MB SURFACE HIGH NEAR 27N32W AND A 1025 MB SURFACE HIGH
NEAR 27N37W. HOWEVER...AN UPPER LEVEL TROUGH N OF THE DISCUSSION
AREA IS ASSOCIATED WITH A COLD FRONT EXTENDING FROM NE OF THE
DISCUSSION AREA TO 32N27W TO 31N38W EXTENDING WESTWARD AS A
STATIONARY FRONT TO 32N42W AND EXTENDING FARTHER NORTHWESTWARD AS A
WARM FRONT TO 32N43W TO NW OF THE DISCUSSION AREA. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE
OF THESE FRONTS. ACROSS THE TROPICAL ATLC...A BROAD UPPER LEVEL
RIDGE IS PRESENT WITH AN AXIS EXTENDING FROM 13N15W TO AN UPPER
LEVEL HIGH NEAR 12N23W TO 6N47W. UPPER LEVEL DIVERGENCE ASSOCIATED
WITH THE UPPER LEVEL RIDGE AND UPPER LEVEL HIGH IS SUPPORTING
CONVECTION ASSOCIATED WITH THE ITCZ.

$$
COHEN




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