[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 232338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT MAY 23 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
2245 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 45W/46W S OF 8N MOVING W NEAR 15
KT. THIS WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER
MOISTURE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS.
SATELLITE IMAGERY INDICATES THAT THE WAVE IS EMBEDDED WITHIN AN
INVERTED-V PATTERN IN THE LOW LEVEL CLOUD COVERAGE...WITH
CYCLONIC CIRCULATION IN THE MOTION OF LOW LEVEL CLOUDS IN THE
VICINITY OF THE WAVE. SCATTERED MODERATE CONVECTION IS WITHIN
240 NM EITHER SIDE OF THE WAVE AXIS FROM 1N-4N.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 9N13W 4N22W 1N31W CROSSING THE
EQUATOR NEAR 47W EXTENDING TO NE BRAZIL NEAR 1S50W. SCATTERED
MODERATE CONVECTION IS S OF 3N BETWEEN 4W-10W. SCATTERED
MODERATE CONVECTION IS ALSO FROM 1N-5N BETWEEN 11W-18W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH IS PRESENT ACROSS THE GULF WITH AN AXIS
EXTENDING FROM AN UPPER LOW NEAR 30N92W TO 27N88W TO 25N81W. AN
ASSOCIATED 1005 MB SURFACE LOW IS LOCATED JUST SE OF PASCAGOULA
MISSISSIPPI NEAR 30N88W...AND A SURFACE TROUGH EXTENDS FROM THE
LOW TO 26N89W TO THE N YUCATAN PENINSULA NEAR 21N90W. LOW LEVEL
CONVERGENCE NEAR THE SURFACE LOW AND SURFACE TROUGH...AS WELL AS
UPPER LEVEL DIFFLUENCE NE OF THE UPPER TROUGH AXIS...ARE
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE GULF N
OF 25N E OF 88W...N OF 28N W OF 88W...AS WELL AS ADJACENT INLAND
LOCATIONS ALONG THE GULF COAST. THE INCREASED SURFACE PRESSURE
GRADIENT BETWEEN THE SURFACE LOW AND A SURFACE RIDGE OVER THE SE
CONUS IS SUPPORTING WIND SPEEDS OF 10 TO 15 KT AROUND THE LOW
ACROSS N PORTIONS OF THE MIDDLE AND E GULF. THE SURFACE LOW IS
FORECAST TO MOVE NORTHWESTWARD DURING THE NEXT DAY AND BE
LOCATED NEAR 34N91W AS A 1008 MB SURFACE LOW AT 24/1800 UTC.
THIS SYSTEM IS LIKELY TO PRODUCE LOCALLY HEAVY RAINS OVER
PORTIONS OF THE SOUTHEASTERN UNITED STATES DURING THE NEXT DAY
OR TWO. THE WINDS AROUND THE LOW ARE FORECAST TO BECOME LIGHTER
LATE THIS WEEKEND INTO NEXT WEEK AS THE PRESSURE GRADIENT ACROSS
THE GULF RELAXES. ACROSS THE SW GULF...DEEP LAYER DRY AIR AND
SUBSIDENCE ASSOCIATED WITH WEST-NORTHWESTERLY FLOW ALOFT IS
SUPPORTING GENERALLY FAIR WEATHER CONDITIONS.

CARIBBEAN SEA...
SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING ACROSS THE
CARIBBEAN N OF 15N BETWEEN 75W-82W. THIS ACTIVITY IS BEING
SUPPORTED BY UPPER LEVEL DIFFLUENCE IN MOIST WESTERLY FLOW ALOFT
BETWEEN AN UPPER LEVEL TROUGH OVER THE CENTRAL AND E
CARIBBEAN...AND AN UPPER LEVEL RIDGE ACROSS THE SW NORTH ATLC.
THE ACTIVITY IS ALSO BEING SUPPORTED BY ATMOSPHERIC INSTABILITY
NEAR THE UPPER LEVEL TROUGH. ADDITIONALLY...ATMOSPHERIC
INSTABILITY NEAR THE UPPER TROUGH IS RESULTING IN SCATTERED
SHOWERS AND THUNDERSTORMS OVER CUBA...HISPANIOLA...PUERTO
RICO...PANAMA...COSTA RICA...AND NEARBY COASTAL WATERS.
ADDITIONAL SHOWERS AND THUNDERSTORMS COULD AFFECT NORTHERN AND
SOUTHWESTERN PORTIONS OF THE CARIBBEAN DURING THE NEXT COUPLE OF
DAYS WITH THE UPPER TROUGH AND ASSOCIATED ATMOSPHERIC
INSTABILITY PERSISTING OVER THE CARIBBEAN. UPPER LEVEL MOISTURE
AND HIGH LEVEL CLOUDS ARE STREAMING GENERALLY EASTWARD ACROSS
THE CARIBBEAN. MEANWHILE...THE SURFACE PRESSURE GRADIENT S OF A
SURFACE RIDGE OVER THE CENTRAL ATLC IS MAINTAINING E TO SE WINDS
OF 20 TO 25 KT ACROSS PORTIONS OF THE E CARIBBEAN.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING FROM 24N-30N W
OF 76W INCLUDING THE NW BAHAMAS AND ADJACENT INLAND LOCATIONS OF
FLORIDA...AS WELL AS S OF 22N BETWEEN 67W-80W INCLUDING PORTIONS
OF CUBA...HISPANIOLA...PUERTO RICO...AND THE SE BAHAMAS. THIS
ACTIVITY IS BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE IN MOIST
SOUTHWESTERLY FLOW ALOFT BETWEEN AN UPPER LEVEL TROUGH OVER THE
GULF OF MEXICO AND AN UPPER LEVEL RIDGE ACROSS THE SW NORTH
ATLC. FARTHER TO THE E...AN UPPER LEVEL TROUGH IS PRESENT WITH
AN AXIS EXTENDING FROM AN UPPER LEVEL LOW NEAR 33N49W TO 30N52W
TO 27N52W. ATMOSPHERIC INSTABILITY NEAR THE UPPER LEVEL LOW AND
TROUGH...AS WELL AS UPPER LEVEL DIFFLUENCE IN MOIST
SOUTHWESTERLY FLOW ALOFT...ARE SUPPORTING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS N OF 28N BETWEEN 37W-50W. ALSO...A
SURFACE TROUGH EXTENDS FROM 29N52W TO A 1017 MB SURFACE LOW NEAR
23N57W CONTINUING SOUTHWESTWARD TO 18N61W. LOW LEVEL CONVERGENCE
NEAR THE SURFACE LOW AND SURFACE TROUGH IS SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FROM 22N-26N BETWEEN 51W-59W.
DURING THE NEXT DAY...THE 1017 MB SURFACE LOW IS FORECAST TO
MOVE EASTWARD AND BE LOCATED NEAR 23N54W AS A 1017 MB SURFACE
LOW AT 24/1800 UTC. ACROSS THE E ATLC...A SURFACE RIDGE IS
PRESENT WHERE MAINLY ZONAL FLOW ALOFT IS OCCURRING AND FAIR
WEATHER CONDITIONS PERSIST. ACROSS THE TROPICAL ATLC...AN UPPER
LEVEL RIDGE IS S OF 10N E OF 40W. UPPER LEVEL DIVERGENCE
ASSOCIATED WITH THE UPPER LEVEL RIDGE IS ENHANCING THE
CONVECTION ASSOCIATED WITH THE ITCZ AND THE TROPICAL WAVE ALONG
45W/46W S OF 8N.

$$
COHEN




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