[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 242335
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN MAY 24 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 53W/54W S OF 17N MOVING W 15-20 KT.
RECENT SURFACE OBSERVATIONS SHOW WELL-DEFINED CYCLONIC
CURVATURE IN THE LOW LEVEL WINDS AROUND THIS WAVE. THIS WAVE IS
ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS. SOUTHEASTERLY LOW LEVEL
FLOW BETWEEN THE TROPICAL WAVE AND A SURFACE TROUGH FARTHER
NORTH APPEAR TO BE ADVECTING CYCLONIC VORTICITY ASSOCIATED WITH
THIS WAVE NORTHWARD. AS A RESULT...THE WAVE HAS BEEN EXTENDED
NORTHWARD TO 17N...CONSISTENT WITH THE NORTHWARD EXTENSION IN
DEEP LAYER MOISTURE. SCATTERED MODERATE CONVECTION IS OCCURRING
WITHIN 180 NM EITHER SIDE OF THE WAVE AXIS S OF 6N...INCLUDING
PORTIONS OF SURINAME...FRENCH GUIANA...AND NE BRAZIL. FARTHER TO
THE NORTH...DEEP CONVECTION IN THE VICINITY OF THIS WAVE IS
BEING SUPPRESSED BY SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE
OVER THE E ATLC. HOWEVER...SCATTERED SHOWERS ARE OCCURRING
WITHIN 90 NM EITHER SIDE OF THE WAVE AXIS FROM 6N-17N.

ADDITIONALLY...TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS
INDICATES THAT A NORTH-SOUTH ELONGATED DEEP LAYER MOISTURE
MAXIMUM IS ALONG 25W S OF 6N MOVING W NEAR 15 KT.
ALSO...COMPUTER MODEL GUIDANCE INDICATES CYCLONIC CURVATURE IN
THE LOW LEVEL FLOW NEAR THIS FEATURE. THIS FEATURE IS ASSOCIATED
WITH SCATTERED MODERATE CONVECTION FROM 3N-5N BETWEEN
19W-24W...WHICH IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE
NEAR THE ITCZ. HOWEVER...RECENT SURFACE OBSERVATIONS AND
SCATTEROMETER DATA DO NOT YET CONFIRM THE PRESENCE OF A LOW
AMPLITUDE TROPICAL WAVE AT THE SURFACE NEAR THIS FEATURE.
HOWEVER...A TROPICAL WAVE IS SUSPECTED TO BE PRESENT
HERE...WHICH WILL CONTINUE TO BE MONITORED.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N21W 1N29W CROSSING THE
EQUATOR NEAR 33W EXTENDING TO 1S41W AND INTO NE BRAZIL NEAR
1S48W. SCATTERED MODERATE CONVECTION IS FROM 1N-3N BETWEEN
1W-6W...S OF 3N BETWEEN 9W-18W...FROM 3N-5N BETWEEN
19W-24W...AND S OF 3N BETWEEN 40W-48W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS PRESENT ACROSS THE GULF WITH AN AXIS
EXTENDING FROM 25N79W TO 27N85W TO 30N89W TO NW OF THE
DISCUSSION AREA. ALSO...SURFACE TROUGHS EXTEND FROM S LOUISIANA
NEAR 29N91W TO 32N91W TO N OF THE DISCUSSION AREA...AND FROM S
TEXAS NEAR 26N97W TO 30N94W TO 31N93W. LOW LEVEL CONVERGENCE
NEAR THE SURFACE TROUGHS...AS WELL AS INSTABILITY ASSOCIATED
WITH THE UPPER LEVEL TROUGH...ARE SUPPORTING SCATTERED SHOWERS
AND THUNDERSTORMS ACROSS THE GULF N OF 23N E OF 89W...N OF 27N W
OF 89W...AS WELL AS ADJACENT INLAND LOCATIONS ALONG THE GULF
COAST. ACROSS THE SW GULF...DEEP LAYER DRY AIR AND SUBSIDENCE
ASSOCIATED WITH WEST-NORTHWESTERLY FLOW ALOFT ARE SUPPORTING
GENERALLY FAIR WEATHER CONDITIONS. A WEAK SURFACE PRESSURE
GRADIENT IS MAINTAINING LIGHT WINDS ACROSS MUCH OF THE GULF.
HOWEVER...SOUTHERLY RETURN FLOW IS FORECAST TO INCREASE OVER THE
FAR WESTERN GULF BEGINNING LATE MONDAY.

CARIBBEAN SEA...
SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING ACROSS THE
CARIBBEAN N OF 15N BETWEEN 73W-81W. THIS ACTIVITY IS BEING
SUPPORTED BY UPPER LEVEL DIFFLUENCE IN MOIST WEST-NORTHWESTERLY
FLOW ALOFT BETWEEN AN UPPER LEVEL TROUGH OVER THE GULF OF
MEXICO...AND AN UPPER LEVEL RIDGE ACROSS THE W CARIBBEAN.
ADDITIONALLY...ATMOSPHERIC INSTABILITY OVER HIGHER TERRAIN IS
RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS AFFECTING
CUBA...HISPANIOLA...PUERTO RICO...PANAMA...COSTA RICA...AND
NEARBY COASTAL WATERS. UPPER LEVEL MOISTURE AND HIGH LEVEL
CLOUDS ARE STREAMING GENERALLY EASTWARD ACROSS THE CARIBBEAN.
MEANWHILE...THE PRESSURE GRADIENT S OF SURFACE HIGH PRESSURE
NEAR BERMUDA IS MAINTAINING E TO SE WINDS UP TO 20 KT ACROSS
PORTIONS OF THE E CARIBBEAN.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING FROM 24N-30N W
OF 74W INCLUDING THE NW BAHAMAS AND ADJACENT INLAND LOCATIONS OF
FLORIDA...AS WELL AS S OF 24N BETWEEN 68W-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 33N44W TO 29N50W
TO 25N55W. THIS UPPER LEVEL LOW AND TROUGH ARE ASSOCIATED WITH A
SURFACE TROUGH EXTENDING FROM A 1018 MB SURFACE LOW NEAR 32N48W
TO 32N44W TO 24N51W TO 21N67W. ATMOSPHERIC INSTABILITY NEAR THE
UPPER LEVEL LOW AND TROUGH...UPPER LEVEL DIFFLUENCE IN MOIST
SOUTHWESTERLY FLOW ALOFT E OF THE UPPER LEVEL LOW AND
TROUGH...AND LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW AND
TROUGH ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS N OF 25N BETWEEN 39W-48W AND FROM 19N-25N BETWEEN
45W-68W. DURING THE NEXT DAY...THE 1018 MB SURFACE LOW IS
FORECAST TO REMAIN STATIONARY. 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...UPPER LEVEL RIDGES ARE PRESENT FROM 1N-7N E OF 13W AND S
OF 5N BETWEEN 23W-48W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH
THE UPPER LEVEL RIDGES IS ENHANCING THE CONVECTION ASSOCIATED
WITH THE ITCZ AND THE TROPICAL WAVE ALONG 53W/54W S OF 17N.

$$
COHEN




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