[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 241757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS ALONG 10N30W TO 21N35W MOVING W NEAR 18
KT. SATELLITE IMAGERY INDICATES A BROAD AREA OF LOW-LEVEL
CYCLONIC TURNING NEAR THE WAVE AXIS AND THIS IS CONFIRMED ON AN
EARLIER QSCAT PASS AROUND 24/0800 UTC...THOUGH WINDS ARE
GENERALLY WEAK. CONVECTION IS MINIMAL AND MOSTLY CONFINED ALONG
THE ITCZ AXIS FROM 8N-11N BETWEEN 28W-32W.

A TROPICAL WAVE IS ALONG 73W S OF 20N MOVING W NEAR 25 KT.
VISIBLE SATELLITE IMAGERY AND TOTAL PRECIPITABLE WATER IMAGES
INDICATE A SLIGHT INVERTED-V SIGNATURE IN THE LOW-LEVEL CLOUDS
ACROSS THE CENTRAL CARIBBEAN. UPPER LEVEL DRY AIR AND A
MID-LEVEL SAHARAN AIR LAYER ARE INHIBITING ANY DEEP CONVECTION.

A TROPICAL WAVE IS ALONG 85W S OF 22N MOVING W NEAR 25 KT.
SATELLITE IMAGES SHOW LITTLE EVIDENCE OF THIS WAVE AT THE
MOMENT...HOWEVER TOTAL PRECIPITABLE WATER IMAGERY INDICATES A
MAXIMUM MOVING OVER THE NW CARIBBEAN AND PORTIONS OF HONDURAS
AND NICARAGUA SUGGESTING THE POSITION OF THE WAVE AS IT TRACKS
WWD. ISOLATED SHOWERS AND TSTMS ARE S OF 12N W OF 81W AND ARE
MORE LIKELY ASSOCIATED WITH UPPER LEVEL DIFFLUENCE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N15W 11N27W 10N32W 9N62W.
SCATTERED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 20W-26W.
ISOLATED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 32W-46W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL DIFFLUENCE AND MOISTURE IN WLY FLOW ALOFT COMBINED
WITH LOW-LEVEL CONVERGENCE ALONG A WEAK COLD FRONT EXTENDING
FROM THE FLORIDA PANHANDLE THROUGH NEW ORLEANS LOUISIANA TO ERN
TEXAS ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED TSTMS N OF
27N BETWEEN 84W-93W. SCATTERED SHOWERS AND TSTMS ARE OVER S
FLORIDA ENHANCED BY A WEAK SURFACE TROUGH THAT EXTENDS FROM WRN
CUBA TO NEAR LAKE OKEECHOBEE. ALSO OF NOTE...AN UPPER LEVEL HIGH
IS CENTERED ALONG THE E/CENTRAL MEXICO COAST NEAR 19N98W AND IS
PROVIDING UPPER DIFFLUENCE FOR SCATTERED SHOWERS AND ISOLATED
TSTMS ACROSS THE WRN BAY OF CAMPECHE FROM 18N-23N W OF 94W.
ELSEWHERE...DEEP LAYER DRY AIR AND SURFACE RIDGING IS PROMOTING
FAIR WEATHER. THE SURFACE RIDGE IS FORECAST TO GRADUALLY SHIFT
EWD THROUGH THE WEEKEND WITH INCREASING SE RETURN FLOW ACROSS
THE WRN GULF BY LATE IN THE WEEKEND AND EARLY NEXT WEEK.

CARIBBEAN SEA...
A BROAD UPPER LEVEL RIDGE EXTENDS ACROSS SRN MEXICO AND THE
YUCATAN PENINSULA TO CUBA...JAMAICA AND HISPANIOLA REMAINING
LARGELY N OF 15N OVER THE NW AND N/CENTRAL CARIBBEAN. UPPER
LEVEL DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE AND LOW-LEVEL
SPEED CONVERGENCE ARE SUPPORTING ISOLATED SHOWERS AND TSTMS OVER
PORTIONS OF WRN CUBA AND NRN CENTRAL AMERICA ALONG WITH THE NW
CARIBBEAN WATERS N OF 17N. UPPER LEVEL DIFFLUENCE IS ALSO
SUPPORTING SCATTERED SHOWERS AND TSTMS OVER THE SW CARIBBEAN S
OF 12N...INCLUDING COSTA RICA AND PANAMA. ACROSS THE ERN
CARIBBEAN...SCATTERED SHOWERS AND ISOLATED TSTMS ARE AFFECTING
THE SE WATERS S OF 13N E OF 67W DUE TO THE PROXIMITY OF THE ITCZ
AXIS THAT EXTENDS ALONG THE NRN BORDER OF VENEZUELA. FAIR
WEATHER EXISTS ACROSS THE CENTRAL CARIBBEAN SUPPORTED BY
MODERATE SUBSIDENCE AND DRY AIR ALOFT.

ATLANTIC OCEAN...
A MID-UPPER LEVEL TROUGH IS OVER THE W ATLC WHILE AN UPPER LEVEL
RIDGE EXTENDS FROM E OF THE BAHAMAS NEAR 25N71W TO BEYOND
32N65W. BETWEEN THESE TWO UPPER LEVEL FEATURES...DIFFLUENCE
ALOFT AND LOW-LEVEL CONVERGENCE ARE SUPPORTING SCATTERED SHOWERS
AND TSTMS FROM 25N-28N BETWEEN 74W-78W WHILE MORE WIDELY
SCATTERED SHOWERS ARE LOCATED N OF 22N BETWEEN 66W-74W. FARTHER
TO THE E...SUBSIDENCE ASSOCIATED WITH A DEEP LAYER RIDGE IS
RESULTING IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL
AND E ATLC. HOWEVER...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN
UPPER LEVEL LOW CENTERED NEAR 26N58W IS SUPPORTING ISOLATED
SHOWERS FROM 22N-25N BETWEEN 53W-62W.

$$
HUFFMAN





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