[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 101047
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 10 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

HURRICANE FRED IS CENTERED NEAR 15.9N 34.6W AT 10/0900 UTC OR
ABOUT 610 NM W OF THE CAPE VERDE ISLANDS MOVING NW AT 10 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 970 MB. MAXIMUM SUSTAINED
WIND SPEED IS 90 KT WITH GUSTS TO 110 KT. SCATTERED MODERATE/
STRONG CONVECTION IS FROM 15N-21N BETWEEN 31W-36W. WIDELY
SCATTERED MODERATE CONVECTION IS ELSEWHERE FROM 13N-21N BETWEEN
29W-39W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 72W S OF 18N MOVING W NEAR 18 KT. THE
WAVE COINCIDES WITH A NARROW MAXIMUM AREA OF DEEP LAYER MOISTURE
OBSERVED IN THE TOTAL PRECIPITABLE WATER IMAGERY AND CONTINUES
TO MOVE BENEATH UPPER LEVEL SWLY FLOW E OF AN UPPER LEVEL TROUGH
AXIS LOCATED ACROSS THE CENTRAL CARIBBEAN. DEEP CONVECTION IS
BEING INHIBITED BY DRY AIR ALOFT AS ONLY HIGH LEVEL CIRRUS IS
NOTED ON SATELLITE IMAGERY.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N18W 15N28W 11N42W 8N60W.
ASIDE FROM CONVECTION ASSOCIATED WITH HURRICANE FRED... ISOLATED
MODERATE CONVECTION IS FROM WITHIN 90 NM EITHER SIDE OF THE AXIS
BETWEEN 19W-27W. ELSEWHERE...SCATTERED MODERATE CONVECTION IS
WITHIN 60 NM EITHER SIDE OF A LINE FROM 12N33W TO 10N43W.

...DISCUSSION...

GULF OF MEXICO...
NWLY UPPER LEVEL FLOW DOMINATES ACROSS THE GULF AS UPPER LEVEL
TROUGHING IS ACROSS THE W ATLC AND FLORIDA PENINSULA WHILE AN
UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER THE ERN
PACIFIC EXTENDS UPPER RIDGING ACROSS CENTRAL MEXICO AND THE WRN
GULF. A FAIR AMOUNT OF UPPER LEVEL MOISTURE IN THE FORM OF HIGH
LEVEL CLOUDINESS IS NOTED ON INFRARED SATELLITE IMAGERY ACROSS
THE GULF THIS MORNING. WITH THE LACK OF ANY SIGNIFICANT SURFACE
FEATURES AND A WEAK PRESSURE GRADIENT PRESENT...UPPER DIFFLUENCE
ASSOCIATED WITH THE UPPER LEVEL RIDGING IS GENERATING SCATTERED
SHOWERS AND TSTMS ACROSS THE N/CENTRAL AND WRN GULF W OF A LINE
FROM NEW ORLEANS LOUISIANA TO 20N96W. AS OF 0900 UTC...A SURFACE
TROUGH EXTENDS FROM NEAR POMPANO BEACH FLORIDA THROUGH 24N83W TO
NEAR CANCUN MEXICO AND REMAINS LOCATED NEAR THE BASE OF THE
AFOREMENTIONED TROUGHING OVER THE W ATLC. LOW-LEVEL CONVERGENCE
ALONG THE SURFACE TROUGH AND AN AREA OF UPPER LEVEL DIFFLUENCE
OVER THE SE GULF ARE GENERATING SCATTERED SHOWERS AND TSTMS S OF
26N E OF 85W...INCLUDING THE STRAITS OF FLORIDA AND FLORIDA KEYS.

CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS FROM THE SE GULF NEAR KEY WEST FLORIDA
OVER THE YUCATAN CHANNEL TO CANCUN MEXICO. LOW-LEVEL CONVERGENCE
NEAR THE SURFACE TROUGH AND UPPER LEVEL DIFFLUENCE LOCATED OVER
CUBA IS SUPPORTING SCATTERED SHOWERS AND TSTMS OVER THE NW
CARIBBEAN FROM 19N-23N BETWEEN 79W-85W. THE REMAINDER OF THE WRN
AND CENTRAL CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER
UNDER DRY SUBSIDENT AIR DUE TO NLY FLOW ALOFT ON THE ERN
PERIPHERY OF AN UPPER LEVEL RIDGE OVER SRN MEXICO AND A LARGE
PORTION OF CENTRAL AMERICA. UPPER LEVEL TROUGHING IS ACROSS THE
CARIBBEAN E OF 82W AND CONTINUES DRAWING UPPER LEVEL MOISTURE
ON SWLY WINDS FROM NRN SOUTH AMERICA AND PANAMA TO OVER THE
S/CENTRAL CARIBBEAN NE TO PUERTO RICO. NEAR THE BASE OF THE
UPPER LEVEL TROUGH OVER THE SW CARIBBEAN...SCATTERED SHOWERS AND
ISOLATED TSTMS ARE S OF 13N BETWEEN 75W-82W. MODERATE TO FRESH
TRADE WINDS CONTINUE ACROSS MUCH OF THE BASIN.

ATLANTIC OCEAN...
A SURFACE TROUGH ENTERS THE DISCUSSION AREA NEAR 32N71W AND
EXTENDS SW TO NEAR POMPANO BEACH FLORIDA. LOW-LEVEL CONVERGENCE
NEAR THE SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS AND
TSTMS OVER MUCH OF THE SW NORTH ATLC S OF 30N BETWEEN 72W-81W...
INCLUDING THE NW AND CENTRAL BAHAMAS AS WELL AS PORTIONS OF THE
FLORIDA STRAITS. THIS ACTIVITY IS ALSO ENHANCED BY UPPER LEVEL
DIFFLUENCE AND MOIST SWLY FLOW ALOFT AROUND AN UPPER LEVEL
TROUGH THAT DIPS SWD FROM THE ERN CONUS OVER THE FLORIDA
PENINSULA AND W ATLC WATERS TO 23N. FARTHER TO THE SE...AN UPPER
LEVEL LOW IS CENTERED NEAR 26N65W AND HAS CONTINUED TO BE
ABSORBED INTO THE MAIN WRN ATLC TROUGH OVER THE PAST 24 HOURS.
UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE UPPER LOW IS
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 19N-23N
BETWEEN 61W-70W. A 1018 MB SURFACE HIGH IS CENTERED NEAR 29N59W.
A WEAKNESS IN THE SUBTROPICAL RIDGE ENTERS THE DISCUSSION AREA
AS A SURFACE TROUGH NEAR 31N45W AND EXTENDS SW TO A 1016 MB LOW
NEAR 28N50W. POSSIBLE ISOLATED SHOWERS ARE WITHIN THE AREA FROM
26N-30N BETWEEN 47W-51W. OVER THE CENTRAL ATLC...A SURFACE
TROUGH EXTENDS FROM 16N47W TO 24N44W. ISOLATED SHOWERS ARE
LOCATED WITHIN 60 NM EITHER SIDE OF THE TROUGH AXIS. THIS
SURFACE TROUGH IS SUPPORTED ALOFT BY AN UPPER LOW CENTERED NEAR
22N46W. ELSEWHERE ACROSS THE TROPICAL ATLC...HURRICANE FRED
REMAINS THE MAIN CONCERN. UPPER LEVEL ANTICYCLONIC FLOW IS OVER
THE ERN ATLC S OF 25N E OF 41W AND CONTINUES TO ENHANCE THE
CONVECTION AND OUTFLOW ASSOCIATED WITH HURRICANE FRED.

$$
HUFFMAN





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