[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 282351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 28 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

HURRICANE NADINE IS CENTERED NEAR 30.1N 35.0W AT 28/2100 UTC OR
ABOUT 615 NM SW OF THE AZORES MOVING NW AT 7 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED
IS 65 KT WITH GUSTS TO 80 KT. SCATTERED MODERATE CONVECTION IS
FROM 29N-33N BETWEEN 31W-37W. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 11N19W TO 17N17W MOVING W AT 10 KT.
EXAMINING A HOVMOLLER DIAGRAM AND UPPER AIR TIME SECTION
ANALYSES...IT APPEARS THE WAVE PASSED DAKAR SENEGAL AROUND
28/1200 UTC AND NOW REMAINS EMBEDDED WITHIN A MONSOONAL GYRE OFF
THE COAST OF AFRICA NEAR 11N19W. TOTAL PRECIPITABLE WATER
IMAGERY ALSO INDICATES DEEP LAYER MOISTURE IN THE VICINITY OF
THE WAVE AXIS FROM 09N-17N E OF 22W. MOST DEEP CONVECTION
REMAINS OVER INLAND PORTIONS OF W AFRICA WITH SCATTERED MODERATE
CONVECTION FROM 10N-13N BETWEEN 11W-17W.

TROPICAL WAVE EXTENDS FROM 09N37W TO 16N34W MOVING W AT 10 KT.
THE WAVE COINCIDES WITH A WEAK 700 MB TROUGH NOTED IN GLOBAL
MODEL GUIDANCE BETWEEN 32W-39W. TOTAL PRECIPITABLE WATER IMAGERY
ALSO INDICATES THE WAVE LIES WITHIN A DEEP LAYER MOISTURE
MAXIMUM FROM 10N-18N BETWEEN 26W-38W. NO SIGNIFICANT CONVECTION
IS NOTED IN THE VICINITY OF THE WAVE AXIS.

TROPICAL WAVE EXTENDS FROM 13N80W TO 21N82W MOVING W AT 5-10 KT.
THE WAVE COINCIDES WITH VERY BROAD 700 MB TROUGHING OVER THE
WESTERN CARIBBEAN AS TOTAL PRECIPITABLE WATER VALUES REMAIN
ELEVATED ACROSS THE REGION BETWEEN 69W-84W. WITH AN UPPER LEVEL
TROUGH OVER THE FLORIDA PENINSULA WITH AXIS ALONG 81W...ENERGY
CONTINUES TO FRACTURE NORTHWARD WHILE SOME ENERGY CONTINUES
WESTWARD. SCATTERED MODERATE CONVECTION IS FROM 20N-24N BETWEEN
73W-84W AND IS LIKELY ENHANCED DUE TO CLOSE PROXIMITY OF THE
UPPER LEVEL TROUGHING. ALSO SCATTERED MODERATE CONVECTION IS
OCCURRING OVER A LARGE PORTION OF THE WESTERN CARIBBEAN SEA FROM
07N-17N BETWEEN 75W-85W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 13N17W TO
11N19W TO 08N36W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 08N36W TO 10N49W. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 04N-09N BETWEEN 15W-30W. A SURFACE TROUGH IS
ANALYZED FROM 09N-15N ALONG 50W AT THE WESTERN EXTENT OF THE
ITCZ AXIS. SCATTERED MODERATE CONVECTION IS FROM 07N-17N BETWEEN
42W-52W...AND IS LIKELY ENHANCED DUE TO AN UPPER LEVEL TROUGH
NOTED BETWEEN 45W-60W OVER THE TROPICAL ATLC.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH AXIS EXTENDS ALONG 81W TO A BASE OVER THE
NW CARIBBEAN SEA. WHILE WATER VAPOR IMAGERY INDICATES FAIRLY DRY
AIR ALOFT OVER THE FAR EASTERN GULF...THE REMAINDER OF THE GULF
IS UNDER NORTH-NORTHWESTERLY FLOW ALOFT DUE TO BROAD UPPER LEVEL
RIDGING OVER MUCH OF MEXICO AND THE SOUTH-CENTRAL CONUS
STRETCHING EASTWARD TO 85W. MIDDLE TO UPPER LEVEL MOISTURE
CONTINUES TO SPILL OVER THE TOP OF THE RIDGE PROVIDING NW
PORTIONS OF THE GULF WITH BROKEN TO OVERCAST CLOUDINESS THIS
EVENING. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALSO
FOUND NW OF A LINE FROM MOBILE BAY NEAR 30N88W TO NEAR TAMPICO
MEXICO. AT THE SURFACE...A RIDGE EXTENDS FROM THE SE CONUS
ANCHORED BY A 1019 MB HIGH CENTERED OVER CENTRAL GEORGIA TO THE
SW GULF NEAR 19N96W WITH PRIMARILY LIGHT EAST TO SOUTHEASTERLY
SURFACE FLOW. OTHERWISE...THE UPPER LEVEL TROUGH ALONG 81W IS
PROVIDING FOR OVERALL BROAD SURFACE TROUGHING ACROSS THE FLORIDA
PENINSULA AND SW NORTH ATLC REGION THAT SUPPORTS EARLY EVENING
SCATTERED SHOWERS AND TSTMS ACROSS THE SOUTHERN FLORIDA
PENINSULA AND PORTIONS OF THE FLORIDA STRAITS.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH EXTENDS FROM OVER THE FLORIDA PENINSULA
INTO THE NW CARIBBEAN AND CONTINUES TO ADVECT MIDDLE TO UPPER
LEVEL MOISTURE NORTHWARD BETWEEN 70W-83W. SCATTERED SHOWERS AND
TSTMS ARE OCCURRING OVER THIS AREA FROM PANAMA AND NORTHERN
COLOMBIA NORTHWARD TO CUBA AND PORTIONS OF HISPANIOLA. TO
FURTHER AID IN LOW TO MIDDLE LEVEL CONVERGENCE AT THE SURFACE
AND DIFFLUENCE ALOFT... A TROPICAL WAVE ALONG 82W IS ALSO ADDING
ATMOSPHERIC ENERGY TO THE CONVECTIVE EQUATION THIS EVENING.
OVERALL...VERY BROAD SYNOPTIC SCALE SURFACE TROUGHING IS ACROSS
THE SW NORTH ATLC REGION AND MUCH OF THE CARIBBEAN WHICH IS A
FAVORABLE ENVIRONMENT FOR THE CONVECTION. EAST OF 70W...AN UPPER
LEVEL RIDGE AXIS EXTENDS ALONG 67W AND PROVIDES THE EASTERN
CARIBBEAN AND LESSER ANTILLES WITH A DRY AND SUBSIDENT NW FLOW
ALOFT. A FEW ISOLATED SHOWERS ARE NOTED OVER THE NE CARIBBEAN
AND PUERTO RICO THIS EVENING...HOWEVER COVERAGE AND INTENSITY
LESSENED DUE TO THE DRIER AIR IN PLACE ALOFT.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH AXIS IS LOCATED OVER THE FLORIDA PENINSULA
THIS EVENING PROVIDING MUCH OF THE SW NORTH ATLC WITH MOIST
SOUTHWESTERLY UPPER LEVEL FLOW BETWEEN 69W-80W. WHILE NO
SPECIFIC SURFACE FRONTAL BOUNDARIES ARE PRESENT...SCATTERED
SHOWERS AND TSTMS ARE OCCURRING W OF 73W. THE OVERALL LARGER
SCALE SYNOPTIC SURFACE TROUGHING EXTENDS FARTHER EAST TO 52W AND
REMAINS S OF 30N. A SURFACE TROUGH IS ANALYZED FROM 20N62W TO
25N57W AND CONTINUES TO PROVIDE FOCUS FOR WEAK LOW-LEVEL
MOISTURE CONVERGENCE AND ISOLATED SHOWERS AND TSTMS FROM 19N-28N
BETWEEN 52W-58W...AND FROM 20N-25N BETWEEN 60W-67W. FARTHER
SE...AN UPPER LEVEL TROUGH AXIS EXTENDS ALONG 30N47W TO 20N50W
TO A BASE NEAR 12N55W. AS MENTIONED IN THE ITCZ SECTION...THIS
TROUGHING IS LIKELY ENHANCING SCATTERED SHOWERS AND TSTMS
PRIMARILY EAST OF A SURFACE TROUGH S OF 15N ALONG 50W. THE
ACTIVITY IS OCCURRING FROM 07N-17N BETWEEN 42W-52W. OTHERWISE...
HURRICANE NADINE IS LOCATED IN THE VICINITY OF 30N35W AND IS
EXPECTED TO EXPERIENCE SOME UPPER LEVEL WIND SHEAR DUE TO THE
PREVIOUSLY MENTIONED MIDDLE TO UPPER LEVEL TROUGH. THE UPPER
LEVEL TROUGH IS ANCHORED BY AN UPPER LEVEL LOW CENTERED NEAR
34N48W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
HUFFMAN



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