[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181157
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 34.5N 33.3W AT 18/1200
UTC OR ABOUT 369 NM WSW OF THE AZORES MOVING NE AT 7 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED
WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. SCATTERED MODERATE
CONVECTION IS FROM 33N-38N BETWEEN 32W-37W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 10N42W TO 18N37W MOVING W AT 10 KT.
THE WAVE REMAINS EMBEDDED WITHIN BROAD CYCLONIC FLOW FROM
10N-17N BETWEEN 37W-44W AND WITHIN A SURGE OF DEEP LAYER
MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED
MODERATE CONVECTION IS FROM 12N-16N BETWEEN 41W-44W.

TROPICAL WAVE EXTENDS FROM 13N67W TO 18N64W MOVING W AT 10-15
KT. THE WAVE REMAINS DIFFICULT TO TRACK WITH LOW-LEVEL CYCLONIC
FLOW EAST OF THE LESSER ANTILLES BETWEEN 57W-62W AND A WEAK 700
MB TROUGH OVER THE EASTERN CARIBBEAN SEA ALONG 68W. THEREFORE
THE POSITION OF THE WAVE IS COMPROMISED BETWEEN THESE TWO
FEATURES WITH TOTAL PRECIPITABLE WATER IMAGERY INDICATING
MAXIMIZED VALUES FROM 13N-19N BETWEEN 55W-70W. ISOLATED MODERATE
CONVECTION IS FROM 13N-15N BETWEEN 57W-60W...WITH ISOLATED
SHOWERS AND TSTMS ELSEWHERE ACROSS THE EASTERN CARIBBEAN SEA
FROM 15N-20N BETWEEN 58W-70W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 16N16W TO
10N22W TO 08N29W TO 09N38W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 10N44W TO 07N58W. SCATTERED MODERATE
CONVECTION IS FROM 04N-08N BETWEEN 24W-31W...AND FROM 08N-10N
BETWEEN 47W-53W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL SHORTWAVE
TROUGH IS LOCATED OVER THE LOWER MISSISSIPPI RIVER VALLEY THAT
EXTENDS AN AXIS INTO THE NW GULF ALONG 32N90W TO 21N97W. THE
TROUGHING SUPPORTS A SLOW MOVING COLD FRONT ANALYZED FROM A 1006
MB LOW CENTERED OVER SW ALABAMA NEAR 31N88W TO 26N93W NEAR NOAA
BUOY 42002. LOW-LEVEL MOISTURE CONVERGENCE IN THE VICINITY OF
THE FRONT ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF
THE TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND TSTMS N OF
25N BETWEEN THE FLORIDA PENINSULA AND THE FRONT. GLOBAL MODELS
SUGGEST THE SURFACE LOW PRESSURE AREA WILL QUICKLY MOVE NE AND
BECOME ABSORBED INTO THE NEXT COLD FRONT CURRENTLY EXTENDING
FROM THE MID-MISSISSIPPI RIVER VALLEY TO THE ARKLATEX REGION AND
INTO WEST-CENTRAL TEXAS. THIS SYNOPTIC SETUP WILL CONTINUE TO
PROVIDE THE CENTRAL AND EASTERN GULF WITH CONTINUED SURFACE
TROUGHING AND AN UNSETTLED WEATHER PATTERN. THE SECONDARY COLD
FRONT IS FORECAST TO STALL AND BECOME STATIONARY OVER THE
EASTERN GULF WEDNESDAY INTO THURSDAY WITH INCREASED PROBABILITY
OF SHOWER AND TSTM ACTIVITY E OF 90W. ELSEWHERE...A FEW ISOLATED
SHOWERS AND TSTMS ARE NOTED ACROSS THE SE GULF S OF 25N BETWEEN
82W-89W AND S OF 20N...INCLUDING INLAND PORTIONS OF THE YUCATAN
PENINSULA AND SOUTHERN MEXICO.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER
SOUTHERN GUATEMALA NEAR 16N91W THAT EXTENDS INFLUENCE EAST TO
82W. A DIFFLUENT ENVIRONMENT REMAINS MAXIMIZED OVER PORTIONS OF
THE NW CARIBBEAN...CENTRAL AMERICA...AND SOUTHERN MEXICO
GENERATING WIDELY SCATTERED SHOWERS AND TSTMS FROM 16N-22N
BETWEEN 87W-95W. FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED
NEAR 15N77W AND EXTENDS AN INVERTED UPPER LEVEL TROUGH AXIS
NORTHWARD FROM THE UPPER LEVEL LOW CENTER TO OVER CENTRAL CUBA
NEAR 21N79W. WATER VAPOR IMAGERY INDICATES THAT MOSTLY DRY AIR
IS ASSOCIATED WITH THIS FEATURE ACROSS THE CENTRAL CARIBBEAN
BETWEEN 72W-82W. SCATTERED SHOWERS AND TSTMS HOWEVER ARE
CONFINED S OF 13N BETWEEN 71W-79W IN ASSOCIATION WITH THE
PROXIMITY OF THE MONSOON TROUGH AXIS WHICH LIES ALONG 10N FROM
COSTA RICA TO NORTHERN COLOMBIA. FINALLY...ACROSS THE EASTERN
CARIBBEAN...AS MENTIONED ABOVE...A TROPICAL WAVE IS ALONG 66W
AND STRADDLES BETWEEN LOW-LEVEL CYCLONIC FLOW ALONG 59W AND A
700 MB TROUGH OVER PUERTO RICO. ISOLATED SHOWERS AND TSTMS ARE
OCCURRING FROM 15N-20N BETWEEN 58W-70W.

ATLANTIC OCEAN...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NW OF PUERTO
RICO NEAR 21N69W AND EXTENDS A RIDGE AXIS NW TO ANOTHER
ANTICYCLONIC CIRCULATION NEAR 31N73W. WATER VAPOR IMAGERY
INDICATES MOST MIDDLE TO UPPER LEVEL MOISTURE IS LOCATED ON THE
SOUTHERN AND WESTERN PERIPHERIES OF THE RIDGE WITH ISOLATED
SHOWERS AND TSTMS OCCURRING FROM 17N-22N BETWEEN 58W-76W...AND
FROM 22N-30N W OF 75W. THE REMAINDER OF THE SW NORTH ATLC IS
UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1024 MB
HIGH CENTERED WELL NORTH OF THE DISCUSSION AREA NEAR 40N61W.
FARTHER EAST...A WEAK UPPER LEVEL TROUGH AXIS EXTENDS ALONG 45W
TO A BASE NEAR 22N49W AND SUPPORTS A SURFACE TROUGH ANALYZED
FROM 32N53W TO 28N60W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING
WITHIN 75 NM EITHER SIDE OF THE BOUNDARY. ASIDE FROM THE
CYCLONIC WINDS ASSOCIATED WITH TROPICAL STORM NADINE N OF 28N
BETWEEN 25W-42W...THE REMAINDER OF THE EASTERN AND CENTRAL ATLC
IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1017 MB
HIGH CENTERED NEAR 28N22W AND A 1016 MB HIGH CENTERED NEAR
26N50W. THE RIDGE AXIS EXTENDS SW FROM THE HIGH CENTER TO 20N39W
THEN W-NW TO 26N50W.

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

$$
HUFFMAN




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