[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 12 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.

...SPECIAL FEATURES...

TROPICAL STORM FRED IS CENTERED NEAR 17.5N 33.7W AT 12/1500 UTC
OR ABOUT 565 NM W OF THE CAPE VERDE ISLANDS. FRED REMAINS
STATIONARY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB.
MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 35 KT WITH GUSTS
TO 45 KT. FRED IS NOW DEVOID OF DEEP CONVECTION...CONSISTING OF
ONLY A TIGHT SWIRL OF LOW CLOUDS. FRED IS FORECAST TO BECOME A
REMNANT LOW WITHIN THE NEXT 24 HOURS AS IT MOVES INTO AN EVEN
MORE HOSTILE ENVIRONMENT. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 20W/21W S OF 18N MOVING W 10 KT WITH A
1012 MB LOW NEAR 12N20W. THE WAVE AND LOW HAVE BEEN ADJUSTED
EASTWARD SLIGHTLY TO FIT THE BROAD AREA OF CYCLONIC TURNING IN
VISIBLE IMAGERY...LOW TO MID-LEVEL CLOUD DRIFT WINDS...AND
SURFACE OBSERVATIONS. SHOWERS AND TSTMS REMAIN DISORGANIZED
WITHIN 180 NM OF THE LOW AND OVER THE CAPE VERDE ISLANDS.

TROPICAL WAVE IS OVER PORTIONS OF CENTRAL AMERICA AND THE GULF
OF HONDURAS ALONG 86W S OF 19N MOVING W 15 KT. THIS WAVE
COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM...AS INDICATED BY
TOTAL PRECIPITABLE WATER IMAGERY. LITTLE SIGNIFICANT CLOUDINESS/
SHOWERS IS ASSOCIATED WITH THIS FEATURE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 15N17W 09N23W 10N47W 10N61W.
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF THE AXIS
BETWEEN 36W-47W AND FROM 10N-13N BETWEEN 57W-61W.

...DISCUSSION...

GULF OF MEXICO...
A LARGE AREA OF SHOWERS AND TSTMS CONTINUE TO AFFECT THE WESTERN
AND NORTHERN PORTIONS OF THE GULF. THE SYNOPTIC FORCING CONSISTS
OF A SLOW MOVING MID TO UPPER TROUGH OVER S TEXAS AND N MEXICO
AND A STALLED OR SLOW MOVING WARM FRONT EXTENDING ACROSS THE FAR
NORTHERN GULF WATERS. SURFACE OBSERVATIONS... RADAR DATA...AND
VISIBLE IMAGERY SHOW A FEW WEAK LOWS EMBEDDED ALONG THE
BOUNDARY. THE MOST DISTINCT IN THE PRESSURE FIELD IS JUST OFF
THE TEXAS COAST NEAR 28N96W...ANALYZED 1006 MB. ANOTHER LOW IS
EVIDENT NEAR THE MISSISSIPPI COAST AND OFF THE NE FLORIDA COAST.
LOW-LEVEL CONVERGENCE AND UPPER DIFFLUENCE ARE PRODUCING
SCATTERED SHOWERS AND TSTMS N OF 21N BETWEEN 92W-96W AND NE OF A
LINE FROM SE LOUISIANA TO NEAR NAPLES FLORIDA.

CARIBBEAN SEA...
GENERALLY QUIET CONDITIONS PREVAIL ACROSS THE REGION. DRY MID TO
UPPER LEVEL AIR...ON THE S/SW SIDE OF AN UPPER LOW CENTERED A
COUPLE HUNDRED NM N OF PUERTO RICO...IS LIMITING THE DEVELOPMENT
OF SIGNIFICANT TSTM ACTIVITY OVER THE EASTERN CARIBBEAN. THE
ATMOSPHERE IS MORE MOIST W OF 78W INFLUENCED BY A TROPICAL WAVE
OVER THE GULF OF HONDURAS AND NORTHEASTERLY MID TO UPPER
FLOW...WHICH IS SPREADING HIGH LEVEL CLOUDINESS INTO THE AREA.
SHOWERS AND TSTMS ARE CONFINED TO THE EXTREME SW CARIBBEAN S OF
11N W OF 75W...WHERE THE UPPER FLOW IS MOST DIFFLUENT. THIS
CONVECTIVE ACTIVITY IS ALSO SUPPORTED BY LOW-LEVEL CONVERGENCE
ASSOCIATED WITH THE ITCZ.  SURFACE OBSERVATIONS AND A 1128 UTC
QUIKSCAT PASS SHOW 15-20 KT EASTERLY TRADES OVER THE SOUTH
CENTRAL CARIBBEAN AND SIMILAR MAGNITUDE SE WINDS OVER THE
NORTHWEST CARIBBEAN.

ATLANTIC OCEAN...
THERE ARE A FEW OF AREAS OF DISTURBED WEATHER ACROSS THE
SUBTROPICS. ONE OF THESE IS OVER THE FAR W ATLC...INCLUDING THE
NORTHERN BAHAMAS...WHERE SCATTERED SHOWERS AND TSTMS EXIST FROM
26N-31N W OF 76W. THIS ACTIVITY IS ASSOCIATED WITH A WEAK AREA
OF LOW PRESSURE ALONG A QUASI-STATIONARY BOUNDARY THAT EXTENDS
FROM NE FLORIDA TO 32N75W.  SIMILAR ACTIVITY IS PRESENT A FEW
HUNDRED NM TO THE EAST FROM 24N-31N BETWEEN 67W-72W ASSOCIATED
WITH DIFFLUENCE ALOFT BETWEEN AN UPPER LOW N OF PUERTO RICO...AN
UPPER RIDGE OVER THE EASTERN GULF OF MEXICO...AND AN UPPER
TROUGH ALONG 70W MAINLY N OF 30N. ANOTHER AREA OF SCATTERED
SHOWERS AND TSTMS IS WITHIN 120 NM OF A STATIONARY FROM THAT
EXTENDS FROM 32N37W TO 29N50W TO 32N60W. THE TROPICS REMAIN
FAIRLY QUIET. BESIDES FOR THE TROPICAL WAVE DISCUSSED
ABOVE...THE ONLY AREA OF CONVECTION IS FROM 10N-13N BETWEEN
56W-61W ASSOCIATED WITH THE ITCZ AND ENHANCED BY A LOW-LEVEL
TROUGH...WHICH WILL LIKELY BE ADDED TO THE 18 UTC ANALYSIS.

$$
CANGIALOSI



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