[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011737
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 01 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1500 UTC.

...SPECIAL FEATURES...

TROPICAL STORM KIRK IS CENTERED NEAR 37.4N 46.5W AT 01/1500 UTC
OR ABOUT 630 NM SSE OF CAPE RACE NEWFOUNDLAND AND ABOUT 925 NM W
OF THE AZORES MOVING NE AT 22 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH
GUSTS TO 75 KT. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF
CENTER EXCEPT 240 NM NE QUADRANT. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE
DETAILS.

TROPICAL STORM LESLIE IS CENTERED NEAR 18.3N 55.7W AT 01/1500
UTC OR ABOUT 355 NM E OF THE LEEWARD ISLANDS MOVING W-NW AT 16
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. NUMEROUS
MODERATE AND SCATTERED STRONG CONVECTION IS WITHIN 270 NM SE
SEMICIRCLE OF CENTER WHILE SCATTERED MODERATE CONVECTION CAN
ALSO BE FOUND NW OF LESLIE FROM 18N-23N BETWEEN 55W AND 59W. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 12N27W TO 19N24W AND IS MOVING W AT
10 KT. A 1011 MB SURFACE LOW IS CENTERED AT THE SOUTHERN EXTENT
OF THE WAVE AXIS NEAR 12N27W. THE 01/1104 UTC ASCAT PASS
INDICATES THAT THIS BROAD LOW CENTER IS MOST LIKELY EMBEDDED IN
THE MONSOON TROUGH. GLOBAL MODEL GUIDANCE SHOWS THE WAVE WILL BE
SLOW TO MOVE WESTWARD OVER THE NEXT DAY OR SO. NO SIGNIFICANT
CONVECTION IS NOTED IN THE VICINITY OF THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM THE BORDER OF WESTERN
SAHARA AND MAURITANIA NEAR 21N17W TO THE AFOREMENTIONED LOW PRES
SYSTEM NEAR 12N27W TO 06N34W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 06N34W TO 05N40W TO 06N48W. NO SIGNIFICANT
DEEP CONVECTION IS NOTED ON SATELLITE IMAGERY NEAR THE AXIS AT
THIS TIME.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 29N94W. A BELT OF
20-30 KT NE TO E WINDS ALOFT LIES S OF THE ANTICYCLONE FROM
21N-27N. DESPITE THE SHEAR ALOFT...SCATTERED MODERATE CONVECTION
LIES WITHIN 120 NM OF THE COAST OF MEXICO FROM 19N-25N.
PRECIPITABLE WATER IMAGERY SHOWS LOW LEVEL MOISTURE IS POOLED
HERE ALONG THE WESTERN GULF COAST AND EXTENDS N-NE INTO THE
MISSISSIPPI VALLEY TOWARD THE REMNANTS OF ISAAC LOCATED NEAR
38.6N 93.6W AT 01/1500 UTC. AT THE SURFACE...HIGH PRES IS
CENTERED NEAR THE ALABAMA/GEORGIA BORDER. LOW LEVEL WINDS ARE
SOUTHEASTERLY ACROSS MUCH OF THE GULF W OF 85W...WITH MODERATE
TO FRESH FLOW FOUND PRIMARILY W OF 90W. A LIGHT TO GENTLE
NORTHEASTERLY BREEZE IS PRIMARILY FOUND E OF 85W ACCORDING TO
THE 01/0552 UTC OSCAT PASS AND OBSERVATIONS. THE SURFACE HIGH IS
FORECAST TO DRIFT W-SW INTO THE NORTHERN GULF OVER THE NEXT FEW
DAYS. THIS WILL WEAKEN THE WINDS OVER THE WESTERN GULF.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH EXTENDING SOUTHWESTWARD FROM A LOW ALOFT
OVER THE SW N ATLC IS DIPPING SOUTHWARD INTO CUBA. FAST MOVING
MID TO UPPER LEVEL CLOUDS ARE RACING OVER THE NE
CARIBBEAN...CAUGHT IN THE 25-30 KT NE FLOW ALOFT W OF THE UPPER
TROUGH. PRECIPITABLE WATER IMAGERY AT THE SURFACE SHOWS ANY
POOLING OF LOW LEVEL MOISTURE ASSOCIATED WITH THIS TROUGH IS
STILL N OF CUBA. ELSEWHERE...WATER VAPOR IMAGERY INDICATES DRY
AIR IS ALOFT OVER MUCH OF THE CARIBBEAN BASIN. MIDDLE TO UPPER
LEVEL MOISTURE INCREASES S OF 15N. THE ONLY AREA OF SIGNIFICANT
DEEP CONVECTION IN THE BASIN LIES WITHIN 120 NM OF THE COAST W
OF 77W AND S OF 13N WHERE SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION CAN BE FOUND. WITH TROPICAL STORM LESLIE LOCATED EAST
OF THE LESSER ANTILLES...MOSTLY NORTHEAST WINDS PREVAIL ACROSS
THE CARIBBEAN SHIFTING MORE EASTERLY W OF 70W. TYPICAL OF THIS
TYPE OF SYNOPTIC PATTERN...THE STRONGEST WINDS ARE NOTED NORTH
OF THE COAST OF COLOMBIA WITH CONFIRMATION BY A 01/1426 UTC
ASCAT PASS. LESLIE IS FORECAST TO LIFT AWAY FROM THE CARIBBEAN
OVER THE NEXT FEW DAYS AND WINDS WILL VERE MORE SOUTHERLY OVER
THE LESSER ANTILLES AND FAR EASTERN CARIBBEAN.

ATLANTIC OCEAN...
THE UPPER LEVEL LOW NEAR 29N70W EXTENDS A TROUGH SOUTHWESTWARD
THROUGH THE SOUTHEASTERN BAHAMAS INTO EASTERN CUBA. WATER VAPOR
IMAGERY SHOWS DRY AIR ALOFT BEHIND THIS TROUGH IS MOVING OVER
THE EASTERN FLORIDA PENINSULA AND THE NORTHERN AND CENTRAL
BAHAMAS. WINDS ARE A LIGHT TO GENTLE BREEZE OVER THE SW N ATLC
UNDER THE INFLUENCE OF A 1022 MB HIGH PRES SYSTEM N OF THE AREA
NEAR 33N76W. A WEAKENING STATIONARY FRONT ASSOCIATED WITH THE
TROUGH ALOFT WAS ANALYZED FROM 29N72W TO 31N61W WITH A TROUGH
ANALYZED FROM 29N66W TO 26N71W. ISOLATED SHOWERS ARE OCCURRING
WITHIN 90 NM EITHER SIDE OF THE STATIONARY FRONT AND TROUGH. THE
UPPER LOW IS FORECAST TO PINCH OFF FROM THE MEAN NORTHERN STREAM
TROUGH OVER THE NEXT FEW DAYS AND RETROGRADE SOUTHWESTWARD
THROUGH THE BAHAMAS. A SECONDARY UPPER TROUGH AXIS ASSOCIATED
WITH THE NORTHERN STREAM MEAN TROUGH EXTENDS ALONG 58W N OF 27N.
THIS TROUGH IS HELPING TO STEER T.S. LESLIE NORTHWARD. AN
ANTICYCLONE CENTERED NEAR 19N60W LIES OVER LESLIE AT THE MOMENT.
THIS ANTICYCLONE IS FORECAST TO MOVE AWAY FROM LESLIE OVER THE
NEXT FEW DAYS AS IT PASSES W-SW THROUGH PUERTO RICO AND INTO THE
NORTHERN CARIBBEAN. TROPICAL STORM KIRK IS LOCATED WELL N OF THE
DISCUSSION AREA. IT IS BEING STEERED NORTHEASTWARD ON THE
LEADING EDGE OF THE AFOREMENTIONED NORTHERN STREAM MEAN TROUGH.
FARTHER E... A SURFACE RIDGE AXIS EXTENDS FROM A 1030 MB HIGH
CENTERED NEAR 43N20W TO BETWEEN KIRK AND LESLIE NEAR 29N51W.
FAIR CONDITIONS ARE ASSOCIATED WITH THE RIDGING. HOWEVER...A
MIDDLE TO UPPER LEVEL LOW CENTERED NEAR 29N35W CONTINUES TO
PROVIDE FOCUS FOR ISOLATED SHOWERS AND THUNDERSTORMS OVER THE
FORECAST AREA N OF 25N BETWEEN 34W-40W AND ISOLATED SHOWERS
WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH ANALYZED FROM
31N31W TO 26N31W. THE GOES-R PG DUST PRODUCT SHOWS A LARGE AREA
OF SAHARAN DUST TO THE S OF THIS TROUGH WITHIN ABOUT 300 NM
EITHER SIDE OF A LINE FROM 30N16W TO 10N35W. THE TROPICAL WAVE
FROM 12N27W TO 19N24W DISCUSSED ABOVE LIES ON THE EASTERN SIDE
OF THIS SAHARAN AIR MASS WHICH IS INHIBITING THE DEVELOPMENT OF
ANY DEEP CONVECTION.

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

$$
SCHAUER




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