[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 18 2013

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
1715 UTC.

...SPECIAL FEATURES...
TROPICAL STORM HUMBERTO IS CENTERED AT 31.3N 43.8W AT 18/1500
UTC OR ABOUT 920 NM W-SW OF THE AZORES MOVING N-NW AT 4 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED
WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PLEASE SEE LATEST
PUBLIC ADVISORIES UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 AND
THE FULL FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/
WTNT24 FOR MORE DETAILS. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE WITHIN 90/120 NM OF LINE FROM 29N39W
31N41W TO 32N45W.

BROAD AREA OF LOW PRESSURE IS ANALYZED AS A SURFACE TROUGH THAT
EXTENDS FROM 22N90W THROUGH A 1004 MB LOW NEAR 20N90W TO N
GUATEMALA NEAR 17N90W. AN UPPER RIDGE IS TO THE E PROVIDING A
DIFFLUENT ENVIRONMENT. SCATTERED TO HEAVY SHOWERS WITH EMBEDDED
THUNDERSTORMS COVER THE AREA FROM 18N-22N BETWEEN 80W-90W. THIS
SYSTEM AT 18/1800 UTC IS NOW CENTERED W OF THE YUCATAN PENINSULA
IN THE BAY OF CAMPECHE BUT REMAINS POORLY ORGANIZED. THIS SYSTEM
IS EXPECTED TO MOVE W-NW OVER THE SW GULF OF MEXICO DURING THE
NEXT COUPLE OF DAYS WHERE ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO BE CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION. THIS
SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT... THIS DISTURBANCE
WILL LIKELY SPREAD HEAVY RAINS OVER PORTIONS OF EASTERN MEXICO
AND COULD CAUSE LIFE-THREATENING FLOODS AND MUDSLIDES OVER AREAS
ALREADY IMPACTED BY TORRENTIAL RAINS DURING THE PAST SEVERAL
DAYS.

...TROPICAL WAVES...
TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS EXTENDING FROM
21N25W TO 13N28W MOVING W NEAR 5 KT. WAVE IS ALONG THE LEADING
EDGE OF SURGE OF DEEP MOISTURE AS DEPICTED ON THE TOTAL
PRECIPITABLE WATER IMAGERY. NO ASSOCIATED CONVECTION.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL
ATLC NEAR 13N16W AND CONTINUES ALONG 13N19W TO 10N26W WHERE THE
ITCZ BEGINS AND CONTINUES ALONG 9N36W 9N47W TO 11N58W. CLUSTERS
OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION FROM 7N-10N
BETWEEN 18W-37W. A SURFACE TROUGH EXTENDS FROM 18N48W TO 11N47W
WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
WITHIN 75 NM OF LINE FROM 13N42W TO THE TROUGH NEAR 16N48W.

...DISCUSSION...

GULF OF MEXICO...
FEATURE TO WATCH THIS AFTERNOON IS THE LOW/SURFACE TROUGH IN THE
SPECIAL FEATURES ABOVE. A BROAD UPPER RIDGE IS ANCHORED OVER
MEXICO EXTENDING A RIDGE AXIS ACROSS THE GULF FROM TAMPICO
MEXICO TO SE LOUISIANA. AN UPPER RIDGE IS OVER THE NW CARIBBEAN
CLIPPING THE SE GULF S OF 25N E OF 85W AND IS PROVIDING
DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 26N BETWEEN 80W-85W. THIS SCENARIO IS
INDUCING AN UPPER TROUGH THAT EXTENDS FROM THE BROAD UPPER
TROUGH IN THE W ATLC ACROSS NE FLORIDA TO 24N87W. THE UPPER
TROUGH OVER THE W ATLC IS SUPPORTING A STATIONARY FRONT THAT
EXTENDS ACROSS FLORIDA FROM SAINT AUGUSTINE CLIPPING APALACHEE
BAY ALONG 30N85W CONTINUING INLAND ALONG THE N GULF COAST TO S
LOUISIANA. ISOLATED SHOWERS/THUNDERSTORMS DOT THE REMAINDER OF
THE GULF THIS AFTERNOON. THE LOW/TROUGH WILL CONTINUE TO MOVE TO
THE W-NW POSSIBLY AS A TROPICAL CYCLONE...AND STALL IN THE W
GULF FRI. THE LOW MAY MOVE SLOWLY E-NE ALONG A COLD FRONT
ENTERING THE NW GULF LATE FRI NIGHT OR WILL STALL OUT AND GET
LEFT BEHIND IN THE W CENTRAL GULF THROUGH THE WEEKEND.

CARIBBEAN SEA...
AN UPPER RIDGE COVERS THE W CARIBBEAN W OF 70W ANCHORED NEAR
20N85W AND PROVIDING A DIFFLUENT ENVIRONMENT FOR THE LOW/SURFACE
TROUGH IN THE SPECIAL FEATURES ABOVE. BENEATH THIS UPPER FLOW IS
A WEAK 1008 MB LOW IN THE SW CARIBBEAN NEAR 11N79W. THE MONSOON
TROUGH EXTENDS FROM COLOMBIA NEAR 10N75W THROUGH THE ABOVE 1008
MB LOW TO OVER NICARAGUA NEAR 13N84W. SCATTERED/NUMEROUS SHOWERS
WITH EMBEDDED THUNDERSTORMS ARE FROM 10N-13N BETWEEN 76W-81W
WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 14N TO INLAND
OVER COLOMBIA/PANAMA BETWEEN 74W-83W. AN UPPER LOW N OF PUERTO
RICO EXTENDS AN UPPER TROUGH ACROSS PUERTO RICO TO THE ABC
ISLANDS. AN E/W UPPER RIDGE ANCHORED IN THE TROPICAL ATLC
EXTENDS OVER THE REMAINDER OF THE E CARIBBEAN. THIS UPPER RIDGE
IS PROVIDING DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS FROM 12N-16N E OF 66W TO OVER THE LESSER
ANTILLES. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN WITH
FAIR WEATHER THIS AFTERNOON. FRESH TO STRONG TRADE WINDS ACROSS
THE S/CENTRAL AND NW CARIBBEAN WILL DIMINISH TO MODERATE BY FRI.
GENTLE TO MODERATE E TRADE WINDS WILL CONTINUE ACROSS THE AREA E
OF 70W THROUGH SUN.

HISPANIOLA...
DAYTIME HEATING IS BEGINNING TO DEVELOP CLOUDS AND ISOLATED
SHOWERS ACROSS THE ISLAND WHERE SKIES HAD BEEN CLEAR THIS
MORNING. AN UPPER LEVEL TROUGH IS JUST TO THE E OF HISPANIOLA
AND WILL REMAIN IN PLACE THROUGH SAT THEN BROADEN OUT THROUGH
SUN WHEN THE UPPER FLOW WILL BECOME WESTERLY. AFTERNOON
SHOWERS/THUNDERSTORMS COULD DEVELOP DAILY WITH THE DAYTIME
HEATING.

ATLANTIC OCEAN...
THE PRIMARY CONCERN THIS AFTERNOON IS T.S. HUMBERTO IN THE
CENTRAL ATLC. SEE SPECIAL FEATURES ABOVE. BROAD UPPER TROUGH
COVERS THE W ATLC N OF 27N W OF 60W SUPPORTING A COLD FRONT THAT
ENTERS THE REGION NEAR 32N61W EXTENDING TO 29N68W WHERE IT
BECOMES STATIONARY ALONG 29N76W THEN ACROSS NE FLORIDA NEAR
SAINT AUGUSTINE. A SURFACE TROUGH IS TO THE S EXTENDING FROM
28N68W TO 24N72W. CLUSTERS OF SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE FROM 24N TO THE FRONT BETWEEN 60W-76W AND N OF
29N W OF 79W. A SURFACE RIDGE COVERS THE E ATLC E OF T.S.
HUMBERTO ANCHORED BY A 1028 MB HIGH NE OF THE AZORES. THE FRONT
OVER THE W ATLC WILL DISSIPATE BY THU NIGHT. A BROAD SURFACE
TROUGH WILL PREVAIL FROM THE CENTRAL ATLC TO THE BAHAMAS THROUGH
SAT WITH THE POSSIBILITY OF A SURFACE LOW FORMING ALONG THE
TROUGH. THE TROUGH WILL FINALLY MOVE INTO THE CENTRAL ATLC ON
SUN.

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

$$
PAW

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