[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190601
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU SEP 19 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...
HUMBERTO WEAKENED TO A TROPICAL DEPRESSION AT 19/0300 UTC. ITS
CENTER IS NEAR 32.5N 43.4W OR ABOUT 867 NM W-SW OF THE AZORES.
PRESENT MOVEMENT IS N AT 8 KNOTS AND THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1009 MB. THE MAXIMUM SUSTAINED WIND SPEED IS
30 KNOTS WITH GUSTS TO 40 KNOTS. PLEASE READ THE PUBLIC
ADVISORIES ABOUT HUMBERTO THAT ARE ISSUED UNDER WMO HEADER
WTNT34 KNHC AND UNDER AWIPS HEADER MIATCPAT4... AND THE
FORECAST/ADVISORIES THAT ARE ISSUED UNDER WMO HEADER WTNT24 KNHC
AND UNDER AWIPS HEADER MIATCMAT4. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 27N-31N BETWEEN 39W-44W.

A 1005 MB LOW PRESSURE CENTER IS OVER THE BAY OF CAMPECHE NEAR
20N92W WITH AN ASSOCIATED TROUGH EXTENDING FROM 22N91W TO
17N92W. PRESENTLY...SCATTERED MODERATE CONVECTION IS S OF 22N E
OF 94W. HOWEVER...HEAVIER CONVECTION IS INLAND S-SE MEXICO AND
IN GUATEMALA. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE
CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION ON
THURSDAY. THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS WHILE IT
MOVES TO THE WEST-NORTHWEST.  THIS DISTURBANCE WILL LIKELY
SPREAD HEAVY RAIN OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO
AND COULD CAUSE LIFE-THREATENING FLOODS AND MUDSLIDES OVER AREAS
ALREADY IMPACTED BY TORRENTIAL RAIN DURING THE PAST SEVERAL DAYS.

...TROPICAL WAVES...
THE AXIS OF A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS
ALONG 21N27W TO 08N29W AND IS MOVING W NEAR 10 KNOTS. METEOSAT
SATELLITE IMAGERY CONTINUE TO SHOW DRY AIR INTRUSION TO THE
NORTHERN SECTOR OF THE WAVE WHICH IS HINDERING CONVECTION.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR
12N16W TO 10N25W. THE ITCZ CONTINUES FROM 10N25W TO 09N40W TO
11N56W. SCATTERED MODERATE CONVECTION IS FROM 04N-09N BETWEEN
23W-33W...FROM 06N-10N BETWEEN 34W-43W AND FROM 07N-13N BETWEEN
44W-51W.

...DISCUSSION...

THE GULF OF MEXICO...
A VERY MOIST ENVIRONMENT AT THE LOWER AND MIDDLE LEVELS DOMINATE
THE GULF WATERS AS DEPICTED IN IMAGERY OF TOTAL PRECIPITABLE
WATER AND WATER VAPOR. HOWEVER...STRONG NORTHWESTERLY WIND SHEAR
IS INHIBITING IN PART CONVECTIVE ACTIVITY ACROSS GREAT PORTIONS
OF THE BASIN. A DISTURBANCE IS BEING ANALYZED IN THE SW GULF.
SEE THE SPECIAL FEATURES SECTION. A WEAK UPPER-LEVEL TROUGH OVER
THE EASTERN GULF SUPPORTS A DISSIPATING STATIONARY FRONT ACROSS
NORTH-CENTRAL FLORIDA TO 28N82W TO 29N86W. ISOLATED SHOWERS
ASSOCIATED WITH THIS FRONTAL BOUNDARY ARE N OF 27N E OF 88W.
DIFFLUENT FLOW ALOFT FROM THE TROUGH OVER THE EASTERN GULF AND AN
UPPER-LEVEL RIDGE COVERING THE WESTERN CARIBBEAN SEA CONTINUES
TO SUPPORT SCATTERED SHOWERS IN THE FLORIDA STRAITS AND THE
YUCATAN CHANNEL. THERE IS A HIGH CHANCE FOR THE DISTURBANCE TO
BECOME A TROPICAL CYCLONE DURING THE NEXT 48. HEAVY RAIN OVER
PORTIONS OF EASTERN AND SOUTHERN MEXICO IS EXPECTED.

THE CARIBBEAN SEA...
A VERY MOIST ENVIRONMENT AT THE LOWER AND MIDDLE LEVELS DOMINATE
THE CARIBBEAN WATERS AS DEPICTED IN IMAGERY OF TOTAL
PRECIPITABLE WATER AND WATER VAPOR. UPPER-LEVEL DIVERGENCE FROM
A BROAD RIDGE COVERING THE BAHAMAS AND THE WESTERN-CENTRAL
CARIBBEAN SEA SUPPORTS SCATTERED SHOWERS AND TSTMS N OF 15N W OF
75W...INCLUDING PORTIONS OF CUBA AND JAMAICA. A CUT-OFF LOW IS
OVER THE CENTRAL-EASTERN BASIN BETWEEN 66W-70W THUS GENERATING
DIFFLUENCE TO SUPPORT SCATTERED MODERATE CONVECTION OVER
SOUTHERN HAITI AND ADJACENT WATERS WITHIN 120 NM OF THE
COASTLINE. SIMILAR CONVECTION IS OVER NW PUERTO RICO...INCLUDING
THE MONA PASSAGE. THIS CUT-OFF LOW IS ALSO GENERATING DIFFLUENCE
ALOFT IN THE SOUTHERN BASIN TO SUPPORT NUMEROUS
MODERATE/ISOLATED STRONG CONVECTION AND TSTMS S OF 13N BETWEEN
72W-76W. SCATTERED MODERATE CONVECTION AND TSTMS ARE JUST WEST
OF THE LEEWARD ISLANDS FROM 14N-17N BETWEEN 61W-65W.

A SURFACE TROUGH IS EXPECTED TO ENTER THE EASTERN CARIBBEAN SEA
SATURDAY AFTERNOON WHILE AN AREA OF LOW PRESSURE IS EXPECTED TO
DEVELOP N OF THE AREA JUST EAST OF THE BAHAMAS. THESE FEATURES
MAY GENERATE SHOWERS POSSIBLY AFFECTING THE GREATER AND LESSER
ANTILLES.

HISPANIOLA...
UPPER-LEVEL DIFFLUENCE FROM AN UPPER-LEVEL RIDGE COVERING THE
BAHAMAS AS WELL AS THE WESTERN-CENTRAL CARIBBEAN AND A CUT-OFF
LOW OVER THE CENTRAL-EASTERN BASIN IS SUPPORTING ISOLATED
SHOWERS AND TSTMS ACROSS THE ISLAND AND ADJACENT WATERS. BESIDES
THE TYPICAL AFTERNOON/EARLY EVENING SHOWERS ACTIVITY DUE TO
SURFACE HEATING...EXPECT LITTLE CHANGES IN THE NEXT 48 HOURS.

THE ATLANTIC OCEAN...
THE MAIN FEATURE IN THE ATLC IS TROPICAL DEPRESSION HUMBERTO
WHICH INFORMATION IS PROVIDED IN THE SPECIAL FEATURES SECTION. A
WEAK UPPER-LEVEL TROUGH IN THE W ATLC SUPPORTS A FRONTAL SYSTEM
THAT ENTERS THE DISCUSSION AREA AS A STATIONARY FRONT FROM
30N66W TO 28N74W WHERE IT TRANSITIONS TO A DISSIPATING
STATIONARY FRONT TO THE EASTERN COAST OF FLORIDA NEAR 28N80W. A
PRE-FRONTAL SURFACE TROUGH EXTENDS FROM 26N67W TO 24N73W.
SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ASSOCIATED WITH
THE FRONT AND THE TROUGH ARE FROM 24N-30N BETWEEN 60W-76W.
DIFFLUENT FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND A RIDGE
COVERING THE BAHAMAS AND THE WESTERN-CENTRAL CARIBBEAN SUPPORTS
SCATTERED SHOWERS IN THE BAHAMAS AND N OF CUBA BETWEEN 75W-83W.
FURTHER EAST...A 1017 MB HIGH PRESSURE CENTER IS NEAR 25N54W
WHICH IS EXPECTED TO DISSIPATE WITHIN THE NEXT 24 HOURS. A PAIR
OF SURFACE TROUGHS ARE OVER THE TROPICAL CENTRAL ATLC...HOWEVER
WITH NO CONVECTION ASSOCIATED WITH IT. ONE SURFACE TROUGH
EXTENDS FROM 20N33W TO 12N33W...JUST W OF A TROPICAL WAVE. THE
SECOND TROUGH IS ALONG 18N48W TO 11N50W.

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

$$
NR


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