[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181141
TWDAT

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

...SPECIAL FEATURES...
THE CENTER OF TROPICAL STORM HUMBERTO AT 18/0900 UTC IS NEAR
31.4N 43.7W OR ABOUT 913 NM W-SW OF THE AZORES. ITS PRESENT
MOVEMENT IS N-NW AT 7 KNOTS AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 35
KNOTS WITH GUSTS TO 45 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. PRESENTLY...MOST OF THE CONVECTION LIES E AND SE OF
THE LOW CENTER AS SCATTERED MODERATE CONVECTION FROM 28N-33N
BETWEEN 38W-42W.

A 1005 MB LOW PRESSURE CENTER IS IN THE YUCATAN PENINSULA NEAR
19N89W. NORTHWESTERLY WIND SHEAR IS KEEPING A CLUSTER OF
MODERATE/ISOLATED STRONG CONVECTION NE OF THE LOW CENTER FROM
19N-22N BETWEEN 86W-88W. NUMEROUS MODERATE TO ISOLATED STRONG
CONVECTION IS OVER THE NW CARIBBEAN SEA FROM 16N-22N BETWEEN 81W-
85W. ENVIRONMENTAL CONDITIONS ARE LIKELY TO BE CONDUCIVE FOR A
TROPICAL DEPRESSION TO FORM OVER THE BAY OF CAMPECHE DURING THE
NEXT COUPLE OF DAYS AFTER THE LOW MOVES INTO THE REGION ON
WEDNESDAY. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS. AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM LATER
TODAY...IF NECESSARY. REGARDLESS OF TROPICAL CYCLONE
FORMATION...THIS DISTURBANCE WILL LIKELY SPREAD HEAVY RAINS OVER
EASTERN MEXICO. THESE RAINS COULD CAUSE LIFE-THREATENING FLOODS
AND MUDSLIDES OVER AREAS ALREADY IMPACTED BY THE TORRENTIAL
RAINS ASSOCIATED WITH INGRID AND MANUEL.

...TROPICAL WAVES...
THE AXIS OF A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS
ALONG 19N24W TO 12N28W AND IS MOVING W NEAR 5 KNOTS. METEOSAT
SATELLITE IMAGERY CONTINUE TO SHOW INTRUSION OF SAHARAN DRY AIR
INTO THE WAVE ENVIRONMENT WHICH IS LIMITING CONVECTIVE ACTIVITY.
SCATTERED SHOWERS ARE NE OF THE WAVE AXIS FROM 19N-
21N...COINCIDING WITH A SMALL REGION OF HIGH MOISTURE DEPICTED
IN TOTAL PRECIPITABLE WATER IMAGERY.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR
16N16W TO 13N25W TO 09N32W. THE ITCZ CONTINUES FROM 09N32W TO
10N42W TO 11N51W. SCATTERED MODERATE CONVECTION IS FROM 05N-12N
BETWEEN 18W-32W...AS WELL AS FROM 07N-09N BETWEEN 40W-43W.

...DISCUSSION...

THE GULF OF MEXICO...
SCATTERED SHOWERS...REMNANTS OF INGRID ARE OVER THE W-NW GULF N
OF 22N WEST OF 90W. AN UPPER-LEVEL SHORTWAVE TROUGH OVER THE NE
GULF CONTINUE TO SUPPORT A STATIONARY FRONT THAT EXTENDS ACROSS
NORTH-CENTRAL FLORIDA TO 29N83W TO 30N85W TO SOUTHERN ALABAMA
NEAR 30N87W. RAINSHOWERS ASSOCIATED WITH THIS FRONTAL BOUNDARY
ARE N OF 28N BETWEEN 85W-88W. A BROAD UPPER-LEVEL RIDGE COVERING
THE WESTERN CARIBBEAN BASIN EXTENDS TO THE FLORIDA STRAITS. JUST
WEST OF THIS RIDGE...AN INVERTED TROUGH IS GENERATING DIFFLUENT
FLOW ALOFT TO SUPPORT THE CONVECTION ASSOCIATED WITH THE
DISTURBANCE OVER THE YUCATAN PENINSULA. SEE THE SPECIAL FEATURES
SECTION. FAIR WEATHER IS ELSEWHERE IN THE BASIN BEING SUPPORTED
BY A TONGUE OF VERY DRY AIR PRESENT IN WATER VAPOR IMAGERY. THE
DISTURBANCE IS EXPECTED TO ENTER THE BAY OF CAMPECHE LATER THIS
MORNING. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL
CYCLONE IN THE NEXT 48 HOURS.

THE CARIBBEAN SEA...
A BROAD UPPER-LEVEL RIDGE COVERS THE WESTERN CARIBBEAN BASIN
WHICH EXTENDS TO THE FLORIDA STRAITS. JUST WEST OF THIS
RIDGE...AN INVERTED TROUGH IS ACROSS THE NORTHERN CENTRAL
AMERICA AND THE YUCATAN PENINSULA THUS GENERATING DIFFLUENT FLOW
ALOFT TO SUPPORT THE CONVECTION IN THE NW BASIN ASSOCIATED WITH
THE DISTURBANCE IN THE YUCATAN PENINSULA. THE MONSOON TROUGH
AXIS EXTENDS FROM NORTHERN COLOMBIA TO NW HONDURAS THUS
SUPPORTING NUMEROUS MODERATE/ISOLATED STRONG CONVECTION AND
TSTMS IN THE SOUTHERN CARIBBEAN S OF 11N BETWEEN 75W-81W. AN
UPPER-LEVEL RIDGE IS CENTERED E OF THE LESSER ANTILLES BUT
EXTENDS TO THE EASTERN CARIBBEAN E OF 65W. DIFFLUENT FLOW ALOFT
GENERATED BY NEARLY EASTERLY UPPER-LEVEL FLOW OVER NORTHERN
SOUTH AMERICA IS SUPPORTING ISOLATED SHOWERS S OF 17N E OF
66W...INCLUDING THE LESSER ANTILLES. THE DISTURBANCE CURRENTLY
MOVING ACROSS THE YUCATAN PENINSULA IS EXPECTED TO MOVE WEST-
NORTHWESTWARD AND EMERGE OVER THE BAY OF CAMPECHE LATER
TODAY...WHERE ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE
CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION OVER THE
NEXT DAY OR TWO. CONVECTIVE ACTIVITY OVER THE NW BASIN IS
EXPECTED TO CONTINUE THROUGH LATE WED NIGHT.

HISPANIOLA...
CURRENTLY DRY STABLE AIR IS ACROSS MOST OF THE ISLAND THIS
MORNING WHICH IS FAVORING FAIR WEATHER. AN UPPER-LEVEL TROUGH
MOVES ACROSS THE DOMINICAN REPUBLIC AND PUERTO RICO WHILE THE
RIDGE OVER THE WESTERN CARIBBEAN EXTENDS TO HAITI. THIS IS
CAUSING DIFFLUENCE ALOFT TO SUPPORT ISOLATED SHOWERS AND TSTMS
ACROSS THE ISLAND. EXPECT RAINSHOWERS TO DEVELOP DURING THE
AFTERNOON AND EVENING HOURS TODAY THOROUGH THURSDAY.

THE ATLANTIC OCEAN...
THE MAIN FEATURE IN THE ATLC IS TROPICAL STORM HUMBERTO WHICH
INFORMATION IS PROVIDED IN THE SPECIAL FEATURES SECTION. AN
UPPER-LEVEL TROUGH IN THE W ATLC SUPPORTS A FRONTAL SYSTEM THAT
ENTERS THE DISCUSSION AREA AS A STATIONARY FRONT FROM 30N67W TO
29N75W TO THE EASTERN COAST OF FLORIDA NEAR 29N81W. DIFFLUENT
FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND THE RIDGE COVERING
THE BAHAMAS AND THE WESTERN CARIBBEAN SUPPORTS SCATTERED SHOWERS
N OF 23N W OF 72W. A SURFACE TROUGH IS FROM 28N66W TO 25N70W
GENERATING SCATTERED SHOWERS AND TSTMS FROM 25N-27N BETWEEN 68W-
70W. A SURFACE TROUGH IS N OF THE ITCZ ALONG 19N44W TO 12N47W
GENERATING SCATTERED SHOWERS FROM 13N-17N BETWEEN 42W-47W.

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

$$
NR/PAW


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