[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201148
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI SEP 20 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...
DROPWINDSONDE DATA FROM THE NASA GLOBAL HAWK SAMPLED 1002 MB FOR
THE LOW PRESSURE CENTER IN THE GULF LOCATED NEAR 21N96W AT
20/0900 UTC. THIS AREA OF LOW PRESSURE IS WITHIN A ZONE OF VERY
MOIST AIR AS DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY.
HOWEVER...STRONG NORTHWESTERLY WIND SHEAR IN THE VICINITY OF THE
LOW IS HINDERING IN PART CONVECTIVE ACTIVITY. MIDDLE-LEVEL
DIFFLUENCE W-SW OF THE LOW CENTER IS SUPPORTING SCATTERED
MODERATE CONVECTION S OF 21N W OF 95W. UPPER-LEVEL DIFFLUENCE SE
OF THE LOW SUPPORTS SCATTERED MODERATE/ISOLATED STRONG
CONVECTION S OF 20N BETWEEN 91W-94W AS WELL AS INLAND SOUTHERN
MEXICO AND GUATEMALA. ENVIRONMENTAL CONDITIONS ARE ONLY
MARGINALLY CONDUCIVE AND SIGNIFICANT DEVELOPMENT OF THIS SYSTEM
IS BECOMING LESS LIKELY THUS GIVING IT A MEDIUM CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS
DISTURBANCE WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAINS OVER
PORTIONS OF EASTERN AND SOUTHERN MEXICO DURING THE NEXT FEW DAYS.

...TROPICAL WAVES...
THE AXIS OF A TROPICAL WAVE EXTENDS ALONG 22N33W TO 10N33W AND
IS MOVING W NEAR 10-15 KNOTS. TOTAL PRECIPITABLE WATER IMAGERY
SHOW MOST OF THE WAVE ENVIRONMENT HAS BEEN UNDERCUT BY VERY DRY
AIR WHICH IS LIMITING CONVECTION. SCATTERED MODERATE CONVECTION
IS IN THE NORTHERN SECTOR OF THE WAVE AXIS FROM 21N-23N BETWEEN
31W-34W AND SE OF THE AXIS FROM 12N-15N BETWEEN 28W-31W. THESE
AREAS OF CONVECTION COINCIDE WITH SMALL SECTORS OF MODERATE
TO VERY MOIST AIR IN TOTAL PRECIPITABLE WATER IMAGERY.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR
11N16W TO 10N30W 07N39W. THE ITCZ CONTINUES FROM 07N39W TO
11N53W. SCATTERED MODERATE CONVECTION IS FROM 06N-12N E OF
21W...FROM 06N-11N BETWEEN 26W-40W AS WELL AS FROM 08N-10N
BETWEEN 43W-49W.

...DISCUSSION...

GULF OF MEXICO...
A VERY MOIST ENVIRONMENT AT THE LOWER LEVELS DOMINATE THE
WESTERN GULF WATERS AS DEPICTED IN IMAGERY OF TOTAL PRECIPITABLE
WATER. HOWEVER...STRONG NORTHWESTERLY WIND SHEAR ACROSS GREAT
PORTIONS OF THE BASIN INHIBITS IN PART CONVECTIVE ACTIVITY THIS
MORNING. A 1002 MB LOW CENTER IS IN THE BAY OF CAMPECHE NEAR
21N96W. MIDDLE-LEVEL DIFFLUENCE W-SW OF THE LOW CENTER IS
SUPPORTING SCATTERED MODERATE CONVECTION S OF 21N W OF 95W.
UPPER-LEVEL DIFFLUENCE SE OF THE LOW SUPPORTS SCATTERED
MODERATE/ISOLATED STRONG CONVECTION S OF 20N BETWEEN 91W-94W AS
WELL AS INLAND SOUTHERN MEXICO AND GUATEMALA. SEE THE SPECIAL
FEATURES SECTION FOR MORE INFORMATION ABOUT THIS DISTURBANCE.
SCATTERED SHOWERS ARE NW OF THE BASIN N OF 28N BETWEEN 92W-96W.
AN UPPER-LEVEL TROUGH EXTENDS ACROSS THE FLORIDA PENINSULA AND
THE STRAITS SUPPORTING ISOLATED SHOWERS OVER THE EASTERN GULF E
OF 85W.

THE DISTURBANCE IN THE SW GULF HAS A MEDIUM CHANCE OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS SYSTEM WILL
CONTINUE TO PRODUCE LOCALLY HEAVY RAINS OVER PORTIONS OF EASTERN
AND SOUTHERN MEXICO DURING THE NEXT FEW DAYS. A COLD FRONT IS
EXPECTED TO ENTER THE NORTHERN GULF WATERS BY SATURDAY
AFTERNOON.

CARIBBEAN SEA...
TOTAL PRECIPITABLE WATER IMAGERY SHOW A REDUCTION IN MOISTURE
ACROSS GREAT PORTIONS OF THE BASIN THIS MORNING. MIDDLE TO UPPER
LEVEL DIFFLUENT FLOW IN THE NW CARIBBEAN BASIN ENHANCES
SCATTERED SHOWERS N OF 16N W OF 74W. ISOLATED SHOWERS ARE
ELSEWHERE IN THE BASIN EXCEPT E OF 70W WHERE FAIR WEATHER
DOMINATES. A SURFACE TROUGH IS EXPECTED TO ENTER THE EASTERN
CARIBBEAN SEA EARLY SUNDAY AFTERNOON GENERATING SHOWERS POSSIBLY
AFFECTING THE LESSER ANTILLES.

HISPANIOLA...
UPPER-LEVEL DIFFLUENCE FROM A TROUGH OVER THE N WESTERN ATLC AND
A RIDGE COVERING WESTERN-CENTRAL CARIBBEAN SEA SUPPORTS
CLOUDINESS AND ISOLATED SHOWERS OVER THE WINDWARD
PASSAGE...HAITI AND WESTERN-CENTRAL DOMINICAN REPUBLIC. BESIDES
THE TYPICAL AFTERNOON/EARLY EVENING SHOWERS ACTIVITY DUE TO
SURFACE HEATING...CONVECTIVE ACTIVITY DUE TO THE UPPER-LEVEL
FEATURES MENTIONED ABOVE IS EXPECTED TO CONTINUE UNTIL SATURDAY
NIGHT.

ATLANTIC OCEAN...
AN UPPER-LEVEL TROUGH IN THE N WESTERN ATLC SUPPORTS A FRONTAL
SYSTEM THAT ENTERS THE DISCUSSION AREA AS A COLD FRONT FROM
30N50W TO 29N55W WHERE IT TRANSITIONS TO A STATIONARY FRONT TO
28N61W. IN ADDITION...THE UPPER-LEVEL TROUGH SUPPORTS A SURFACE
TROUGH ASSOCIATED WITH A 1011 MB LOW PRESSURE CENTER NEAR
26N68W. SCATTERED MODERATE CONVECTION AND TSTMS ASSOCIATED WITH
THE FRONT AND THE LOW ARE FROM 21N-33N BETWEEN 59W-69W.
DIFFLUENT FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND A RIDGE
COVERING THE WESTERN-CENTRAL CARIBBEAN SUPPORTS SCATTERED
SHOWERS IN THE BAHAMAS AND EASTERN CUBA. A SURFACE TROUGH
EMBEDDED WITHIN A VERY MOIST ENVIRONMENT EXTENDS ALONG 18N52W TO
11N53W. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS IS FROM
12N-18N BETWEEN 48W-55W.

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

$$
NR


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