[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE SEP 24 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS WITH AXIS
EXTENDING FROM 18N27W TO 10N30W AND MOVING WEST NEAR 15-20 KT.
TOTAL PRECIPITABLE WATER AND WATER VAPOR IMAGERY SHOW THE WAVE
IS EMBEDDED IN A MODERATE TO HIGH MOIST ENVIRONMENT.
HOWEVER...NO CONVECTIVE ACTIVITY IS ASSOCIATED WITH IT DUE IN
PART TO STRONG DEEP LAYER SOUTHWESTERLY WIND SHEAR.

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS EXTENDING
FROM 16N43W TO 09N40W AND MOVING WEST NEAR 15-20 KT. SIMILAR TO
THE PREVIOUS WAVE...THIS WAVE IS EMBEDDED IN A MODERATE TO HIGH
MOIST ENVIRONMENT AND DEEP LAYER SOUTHWESTERLY WIND SHEAR IS
AFFECTING IT. HOWEVER...AN ELONGATED UPPER-LEVEL LOW IS
SUPPORTING A LINE OF SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN
180 NM EAST OF THE WAVE AXIS.

A TROPICAL WAVE IS ABOUT 480 NM NE OF THE LEEWARD ISLANDS. THE
AXIS OF THIS WAVE EXTENDS FROM 21N52W TO A 1014 MB LOW NEAR
19N54W TO 13N54W AND IS MOVING W-NW NEAR 15 KT. TOTAL
PRECIPITABLE WATER AND WATER VAPOR IMAGERY SHOW THE WAVE IS
EMBEDDED WITHIN A DRY ENVIRONMENT WHICH ALONG WITH MODERATE DEEP
LAYER NORTHERLY WIND SHEAR INHIBIT CONVECTIVE ACTIVITY AT THE
TIME.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH AXIS PASSES THROUGH SENEGAL AFRICA NEAR
12N16W TO 13N24W 08N30W 07N39W. THE ITCZ  CONTINUES FROM 06N40W
TO NEAR THE COAST OF BRAZIL AT 03N50W. SCATTERED MODERATE
CONVECTION IS FROM 06N-08N BETWEEN 18W-21W AND FROM 04N-10N
BETWEEN 26W-32W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM THE UPPER MIDWEST TO
THE NW GULF SUPPORTING A 1008 MB LOW PRESSURE CENTER NEAR
27N93W. THE TROUGH ALOFT ALSO SUPPORTS A SURFACE TROUGH FROM SE
LOUISIANA NEAR 29N91W TO THE LOW CENTER TO 26N96W. HOWEVER...THE
PRESENCE OF VERY DRY AIR IN THE LOWER AND MIDDLE LEVELS IN THE
WESTERN GULF...AS SHOWN IN TOTAL PRECIPITABLE WATER AND WATER
VAPOR IMAGERY...IS VOIDING CONVECTIVE ACTIVITY W OF 91W. AN
UPPER-LEVEL TROUGH IN THE N WESTERN ATLC SUPPORTS A STATIONARY
FRONT THAT EXTENDS ACROSS THE NORTHERN FLORIDA PENINSULA TO THE
NE GULF NEAR 29N85W TO SOUTHERN ALABAMA NEAR 30N87W. THIS
FRONTAL BOUNDARY IS ENHANCING A SWATH OF SHOWERS AND TSTMS FROM
NEW SMYRNA BEACH TO CRYSTAL RIVER FLORIDA TO THE NE GULF N OF
28N EAST OF 87W. HOWEVER...A SECTOR OF UPPER-LEVEL DIFFLUENCE
COINCIDING WITH A SURGE OF DEEP MOISTURE OVER THE EASTERN GULF
SUPPORTS A LINE OF SHOWERS AND TSTMS OVER THE CENTRAL GULF N OF
24N BETWEEN 87W-90W AND SCATTERED MODERATE CONVECTION OVER THE
EASTERN GULF FROM 25N-28N E OF 84W. THE LOW PRESSURE IS EXPECTED
TO DRIFT E-NE AND MOVE OVER THE N SW ATLC WED AFTERNOON. SHOWER
ACTIVITY IS EXPECTED TO CONTINUE OVER THE NORTH-CENTRAL AND NE
GULF WITHIN THAT PERIOD.

THE CARIBBEAN SEA...
EXCEPT FOR THE SOUTHERN CARIBBEAN...DRY AIR SUBSIDENCE DOMINATES
ACROSS THE BASIN SUPPORTING FAIR WEATHER. AN UPPER-LEVEL LOW IS
OVER THE SOUTHERN CARIBBEAN CENTERED NORTH OF THE PANAMA CHANNEL
WHICH ALONG THE MONSOON TROUGH SUPPORTS SCATTERED MODERATE
CONVECTION AND TSTMS SW OF A LINE FROM 14N83W TO 11N74W. SHOWERS
AND TSTMS ARE ACROSS THE MONA PASSAGE. A TROPICAL WAVE WILL PASS
NORTH OF THE LEEWARD ISLANDS BY WED AFTERNOON POSSIBLY ENHANCING
SHOWERS IN THE NE CARIBBEAN.

HISPANIOLA...
A REGION OF MIDDLE-LEVEL DIFFLUENCE BETWEEN CUBA AND HISPANIOLA
IS ENHANCING SHOWERS AND ISOLATED TSTMS ACROSS THE ISLAND. A DRY
AIRMASS IS EXPECTED TO MOVE ACROSS THE ISLAND FROM WED
TO THU AFTERNOON THUS SUPPORTING FAIR WEATHER.

THE ATLANTIC OCEAN...
AN UPPER-LEVEL TROUGH OVER THE N WESTERN ATLC SUPPORTS A COLD
FRONT THAT ENTERS THE AREA OF DISCUSSION NEAR 30N68W TO 27N71W
WHERE IT TRANSITIONS TO A STATIONARY FRONT TO 29N77W TO THE NE
FLORIDA COAST NEAR 29N81W. A PRE-FRONTAL TROUGH EXTENDS FROM
26N70W TO 24N70W. SCATTERED MODERATE CONVECTION AND ISOLATED
TSTMS ARE FROM 23N-30N W OF 76W AS WELL AS FROM 23N-30N BETWEEN
60W-72W. A 1020 MB HIGH PRESSURE CENTER IS NEAR 25N36W AND IS
EXPECTED TO STALL FOR THE NEXT 24 HOURS. FURTHER NORTH A COLD
FRONT EXTENDS FROM 30N17W TO 28N21W WHERE IT TRANSITIONS TO A
STATIONARY FRONT TO 28N37W. THERE IS NO CONVECTION ASSOCIATED
WITH THIS FRONTAL BOUNDARY.

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

$$
NR


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