[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU JUL 09 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2300 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 15N24W TO 6N27W MOVING W NEAR 15
KT. ALTHOUGH LACKING A DEFINED SATELLITE PRESENTATION DUE TO A
LARGE AREA OF SAHARAN DUST ACROSS THE ERN TROPICAL ATLC...THIS
WAVE TRACKED W OF DAKAR AROUND 07/1800 UTC...BASED ON THE UPPER
AIR TIME SECTION ANALYSES FROM DAKAR SENEGAL. THIS WAVE ALSO IS
JUST W OF A DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. DEEP CONVECTION IS LIMITED DUE TO
THE SAHARAN AIR LAYER. HOWEVER...SCATTERED MODERATE CONVECTION
IS FROM 8N-10N BETWEEN 23W-26W.

A TROPICAL WAVE IS ALONG 56W S OF 18N MOVING W 20-25 KT. THIS
WAVE COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE MAXIMUM
OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. WHILE STILL ON THE
LEADING EDGE OF A LARGE AREA OF SAHARAN AIR...SCATTERED
MODERATE/ISOLATED STRONG CONVECTION HAS RECENTLY FORMED W OF THE
WAVE AXIS FROM 9N-13N BETWEEN 57W-61W.

A TROPICAL WAVE EXTENDS FROM THE WRN BAY OF CAMPECHE NEAR 20N95W
ACROSS SRN MEXICO INTO THE E PACIFIC MOVING W NEAR 15 KT. THIS
WAVE COINCIDES WITH A LARGE AREA OF INCREASED PRECIPITABLE WATER
ACROSS THE S/CENTRAL GULF OF MEXICO...YUCATAN PENINSULA AND A
LARGE PORTION OF CENTRAL AMERICA. WHILE THE MAJORITY OF DEEP
CONVECTION ASSOCIATED WITH THIS WAVE IS IN THE E
PACIFIC...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OVER
SRN MEXICO AND THE SRN BAY OF CAMPECHE FROM 17N-19N BETWEEN
92W-95W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N12W 10N25W 6N36W 6N45W 8N54W.
ISOLATED MODERATE CONVECTION IS FROM 9N-12N BETWEEN 20W-23W.
SCATTERED MODERATE CONVECTION IS FROM 9N-11N BETWEEN 51W-54W.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONT BORDERS THE NERN GULF OF MEXICO EXTENDING
ACROSS THE FLORIDA PANHANDLE FROM 31N81W TO A 1015 MB SURFACE
LOW NEAR 30N84W CONTINUING TO A SECOND 1015 MB SURFACE LOW NEAR
30N89W AND INTO LOUISIANA TO NEAR 30N92W. A SURFACE TROUGH
EXTENDS FROM THE FIRST LOW FROM 30N84W TO 29N87W. SURFACE
CONVERGENCE NEAR THESE FEATURES IS GENERATING SCATTERED
SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF N OF 28N E OF 93W. THE
FRONT...SURFACE LOWS...AND SURFACE TROUGH ARE SUPPORTED BY AN
UPPER LEVEL TROUGH ACROSS THE ERN CONUS EXTENDING OVER THE NERN
GULF TO 26N86W. UPPER LEVEL DIFFLUENCE AND MOIST SWLY FLOW ALOFT
ARE ALSO SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE
CENTRAL/ERN GULF OF MEXICO INCLUDING MOST OF CENTRAL FLORIDA
FROM 25N-28N E OF 90W. A TROPICAL WAVE OVER THE WRN BAY OF
CAMPECHE IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM
17N-19N BETWEEN 92W-95W. UPPER LEVEL DIFFLUENCE AROUND AN UPPER
LEVEL LOW NEAR 17N98W IS ENHANCING THIS ACTIVITY AS WELL AS
SCATTERED SHOWERS/THUNDERSTORMS OVER THE YUCATAN PENINSULA NOT
ASSOCIATED WITH THE WAVE FROM 16N-23N BETWEEN 88W-92W. THE NW
GULF REMAINS RELATIVELY CALM WITH MOSTLY SE WINDS OF 10-15 KT
AS A WEAK SURFACE RIDGE EXTENDS FROM THE W ATLC ALONG 24N TO 99W.

CARIBBEAN SEA...
NELY FLOW ALOFT AROUND AN UPPER LEVEL LOW OVER THE CENTRAL
CARIBBEAN NEAR 18N76W IS PROVIDING MODERATE TO STRONG SUBSIDENCE
TO THE NW CARIBBEAN RESULTING IN GENERALLY FAIR WEATHER.
HOWEVER...UPPER LEVEL DIFFLUENCE ON THE SRN PERIPHERY OF THIS
UPPER LEVEL TROUGH ALONG WITH SURFACE CONVERGENCE DUE TO THE
PROXIMITY OF THE E PACIFIC ITCZ ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS OVER THE MAJORITY OF CENTRAL AMERICA
INCLUDING NICARAGUA...COSTA RICA...PANAMA...AND THE ADJACENT
WATERS S OF 13N W OF 78W. UPPER LEVEL DIFFLUENCE BETWEEN THE
UPPER LEVEL TROUGH OVER THE W CARIBBEAN AND AN UPPER LEVEL HIGH
OVER THE ERN CARIBBEAN NEAR 13N66W IS SUPPORTING SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ACROSS THE CENTRAL CARIBBEAN FROM
11N-16N BETWEEN 67W-75W. SURFACE CONVERGENCE NEAR A SURFACE
TROUGH IN THE SW NORTH ATLC WHICH EXTENDS TO 20N67W IS
SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS OVER PUERTO RICO AND
HISPANIOLA. A TROPICAL WAVE ALONG 56W IS SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS OVER THE WINDWARD ISLANDS S OF 14N W OF
62W.

ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW NORTH ATLC N
OF 26N W OF 77W S OF A STATIONARY FRONT THAT EXTENDS FROM THE NE
INTO THE DISCUSSION TO NEAR 32N78W CONTINUING TO A 1015 MB
SURFACE LOW NEAR 30N84W. THIS ACTIVITY IS ENHANCED BY UPPER
LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN
CONUS AND AN UPPER LEVEL HIGH OVER THE W ATLC NEAR 33N55W ALONG
WITH MOIST SWLY FLOW ALOFT. THE REMAINDER OF THE ATLC IS UNDER A
BROAD SURFACE RIDGE ANCHORED BY A 1026 MB SURFACE HIGH NEAR
30N47W BRINGING GENERALLY FAIR WEATHER ACROSS THE AREA...WITH
THE EXCEPTION OF A WWD PROPAGATING SURFACE TROUGH EXTENDING FROM
26N57W TO 20N67W. ISOLATED SHOWERS ARE WITHIN 100 NM TO THE W OF
THE TROUGH AXIS...INCLUDING PORTIONS OF PUERTO RICO AND
HISPANIOLA.

$$
WALTON






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