[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE JUL 21 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 38W S OF 13N MOVING W NEAR 23 KT. THIS
WAVE COINCIDES WITH A MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION
BASED ON THE CIMSS WAVETRAK PRODUCT AND 600-950 MB CLOUD DRIFT
WINDS. DEEP CONVECTION IS LIMITED NEAR THE WAVE AS A LARGE AREA
OF SAHARAN AIR IS OBSERVED ON VISIBLE SATELLITE IMAGERY E OF
60W. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 5N-10N
BETWEEN 36W-39W.

A TROPICAL WAVE IS ALONG 57W S OF 20N MOVING W NEAR 25 KT. THIS
WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON
THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THIS WAVE IS
FOLLOWED BY ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS
LIMITING THE AREAL COVERAGE OF DEEP CONVECTION IN THE VICINITY
OF THE WAVE. HOWEVER...SCATTERED SHOWERS ARE FROM 14N-17N
BETWEEN 54W-60W.

A TROPICAL WAVE IS ALONG 69W S OF 22N MOVING W NEAR 25 KT. THIS
WAVE COINCIDES WITH A LARGE AREA OF MAXIMUM TOTAL PRECIPITABLE
WATER ACROSS MUCH OF THE CARIBBEAN BASIN WITH A MAXIMUM IN
LOW-LEVEL CYCLONIC CURVATURE ALONG THE WAVE AXIS. VISIBLE
SATELLITE AND SAN JUAN DOPPLER RADAR DATA DEPICT NUMEROUS
SHOWERS AND SCATTERED TSTMS FROM 14N-19N BETWEEN 63W-69W.

A TROPICAL WAVE IS ALONG 85W S OF 23N MOVING W NEAR 20 KT. THIS
WAVE CONTINUES TRACKING WWD ACROSS THE NW CARIBBEAN AND SRN
PORTIONS OF CENTRAL AMERICA WHILE UNDER AN ANTICYCLONIC
CIRCULATION ALOFT CENTERED NEAR 15N80W. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 8N-16N BETWEEN 80W-85W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 15N17W 8N36W 6N40W 6N55W AND
ACROSS NRN VENEZUELA. SCATTERED MODERATE CONVECTION IS FROM
10N-19N BETWEEN 15W-20W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 3N-8N BETWEEN 42W-54W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH AXIS EXTENDS ALONG THE ERN U.S. SEABOARD
ACROSS FLORIDA AND INTO THE SE GULF AND STRAITS OF FLORIDA. AS
OF 1500 UTC...THIS UPPER TROUGH SUPPORTS A WEAK SURFACE TROUGH
THAT EXTENDS FROM A 1016 MB LOW NEAR SAVANNAH GEORGIA THROUGH
THE FLORIDA BIG BEND REGION ALONG 29N83W 25N85W. DRY AIR IN THE
BASE OF THE UPPER LEVEL TROUGH IS INHIBITING DEEP CONVECTION
NEAR THE SURFACE TROUGH...AS WELL AS ACROSS THE SRN GULF S OF
25N. HOWEVER...TO THE SE OF THE BOUNDARY ACROSS S FLORIDA AND
THE FLORIDA KEYS...LOW LEVEL CONVERGENCE IS INTERACTING WITH
DEEP LAYER MOISTURE TO RESULT IN ISOLATED SHOWERS AND TSTMS S OF
26N E OF 83W. ACROSS THE W GULF...A UPPER LEVEL RIDGE AXIS
EXTENDS FROM BROWNSVILLE TEXAS TO NEAR 25N90W AND IS PROVIDING
SUBSIDENCE IN NLY FLOW ALOFT THAT CONTINUES TO SUPPORT GENERALLY
FAIR WEATHER. HOWEVER...HIGH LEVEL DEBRIS CLOUDS FROM SHOWER AND
TSTM ACTIVITY OVER TEXAS AND LOUISIANA ARE BEING ADVECTED SWD
ACROSS THE NW GULF.

CARIBBEAN SEA...
A BROAD UPPER LEVEL RIDGE IS ACROSS MUCH OF THE CARIBBEAN...
WHICH IS ANCHORED BY AN UPPER LEVEL HIGH NEAR 15N80W. UPPER
LEVEL DIVERGENCE ACROSS THE NRN PERIPHERY OF THIS RIDGE IS
INTERACTING WITH ATMOSPHERIC INSTABILITY TO RESULT IN THE
NUMEROUS SHOWERS AND SCATTERED TSTMS ASSOCIATED WITH THE
TROPICAL WAVE ALONG 69W THAT IS IMPACTING PUERTO RICO...THE
US/UK VIRGIN ISLANDS AND NEARBY COASTAL WATERS. MORE WIDELY
SCATTERED SHOWERS ARE ALSO NOTED OVER THE LESSER ANTILLES AS THE
TROPICAL WAVE HAS ALREADY PASSED TO THE W...WHILE AN INCREASE IN
SHOWER AND TSTM ACTIVITY IS FORECAST FOR HISPANIOLA AND THE
N/CENTRAL CARIBBEAN WATERS THROUGH TONIGHT INTO WEDNESDAY. THIS
TROPICAL WAVE IS INTERACTING WITH A SURFACE RIDGE N OF THE
CARIBBEAN LOCATED IN THE SW NORTH ATLC RESULTING IN FRESH TO
STRONG WINDS ACROSS THE ERN CARIBBEAN AND THESE WINDS ARE
FORECAST TO CONTINUE THROUGH THE REMAINDER OF THE WEEK.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH AXIS IS ALONG THE ERN U.S. SEABOARD
DIPPING S OVER THE FLORIDA PENINSULA TO WRN CUBA. THIS UPPER
LEVEL TROUGH SUPPORTS A LARGE AREA OF MOIST LOW-LEVEL SLY FLOW
AND CONVERGENCE FOCUSED ALONG A SURFACE TROUGH THAT EXTENDS FROM
23N78W ACROSS THE NW BAHAMAS TO 28N77W. SCATTERED SHOWERS AND
TSTMS COVER A LARGE PORTION OF THE SW NORTH ATLC FROM 22N-32N
FROM 69W-80W. TO THE SE...DEEP LAYER MOISTURE ASSOCIATED WITH
THE TROPICAL WAVE ALONG 69W IS INTERACTING WITH UPPER LEVEL
DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE TO RESULT IN
SCATTERED SHOWERS AND TSTMS S OF 22N BETWEEN 63W-72W. FARTHER TO
THE E...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS RESULTING
IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E ATLC.
THIS SURFACE RIDGE IS ASSOCIATED WITH A 1030 MB SURFACE HIGH
NEAR 37N58W. ACROSS THE TROPICAL ATLC...A DISSIPATING 1016 MB
LOW IS CENTERED NEAR 22N20W WITH A SURFACE TROUGH EXTENDING NE
TO 25N16W AND ANOTHER SURFACE TROUGH EXTENDING FROM THE LOW S TO
NEAR 18N23W. SCATTERED SHOWERS ARE WITHIN 90/120 NM EITHER SIDE
OF THE SURFACE TROUGHS.

$$
HUFFMAN




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