[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 012349
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 01 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 2315 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE OVER THE TROPICAL ATLC EXTENDS FROM 23N35W TO
20N34W TO 16N31W TO 6N30W MOVING W NEAR 15 KT. SATELLITE-DERIVED
WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 950-800
MB LAYER NEAR THIS WAVE...AND RECENT SATELLITE IMAGERY INDICATES
THAT THIS WAVE COINCIDES WITH A LOW/MID-LEVEL CYCLONIC
CIRCULATION CENTER NEAR 13N30W. THE N PORTION OF THIS WAVE IS
NEAR A CLOSED UPPER LEVEL LOW NEAR 17N29W...WITH THE TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS INDICATING AN AREA OF DEEP
LAYER MOISTURE ACROSS THE NORTHERN ONE-THIRD OF THE WAVE. NEAR
THIS N PORTION OF THE WAVE...SCATTERED SHOWERS ARE OCCURRING
FROM 21N-28N BETWEEN 31W-38W. ACROSS THE CENTRAL ONE-THIRD OF
THIS WAVE...DRY LOW/MID-LEVEL SAHARAN AIR HAS WRAPPED
CYCLONICALLY AROUND THE WAVE INHIBITING THE DEVELOPMENT OF DEEP
CONVECTION. ACROSS THE SOUTHERN ONE-THIRD OF THE WAVE...DEEP
LAYER MOISTURE IS ALSO MAXIMIZED...WITH SCATTERED MODERATE
CONVECTION FROM 8N-11N BETWEEN 27W-32W.

A TROPICAL WAVE OVER THE TROPICAL ATLC EXTENDS FROM 24N55W TO
22N56W TO 7N55W MOVING W NEAR 20 KT. RECENT VISIBLE SATELLITE
IMAGERY DEPICTS INVERTED-V STRUCTURES ASSOCIATED WITH LOW-LEVEL
CLOUD BANDS NEAR THIS WAVE. ADDITIONALLY...THIS WAVE IS AT THE
LEADING EDGE OF A BROAD...ALTHOUGH WEAK...MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. THE QUIKSCAT PASS AROUND 01/1300 UTC INDICATED CYCLONIC
CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE...WITH NE TO E
WINDS OF 10 TO 15 KT WITHIN 60 NM E OF THE WAVE AXIS...AND NE
WINDS OF AROUND 15 KT WITHIN 60 NM W OF THE WAVE AXIS. ALSO...
SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW
WITHIN THE 950-800 MB LAYER IN THE VICINITY OF THIS WAVE.
SCATTERED MODERATE CONVECTION IS FROM 9N-12N BETWEEN
52W-55W...WHICH IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR
THE ITCZ.

A TROPICAL WAVE OVER THE W CARIBBEAN EXTENDS FROM 22N81W TO THE
COAST OF HONDURAS NEAR 15N84W TO THE E PACIFIC REGION NEAR 1N86W
MOVING W NEAR 20 KT. THIS WAVE IS EMBEDDED WITHIN A WELL-DEFINED
MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE
WATER PRODUCT FROM CIMSS. ALSO...SATELLITE-DERIVED WINDS
INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 800-600 MB
LAYER IN THE VICINITY OF THIS WAVE. SCATTERED MODERATE
CONVECTION IS FROM 12N-18N BETWEEN 82W-87W INCLUDING PORTIONS OF
E HONDURAS AND E NICARAGUA...WHICH IS BEING ENHANCED BY
ATMOSPHERIC INSTABILITY CAUSED BY DIURNAL HEATING OVER LAND.
ADDITIONALLY...SCATTERED MODERATE CONVECTION IS FROM 19N-23N
BETWEEN 78W-85W...WHICH IS BEING ENHANCED BY ATMOSPHERIC
INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER THE NW
CARIBBEAN NEAR 21N84W.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N14W 9N26W 10N40W 10N52W
9N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
8N-13N E OF 19W. SCATTERED MODERATE CONVECTION IS FROM 7N-11N
BETWEEN 36W-41W. SCATTERED MODERATE CONVECTION IS ALSO FROM
8N-10N BETWEEN 47W-50W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE EXTENDS EASTWARD FROM AN UPPER LEVEL HIGH
OVER NE MEXICO ACROSS THE N GULF OF MEXICO. UPPER LEVEL
DIFFLUENCE BETWEEN THIS UPPER LEVEL RIDGE AND A BROAD UPPER
LEVEL TROUGH OVER THE E UNITED STATES IS SUPPORTING SCATTERED
SHOWERS AND THUNDERSTORMS OVER THE N GULF N OF 27N E OF 90W.
ADDITIONALLY...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE
OCCURRING S OF 26N E OF 85W...WHICH ARE RESULTING FROM
ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH.
THIS UPPER LEVEL TROUGH EXTENDS NORTHWARD INTO THE FAR SE GULF
AND SW NORTH ATLC FROM AN UPPER LEVEL LOW CENTERED OVER THE NW
CARIBBEAN SEA NEAR 21N84W. ACROSS MUCH OF THE CENTRAL AND SW
GULF...DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTHEASTERLY FLOW
ALOFT S OF THE AFOREMENTIONED UPPER LEVEL RIDGE ARE SUPPORTING
GENERALLY FAIR WEATHER. THIS SUBSIDENCE IS ALSO SUPPORTING A
SURFACE RIDGE ACROSS THE N GULF. THE INCREASED PRESSURE GRADIENT
S AND W OF THIS SURFACE RIDGE IS SUPPORTING SE WINDS OF 10 TO 15
KT ACROSS THE W GULF.

CARIBBEAN SEA...
SCATTERED MODERATE CONVECTION IS OCCURRING OVER THE W CARIBBEAN
IN ASSOCIATION WITH THE TROPICAL WAVE EXTENDING FROM 22N81W TO
15N84W TO THE E PACIFIC REGION NEAR 1N86W...AS WELL AS AN UPPER
LEVEL LOW OVER THE NW CARIBBEAN CENTERED NEAR 21N84W. THE
TROPICAL WAVE AND UPPER LEVEL LOW ARE DISCUSSED IN THE TROPICAL
WAVES SECTION ABOVE. ACROSS THE CENTRAL AND E CARIBBEAN...DEEP
LAYER DRY AIR...INCLUDING DRY LOW/MID-LEVEL SAHARAN AIR...IS
SUPPORTING GENERALLY FAIR WEATHER. HOWEVER...ATMOSPHERIC
INSTABILITY NEAR A WEAK UPPER LEVEL TROUGH OVER THE N CENTRAL
CARIBBEAN IS SUPPORTING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS FROM 17N-19N BETWEEN 73W-78W INCLUDING PORTIONS OF
JAMAICA. FRESH TO STRONG TRADE WINDS ARE PRESENT ACROSS MUCH OF
THE CENTRAL AND S CARIBBEAN TO THE S OF A SURFACE RIDGE OVER THE
CENTRAL ATLC. THE STRONGEST WINDS ARE FOUND NEAR THE COAST OF
COLOMBIA...WHERE E WINDS OF 25 AND 30 KT ARE OCCURRING.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING OVER
THE SW NORTH ATLC S OF 25N W OF 79W DUE TO ATMOSPHERIC
INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH. THIS UPPER
LEVEL TROUGH EXTENDS NORTHWARD INTO THE SW NORTH ATLC AND FAR SE
GULF OF MEXICO FROM AN UPPER LEVEL LOW CENTERED OVER THE NW
CARIBBEAN SEA NEAR 21N84W. FARTHER TO THE E...SUBSIDENCE IS
OCCURRING NEAR A BROAD SURFACE RIDGE AND IS RESULTING IN
GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E ATLC.
THIS BROAD SURFACE RIDGE IS ASSOCIATED WITH A 1027 MB SURFACE
HIGH NEAR 36N53W AND A 1027 MB SURFACE HIGH NEAR 35N44W.
HOWEVER...ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW
CENTERED NEAR 32N61W IS SUPPORTING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS N OF 28N BETWEEN 52W-66W. ANOTHER UPPER
LEVEL LOW IS CENTERED NEAR 29N42W WITH ATMOSPHERIC INSTABILITY
SUPPORTING SCATTERED SHOWERS FROM 27N-31N BETWEEN 41W-46W.
ALSO...AN UPPER LEVEL TROUGH AXIS OVER THE E ATLC EXTENDS FROM
AN UPPER LEVEL LOW OVER W AFRICA NEAR 17N14W TO 21N18W TO
23N20W. THIS UPPER LEVEL TROUGH IS SUPPORTING A SURFACE TROUGH
THAT EXTENDS FROM 20N28W TO 21N20W TO W AFRICA NEAR 24N12W. THE
SURFACE TROUGH IS ASSOCIATED WITH W TO NW WINDS OF 10 TO 15 KT
WITHIN 60 NM N OF THE SURFACE TROUGH AND SW TO W WINDS OF 10 TO
15 KT WITHIN 60 NM S OF THE SURFACE TROUGH. ABUNDANT DRY
LOW/MID-LEVEL SAHARAN AIR IS INHIBITING PRECIPITATION NEAR THIS
SURFACE TROUGH.

$$
COHEN




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