[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230002
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUL 22 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 IS ALONG 51W/52W MOVING W NEAR 25 KT. THIS WAVE
COINCIDES WITH A LOW AMPLITUDE 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 INHIBITING THE AREAL COVERAGE OF DEEP CONVECTION NEAR
THE WAVE. HOWEVER...SCATTERED SHOWERS ARE FROM 10N-16N BETWEEN
48W-54W.

A TROPICAL WAVE IS ALONG 67W/68W S OF 20N MOVING W NEAR 20 KT.
THIS WAVE IS NOT PARTICULARLY WELL DEFINED...AND DEEP LAYER DRY
AIR AND SUBSIDENCE IN NORTHEASTERLY FLOW ALOFT ARE INHIBITING
DEEP CONVECTION NEAR THIS WAVE. HOWEVER...THIS WAVE IS
ASSOCIATED WITH SCATTERED SHOWERS ARE OCCURRING FROM 13N-17N
BETWEEN 66W-69W.

A TROPICAL WAVE EXTENDS FROM 23N81W TO 13N83W TO THE E PACIFIC
REGION NEAR 5N82W MOVING W 25 KT. THIS WAVE IS EMBEDDED WITHIN A
BROAD AREA OF DEEP LAYER MOISTURE BASED ON THE TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS. THIS WAVE IS ALSO
ENHANCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM
10N-17N BETWEEN 82W-87W INCLUDING PORTIONS OF NICARAGUA AND
HONDURAS...WHICH IS BEING ENHANCED BY ATMOSPHERIC INSTABILITY
DRIVEN BY DIURNAL HEATING OVER CENTRAL AMERICA.

A TROPICAL WAVE IS ALONG 94W/95W S OF 18N MOVING W NEAR 20 KT.
DEEP CONVECTION ASSOCIATED WITH THIS WAVE IS IN THE E PACIFIC
REGION...AND IS DISCUSSED IN THE TROPICAL WEATHER DISCUSSION FOR
THE E PACIFIC REGION UNDER AWIPS/WMO HEADERS MIATWDEP/AXPZ20
KNHC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 11N29W 11N39W 11N48W
9N62W. SCATTERED MODERATE CONVECTION IS FROM 10N-13N BETWEEN
19W-24W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS FROM
9N-13N BETWEEN 54W-61W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL DIFFLUENCE AND MOISTURE IN NORTHWESTERLY FLOW ALOFT
ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE N
GULF N OF 28N BETWEEN 88W-96W. FARTHER TO THE SOUTH...DEEP LAYER
DRY AIR IS PRESENT ACROSS MUCH OF THE SE GULF...WHERE GENERALLY
FAIR WEATHER IS PRESENT. OVER THE CENTRAL GULF...UPPER LEVEL
CONFLUENCE IS SUPPORTING A SURFACE RIDGE. THE SURFACE RIDGE IS
FORECAST TO GRADUALLY SHIFT EASTWARD THROUGH THE WEEKEND WITH
INCREASING SE RETURN FLOW ACROSS THE W GULF BY LATE IN THE
WEEKEND.

CARIBBEAN SEA...
A BROAD UPPER LEVEL ANTICYCLONE IS OVER THE W CARIBBEAN...
CENTERED NEAR 18N79W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH
THIS ANTICYCLONE IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS THE SW CARIBBEAN S OF 11N BETWEEN
77W-80W...AS WELL AS THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE AFFECTING THE W CARIBBEAN AND EXTENDING FROM 23N81W TO
13N83W TO THE E PACIFIC REGION NEAR 5N82W. THE UPPER LEVEL
DIFFLUENCE IS ALSO SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS OVER CUBA AND JAMAICA...WHERE ATMOSPHERIC
INSTABILITY IS BEING ENHANCED BY DIURNAL HEATING. ACROSS THE E
CARIBBEAN...GENERALLY FAIR WEATHER IS OCCURRING WHERE DEEP LAYER
DRY AIR AND SUBSIDENCE IN NORTHEASTERLY FLOW ALOFT ARE PRESENT.
HOWEVER...UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS ARE
STREAMING SOUTHWESTWARD ACROSS THE NE CARIBBEAN. FRESH TO STRONG
WINDS WILL CONTINUE ACROSS THE E AND CENTRAL CARIBBEAN THROUGH
THE REMAINDER OF THIS WEEK S OF A SURFACE RIDGE OVER THE CENTRAL
AND E ATLC.

ATLANTIC OCEAN...
A SHARP UPPER LEVEL TROUGH IS N OF 23N BETWEEN 75W-80W. THIS
TROUGH IS ASSOCIATED WITH A SURFACE TROUGHS EXTENDING FROM
25N79W TO 31N79W. STRONG UPPER LEVEL DIFFLUENCE IN MOIST
SOUTHWESTERLY FLOW ALOFT BETWEEN THE UPPER LEVEL TROUGH AND AN
UPPER LEVEL RIDGE FARTHER TO THE E ANCHORED BY AN UPPER LEVEL
HIGH NEAR 26N69W IS SUPPORTING NUMEROUS SHOWERS THUNDERSTORMS N
OF 23N BETWEEN 69W-77W. THIS ACTIVITY IS ALSO BEING ENHANCED BY
LOW LEVEL CONVERGENCE NEAR THE SURFACE TROUGH. THE SURFACE
PRESSURE GRADIENT E OF THE SURFACE TROUGHS IS SUPPORTING SE TO S
WINDS OF 20 TO 25 KT S OF 29N BETWEEN 69W AND 74W BASED ON THE
ASCAT PASS AROUND 22/1445 UTC AND GLOBAL MODEL GUIDANCE. 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 1028 MB
SURFACE HIGH NEAR 38N51W. ACROSS THE TROPICAL ATLC...
ATMOSPHERIC INSTABILITY AND UPPER LEVEL DIFFLUENCE ASSOCIATED
WITH A SHORTWAVE TROUGH EMBEDDED WITHIN EASTERLY UPPER LEVEL
FLOW IS SUPPORTING THE CONVECTION ASSOCIATED WITH THE ITCZ FROM
9N-13N BETWEEN 54W-61W

$$
COHEN




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