[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151724
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED JUL 15 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 1645 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 25W S OF 15N MOVING W NEAR 15 KT.
VISIBLE SATELLITE IMAGERY INDICATES MID-LEVEL CYCLONIC FLOW IN
THE VICINITY OF THIS WAVE. THIS WAVE ALSO COINCIDES WITH A LOW
AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS
FROM 6N-13N BETWEEN 23W-27W.

A TROPICAL WAVE IS ALONG 41W/42W S OF 16N MOVING W NEAR 15 KT.
THIS WAVE COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE
MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP
CONVECTION IS CURRENTLY ASSOCIATED WITH THIS WAVE.

A HIGHLY-AMPLIFIED TROPICAL WAVE IS OVER THE SW NORTH ATLC AND E
CARIBBEAN EXTENDING FROM 24N67W TO 6N68W MOVING W NEAR 20 KT.
VISIBLE SATELLITE IMAGERY SHOWS A WELL-DEFINED AND
HIGHLY-AMPLIFIED INVERTED-V PATTERN IN THE LOW-LEVEL CLOUDS NEAR
THE WAVE. THE WAVE ALSO COINCIDES WITH A HIGH AMPLITUDE MOISTURE
MAXIMUM IN TOTAL PRECIPITABLE WATER. THE WAVE IS AT THE LEADING
EDGE OF AN ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR LAYER. THE DRY
AIR...ALONG WITH STABLE ATMOSPHERIC CONDITIONS BENEATH AN UPPER
LEVEL HIGH OVER THE E CARIBBEAN...ARE LIMITING DEEP CONVECTION
NEAR THE WAVE. HOWEVER...SCATTERED SHOWERS ARE WITHIN 100 NM OF
THE WAVE AXIS FROM 15N-22N.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 11N23W 9N34W 10N45W 9N63W
SCATTERED MODERATE CONVECTION IS FROM 6N-12N E OF 23W. SIMILAR
CONVECTION IS FROM 9N-11N BETWEEN 62W-68W.
...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE ANCHORED BY A 1019 MB SURFACE HIGH NEAR 27N85W
DOMINATES THE GULF OF MEXICO BRINGING GENERALLY FAIR WEATHER
ACROSS THE AREA. HOWEVER...A STATIONARY FRONT N OF THE
DISCUSSION AREA IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS
ACROSS THE NRN GULF N OF 27N BETWEEN 88W-93W AND ACROSS THE
FLORIDA PENINSULA N OF 24N E OF 85W. AN UPPER LEVEL HIGH OVER
THE NW GULF NEAR 27N96W SUPPORTS THE SURFACE RIDGE.
ANTI-CYCLONIC FLOW IS PRESENT AROUND THE SURFACE RIDGE WITH
WINDS REACHING 15 KT ACROSS THE S GULF. EXPECT THE SURFACE RIDGE
TO PERSIST OVER THE NEXT FEW DAYS.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE
SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER
NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST
OF COLOMBIA. IN FACT...GALE CONDITIONS ARE FORECAST TO BEGIN
LATER TONIGHT. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL
TROUGH OVER THE NW CARIBBEAN WITH AXIS ALONG 18N84W TO 22N78W
AND INTO THE SW NORTH ATLC AND AN UPPER LEVEL RIDGE CENTERED
AROUND AN UPPER LEVEL HIGH OVER HISPANIOLA NEAR 19N72W IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE COAST OF
CENTRAL AMERICA S OF 19N W OF 82W. SURFACE CONVERGENCE NEAR A
1010 MB SURFACE LOW OVER PANAMA NEAR 9N79W IS SUPPORTING
NUMEROUS SHOWERS/THUNDERSTORMS S OF 12N W OF 78W INCLUDING
PORTIONS OF COSTA RICA AND PANAMA. THE REMAINDER OF THE
CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER DUE TO DRY AIR
AND SUBSIDENCE ALOFT. A TROPICAL WAVE IS IN E/CENTRAL
CARIBBEAN...HOWEVER THE DRY AIR ALOFT IS SUPPRESSING ANY DEEP
CONVECTION.

ATLANTIC OCEAN...
A STATIONARY FRONT N OF THE DISCUSSION AREA IS SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF
28N W OF 71W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH
OVER ALABAMA NEAR 32N86W AND AN UPPER LEVEL TROUGH ACROSS THE NW
ATLC SUPPORTS THE FRONT AS WELL AS A PAIR OF SURFACE TROUGHS IN
THE SW NORTH ATLC. THE FIRST SURFACE TROUGH EXTENDS FROM 25N74W
TO 30N68W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS WITHIN 100 NM OF THE TROUGH
AXIS..AS WELL AS SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE
CENTRAL BAHAMAS AND N OF CUBA FROM 22N-27N BETWEEN 77W-80W. THE
SECOND SURFACE TROUGH FORMED AS A FRACTURE OF THE HIGH-AMPLITUDE
TROPICAL WAVE IN THE E/CENTRAL CARIBBEAN...AND EXTENDS FROM
26N67W TO 30N63W. SCATTERED SHOWERS/THUNDERSTORMS ARE NEAR THE N
PORTION OF THE TROUGH N OF 29N BETWEEN 60W-65W. A BROAD SURFACE
RIDGE DOMINATES THE REMAINDER OF THE ATLC ANCHORED BY A 1028 MB
SURFACE HIGH N OF THE DISCUSSION AREA NEAR 35N44W...EXCEPT FOR A
COLD FRONT THAT ENTERS THE AREA NEAR 32N32W TO 30N37W TO 31N40W.
NO SHOWERS ARE CURRENTLY ASSOCIATED WITH THE FRONT. ACROSS THE
TROPICAL ATLC...A BROAD UPPER LEVEL RIDGE IS S OF 24N ENHANCING
CONVECTION ALONG THE E PORTION OF THE ITCZ.

$$
WALTON



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