[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041738
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 04 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
1700 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 22W/23W S OF 16N MOVING W NEAR 10 KT.
VISIBLE SATELLITE IMAGERY INDICATES LOW-LEVEL CYCLONIC FLOW IN
THE VICINITY OF THE WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A
DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
11N-15N BETWEEN 22W-25W.

AN ACTIVE SURFACE TROUGH IS ALONG 34W/35W S OF 12N. WHILE IT IS
CURRENTLY NOT ANALYZED AS A TROPICAL WAVE...IT MAY BE
TRANSITIONED TO ONE ON FUTURE SURFACE ANALYSIS. MID-LEVEL
CYCLONIC CIRCULATION IS NEAR THE TROUGH AXIS SUPPORTING
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 7N-10N
BETWEEN 33W-37W. HOWEVER...VISIBLE SATELLITE IMAGERY AND
QUIKSCAT DATA AROUND 0800 UTC INDICATES THAT LOW LEVEL
CYCLONIC CIRCULATION IS FARTHER E AROUND 30W.

A TROPICAL WAVE EXTENDS ALONG 18N51W 14N48W 9N47W MOVING W NEAR
18 KT. VISIBLE SATELLITE IMAGERY AND SATELLITE DERIVED WINDS
INDICATE LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE
AXIS. THIS WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE
MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. THIS WAVE
LEADS A DRY SAHARAN AIR LAYER WHICH IS INHIBITING DEEP
CONVECTION NEAR THE WAVE.

A TROPICAL WAVE IS ALONG 70W/71W S OF 18N MOVING W 15-20 KT.
THIS WAVE HAS BEEN RELOCATED FROM ITS PREVIOUS POSITION ALONG
61W BASED ON CURRENT SATELLITE IMAGERY WHICH INDICATES LOW-LEVEL
CYCLONIC FLOW OVER THE CENTRAL CARIBBEAN NEAR ITS CURRENT
POSITION...AND TOTAL PRECIPITABLE WATER IMAGERY WHICH INDICATES
A BROAD AREA OF INCREASED MOISTURE NEAR THE CURRENT WAVE
POSITION. WHILE NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH
THE WAVE...SCATTERED SHOWERS ARE S OF HISPANIOLA FROM 17N-18N
BETWEEN 69W-71W.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 11N28W 9N36W 12N50W
9N61W. SCATTERED MODERATE CONVECTION IS JUST OFF THE AFRICA
COAST FROM 9N-13N BETWEEN 15W-18W.

...DISCUSSION...

THE GULF OF MEXICO...
A BROAD SURFACE RIDGE IS ACROSS THE GULF OF MEXICO ANCHORED BY A
1019 MB SURFACE HIGH NEAR 28N87W BRINGING GENERALLY FAIR WEATHER
ACROSS THE AREA. HOWEVER...A SURFACE TROUGH IS ACROSS THE NRN
FLORIDA PENINSULA FROM 29N84W TO 29N81W AND INTO THE ATLC.
SURFACE CONVERGENCE NEAR THE TROUGH ALONG WITH UPPER LEVEL
DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN CONUS AND
AN UPPER LEVEL HIGH N OF THE BAHAMAS NEAR 27N79W ARE SUPPORTING
ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE NE GULF FROM 26N-30N E
OF 90W. ANTICYCLONIC SURFACE FLOW IS PRESENT AROUND THE SURFACE
RIDGE WITH WINDS REACHING 15 KT IN THE SW GULF. EXPECT THE
SURFACE RIDGE TO PERSIST...AND A SURFACE TROUGH OVER ERN CUBA TO
MOVE ACROSS THE STRAITS OF FLORIDA LATER TONIGHT.

THE CARIBBEAN SEA...
UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE
YUCATAN PENINSULA AND AN UPPER LEVEL RIDGE OVER THE WRN
CARIBBEAN CENTERED NEAR 10N83W OFF THE COAST OF COSTA RICA IS
SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE NW
CARIBBEAN N OF 16N W OF 78W. A SURFACE TROUGH...ORIGINALLY THE
NRN PORTION OF THE TROPICAL WAVE ALONG 70W/71W...EXTENDS OVER
ERN CUBA FROM 19N77W TO 21N78W AND INTO THE ATLC. SURFACE
CONVERGENCE NEAR THE TROUGH IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS N OF 18N BETWEEN 75W-78W. SCATTERED
SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN S OF 12N
BETWEEN 80W-84W ENHANCED BY SURFACE CONVERGENCE IN THE PROXIMITY
OF THE E PACIFIC ITCZ. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO
S OF HISPANIOLA FROM 17N-18N BETWEEN 69W-71W DUE TO THE TROPICAL
WAVE ALONG 70W/71W. ACROSS THE REMAINDER OF THE
CARIBBEAN...GENERALLY FAIR WEATHER IS PRESENT DUE TO DRY AIR
ALOFT DESPITE UPPER LEVEL TROUGHING E OF 75W. EXPECT THE
TROPICAL WAVE ALONG 70W/71W TO PROPAGATE WWD...AND THE NEXT
TROPICAL WAVE TO REACH THE ERN CARIBBEAN TOMORROW.

THE ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS ACROSS THE NRN FLORIDA PENINSULA FROM
29N81W TO 32N77W CONTINUING OUT OF THE DISCUSSION AREA TO THE
NE. SURFACE CONVERGENCE NEAR THE TROUGH ALONG WITH UPPER LEVEL
DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN CONUS AND
AN UPPER LEVEL HIGH N OF THE BAHAMAS NEAR 27N79W ARE SUPPORTING
SCATTERED
SHOWERS/THUNDERSTORMS N OF 28N W OF 71W. A SURFACE TROUGH
EXTENDS ACROSS ERN CUBA TO THE BAHAMAS FROM 21N76W TO 25N75W
SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS S OF 24N
BETWEEN 75W-80W. THIS TROUGH ORIGINATED AS THE NRN PORTION OF
THE TROPICAL WAVE ALONG 70W/71W. ANOTHER SURFACE TROUGH EXTENDS
FROM 19N55W TO 22N57W. THIS TROUGH ALSO ORIGINATED AS THE NRN
PORTION OF A TROPICAL WAVE EXTENDING ALONG 18N51W 14N48W 9N47W.
ISOLATED SHOWERS ARE WITHIN 200 NM W OF THE TROUGH AXIS.
ELSEWHERE ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES
ANCHORED BY A 1028 MB SURFACE HIGH NEAR 36N49W BRINGING
GENERALLY FAIR WEATHER ACROSS THE REMAINDER OF THE BASIN. IN THE
UPPER LEVELS...AN UPPER LEVEL TROUGH IS BETWEEN 60W-70W CENTERED
NEAR 28N63W. A BROAD UPPER LEVEL RIDGE DOMINATES THE ERN ATLC
CENTERED NEAR 18N49W.

$$
WALTON






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