[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221755
TWDAT

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

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 47W S OF 18N MOVING W NEAR 25 KT. THIS
WAVE COINCIDES WITH A WEAK MAXIMUM IN TOTAL PRECIPITABLE WATER
AND EXHIBITS WEAK LOW LEVEL CYCLONIC CIRCULATION IN THE
SATELLITE CLOUD DRIFT WINDS. CONFLUENT SELY FLOW ALOFT TO THE E
OF THE WAVE AXIS AND THE PRESENCE OF DRY LOW/MID-LEVEL SAHARAN
AIR ARE LIMITING DEEP CONVECTION TO THE W OF THE WAVE AXIS WITH
SCATTERED MODERATE CONVECTION FROM 10N-13N BETWEEN 47W-53W.
HOWEVER...MUCH OF THIS ACTIVITY APPEARS TO BE MORE ASSOCIATED
WITH THE ITCZ AXIS ALONG 9N W OF 49W.

A TROPICAL WAVE IS ALONG 65W S OF 20N MOVING W NEAR 18 KT. THIS
WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON
THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS AND IS FOLLOWED
BY ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS INHIBITING
THE AREAL COVERAGE OF DEEP CONVECTION NEAR THE WAVE ACROSS THE
ERN CARIBBEAN. HOWEVER...ISOLATED SHOWERS ARE WITHIN 90 NM
EITHER SIDE OF THE WAVE AXIS.

A TROPICAL WAVE IS ALONG 79W S OF 23N MOVING W NEAR 25 KT.
WHILE THE WAVE IS BEING STRETCHED NWD AS AN UPPER LEVEL TROUGH
IS PRESENT OVER THE FLORIDA PENINSULA AND ALONG THE ERN U.S.
SEABOARD...LOW-LEVEL CONVERGENCE LOCATED NE OF THE WAVE ACROSS
THE SW NORTH ATLC IS GENERATING SCATTERED MODERATE/ISOLATED
STRONG CONVECTION N OF 17N BETWEEN 68W-78W. UPPER DIFFLUENCE E
OF THE UPPER TROUGH AXIS IS ACTING TO ENHANCE THIS ACTIVITY
ACROSS HISPANIOLA...THE TURKS AND CAICOS ISLANDS...AND BAHAMAS
WITH LOCALLY HEAVY RAINFALL AND GUSTY WINDS POSSIBLE.

A TROPICAL WAVE IS ALONG 93W S OF 20N MOVING W NEAR 18 KT.
RECENT SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITH
A BROAD AREA OF LOW/MID-LEVEL CYCLONIC TURNING OVER PORTIONS OF
SRN MEXICO EXTENDING INTO THE E PACIFIC REGION. THIS WAVE IS
ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE
TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. MOST CONVECTION
WITH THIS WAVE IS LOCATED IN THE E PACIFIC REGION S OF 16N.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N16W 12N45W 11N49W 7N59W.
SCATTERED MODERATE CONVECTION IS FROM 10N-15N BETWEEN 18W-22W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-13N
BETWEEN 49W-60W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL TROUGHING IS ACROSS THE ERN CONUS AND DIPS SWD OVER
THE SE CONUS TO THE FLORIDA PANHANDLE. THIS TROUGH IS SUPPORTING
A STATIONARY FRONT DRAPED ACROSS CENTRAL LOUISIANA AND INTO ERN
TEXAS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS ALONG AND
S OF THE FRONTAL BOUNDARY TO 29N BETWEEN 90W-95W. THE REMAINDER
OF THE GULF IS UNDER ANTICYCLONIC FLOW ALOFT EXTENDING FROM AN
UPPER LEVEL HIGH CENTERED OVER NWRN MEXICO. STABLE AND DRY AIR
PREVAILS S OF 29N WITH GENERALLY 10-15 KT SE TO SLY SURFACE FLOW
PER SHIP AND BUOY OBSERVATIONS A WELL AS A 1230 UTC QSCAT PASS.
HIGH CONVECTIVE DEBRIS CLOUDS ARE SEEN ON VISIBLE SATELLITE
IMAGERY STREAMING SWD FROM THE INLAND CONVECTION ACROSS
MISSISSIPPI...LOUISIANA AND ERN TEXAS. THE SURFACE RIDGE IS
FORECAST TO PERSIST THROUGH THE WEEKEND WITH E TO SE RETURN FLOW
ACROSS MUCH OF THE GULF.

CARIBBEAN SEA...
A BROAD UPPER LEVEL ANTICYCLONE IS OVER THE WRN CARIBBEAN...
CENTERED NEAR 17N79W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH
THIS ANTICYCLONE IS SUPPORTING SCATTERED SHOWERS AND TSTMS
ACROSS THE SW CARIBBEAN S OF 12N W OF 76W TO INLAND OVER
PORTIONS OF CENTRAL AMERICA AS WELL AS SCATTERED SHOWERS AND
TSTMS ALONG AND E OF THE TROPICAL WAVE ALONG 79W N OF 17N
BETWEEN 69W-80W. ACROSS THE ERN CARIBBEAN...N-NE FLOW ALOFT IS
ADVECTING DRY AIR E OF 70W PROMOTING SUBSIDENCE. HOWEVER...AS
THE TROPICAL WAVE ALONG 65W TRACKS WWD...ISOLATED SHOWERS ARE
CONTINUING TO BE USHERED IN ON 15-20 KT ELY TRADE WIND FLOW.
THESE TRADES ARE FORECAST TO REMAIN FRESH TO STRONG THROUGH THE
WEEKEND AS THE CENTRAL ATLC SURFACE RIDGE STRENGTHENS.

ATLANTIC OCEAN...
A SHARP UPPER LEVEL TROUGH IS LOCATED OFF THE NE FLORIDA COAST
AND EXTENDS UPPER LEVEL TROUGHING TO WRN CUBA. THIS TROUGH
SUPPORTS A SURFACE TROUGH ANALYZED FROM 25N79W TO 30N78W. STRONG
UPPER LEVEL DIFFLUENCE IN MOIST SWLY FLOW ALOFT BETWEEN THE
UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE FARTHER TO THE E
WITH AXIS ALONG 70W IS SUPPORTING NUMEROUS SHOWERS AND SCATTERED
TSTMS WITHIN 150 NM OF A LINE FROM 20N69W 31N77W. THIS ACTIVITY
IS ALSO BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE SURFACE
TROUGH AND NEAR NRN PORTIONS OF THE TROPICAL WAVE ALONG 79W S OF
23N. THE SURFACE PRESSURE GRADIENT SE OF THE SURFACE TROUGH IS
SUPPORTING SE WINDS OF 20 TO 25 KT FROM 18N-27N BETWEEN 60W-75W
BASED ON A 1100 UTC QSCAT PASS 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 39N54W. HOWEVER...A STATIONARY FRONT
EXTENDS ALONG 32N BETWEEN 22W-40W OVER THE NE ATLC WITH
SCATTERED SHOWERS LOCATED WITHIN 150 NM S OF THE FRONT.

$$
HUFFMAN





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