[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 22 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION FOUR IS CENTERED NEAR 13.6N 26.1W 0R ABOUT
140 NM SOUTHWEST OF THE SOUTHERN MOST CAPE VERDE ISLANDS AT
22/1500 UTC MOVING WNW AT 15 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH
GUSTS TO 40 KT. A 24 HOUR INFRARED SATELLITE LOOPS SHOWS THAT
THE DEPRESSION HAS NOT GAINED CONVECTION OR MUCH ORGANIZATION TO
IT. ONE POSSIBLE REASON IS BECAUSE OF THE LARGE AMOUNT STABLE
AIR AND SAHARAN DUST TO THE N OF THE CYCLONE. SOME OF THE
STRATOCUMULUS CLOUDS ARE WRAPPING INTO THE CIRCULATION OF THE
DEPRESSION. SCATTERED SHOWERS AND TSTMS ARE MAINLY CONFINED FROM
12N-15N BETWEEN 25W-29W. STRENGTHENING IS FORECAST. FOR MORE
DETAILS SEE LATEST NHC FORECAST/ADVISORY UNDER HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 46W S OF 20N MOVING W NEAR 15 KT. THIS
WAVE CONTINUES TO BE FAIRLY WELL-DEFINED WITH BROAD LOW-MID
CYCLONIC TURNING NOTED ABOUT THE AXIS. A LOW-MID LEVEL SWIRL IS
STILL EVIDENT ALONG THE WAVE NEAR 10.5N. DESPITE ITS
STRUCTURE...DEEP CONVECTION REMAINS MINIMAL AND CONFINED WITHIN
THE ITCZ. FURTHER DEVELOPMENT OF THIS WAVE DOES NOT APPEAR
LIKELY AS ITS OVERALL STRUCTURE REMAINS BROAD AND THE NRN
EXTENSION OF THE WAVE REMAINS EMBEDDED IN A LARGE AREA OF
SAHARAN DUST.

TROPICAL WAVE IS NEARING THE LESSER ANTILLES ALONG 60W/61W S OF
20N MOVING W 15-20 KT. AN ILL-DEFINED INVERTED-V SHAPE IS NOTED
ON SATELLITE IMAGERY AND HELPED LOCATE THE AXIS. SCATTERED
SHOWERS AND TSTMS COVER A LARGE AREA EMBEDDED IN THE ITCZ FROM
10N-14N BETWEEN 53W-72W.

A WEAK TROPICAL WAVE IS IN THE WRN CARIBBEAN ALONG 77W/78W S OF
18N MOVING W 15 KT. ONLY A SLIGHT HINT OF LOW CLOUD CURVATURE IS
NOTED ON VIS IMAGES ABOUT THE AXIS. THIS WAVE IS EMBEDDED IN A
DRY STABLE ENVIRONMENT PRODUCING ONLY ISOLATED SHOWERS IN ITS
VICINITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 16N16W 9N26W 10N44W 10N60W ACROSS
NRN S AMERICA AND PANAMA INTO THE E PAC. BESIDES FOR THE
TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS OVER CNTRL
AMERICA FROM 8N-11N W OF 82W INTO THE E PAC.

...DISCUSSION...
GULF OF MEXICO...
AN UPPER TROUGH STRETCHES ACROSS THE AREA FROM AN UPPER LOW JUST
S OF THE FL PANHANDLE NEAR 29N86W SW TO ANOTHER UPPER LOW IN THE
W GULF NEAR 25N96W ACROSS CNTRL MEXICO. CONSIDERABLE CLOUDINESS
COVERS THE MAJORITY OF THE REGION EXCEPT FOR THE NW PORTION
WHICH LIES UNDER THE SRN PERIPHERY OF A U.S. MID-UPPER RIDGE.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE MOST ORGANIZED NEAR THE
UPPER LOW CENTERS FROM 26N-30N BETWEEN 83W-88W AND FROM 19N-26N
W OF 92W. AT THE SFC...WEAK RIDGING FROM THE ATLC STRETCHES INTO
THE AREA PRODUCING LIGHT S-SE WINDS IN THE E GULF AND MAINLY E
WINDS IN THE W GULF. THE SE FLOW IN THE E GULF IS DRAWING
TROPICAL MOISTURE FROM THE NW CARIBBEAN INTO THE EXTREME SRN
PORTION OF THE AREA. THIS MOISTURE WILL CONTINUE TO PUSH N-NW
INTO THE REGION OVER THE NEXT DAY OR SO.

CARIBBEAN SEA...
THERE ARE TWO MAIN AREAS OF UNSETTLED WEATHER IN THE CARIBBEAN.
SCATTERED SHOWERS AND TSTMS ARE IN THE NW CARIBBEAN FROM 17N-23N
BETWEEN 81W-88W. THIS ACTIVITY IS PRODUCED MOSTLY BY UPPER
DIFFLUENCE IN THE REGION. SHIP AND BUOY OBS IN THE AREA SHOW
ISOLATED WINDS TO 30 KT IN THE DEEP CONVECTION. OVER THE PAST
SEVERAL HOURS...THE LARGE MASS OF CONVECTION HAS GENERALLY
WEAKENED WITH A NEW BURST JUST S OF CUBA. THIS AREA OF WEATHER
HAS BEEN MOVING N IN THE CARIBBEAN OVER THE PAST COUPLE OF DAYS
BUT IS SHOWING NO SIGNS OF ORGANIZING AND SFC PRESSURES ARE
RISING. THE OTHER AREA OF UNSETTLED WEATHER IS IN THE ERN
CARIBBEAN ASSOCIATED WITH A TROPICAL WAVE AND THE ITCZ.
SCATTERED SHOWERS AND TSTMS ARE E OF 72W S OF 15N.  UPPER
CONFLUENCE IS PRODUCING UPPER SUBSIDENCE BETWEEN THESE TWO
AREAS. A TROPICAL WAVE IS EMBEDDED IN THIS DRY ENVIRONMENT
PRODUCING LITTLE WEATHER. TIGHTENED PRES GRAD BETWEEN THE
BUILDING ATLC RIDGE AND LOWER PRES OVER S AMERICA AND TROPICAL
WAVES IS PRODUCING MODERATE TO STRONG TRADES E OF 78W. THESE
WINDS ARE LIKELY TO REMAIN THAT WAY OVER THE NEXT COUPLE OF
DAYS.

ATLANTIC OCEAN...
AN UPPER TROUGH EXTENDS ACROSS A PORTION OF THE W ATLC FROM AN
UPPER LOW 550 NM SE OF BERMUDA NEAR 29N54W SW TO 26N72W. A SMALL
WEAK SFC REFLECTION AS A TROF IS EMBEDDED IN THE UPPER TROUGHING
ALONG 24N73W 29N69W. SCATTERED SHOWERS ARE WITHIN 120 NM E OF
THE SFC BOUNDARY. SIMILAR ACTIVITY IS OVER THE BAHAMAS FROM
24N-27N BETWEEN 75W-78W AND FARTHER NE FROM 26N-31N BETWEEN
54W-60W. WEAK UPPER RIDGING EXTENDS FROM THE CARIBBEAN ACROSS E
CUBA TO THE CENTRAL BAHAMAS NEAR 23N72W. THE REMAINDER OF THE
ATLC IS DOMINATED BY MOSTLY BENIGN FEATURES WHICH INCLUDE AN
UPPER TROUGH EXTENDING FROM THE E ATLC NEAR 32N19W THRU AN UPPER
LOW NEAR 29N27W TO THE TROPICAL ATLC NEAR 20N50W. DRY STABLE
UPPER LEVEL AIR IS IN PLACE ACROSS A GOOD PORTION OF THE E AND
CNTRL ATLC TO THE N OF A T.D. FOUR. IN ADDITION TO THE STABLE
UPPER LEVEL AIR...SAHARAN DUST IS WIDESPREAD IN THE MID-LEVELS
SPREADING TO 65W FROM 11N-25N ACCORDING TO THE MILKY LOOK ON VIS
IMAGES AND THE CIMSS SAL TRACKING PRODUCT. THE DUST MIGHT BE
LESS DENSE NEAR THE DEPRESSION WITH ANOTHER SURGE TO ITS E. AT
THE SFC..BESIDES FOR T.D. 4 AND THE WAVES A BROAD SURFACE RIDGE
DOMINATES THE ATLC WITH THE ANALYZED HIGH CENTERS N OF THE
DISCUSSION AREA.

$$
CANGIALOSI


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