[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 042345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON SEP 04 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL DEPRESSION SIX AT 04/2100 UTC IS CENTERED
NEAR 16.9N 43.8W IN THE TROPICAL ATLANTIC. IT IS MOVING
NORTHWEST AT 10 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1005 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO
40 KT. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC ADVISORY
UNDER MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS. SATELLITE PICTURES
SHOW THAT THE DEPRESSION HAS NOT STRENGTHENED AND CURRENTLY IT
LOOKS LESS ORGANIZED THAN 6 HOURS AGO. SOUTHWESTERLY SHEAR SEEMS
TO BE INHIBITING STRENGTHENING AT THIS TIME...BUT THE SHEAR IS
FORECAST TO RELAX AS A LARGE MID-UPPER LEVEL TROUGH OVER THE
CENTRAL ATLANTIC DEPARTS DURING THE NEXT FEW DAYS. THIS WILL
ALLOW THE DEPRESSION TO STRENGTHEN AND THE SYSTEM COULD BECOME A
TROPICAL STORM WITHIN THE NEXT 24 HOURS OR SO. THE CENTER IS
BETWEEN TWO BANDING FEATURES OF MODERATE TO STRONG CONVECTION.
THE MOST ACTIVE BAND IS FROM 13N-18N BETWEEN 44W-48W. BASED ON
THE OFFICIAL FORECAST TRACK...THIS TROPICAL CYCLONE WILL REMAIN
OVER THE OPEN OCEAN WATERS TROUGH SATURDAY.

...TROPICAL WAVES...
A TROPICAL WAVE ACCOMPANIED BY A BROAD SURFACE LOW PRESSURE
SYSTEM IS ALONG 29W SOUTH OF 21N OR ABOUT 300 MILES WEST OF THE
CAPE VERDE ISLANDS. ALTHOUGH SHOWER ACTIVITY IS CURRENTLY
DISORGANIZED...ENVIRONMENTAL CONDITIONS APPEAR SOMEWHAT
FAVORABLE FOR SOME SLOW DEVELOPMENT TO OCCUR DURING THE NEXT
COUPLE OF DAYS AS THE SYSTEM MOVES WESTWARD AT ABOUT 10 KT.
SCATTERED SHOWERS AND TSTMS ARE MOST ORGANIZED IN A BROKEN
CURVED BAND FEATURE WRAPPING AROUND THE SFC LOW...FROM 13N-18N
BETWEEN 30W-34W.

A TROPICAL WAVE IS ALONG 56/57W SOUTH OF 21N. SATELLITE IMAGERY
SHOWS A WELL DEFINED LOW CLOUD INVERTED V PATTERN. IT APPEARS
THAT A MOIST ELY SURGE IS WELL AHEAD OF THE WAVE AXIS OVER THE
EASTERN CARIBBEAN. SCATTERED MODERATE CONVECTION IS FROM 13N-17N
BETWEEN 62W-68W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 73W SOUTH OF 20N MOVING
WEST NEAR 10 KT. A SHARP UPPER TROUGH IN THE AREA IS MASKING THE
LOW-LEVEL SIGNATURE. THE INTERACTION OF THIS WAVE AND THE UPPER
TROUGH IS TRIGGERING SCATTERED SHOWERS AND TSTMS OVER
HISPANIOLA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 14N17W 15N28W 13N35W 12N50W 11N60W
OUTSIDE THE CONVECTIVE ACTIVITY ASSOCIATED WITH T.D. SIX AND THE
TROPICAL WAVES...CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
MOVING OUT OF THE AFRICAN COAST E OF 16W FROM 9N-13N. SIMILAR
CONVECTION IS FOUND OVER PANAMA AND COSTA RICA DUE TO THE CLOSE
PROXIMITY OF THE ITCZ AXIS.

...DISCUSSION...

THE GULF OF MEXICO...
A WEAK SURFACE TROUGH OF LOW PRESSURE INTERACTING WITH A MID-TO
UPPER-LEVEL LOW PRESSURE SYSTEM LOCATED NEAR 25N87W IS PRODUCING
A BROAD AREA OF SHOWERS AND SCATTERED THUNDERSTORMS OVER MUCH OF
THE CENTRAL AND NORTHWESTERN BAHAMAS...AND EXTENDING WESTWARD
ACROSS THE SOUTHERN FLORIDA PENINSULA...THE FLORIDA KEYS...
CENTRAL AND WESTERN CUBA...AND INTO THE SOUTHEASTERN GULF OF
MEXICO. SURFACE PRESSURES ARE HIGH...AND DEVELOPMENT...IF
ANY...OF THE SYSTEM SHOULD BE SLOW TO OCCUR. HOWEVER...SINCE
THIS SYSTEM IS MOVING LITTLE...LOCALLY HEAVY RAINFALL WILL BE
POSSIBLE OVER CUBA...THE FLORIDA KEYS...AND SOUTH FLORIDA DURING
THE NEXT DAY OR SO. LATEST SATELLITE PICTURES SHOW CLUSTERS OF
SCATTERED MODERATE CONVECTION MAINLY OVER PARTS OF CUBA. AN
UPPER HIGH IS ANCHORED OVER NW MEXICO WITH A RIDGE EXTENDING
NEWD ACROSS THE S U.S. AND N GULF. THE UPPER LEVEL MOISTURE FROM
THE REMNANTS OF JOHN...WHICH IS OVER THE GULF OF CALIFORNIA IS
SPREADING ACROSS NORTHERN MEXICO...NEW MEXICO AND TEXAS. ANOTHER
WEAK UPPER HIGH IS CENTERED NEAR TAMPICO MEXICO AND COVERS THE
BAY OF CAMPECHE. A SURFACE TROUGH...REFLECTION OF A NARROW
UPPER LEVEL TROUGH EXTENDS ALONG 29N86W 27N92W 23N96W. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE WITHIN 60 NM  AHEAD OF THE TROUGH
AXIS. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE OVER THE NE
PORTION OF THE YUCATAN PENINSULA AND NORTHERN GUATEMALA.

THE CARIBBEAN SEA...
A SHARP UPPER TROUGH EXTENDS FROM THE SE BAHAMAS ACROSS THE
WINDWARD PASSAGE TO NEAR NICARAGUA. A FAIR AMOUNT OF MOISTURE IS
ON THE NW CARIBBEAN WITH SCATTERED SHOWERS AND TSTMS. UPPER
DIFFLUENCE NEAR THE BASE OF THE TROUGH IS SUPPORTING THE
DEVELOPMENT OF A CLUSTER OF MODERATE CONVECTION OVER THE SW
CARIBBEAN. AN UPPER HIGH OVER PUERTO RICO DOMINATES THE EASTERN
CARIBBEAN. THIS SYSTEM IS ALSO ENHANCING THE SHOWER/TSTM
ACTIVITY OVER THE AREA. SCATTERED MODERATE CONVECTION IS OVER NW
VENEZUELA IN THE LAKE MARACAIBO AREA. TRADE WINDS ARE GENERALLY
IN THE 15-20 KT RANGE E OF 80W...LIGHTER WINDS W OF THERE.
COMPUTER MODELS  INDICATE THAT THE MOST ORGANIZED TROPICAL
MOISTURE WILL REMAIN IN THE E CARIBBEAN TOMORROW AS THE TROPICAL
WAVE NOW NEAR 57W ENTERS THE BASIN.

THE ATLANTIC OCEAN...
A RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE ATLANTIC OCEAN. A
LARGE MID-UPPER LEVEL TROUGH IS OVER THE CENTRAL ATLANTIC.
MODERATE SWLY SHEAR ASSOCIATED WITH THIS TROUGH IS AFFECTING
T.D. SIX. THE ASSOCIATED FRONTAL BOUNDARY ENTERS THE AREA NEAR
31N36W AND EXTENDS SW ALONG 25N45W 25N56W. SCATTERED SHOWERS ARE
WITHIN 40-60 NM ON EITHER SIDE OF THE FRONT. MOST ORGANIZED
PRECIP IS IN THE W BAHAMAS...CUBA AND NEAR THE SE FLORIDA
COAST...WHERE UPPER DIFFLUENCE IS STRONGEST E OF AN UPPER LOW
LOCATED OVER THE GULF OF MEXICO. A MID-UPPER HIGH IS SITUATED
NEAR 30N65W. ANOTHER UPPER HIGH IS OVER PUERTO RICO.  FARTHER
EAST...A BROAD MID-UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE
OCEAN WITH THE MAIN HIGH CENTER NEAR 22N27W. AT THE SFC...
RIDGING LIES TO THE E OF THE FRONT ANCHORED FROM A 1023 MB HIGH
LOCATED E OF THE AZORES. A SMALL 1021 MB HIGH IS NEAR 29N67W.

$$
GR


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