[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 152354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU NOV 15 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 48W SOUTH OF 17N MOVING WEST 10-15
KT. CYCLONIC TURNING IS NOTED ALONG THE WAVE AXIS NEAR 10N. THE
CIMSS 850 MB VORTICITY PRODUCT PROVIDES GOOD SUPPORT FOR THE
WAVE POSITION INDICATED. THIS WAVE ALSO SHOWS UP IN THE TPW
PRODUCT AS A LOW/MID AMPLITUDE MOISTURE SURGE. SCATTERED
MODERATE CONVECTION IS MAINLY BEHIND WAVE AXIS FROM 8N-13N
BETWEEN 43W-49W.

A TROPICAL WAVE IS ALONG 71W SOUTH OF 20N MOVING WEST 10-15 KT.
THE WAVE IS MOVING ACROSS HISPANIOLA AND WESTERN VENEZUELA
GENERATING SCATTERED SHOWERS. A WELL DEFINED INVERTED-V LOW
LEVEL CLOUD SIGNATURE IS NOTED ON SATELLITE IMAGERY. THE
MIMIC-TPW ALSO SHOWS A GOOD SURGE OF MOISTURE ASSOCIATED WITH
THIS FEATURE.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 10N14W 6N25W 7N40W 9N61W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE...SCATTERED MODERATE CONVECTION IS FROM 2N-7N EAST OF 20W
TO THE COAST OF W AFRICA. SIMILAR CONVECTION IS WITHIN 80-100 NM
EITHER SIDE OF THE AXIS BETWEEN 30W-40W.

DISCUSSION...

THE GULF OF MEXICO...
AS OF 2100 UTC...A FAST MOVING COLD FRONT EXTENDS FROM W-CENTRAL
FLORIDA...ACROSS THE TAMPA BAY AREA INTO THE GULF TO JUST N OF
VERACRUZ MEXICO. TAMPICO REPORTED A WIND GUST OF 40 KT AND LIGHT
RAIN WITH THE PASSAGE OF THE FRONT. THE LEADING EDGE OF THE
FRONT IS A VERY THIN LINE OF SCATTERED SHOWERS WITHIN 30 NM OF
THE FRONT. 20-30 KT NLY WINDS ARE OVER THE NRN GULF OF MEXICO N
OF THE FRONT. SFC OBSERVATIONS AND AN EARLIER ASCAT PASS
CONFIRMED THESE WINDS. COLD AIR HAS PENETRATED INTO THE EASTERN
SLOPES OF THE SIERRA MADRE MOUNTAINS AS DEPICTED BY RATHER
UNIFORM LOW CLOUDS COVER WITH DRIZZLE/LIGHT RAIN JUST N OF
VERACRUZ. THE REMAINDER OF THE GULF S OF THE FRONT HAS 10 KT
NELY FLOW WITH FAIR WEATHER. IN THE UPPER LEVELS...A DEEP
LAYERED TROUGH IS MOVING ACROSS THE EASTERN U.S WHILE A RIDGE
DOMINATES THE MEXICO AND MOST OF THE GULF GIVING THE AREA W TO
NW UPPER LEVEL WINDS. THIS UPPER TROUGH SUPPORTS THE ABOVE
MENTIONED COLD FRONT THAT IS FORECAST TO MOVE ACROSS THE CENTRAL
FLORIDA PENINSULA THIS EVENING AND THEN CONTINUE TO PASS THROUGH
SOUTH FLORIDA OVERNIGHT USHERING A DRY AND COOL AIR MASS.

THE CARIBBEAN SEA...
THE COLD THAT IS CURRENTLY MOVING ACROSS THE GULF WILL REACH
WESTERN CUBA/NW CARIBBEAN LATE TONIGHT INTO EARLY FRIDAY
MORNING. HIGH PRES WILL BUILD BEHIND THE FRONT PRODUCING AN
INCREASE IN WINDS AND SEAS OVER THE NW CARIBBEAN. A TROPICAL
WAVE IS MOVING ACROSS THE CENTRAL CARIBBEAN. SEE ABOVE. BROKEN
TO OVERCAST LOW/MID CLOUDS WITH EMBEDDED SHOWERS AND ISOLATED
TSTMS ARE AFFECTING THE WINDWARD ISLANDS...PARTICULARLY
GRENADA...TRINIDAD AND TOBAGO. THIS ACTIVITY MAY BE ASSOCIATED
WITH THE NORTHWARD MODULATION OF THE ITCZ DUE TO THE PRESENCE OF
THE TROPICAL WAVE ALONG 71W. MOIST ONSHORE NE WINDS IS
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS ALONG THE COAST
OF NICARAGUA AND COSTA RICA. UPPER DIFFLUENCE ASSOCIATED WITH AN
UPPER LEVEL HIGH CENTERED OVER NICARAGUA  IS ENHANCING THIS
SHOWER ACTIVITY.  SIGNIFICANT UPPER LEVEL MOISTURE AND HIGH
CLOUDS ARE OVER THE SW CARIBBEAN AND CENTRAL AMERICA FROM PANAMA
TO HONDURAS. A NEARLY ZONAL FLOW IS OVER THE E CARIBBEAN E OF
70W WITH A SHORT WAVE TROUGH OVER THE NE CARIBBEAN/LEEWARD
ISLANDS. TRADE WINDS ARE EXPECTED TO INCREASE DURING THE
UPCOMING WEEKEND AS HIGH PRES OVER THE N GULF WATERS MOVES EWD
ACROSS THE W ATLC. THE NOAA WAVE-WATCH MODEL...NWW3...INDICATES
E WINDS OF 20 TO 25 KT AND SEAS UP TO 9 FT.

THE ATLANTIC OCEAN...
A COLD FRONT IS ENTERING THE EXTREME NW PORTION OF THE AREA WITH
A NARROW BAND OF LOW/MID CLOUDS WITH ISOLATED SHOWERS. THIS
FRONT EXTENDS ACROSS N-CENTRAL FLORIDA AND THE GULF. ANOTHER
COLD FRONT ENTERS THE AREA NEAR 31N27W THEN CONTINUES SW TO NEAR
22N50W. SCATTERED SHOWERS ARE WITHIN 90 NM OF THE FRONT. BETWEEN
FRONTS...A 1026 MB HIGH PRES IS NEAR 35N49W COVERING MOST OF THE
W-CENTRAL ATLC. A WEAK SFC LOW HAS DEVELOPED WITHIN 160 NM E OF
THE CENTRAL BAHAMAS. A SWIRL OF LOW CLOUDS DEFINES THE LOW. THIS
FEATURE IS FORECAST TO DISSIPATE WHILE BE ABSORBED BY THE
APPROACHING COLD FRONT. IN THE UPPER LEVELS...A LONG WAVE TROUGH
IS MOVING ACROSS THE EASTERN U.S. INTO THE W ATLC. A SHORT WAVE
TROUGH IS ALONG 70N BETWEEN 24N-30N. AN AREA OF MULTILAYERED
CLOUDS WITH SHOWERS AND SCATTERED TSTMS ARE AHEAD OF THIS TROUGH
AFFECTING FROM 22N-32N BETWEEN 58W-68W. LIGHTNING DATA DEPICTS
MOST OF TSTMS ACTIVITY NEAR 26N61W. UPPER DIFFLUENCE BETWEEN
THIS TROUGH AND A RIDGE OVER THE CENTRAL ATLC IS HELPING TO
INDUCE THIS ACTIVITY. ANOTHER UPPER-LEVEL TROUGH ENTERS THE
FORECAST REGION NEAR 32N38W THEN EXTENDS TO 22N48W. DRY AIR IS
NOTED ALONG THE TROUGH AXIS. AN UPPER RIDGE EXTENDING NEWD FROM
THE TROPICAL ATLC NEAR 7N38W COVERS THE REMAINDER OF THE OCEAN
AND NW AFRICA.

$$
GR





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