[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 062350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT OCT 06 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.

...SPECIAL FEATURE...

AN AREA OF LOW PRESSURE CENTERED ABOUT 520 NM EAST OF THE LESSER
ANTILLES HAS BECOME LESS ORGANIZED THIS AFTERNOON. A 1009 MB SFC
LOW WAS ANALYZED NEAR 15N52W ON THE 1800 UTC SURFACE MAP. THE
LOW IS EMBEDDED IN A TROPICAL WAVE WITH THE AXIS ALONG 52W.
UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR SIGNIFICANT
DEVELOPMENT...AND THE CHANCES FOR THIS SYSTEM TO BECOME A
TROPICAL DEPRESSION ARE DIMINISHING DUE TO THE PRESENCE OF
STRONG SLY UPPER-LEVEL WINDS. THE EXPOSED LOW LEVEL CENTER IS
WELL DEFINED BY CU LINES ON LATEST VIS SAT IMAGERY. SCATTERED
MODERATE CONVECTION IS JUST E OF THE TROPICAL WAVE AXIS/LOW FROM
13N-20N BETWEEN 46W-52W. THIS LOW IS EXPECTED TO MOVE SLOWLY
NORTHWESTWARD DURING THE NEXT DAY OR SO.


...TROPICAL WAVES...

THERE IS ONLY ONE TROPICAL WAVE BETWEEN AFRICA AND THE LESSER
ANTILLES. THE WAVE IS ALONG 52W S OF 21N MOVING W 10 KT. A 1009
MB LOW IS ALONG THE WAVE AXIS NEAR 15N. SEE SPECIAL FEATURE.

...THE ITCZ...
AXIS IS CENTERED ALONG 10N14W 7N30W 11N48W 13N54W 11N62W.
BESIDES THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE...WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 100 NM
EITHER SIDE OF AXIS BETWEEN 25W-45W. SCATTERED MODERATE
CONVECTION IS NEAR 5N22W...AND NEAR 5N19W. A CLUSTER OF MODERATE
TO ISOLATED STRONG CONVECTION IS MOVING OUT OF THE AFRICAN COAST
JUST N OF THE ITCZ AXIS.

DISCUSSION...

THE GULF OF MEXICO...
A SURFACE RIDGE AXIS DOMINATES THE SE U.S. AND THE NORTHERN GULF
WATERS N OF 25N. PRESSURE GRADIENT BETWEEN THIS RIDGE AND A SFC
LOW OVER THE NW CARIBBEAN IS PRODUCING ELY WINDS OF 15 TO 25 KT
OVER FLORIDA AND THE EASTERN GULF. WIDELY SCATTERED SHOWERS ARE
MOVING FROM THE W ATLC THROUGH FLORIDA INTO THE EASTERN GULF
UNDER THE INFLUENCE OF THESE WINDS. LIGHTNING DATA ALSO DEPICTS
ISOLATED TO SCATTERED TSTMS MAINLY OVER THE FLORIDA PANHANDLE
AND NEAR 27N89W. THE REMAINDER OF THE GULF HAS LIGHT 5-10 KT
WINDS WITH MOSTLY FAIR WEATHER OVER THE WESTERN GULF...WHERE A
MID/TO UPPER DRY AIR MASS PREVAILS. ALOFT...AN UPPER-LEVEL RIDGE
ANCHORED ON A HIGH OVER THE SE U.S. DOMINATES THE GULF MOST OF
THE GULF WHILE AN UPPER LOW IS OVER NE MEXICO GENERATING SOME
SHOWER/TSTM ACTIVITY. THE RIDGE OVER THE NORTHERN GULF WILL
PERSIST THE REST OF THE WEEKEND AND WILL WEAKEN MONDAY.

THE CARIBBEAN SEA...
THE MAIN WEATHER FEATURE ACROSS THE REGION IS A BROAD AREA OF
LOW PRESSURE CENTERED BETWEEN HONDURAS AND THE CAYMAN ISLANDS.
SURFACE PRESSURES ARE FALLING IN THE AREA WITH BUOYS REPORTING
NEAR 1005 MB OVER THE NW CARIBBEAN. AS OF 2100 UTC...A 1005 MB
SFC LOW WAS ANALYZED NEAR 17N83W. FURTHER DEVELOPMENT OF THIS
SYSTEM IS POSSIBLE OVER THE NEXT FEW DAYS AS IT REMAINS NEARLY
STATIONARY. CLIMATOLOGICALLY...THE NW CARIBBEAN IS A FAVORABLE
AREA FOR TROPICAL CYCLONE DEVELOPMENT DURING THE MONTH OF
OCTOBER. A CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION IS
JUST SOUTH OF THE SFC LOW. SCATTERED MODERATE CONVECTION DOTS
THE CENTRAL AND WESTERN CARIBBEAN FROM THE DOMINICAN REPUBLIC TO
THE GULF OF HONDURAS. AN UPPER RIDGE IS HELPING TO INDUCE THIS
ACTIVITY. NUMEROUS SHOWERS AND TSTMS ARE SEEN OVER CUBA. AN
UPPER-LEVEL TROUGH THAT EXTENDS WWD FROM AN UPPER LOW OVER
HISPANIOLA IS ENHANCING THIS CONVECTIVE ACTIVITY. ABUNDANT MID
TO UPPER LEVEL MOISTURE COVERS MOST OF THE BASIN. AN AREA OF
DISTURBED WEATHER ASSOCIATED WITH A SURFACE TROUGH AND AN
UPPER-LEVEL LOW IS CENTERED ABOUT 150 MILES NORTH-NORTHWEST OF
PUERTO RICO. THIS SYSTEM REMAINS POORLY ORGANIZED AND
ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME LESS FAVORABLE
FOR DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS IT MOVES SLOWLY
NORTHWESTWARD. POCKETS OF MODERATE CONVECTION ARE OVER WESTERN
VENEZUELA AND NORTHERN COLOMBIA...AS WELL AS OVER PANAMA AND
COSTA RICA PRIMARILY ASSOCIATED WITH THE ITCZ.

THE ATLANTIC OCEAN...
A PAIR OF SFC TROUGHS ARE GENERATING SCATTERED SHOWERS AND TSTMS
OVER THE WEST AND CENTRAL ATLC. THE FIRST ONE RUNS FROM 24N67W
TO THE SE BAHAMAS. AN AREA OF DISTURBED WEATHER IS ASSOCIATED
WITH THIS TROUGH AND AN UPPER LOW. SEE THE CARIBBEAN SEA
SECTION. THE SECOND ONE EXTENDS FROM 23N55W TO 25N46W TO 28N41W.
CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE WITHIN
100 NM EITHER SIDE OF TROUGH BETWEEN 50W-53W. SCATTERED SHOWERS
ARE FOUND ALONG THE REMAINDER OF THE TROUGH. A 1023 MB HIGH
LOCATED NEAR 35N65W EXTENDS A RIDGE OVER THE W ATLC...THE SE
U.S. AND THE STATE OF FLORIDA. THE E ATLC IS ALSO DOMINATED BY A
1020 MB SFC HIGH SITUATED NEAR 27N27W. THIS FEATURE IS FORECAST
TO MOVE NWD AND OUT OF AREA DURING THE NEXT 24 HOURS BUT A RIDGE
WILL REMAIN IN PLACE. PRES GRADIENT WILL TIGHTEN BETWEEN THIS
RIDGE AND LOWER PRES OVER WESTERN AFRICA DURING THE NEXT DAY OR
SO PRODUCING MODERATE TO STRONG NELY WINDS BETWEEN THE CAPE
VERDE ISLANDS AND THE AFRICAN COAST. TRADES ARE ALSO EXPECTED TO
INCREASE ACROSS THE TROPICS. IN THE UPPER LEVELS...A RIDGE IS
OVER THE W ATLANTIC N OF 20N AND W OF 70W. AN UPPER TROUGH
EXTENDS ACROSS THE CENTRAL ATLC TO THE UPPER LOW OVER
HISPANIOLA. MODERATE TO STRONG WLY UPPER LEVEL WINDS ARE OVER
THE FORECAST AREA N OF 20N E OF 50W WITH A JET STREAM BRANCH OF
70-90 KT CLIPPING THE REGION E OF 36W. IN THE TROPICS AN UPPER
LEVEL HIGH IS CENTERED NEAR 13N37W.

$$
GR






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