[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121719
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN OCT 12 2008

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
1645 UTC.

...SPECIAL FEATURES...
A 1006 MB SURFACE LOW IS LOCATED IN THE S/CENTRAL ATLANTIC NEAR
16N37W. VISIBLE SATELLITE IMAGERY INDICATES THAT CONVECTION
AROUND THIS SYSTEM HAS BECOME BETTER ORGANIZED THIS MORNING WITH
SCATTERED MODERATE TO STRONG CONVECTION E OF THE CENTER FROM
12N-19N BETWEEN 33W-37W. THIS SYSTEM HAS THE POTENTIAL TO FORM A
TROPICAL DEPRESSION IN THE NEXT 24 HOURS...HOWEVER UPPER LEVEL
WINDS REMAIN UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 42W/43W S OF 20N MOVING W AT 10-15 KT.
THIS WAVE IS EMBEDDED IN A LARGE AREA OF DISTURBED WEATHER.
VISIBLE SATELLITE IMAGERY REVEALS A LOW-AMPLITUDE INVERTED-V
SIGNATURE S OF 13N. A WEAK LOW-LEVEL CIRCULATION CENTER IS ALONG
THE AXIS NEAR 12N43W. SCATTERED MODERATE CONVECTION IS WITHIN 90
NM EITHER SIDE OF THE AXIS FROM 10N-13N.

A TROPICAL WAVE IS ALONG 55W S OF 21N MOVING W NEAR 10 KT. MIMIC
TPW SHOWS A MOISTURE MAXIMUM IN THE VICINITY OF THE WAVE THAT IS
DECREASING IN MAGNITUDE DUE TO UPPER-LEVEL SWLY SHEAR. NO
SIGNIFICANT CONVECTION IS ASSOCIATED WITH THE WAVE AND THE AXIS
REMAINS ILL-DEFINED.

A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 69W FROM THE
EASTERN TIP OF THE DOMINICAN REPUBLIC TO VENEZUELA. THE WAVE IS
MOVING W NEAR 10 KT. VISIBLE SATELLITE IMAGERY AND QUIKSCAT
WINDS DEPICT A BROAD AREA OF CYCLONIC TURNING AROUND THE AXIS
WITH A 1009 MB SFC LOW TO THE EAST OF THE WAVE NEAR 14N66W. A
LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS AROUND THE LOW
FROM 12N-16N BETWEEN 64W-67W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 2N27W 8N40W 11N45W 11N53W. IN
ADDITION TO CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS E OF 18W TO THE
AFRICAN COAST FROM 8N-11N. WIDELY SCATTERED MODERATE CONVECTION
IS FROM 1S-7N BETWEEN 25W-33W. SCATTERED MODERATE CONVECTION IS
WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 45W-53W.

...DISCUSSION...

GULF OF MEXICO...
THE BASE OF A SFC HIGH PRESSURE RIDGE EXTENDING FROM THE NE
CONUS COVERS THE GULF. ANTICYCLONIC FLOW OF 15-20 KT BLANKET THE
REGION WITH ONSHORE WINDS ENHANCING AN AREA OF ISOLATED SHOWERS
ALONG THE COAST OF MEXICO FROM 24N-26N. SCATTERED SHOWERS ARE
MOVING WESTWARD THROUGH THE FLORIDA STRAIGHTS AND INTO THE
EASTERN GULF DUE TO INSTABILITY AROUND AN UPPER-LEVEL LOW OVER
THE YUCATAN CHANNEL. ALOFT...STRONG SUBSIDENCE AND DRY STABLE
AIR AROUND AN UPPER-LEVEL HIGH OVER SOUTH TEXAS IS INHIBITING
SIGNIFICANT CONVECTION FROM DEVELOPING W OF 86W. EXPECT WINDS IN
THE GULF TO INCREASE OVER THE NEXT 24-48 HOURS AS HIGH PRESSURE
OVER THE NE CONUS DRIFTS SOUTHWARD.

CARIBBEAN SEA...
A LARGE CLUSTER OF MODERATE TO STRONG CONVECTION ASSOCIATED WITH
A 1009 MB SFC LOW CENTERED NEAR 14N66W DOMINATES THE CARIBBEAN E
OF 67W. THIS LOW WILL MOVE NW-WARD OVER THE NEXT DAY OR TWO
AFFECTING HISPANIOLA ON MONDAY BEFORE MOVING INTO THE ATLC ON
TUE. A SECOND SFC LOW PRESSURE IS IN THE FAR SW CARIBBEAN NEAR
11N81W. UPPER LEVEL DIVERGENCE IN THIS REGION IS ENHANCING
CONVECTION ASSOCIATED WITH THE LOW...PRODUCING SCATTERED SHOWERS
S OF 15N AND W OF 77W. SCATTERED SHOWERS ARE ALSO MOVING OVER
WESTERN CUBA...THE YUCATAN CHANNEL...AND THE NW CARIBBEAN N OF
18N. THESE SHOWERS ARE BEING DRIVEN BY UPPER-LEVEL DIVERGENCE
AND INSTABILITY AROUND AN UPPER LOW OVER THE YUCATAN CHANNEL.
EASTERLY WINDS OF 10-15 KT ARE OVER THE CARIBBEAN W OF THE
TROPICAL WAVE ALONG 69W. WINDS INCREASE TO 15-20 KT E OF THE
WAVE.

ATLANTIC OCEAN...
A SFC TROUGH LIES ALONG THE SE COAST OF THE CONUS AND MOVES
INLAND NEAR THE FLORIDA/GEORGIA BORDER. SATELLITE IMAGERY AND
NWS DOPPLER RADAR REVEAL SCATTERED SHOWERS AND THUNDERSTORMS IN
THE W ATLC WITHIN 90 NM SE OF THE TROUGH. FURTHER EAST...A
CLUSTER OF MODERATE CONVECTION ASSOCIATED WITH UPPER-LEVEL
DIVERGENCE FROM 25N-29N BETWEEN 66W-70W HAS STARTED TO WEAKEN. A
NARROW...BUT DEEP-LAYER TROUGH OVER THE CENTRAL ATLC EXTENDS A
STATIONARY FRONT INTO THE DISCUSSION AREA FROM 31N45W TO 28N50W.
A BAND OF SCATTERED MODERATE CONVECTION EXTENDS UP TO 120 NM
AHEAD OF THE BOUNDARY N OF 27N. A SFC HIGH PRESSURE RIDGE COVERS
THE EASTERN ATLC. TO THE SOUTH...A LARGE AREA OF MODERATE TO
STRONG CONVECTION SURROUNDS A 1006 MB SFC LOW NEAR 16N37W...SEE
SPECIAL FEATURES SECTION FOR MORE DETAILS. IN THE TROPICS...
DIVERGENCE AROUND AN UPPER-LEVEL HIGH NEAR 8N20W AND A SECOND
UPPER-LEVEL HIGH NEAR 11N46W IS ENHANCING CONVECTION ALONG THE
ITCZ.

$$
WADDINGTON



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