[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 072342
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN OCT 07 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

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

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 17N32W TO 9N32W MOVING W AT 10-15 KT.
THE WAVE IS EMBEDDED WITHIN BROAD CYCLONIC FLOW AROUND THE
MONSOON TROUGH THAT IS CENTERED NEAR THE SOUTHERN EXTENT OF THE
WAVE WHERE A 1010 MB SURFACE LOW HAS BEEN ANALYZED. THE WAVE
CONTINUES TO LIE ON THE WESTERN SIDE OF A SURGE OF DEEP LAYER
MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. CONVECTION
IS LIMITED TO THE MONSOON TROUGH REGION NEAR THE LOW PRESSURE
CENTER. NUMEROUS STRONG CONVECTION IS FROM 6N-8N BETWEEN
31W-33W...WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION
ELSEWHERE FROM 4N-9N BETWEEN 30W-33W.

TROPICAL WAVE IN THE CARIBBEAN IS FROM 20N811W TO 13N81W MOVING
W AT 15-20 KT. THE WAVE IS EMBEDDED WITHIN BROAD MONSOONAL FLOW
AROUND AN EXTENSION OF THE E PAC MONSOON TROUGH. AN ASCAT PASS
FROM EARLIER TODAY ALSO INDICATED LOW-LEVEL CYCLONIC FLOW IS
AROUND THE NORTHERN PORTIONS OF THE WAVE. ONLY A FEW ISOLATED
SHOWERS ARE NEAR THE NORTHERN PORTIONS OF THE WAVE...WHILE MORE
SCATTERED ACTIVITY IS NEAR THE SOUTHERN EXTENT OF THE WAVE NEAR
THE MONSOON TROUGH. A SMALL CLUSTER OF MODERATE CONVECTION IS
FROM 12N-13N BETWEEN 80W-81W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA-BISSAU AT 12N16W CONTINUING ALONG 9N19W 9N27W 7N37W
8N42W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
5N-22N BETWEEN 21W-25W. SCATTERED MODERATE/STRONG CONVECTION IS
FROM 3N-7N BETWEEN 25W-28W. A LARGE CLUSTER OF STRONG CONVECTION
IS FROM 7N-9N BETWEEN 38W-40W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 8N-9N BETWEEN 35W-38W...AND FROM 5N-7N
BETWEEN 41W-44W.

...DISCUSSION...

GULF OF MEXICO...
THE FRONT ACROSS THE GULF OF MEXICO HAS BECOME STATIONARY AS OF
2100 UTC. IT EXTENDS FROM NE FLORIDA NEAR 31N82W ALONG 27N90W
26N96W AND CONTINUES INTO MEXICO ALONG 23N99W 29N104W. THE FRONT
HAS STALLED DUE TO THE BROADNESS OF THE UPPER LEVEL TROUGH
SUPPORTING IT...WHICH SITS OVER THE ENTIRE EASTERN UNITED
STATES. A NARROWER UPPER TROUGH EXTENDS DOWN MEXICO HELPING
PROVIDE MOIST SWLY FLOW ALOFT ACROSS THE MAJORITY OF THE BASIN
EXCEPT FOR THE NW CORNER. HOWEVER...LOW LEVEL CLOUDS ARE
COVERING THE NW CORNER. A SURFACE TROUGH IS ANALYZED OVER THE SW
GULF FROM 22N95W TO 17N93W. THE COMBINATION OF THESE FEATURES
AND THE UPPER LEVEL MOISTURE IS HELPING PRODUCE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS IN THE CENTRAL GULF FROM 24N-28N
BETWEEN 84W-90W. ISOLATED SHOWERS/THUNDERSTORMS ARE IN THE SW
GULF FROM 19N-24N BETWEEN 94W-97W. A LINE OF
SHOWERS/THUNDERSTORMS IS ALSO ALONG THE WEST COAST OF FLORIDA
WITH WIDESPREAD SHOWERS CONTINUING ACROSS SOUTH FLORIDA. A
SHORTWAVE TROUGH STILL OVER THE SOUTHWEST UNITED STATES WILL
EVENTUALLY PUSH THE FRONTAL BOUNDARY THROUGH THE AREA MIDWEEK
FINALLY PROVIDING RELIEF FROM THE MOIST CONDITIONS. SURFACE
RIDGING WILL BUILD IN BEHIND THE FRONT.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE COVERS THE WESTERN CARIBBEAN PROVIDING DRY
AIR ALOFT AND FAIR CONDITIONS OVER THE NW CORNER. HOWEVER...THE
RIDGE IS DRAWING MOIST AIR AROUND ITS OUTER WESTERN
SIDE...PRODUCING SHOWERS/THUNDERSTORMS ACROSS MUCH OF CENTRAL
AMERICA...BUT IS INHIBITING CONVECTION NEAR THE NORTHERN HALF OF
A TROPICAL WAVE THAT EXTENDS INTO THE SW CARIBBEAN ALONG 81W.
THE SOUTHERN HALF OF THE WAVE IS PRODUCING SHOWERS/THUNDERSTORMS
AS IT IS EMBEDDED WITHIN THE BROAD CYCLONIC FLOW AROUND THE
MONSOON TROUGH THAT EXTENDS FROM NORTHERN COSTA RICA TO NORTHERN
COLOMBIA. SEE TROPICAL WAVE SECTION FOR MORE DETAILS. BROAD
UPPER TROUGHING COVERS THE REMAINDER OF THE BASIN...AND IS
KEEPING THE CENTRAL AND EASTERN CARIBBEAN UNDER MOSTLY FAIR
CONDITIONS BESIDES A FEW ISOLATED SHOWERS/THUNDERSTORMS EAST OF
68W. LITTLE CHANGE IS EXPECTED OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
MOIST SOUTHWESTERLY FLOW ALOFT IS ACROSS THE FAR WESTERN ATLC
SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WEST OF 74W
TO THE FLORIDA COAST AND NORTH OF 24N. AN UPPER RIDGE COVERS THE
REMAINDER OF THE WEST ATLC. HOWEVER...A 1008 MB SURFACE LOW IS
CENTERED OVER THE SW BAHAMAS NEAR 22N73W PRODUCING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS FROM 23N-26N BETWEEN 70W-74W. AN
UPPER LEVEL LOW CONTINUES TO SPIN IN THE CENTRAL ATLC NEAR
24N56W SUPPORTING SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS FROM
19N-26N BETWEEN 52W-57W. SOME OF THIS ACTIVITY MAY BE INFLUENCE
BY A STATIONARY FRONT THAT ENTERS THE DISCUSSION AREA WELL TO
THE EAST NEAR 32N22W AND CONTINUES ALONG 23N40W 26N55W 26N63W.
ISOLATED SHOWERS ARE ALONG THE FRONTAL BOUNDARY ELSEWHERE. AN
UPPER LEVEL RIDGE IS EAST OF THE UPPER LOW ALONG 41W...WHILE
ANOTHER UPPER TROUGH COVERS THE FAR EASTERN ATLC EXTENDING FROM
NW AFRICA TO THE CAPE VERDE ISLANDS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON




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