[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221050
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN OCT 22 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1045 UTC.

...TROPICAL WAVES...
A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 46W S OF 24N MOVING W
NEAR 10 KT. THIS WAVE HAS DEVELOPED A CLASSIC INVERTED V
SIGNATURE. THE WEAK SFC LOW PREVIOUSLY ANALYZED ALONG THIS WAVE
HAS BEEN DROPPED DUE TO THE LACK OF A CLOSED CIRCULATION BASED
ON SATELLITE IMAGES AND QUIKSCAT DATA. ASSOCIATED CONVECTION IS
MINIMAL AND MAINLY EMBEDDED IN THE ITCZ EXCEPT FOR A PATCH OF
SCATTERED MODERATE CONVECTION FROM 18N-21N BETWEEN 42W-44W.
GLOBAL MODELS...THAT HAVE THIS FEATURE INITIALIZED...CONTINUE TO
TRACK IT WNW AS AN OPEN WAVE.

THE WEAK TROPICAL WAVE THAT WAS PREVIOUSLY ANALYZED NEAR THE
LESSER ANTILLES HAS BEEN REMOVED FROM THE SFC ANALYSIS DUE TO
THE LACK OF EVIDENCE OVER THE PAST SEVERAL DAYS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N17W 7N30W 6N41W 8N48W 7N59W.
SCATTERED MODERATE CONVECTION IS WITHIN 300 NM S OF THE AXIS E
OF 20W. SIMILAR CONVECTION IS WITHIN 240 NM EITHER SIDE BETWEEN
21W-45W. SOME OF THIS CONVECTION IS BEING ENHANCED BY THE LARGE
TROPICAL WAVE ALONG 46W.

...DISCUSSION...
THE GULF OF MEXICO...
QUIET WEATHER EXISTS ACROSS MUCH OF THE GULF OF MEXICO THIS
MORNING THANKS TO DRY STABLE AIR ALOFT GENERATED BY AN ELONGATED
UPPER RIDGE STRETCHED ACROSS THE AREA ORIGINATING FROM A HIGH
CENTER IN THE SW GULF. AT THE SFC...A WARM FRONT EXTENDS ACROSS
N FLORIDA FROM NEAR DAYTONA BEACH TO THE MS/FL BORDER NEAR 31N
86.5W. SFC FLOW IS GENERALLY LIGHT FROM THE SE TO S ACROSS MOST
OF THE GULF PRODUCING TYPICAL EARLY FALL WARM AND HUMID
CONDITIONS. HOWEVER A CHANGE IN AIRMASS IS IN STORE FOR THE AREA
AS A STRONG COLD FRONT HAS PUSHED OFF THE SE TEXAS COASTLINE. AS
OF 09 UTC...THE COLD FRONT WAS ANALYZED FROM CENTRAL LOUISIANA
TO S TEXAS. TEMPS HAVE FALLEN INTO THE 40'S AND 50'S BEHIND THE
BOUNDARY IN TEXAS AND NRN LOUISIANA WITH DEWPOINTS IN THE 30'S.
S AND E OF THE FRONT THESE VALUES ARE IN THE 70'S. A TROUGH WAS
ANALYZED AHEAD OF THE FRONT EARLIER THIS MORNING...BUT BECAUSE
OF THE FAST MOTION OF THE COLD FRONT IT APPEARS THAT THESE
FEATURES HAVE MERGED. A LINE OF SHOWERS AND TSTMS ARE WITHIN 90
NM AHEAD OF THE BOUNDARY. THIS FRONTAL SYSTEM WILL LIKELY CLEAR
THE ENTIRE AREA LATE MON BRINGING MODIFIED COOLER AND MUCH DRIER
AIR WITH IT. AN INCREASE IN NLY WINDS AND SEAS WILL FOLLOW THE
BOUNDARY AS SFC HIGH PRES BUILDS IN BEHIND IT.

THE CARIBBEAN SEA...
THE WEATHER IN THE CARIBBEAN HAS BECOME MUCH LESS ACTIVE THIS
MORNING COMPARED TO THE PAST COUPLE OF DAYS. ONLY ISOLATED
SHOWERS AND TSTMS ARE EMBEDDED IN A THINNING UPPER LEVEL
MOISTURE PLUME E OF 70W. THIS MOISTURE IS MAINLY ASSOCIATED WITH
DEBRIS TROPICAL MOISTURE ROTATING AROUND AN ANTICYCLONE CENTERED
OVER THE LEEWARD ISLANDS. MORE IMPRESSIVE CONVECTION IS ON THE N
SIDE OF THE RIDGE ASSOCIATED WITH A SFC LOW LOCATED ABOUT 300 NM
NNE OF PUERTO RICO. THE CENTRAL AND WRN CARIBBEAN REMAIN QUIET
WITH ONLY WIDELY SCATTERED SHOWERS. HOWEVER THE ATMOSPHERE ALOFT
IS NOT AS STABLE AS IT WAS OVER THE PAST FEW DAYS DUE TO AN
UPPER LOW...WHICH IS MOISTENING THE AIR SLIGHTLY...TRACKING WWD
NOW CENTERED ABOUT 150 NM SW OF JAMAICA. A WEAK SFC TROUGH IS
ANALYZED FROM THE LOW NE OF PUERTO RICO TO HISPANIOLA CONTINUING
SOUTHWESTWARD TO THE BORDER OF HONDURAS/NICARAGUA. SFC WINDS ARE
LIGHT AND VARIABLE NEAR THE TROUGH BUT APPEAR TO BE FROM A MORE
TYPICAL EAST DIR ELSEWHERE. THESE WINDS ARE EXPECTED TO BECOME
MORE UNIFORM FROM THE E AND INCREASE SLIGHTLY OVER THE NEXT DAY
OR TWO.

THE ATLANTIC OCEAN...
IN THE WRN ATLC...AN UPPER HIGH IN THE SW GULF OF MEXICO HAS
RIDGING THAT EXTENDS NE ACROSS THE NRN BAHAMAS. ANOTHER UPPER
LEVEL RIDGE IS CENTERED OVER THE ERN CARIBBEAN AND CENTRAL ATLC
WITH TWO HIGH CENTERS ONE NEAR 28N50W...WHICH IS GETTING PUSHED
QUICKLY ESE...AND THE OTHER DRIFTING W OVER THE LEEWARD ISLANDS.
A SLIGHT WEAKNESS IN THE RIDGE EXISTS OVER THE SRN BAHAMAS DUE
TO THE UPPER LOW IN THE WRN CARIBBEAN. THIS PATTERN HAS PRODUCED
PLENTY OF VERY DRY STABLE AIR N OF 25N W OF 45W.

A THINNING MOISTURE PLUME EXISTS S OF 26N BETWEEN 53W AND 70W.
MOST OF THE MOISTURE IN THIS REGION IS NOT DEEP IN NATURE EXCEPT
FOR ONE AREA OF CONVECTION THAT HAS BEEN PERSISTING FROM 22N TO
25N BETWEEN 61W AND 65W. THIS CONVECTION IS ASSOCIATED WITH A
1011 MB SFC LOW PRES SYSTEM NEAR 24N65W WITH A TROUGH EXTENDING
FROM THIS LOW SOUTHWESTWARD TO HISPANIOLA AND NORTHEASTWARD TO
29N61W. THE SFC CIRCULATION IS CLEARLY EXPOSED...LOCATED ABOUT
30-50 NM W OF THE WRN EDGE OF THE DEEP CONVECTION. WLY UPPER
LEVEL WINDS...ON THE N PERIPHERY OF THE ANTICYCLONE OVER THE
LEEWARD ISLANDS...IS PROVIDING UNFAVORABLE CONDITIONS
RESTRICTING THE CONVECTION TO WRAP AROUND THE SFC LOW. THE UPPER
LEVEL ENVIRONMENT MAY BECOME SLIGHTLY LESS HOSTILE OVER THE NEXT
DAY OR SO BEFORE BECOMING VERY UNFAVORABLE AS A LARGE TROUGH
MOVES OFF THE U.S. COAST.

THE TROPICAL ERN ATLC IS DOMINATED BY UPPER RIDGING WITH AN
ANTICYCLONE CENTERED A COUPLE HUNDRED NM SSW OF THE CAPE VERDE
ISLANDS. UPPER LEVEL EASTERLY FLOW ON THE S SIDE OF THE RIDGE IS
ENHANCING CONVECTION IN THE ITCZ E OF 45W. AN ELONGATED TROUGH
STRETCHES FROM THE CANARY ISLANDS WSW ALONG 26N25W TO A
DEVELOPING CUT OFF NEAR 24N35W. THE SFC PATTERN IS DOMINATED BY
E-W RIDGING...WHICH IS FAIRLY FAR S IN THE SUBTROPICS...FROM A
1019 MB HIGH NEAR 28N53W TO A 1018 MB HIGH NEAR 25N30W. THIS
RIDGE IS BLEMISHED BY THE LARGE TROPICAL WAVE IN THE REGION AND
A BENIGN SFC TROUGH ALONG 32N38W 28N41W.

$$
CANGIALOSI




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