[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200544
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI OCT 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0530 UTC.

...TROPICAL WAVES...
A FAIRLY LARGE TROPICAL WAVE IS ALONG 38W S OF 20N MOVING W 10
TO 15 KT. A 1008 MB LOW IS ALONG THE WAVE NEAR 14N. BROAD LOW TO
MID LEVEL CLOUDS ARE TURNING CYCLONICALLY ABOUT THE WAVE AXIS
ESPECIALLY NEAR THE WEAK AREA OF LOW PRES. A 2024 UTC QUIKSCAT
PASS INDICATED THAT THE STRONGEST UNCONTAMINATED WINDS ARE NEAR
20 KT. SWLY UPPER LEVEL WINDS ARE SHEARING MUCH OF THE
CONVECTION AND STRETCHING HIGH CLOUDINESS WELL TO THE NE OF THE
WAVE LEAVING THE SFC LOW EXPOSED. ISOLATED MODERATE CONVECTION
IS WITHIN 240 NM E OF THE WAVE AXIS.

A WEAK TROPICAL WAVE IS ALONG 50W S OF 18N MOVING W NEAR 15 KT.
THIS WAVE HAS BECOME DIFFICULT TO LOCATE AS LITTLE...IF
ANY...WAVE SIGNATURE IS OBVIOUS IN SATELLITE IMAGERY AND SFC
OBSERVATIONS. THIS FEATURE IS MOVING INTO AN AREA OF PERSISTENT
UNSETTLED WEATHER ASSOCIATED WITH A CENTRAL ATLC TROUGH AND
WILL LIKELY BE CHALLENGING TO TRACK OVER THE NEXT COUPLE DAYS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N15W 10N32W 13N37W 9N51W 12N70W
11N84W. SCATTERED MODERATE CONVECTION IS E OF 19W FROM 8N-11N.
SIMILAR CONVECTION IS WITHIN 300 NM N OF THE AXIS BETWEEN
22W-33W...LIKELY ENHANCED OR ASSOCIATED WITH THE TROPICAL WAVE
ALONG 38W. SCATTERED MODERATE IS WITHIN 300 NM S OF THE AXIS
BETWEEN 58W-76W...WHICH IS MOSTLY INLAND OVER NRN S AMERICA.

...DISCUSSION...
THE GULF OF MEXICO...
THE LARGE MID/UPPER LEVEL ANTICYCLONE THAT HAS BEEN CENTERED
OVER THE GULF OVER THE PAST FEW DAYS IS BECOMING ELONGATED AND
PUSHED E...NOW CENTERED IN THE E GULF NEAR 27N85W...AS A RATHER
STRONG SHORTWAVE TROUGH MOVES INTO THE NW PORTION. AN ASSOCIATED
COLD FRONT STRETCHES FROM THE FLORIDA PANHANDLE SOUTHWESTWARD
ALONG 28N91W 24N96W 22N98W THEN STATIONARY ALONG THE E SLOPES OF
THE SIERRA MADRE MOUNTAINS IN MEXICO. ONLY ISOLATED TO SCATTERED
SHOWERS ARE ALONG THE FRONT. THIS FRONTAL BOUNDARY IS EASILY
NOTICEABLE WITH TEMPS AND DEWPOINTS SHARPLY FALLING BEHIND THE
BOUNDARY. AHEAD OF THE FRONT TEMPS AND DEWPOINTS ARE IN THE MID
TO UPPER 70'S IN N FLORIDA. THESE VALUES ARE IN THE 50'S AND
60'S BEHIND THE BOUNDARY ACROSS COASTAL MS/LA...AND EVEN
COOLER/DRIER TO THE N AND W. LITTLE SHOWER ACTIVITY EXISTS
ACROSS MOST OF THE AREA WITH MODERATE DRY AIR ALOFT IN PLACE.
HOWEVER...CLUSTERS OF MODERATE CONVECTION ARE LOCATED JUST W OF
THE AREA OVER A PORTION OF ERN MEXICO ASSOCIATED WITH TROPICAL
MOISTURE DRAWN NWD FROM THE ITCZ AND AN AREA OF LOW PRES IN THE
EPAC.

THE CARIBBEAN SEA...
SOME UNSETTLED WEATHER IS STILL OCCURRING IN THE ERN CARIBBEAN
ASSOCIATED WITH A 1005 MB LOW OVER HISPANIOLA AND A SFC TROUGH
THAT EXTENDS FROM THIS LOW TO THE NRN COAST OF COLOMBIA. THIS
SFC LOW IS POORLY ORGANIZED WITH LITTLE CONVECTION NEAR ITS
BROAD CENTER. SCATTERED SHOWERS AND TSTMS ARE WITHIN 120 NM OF
THE SFC BOUNDARY. MOST OF THE WEATHER IS FURTHER E ACROSS THE
VIRGIN ISLANDS EXTENDING NE FOR 200 NM. MORE SHOWER ACTIVITY IS
E OF THE LESSER ANTILLES WHERE UPPER DIFFLUENCE IS STRONGER.
FAIR WEATHER EXISTS ACROSS MOST OF THE CENTRAL AND WRN
CARIBBEAN...W OF 75W...AS VERY DRY STABLE AIR CONTINUES TO BE
ADVECTED INTO THE REGION ON THE SRN PERIPHERY OF THE GULF OF
MEXICO UPPER RIDGE. SFC WINDS ARE LIGHT AND VARIABLE ACROSS THE
AREA WITH WLY WINDS BEING REPORTED W OF THE TROUGH TO 75W OR SO.
THESE WINDS ARE EXPECTED TO REMAIN RATHER VARIABLE FRI AND SAT
WITH THE SFC TROUGH DRIFTING WWD.

THE ATLANTIC OCEAN...
A LONGWAVE RIDGE/TROUGH/RIDGE PATTERN EXISTS ACROSS THE ATLC
BASIN. STARTING FROM W TO E...A SPRAWLING ELONGATED UPPER RIDGE
CENTERED OVER THE ERN GULF HAS RIDGING THAT EXTENDS WELL NE OF
BERMUDA. DRY STABLE AIR ALOFT IS ASSOCIATED WITH THE RIDGE...
WITH THE DRIEST AIR LOCATED BETWEEN 65W AND 80W. A COMPLEX
TROUGH PATTERN LIES E OF THE RIDGE COVERING THE CENTRAL ATLC
BETWEEN 40W AND 65W. TWO SFC LOWS ARE EMBEDDED IN THIS
TROUGHING. A 1010 MB LOW IS POSITIONED AT THE BASE OF A FRONT
NEAR 30N51W WITH A SFC TROUGH EXTENDING SWD TO 24N57W. A 1005 MB
LOW IS LOCATED OVER HISPANIOLA WITH A SFC TROUGH EXTENDING WELL
S TOWARDS S AMERICA. A FAIR AMOUNT OF MOISTURE EXISTS IN THIS
COMPLEX TROUGH BETWEEN 40W AND 65W S OF 25W AND BETWEEN 40W AND
52W N OF 25N. HOWEVER...MOST OF THE MOISTURE IS NOT VERY DEEP IN
NATURE EXCEPT FOR A CLUSTER OF MODERATE CONVECTION FROM 17N TO
20N BETWEEN 55W AND 58W. FARTHER E...AN UPPER ANTICYCLONE IS
CENTERED JUST E OF THE CAPE VERDE ISLANDS WITH RIDGING EXTENDING
N/NE TO THE CANARY ISLANDS. THIS PATTERN IS ENHANCING CONVECTION
IN THE ITCZ BETWEEN 22W AND 35W. SWLY FLOW ON THE WRN PERIPHERY
OF THE RIDGE IS SHEARING HIGH CLOUDS AND DEEP CONVECTION NE AWAY
FROM THE TROPICAL WAVE AND WEAK AREA OF LOW PRES NEAR 38W. THE
SFC PATTERN IS FAIRLY WEAK ACROSS THE E ATLC WITH THE DOMINANT
FEATURE BEING A 1020 MB HIGH NEAR 27N36W.

$$
CANGIALOSI




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