[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201043
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC.

...TROPICAL WAVES...
A FAIRLY LARGE TROPICAL WAVE IS ALONG 39W/40W S OF 20N MOVING W
10 TO 15 KT OVER THE PAST 24 HOURS. A 1009 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. S TO SWLY UPPER LEVEL WINDS...ON THE SW PERIPHERY
OF AN UPPER RIDGE CENTERED NEAR THE CAPE VERDE ISLANDS...ARE
SHEARING MUCH OF THE CONVECTION AND STRETCHING HIGH CLOUDINESS
WELL TO THE N/NE OF THE WAVE LEAVING THE SFC LOW EXPOSED.
ISOLATED MODERATE CONVECTION IS WITHIN 240 NM E OF THE WAVE
AXIS. MORE ORGANIZED MODERATE CONVECTION IS FURTHER E FROM
12N-16N BETWEEN 30W-34W.

A WEAK TROPICAL WAVE IS ALONG 51W S OF 16N 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 10N14W 10N32W 12N37W 9N52W 11N63W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...CLUSTERS OF MODERATE CONVECTION IS WITHIN 360 NM S OF
THE AXIS BETWEEN 58W-63W...WHICH IS MAINLY INLAND OVER 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 OVER SW FLORIDA...AS A RATHER STRONG
SHORTWAVE TROUGH MOVES INTO THE NW PORTION. AN ASSOCIATED COLD
FRONT STRETCHES FROM THE FLORIDA PANHANDLE SOUTHWESTWARD ALONG
28N88W 23N96W 21N98W 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
LOW 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...SMALL CLUSTERS OF MODERATE CONVECTION ARE LOCATED JUST
W OF THE AREA OVER A PORTION OF ERN MEXICO ASSOCIATED WITH
TROPICAL MOISTURE DRAWN NWD FROM 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 ANALYZED JUST N OF HISPANIOLA AND
A SFC TROUGH THAT EXTENDS FROM THIS LOW TO THE NRN COAST OF
COLOMBIA. WHILE PRESSURES ARE LOW IN THE AREA...THE LOW ITSELF
IS POORLY ORGANIZED WITH LITTLE CONVECTION NEAR ITS BROAD
ILL-DEFINED CENTER. SCATTERED SHOWERS AND TSTMS ARE WITHIN 240
NM OF THE SFC BOUNDARY...ESPECIALLY S OF 16N. SIMILAR ACTIVITY
IS ALSO OCCURRING FARTHER E ACROSS THE VIRGIN ISLANDS EXTENDING
NE FOR 200 NM. THIS ACTIVITY IS MAINLY PRODUCED BY UPPER
DIFFLUENT AIR AND MOIST SWLY FLOW ON THE E SIDE OF THE LARGE CUT
OFF LOW OVER HISPANIOLA. FAIR WEATHER DOMINATES MUCH 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'S 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 AS THE SFC TROUGH REMAINS NEARLY
STATIONARY. THEREAFTER MORE TYPICAL EASTERLY TRADES WILL RESUME.

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. THE
DRIEST AIR NOTED ON WATER VAPOR IMAGES IS LOCATED BETWEEN 63W
AND 80W. A COMPLEX TROUGH PATTERN LIES E OF THE RIDGE COVERING
THE CENTRAL ATLC BETWEEN 40W AND 65W-70W. TWO SFC LOWS ARE
EMBEDDED IN THIS TROUGHING. A 1010 MB FRONTAL LOW IS LOCATED
NEAR 31N51W WITH A COLD FRONT EXTENDING SWD TO 27N54W. A 1005 MB
LOW IS LOCATED NEAR HISPANIOLA WITH A SFC TROUGH EXTENDING WELL
S TOWARDS S AMERICA AND N TO 26N67W. 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 19N BETWEEN 55W AND 57W AND ANOTHER
CLUSTER NEAR THE VIRGIN ISLANDS. 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 25W 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 40W. THE SFC PATTERN IS DOMINATED BY A E-W RIDGE
AXIS FROM A 1019 MB HIGH NEAR 27N33W AND A 1017 MB HIGH NEAR
28N14W.

$$
CANGIALOSI




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