[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 242350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE OCT 24 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2330 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 38W S OF 17N MOVING W NEAR 15 KT. LOW TO
MID LEVEL CYCLONIC TURNING IS NOTED ABOUT THE WAVE AXIS ON VIS
AND SHORTWAVE IR IMAGES. A FEW SFC OBS ALSO SHOWED GOOD TURNING
IN THE WINDS FROM S-SE E OF THE WAVE TO ENE W OF THE
WAVE...MAKING IT RELATIVELY EASY TO LOCATE. THIS WAVE IS
CURRENTLY UNDERNEATH A SMALL UPPER HIGH WHICH IS SPREADING UPPER
LEVEL MOISTURE ANTICYCLONICALLY AROUND THE FEATURE. STRONG WLY
WINDS ON THE N SIDE OF THE UPPER HIGH IS PROVIDING AN
UNFAVORABLE ENVIRONMENT ACROSS THE NRN EXTENSION OF THE WAVE.
SCATTERED MODERATE CONVECTION IS WITHIN 300 NM EITHER SIDE OF
THE AXIS S OF 14N.

A FAIRLY LARGE TROPICAL WAVE IS NEARING THE LESSER ANTILLES
ALONG 60W S OF 20N MOVING W NEAR 15 KT. THE WAVE AXIS IS
ANALYZED NEAR THE WRN EDGE OF A WIDE AREA OF ISOLATED TO
SCATTERED MODERATE CONVECTION BETWEEN 50W-59W FROM 12N-18N. SFC
OBSERVATIONS HELPED LOCATE THE AXIS. NWLY UPPER LEVEL
FLOW...BETWEEN AN UPPER HIGH IN THE ERN CARIBBEAN AND AN UPPER
LOW NE OF THE WAVE...IS SHEARING MUCH OF THE CONVECTION E OF THE
WAVE AXIS.

TROPICAL WAVE IS ALONG 76W S OF 19N DRIFTING SLOWLY TO THE W. IT
APPEARS THIS WAVE IS SLOWING AND BECOMING TILTED FROM SE TO
NW...AND MAY BECOME EVEN MORE DIFFICULT TO TRACK AS IT INTERACTS
WITH THE APPROACHING FRONTAL SYSTEM FROM THE NW. DEEP CONVECTION
IS MINIMAL WITH A FEW ISOLATED SHOWERS/TSTMS NOTED WITHIN 100NM
OF THE AXIS...WHICH IS LIKELY ENHANCED OR ASSOCIATED WITH MOIST
SSW UPPER LEVEL FLOW ON THE E SIDE OF AN UPPER LOW IN THE WRN
CARIBBEAN.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 9N30W 11N40W 14N57W 11N64W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS WITHIN 180 NM N OF THE
AXIS BETWEEN 42W-50W. SCATTERED MODERATE IS ALSO WITHIN 180 NM S
OF THE AXIS BETWEEN 61W-71W...THIS IS MOSTLY INLAND OVER NRN S
AMERICA.

...DISCUSSION...
GULF OF MEXICO...
A STRONG COLD FRONT CLEARED THE ENTIRE AREA LATE YESTERDAY
ALLOWING MUCH COOLER AND DRIER AIR TO BUILD INTO THE ERN PORTION
OF THE AREA. TEMPS AND DEWPOINTS ARE UNSEASONABLY LOW ACROSS THE
STATE OF FLORIDA. NLY SFC WINDS WHICH WERE IN THE 15-25 KT RANGE
EARLIER TODAY IN THE ERN GULF ARE SUBSIDING. MILDER CONDITIONS
EXIST ACROSS THE CENTRAL AND WRN GULF UNDER MAINLY ELY WINDS S
OF THE SFC HIGH PRES SYSTEM OVER THE CENTRAL U.S. THE ONLY AREA
OF SHOWER ACTIVITY IS IN THE SW GULF FROM 18N-22N BETWEEN
94W-97W. THESE SCATTERED SHOWERS ARE ASSOCIATED WITH A SFC
TROUGH...WHICH BROKE OFF FROM THE MAIN FRONTAL SYSTEM IN THE WRN
ATLC/CARIBBEAN...AND SOME ENHANCEMENT FROM SLY UPPER LEVEL FLOW
ON THE W SIDE OF AN UPPER HIGH CENTERED NEAR 21N93W. SFC HIGH
PRES WILL CONTINUE TO MOVE EWARD ALLOWING WARMER RETURN FLOW TO
DEVELOP BEFORE THE NEXT COLD FRONT ENTERS THE NW PART OF THE
AREA LATE THU/EARLY FRI.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH/RIDGE PATTERN IS ESTABLISHED ACROSS THE
CARIBBEAN. AN UPPER LOW REMAINS NEARLY STATIONARY OVER THE WRN
CARIBBEAN NEAR 17N82W. THE WEAK SFC TROUGH ASSOCIATED WITH THIS
UPPER LOW...THAT ALSO HAS BEEN STATIONARY OVER THE PAST COUPLE
OF DAYS...APPEARS TO HAVE DISSIPATED. THE TAIL END OF AN ATLC
FRONTAL BOUNDARY CUTS ACROSS THE NW CARIBBEAN FROM CENTRAL CUBA
TO THE YUCATAN PENINSULA NEAR 19N88W. ISOLATED SHOWERS AND TSTMS
ARE WITHIN 90 NM S OF THE BOUNDARY. SIMILAR ISOLATED ACTIVITY
EXISTS ACROSS THE SW CARIBBEAN ASSOCIATED WITH A WEAK TROPICAL
WAVE ALONG 76W AND MOIST SLY FLOW...ON THE E SIDE OF THE UPPER
LOW MENTIONED...ADVECTING SOME TROPICAL MOISTURE FROM THE ITCZ
NWD. THE ERN CARIBBEAN IS DOMINATED BY AN UPPER RIDGE WHICH IS
CENTERED NEAR 16N64W. MODERATELY DRY AIR ALOFT IS ASSOCIATED
WITH THE RIDGE. SCATTERED MODERATE TO STRONG CONVECTION HAS
BLOSSOMED OVER THE PAST FEW HOURS OVER THE ISLANDS OF PUERTO
RICO AND HISPANIOLA...WHICH IS LIKELY ASSOCIATED WITH LOCAL
TOPOGRAPHIC LIFT...LOW LEVEL CONVERGENCE NEAR A PRE-FRONTAL
TROUGH AND SLY UPPER FLOW. SOME MOISTURE...ASSOCIATED WITH A
LARGE TROPICAL WAVE E OF THE AREA...WILL BEGIN TO SPREAD ACROSS
THE LESSER ANTILLES LATER TOMORROW AND THU.

ATLANTIC OCEAN...
THE WRN ATLC IS DOMINATED BY A LARGE DEEP LAYER TROUGH WITH
PLENTY OF VERY DRY AIR ALOFT N OF 25N W OF 62W. AN ASSOCIATED
STRONG SURFACE COLD FRONT IS PUSHING THROUGH THE AREA ANALYZED
ALONG 32N62W 26N70W TO CENTRAL CUBA. THIS HAS USHERED IN SOME OF
THE COOLEST AIR OF THE SEASON THUS FAR WITH WIDESPREAD COLD AIR
STRATOCUMULUS CLOUDS BEHIND THE BOUNDARY...ALONG WITH INCREASING
N/NW FLOW AND RISING SHORT TO MEDIUM PERIOD SWELL. ASSOCIATED
SWELL WILL SPREAD E THROUGH THE CARIBBEAN THROUGH THE END OF THE
WORK WEEK BRINGING THE FIRST APPRECIABLE WINTER-LIKE SWELL EVENT
OF THE SEASON...SEE STATEMENTS FROM LOCAL WEATHER SERVICE
OFFICES AND MIAOFFNT3 FOR MORE DETAILS. A PREFRONTAL TROUGH
ANALYZED ALONG 21N68W 29N63W MAY BE EXTENDED SLIGHTLY FURTHER S
TO ACCOUNT FOR THE CONVECTIVE BLOW-UP OVER HISPANIOLA.
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM E OF THE SFC
TROUGH...MOVING QUICKLY EWARD.

IN THE CENTRAL ATLC...A WELL DEFINED UPPER LOW IS CENTERED NEAR
22N50W. NW-W UPPER LEVEL FLOW ON THE SW PERIPHERY OF THIS
FEATURE IS PROVIDING MODERATE TO STRONG SHEAR ACROSS THE
TROPICAL WAVE NEAR THE LESSER ANTILLES. AN AMPLIFIED MID-LEVEL
SUBTROPICAL RIDGE CENTERED NEAR 27N42W IS SURROUNDED BY VERY DRY
AIR BETWEEN 30W AND 55W. A 1019 MB SFC HIGH IS BENEATH IT NEAR
29N44W WITH ANOTHER WEAKENING 1017 MB HIGH NEAR 22N34W. A WEAK
SFC TROUGH LIES BETWEEN THE HIGHS ALONG 22N51 26N37W. ONLY A
LINE OF LOW CLOUDS AND WEAK ISOLATED SHOWERS ARE NEAR THE
BOUNDARY. LARGE UPPER TROUGHING DOMINATES THE ERN ATLC FROM THE
CANARY ISLANDS TO A CUT OFF LOW CENTERED NEAR 18N27W. ASSOCIATED
MOISTURE IS CONFINED TO WITHIN 360 NM E OF THE THE UPPER LOW.

$$
CANGIALOSI




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