[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202334
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE NOV 20 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

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

...TROPICAL WAVES...
TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 81W S OF 19N MOVING W
10-15 KT. THE MIMIC TPW ANIMATION SHOWS SOME CONTINUITY
SUPPORTING THE ANALYZED POSITION. THERE IS A GOOD AMOUNT OF
CLOUDINESS...WITH EMBEDDED SCATTERED SHOWERS/ISOLATED TSTMS OVER
THE W CARIB S OF 17N W OF 75W. AN UPPER DIFFLUENT PATTERN SEEN
IN WATER VAPOR IMAGES IS LIKELY THE MAIN CULPRIT FOR THIS
UNSETTLED WEATHER BUT THE WAVE MAY BE AIDING IN SOME OF THE
ACTIVITY.

NRN PORTION OF A TROPICAL WAVE EXTENDS INTO THE BAY OF CAMPECHE
ALONG 94W/95W S OF 22N MOVING W 10-15 KT. VISIBLE IMAGES SHOW A
WWD SURGE OF LOW CLOUDS AND POSSIBLE SHALLOW ISOLATED SHOWERS
WITHIN 60 NM OF THE WAVE AXIS. THIS LIGHT ACTIVITY WILL LIKELY
SPREAD ACROSS SOUTHEASTERN MEXICO LATER TONIGHT OR TOMORROW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 8N26W 9N36W 8N53W 7N62W.
SCATTERED MODERATE CONVECTION IS FROM 9N-14N BETWEEN 29W-38W
...ENHANCED BY AN EMBEDDED LOW-LEVEL TROUGH AND AN UPPER JET.

DISCUSSION...

GULF OF MEXICO...
SFC HIGH PRES CENTERED JUST OFF THE SOUTHEAST COAST CONTROLS THE
PATTERN. TIGHTENED PRES GRADIENT BETWEEN THE HIGH AND LOWER PRES
IN THE CARIB IS PRODUCING AN AREA OF 20 KT ELY WINDS IN THE SE
GULF AS NOTED IN A RECENT ASCAT PASS. LIGHTER E TO SE WINDS
EXISTS ELSEWHERE. THIS FLOW IS ADVECTING PATCHES OF LOW-LEVEL
CLOUDS...WHICH LIKELY CONTAIN ISOLATED SHOWERS...ACROSS THE
REGION. THE CLOUDS APPEAR THICKEST IN THE FLA STRAITS...WHERE
DOPPLER RADAR IS DETECTING SOME SHOWER ACTIVITY...AND N OF 26N
BETWEEN 88W-91W. IN THE MID AND UPPER LEVELS...FAIRLY AMPLIFIED
PATTERN EXISTS CONSISTING OF RIDGING CENTERED ALONG 83W/84W AND
A SHARP SHORTWAVE OVER NRN MEXICO. FAIRLY STRONG SUBTROPICAL JET
BETWEEN THESE FEATURES IS ADVECTING A PLUME OF MID-HIGH LEVEL
MOISTURE FROM THE EPAC ACROSS CENTRAL/SRN MEXICO AND INTO THE
WRN GULF. NEXT COLD FRONT EXPECTED TO MOVE OFF THE TEXAS AND
LOUISIANA COASTS TOMORROW NIGHT. NLY WINDS WILL INCREASE
SIGNIFICANTLY BEHIND THE BOUNDARY...BUT NO LONGER EXPECTED TO BE
GALE FORCE.

CARIBBEAN SEA...
ABUNDANT CLOUDINESS...SCATTERED SHOWERS AND ISOLATED TSTMS COVER
A GOOD PORTION OF THE W CARIB S OF 17N W OF 75W. THIS MOISTURE
IS ASSOCIATED WITH A DIFFLUENT UPPER PATTERN ALONG AN ELONGATED
UPPER RIDGE AXIS STRETCHING NW FROM AN ANTICYCLONE OVER SOUTH
AMERICA.  TSTM ACTIVITY IS MOST ORGANIZED OVER AND NEAR THE
COASTS OF PANAMA AND COSTA RICA WHERE THERE IS SOME INFLUENCE
FROM THE ITCZ. SCATTERED SHOWERS AND ISOLATED TSTMS ALSO COVER A
PORTION OF THE CENTRAL AND ERN CARIB N OF 15N BETWEEN 64W-75W.
THIS ACTIVITY IS ASSOCIATED WITH THE TAIL END OF A PRE-FRONTAL
TROUGH. THE MAIN FRONT IS FAIRLY FAR S NOT FAR AWAY FROM
PUERTO RICO AND HISPANIOLA. THE REMAINDER OF THE REGION IS
TRANQUIL UNDER ZONAL MID AND UPPER FLOW AND MODERATE TO FRESH
TRADE WINDS.

ATLANTIC OCEAN...
VIGOROUS 988 MB LOW PRES SYSTEM IS CENTERED WELL N OF THE AREA
NEAR 39N53W. AN ASSOCIATED FAST MOVING COLD FRONT SWEEPS SWD
INTO THE DISCUSSION AREA FROM 32N56W TOWARD THE N COAST OF
HAITI.  SECONDARY FRONT CLIPS THE AREA ENDING NEAR 30N59W. THIS
STRONG LOW IS GENERATING WINDS TO HURRICANE FORCE...BUT THIS IS
ALL N OF THE AREA. N TO NW WINDS NEAR GALE FORCE ARE OCCURRING N
OF 27N BETWEEN THE MAIN FRONT AND ABOUT 72W. SCATTERED SHOWERS
AND TSTMS ARE WITHIN 180 NM E OF THE FRONTS. MODEL GUIDANCE
SHOWS THIS LOW OSCILLATING AROUND WITH A GENERAL MOVEMENT TOWARD
THE SE OVER THE NEXT COUPLE OF DAYS. AN ILL-DEFINED PRE-FRONTAL
TROUGH IS ANALYZED AHEAD OF THE FRONT ALONG 30N46W 17N69W AND
THEN WWD INTO THE CARIB. THE NRN PORTION OF THIS TROUGH WILL
LIKELY BE REMOVED FROM THE 00Z MAP AS THE FLOW HAS BECOME
UNIFORM SELY AHEAD OF THE FAST APPROACHING FRONT. HOWEVER
...THERE IS STILL WEAK CONVERGENCE E OF THE LESSER ANTILLES AND
ESPECIALLY IN THE CENTRAL CARIB SO PLAN ON KEEPING THAT
REPRESENTED. ONLY PATCHY LOW LEVEL CLOUDS AND MAYBE AN ISOLATED
SHOWER IS IN THE VICINITY OF THE TROUGH.

THE SFC PRES PATTERN IN THE E ATLC IS VERY WEAK SUPPORTED BY A
1018 MB HIGH DISPLACED IN THE TROPICS NEAR 20N26W. THIS IS
ALLOWING WINDS TO BE MAINLY LIGHT AND ANTICYCLONIC ACROSS THE
REGION. A WEAK LOW-LEVEL TROUGH OR LOW AMPLITUDE TROPICAL WAVE
IS PERTURBING THE ITCZ SLIGHTLY ALONG 34W S OF 13N. THE
COMBINATION OF THIS LOW-LEVEL BOUNDARY AND DIFFLUENCE TO THE SE
OF AN UPPER JET IS SUPPORTING CONVECTION IN THE ITCZ AND
SPREADING DEBRIS CLOUDINESS TO AFRICA WITHIN 540 NM SE OF A LINE
ALONG 13N38W 21N17W. A STALLED FRONT LIES JUST N OF THE AREA
ALONG 33N/34N E OF ABOUT 35W. CONVERGENCE IN THE LOW-LEVELS NEAR
THE FRONT ALONG WITH MID-UPPER LEVEL INSTABILITY IS GENERATING
SCATTERED SHOWERS N OF 30N E OF 35W.

$$
CANGIALOSI


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