[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT OCT 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 48W S OF 18N MOVING W NEAR 10 KT.
POSITION IS BASED ON THE UW-CIMSS TPW THAT SHOWS A GOOD SURGE OF
MOISTURE ASSOCIATED WITH THE WAVE. ALSO...THERE IS A VORTICITY
MAXIMUM NEAR 10N48W. SCATTERED MODERATE CONVECTION IS FROM
7N-14N BETWEEN 45W-51W.

WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 77W S OF
19N MOVING W 10-15 KT. THE CIMSS VORTICITY PRODUCT PROVIDES SOME
SUPPORT FOR THE WAVE POSITION INDICATED. THE WAVE COUPLED WITH
THE ITCZ IS GENERATING A CLUSTER OF MODERATE TO ISOLATED STRONG
CONVECTION OVER THE SW CARIBBEAN JUST OFF THE COAST OF PANAMA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 7N12W 6N30W 10N46W 10N50W 8N61W.
BESIDES FOR THE ACTIVITY ASSOCIATED WITH THE TROPICAL
WAVE...THERE IS SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 120
NM EITHER SIDE OF AXIS E OF 20W TO THE AFRICAN COAST. SIMILAR
CONVECTIVE ACTIVITY IS WITHIN 90 NM N OF AXIS BETWEEN 27W-32W.

DISCUSSION...

GULF OF MEXICO...
A FRONTAL SYSTEM...SUPPORTED BY A DEEP LAYERED TROUGH OVER THE
EASTERN U.S. IS MOVING ACROSS THE FLORIDA PENINSULA AND THE GULF
WATERS. AS OF 15Z...THE FRONT IS ANALYZED FROM CENTRAL FLORIDA
TO NEAR 24N90W WHERE IT BECOMES NEARLY STATIONARY...THEN
CONTINUES TO NEAR TAMPICO MEXICO. MOST OF THE SHOWER ACTIVITY
ASSOCIATED WITH THE FRONT IS FOUND OVER THE EASTERN GULF NEAR
THE FLORIDA PENINSULA. THE MOSAIC DOPPLER RADAR FROM THE SE U.S.
SHOWS SCATTERED SHOWERS WITH ISOLATED TSTMS OVER CENTRAL FLORIDA
JUST N OF LAKE OKEECHOBEE AND ALONG THE W COAST SOUTH OF
TAMPA...INCLUDING ALSO DE FLORIDA KEYS. THE FRONT IS FORECAST TO
MOVE SLOWLY SOUTHEAST TO NEAR THE LAKE OKEECHOBEE AREA LATE THIS
AFTERNOON. AN AREA OF MODERATE TO STRONG CONVECTION DEVELOPED
THIS MORNING OVER THE WESTERN PART OF THE BAY OF CAMPECHE BUT
LATEST SATELLITE IMAGERY INDICATES THAT CONVECTION IS
DIMINISHING OVER THE AREA. BEHIND THE FRONT...MUCH DRIER AND
SLIGHTLY COOLER AIR IS FILTERING IN WITH DEWPOINTS  DROPPING
INTO THE 50'S F ALONG THE NORTHERN GULF WATERS. THE NEXT
FRONT...WHICH WILL LIKELY BE STRONGER...SHOULD ENTER THE REGION
MONDAY BRINGING A POSSIBILITY OF GALE FORCE WINDS OVER THE
WESTERN GULF LATE MON THROUGH TUE.

CARIBBEAN SEA...
THE COMBINATION OF AN UPPER LOW OVER THE SE PORTION OF THE GULF
OF MEXICO AND A RIDGE OVER THE SW ATLC IS DRAWING ABUNDANT
TROPICAL MOISTURE FROM CENTRAL AMERICA ALL THE WAY N TO WESTERN
CUBA AND THE STRAITS OF FLORIDA. AS OF 1500 UTC...A SFC TROUGH
IS ANALYZED OVER THE AREA EXTENDING FROM 24N83W TO THE COAST OF
HONDURAS NEAR 15N86W. SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS MAINLY EAST OF THE TROUGH AXIS. THIS MOISTURE
PLUME HAS BEEN SHIFTING WNW WITH THE UPPER LOW OVER THE PAST FEW
DAYS. MUCH DRIER MID TO UPPER LEVEL AIR IS OVER THE CARIBBEAN
WATERS...PARTICULARLY BETWEEN 65W AND 80W ADVECTED BY A NE
UPPER-LEVEL FLOW AROUND THE AFOREMENTIONED RIDGE. A CUT-OFF LOW
LOCATED SOUTH OF PUERTO RICO PAIRED WITH AN UPPER HIGH SITUATED
OVER THE DEEP TROPICS NEAR 11N35W IS CREATING AN AREA OF UPPER
DIFFLUENT OVER THE FAR E CARIBBEAN AND THE LESSER ANTILLES. AS A
RESULT...SATELLITE IMAGERY SHOWS CLUSTERS OF MODERATE TO
ISOLATED STRONG CONVECTION FROM 9N-17N BETWEEN 56W AND 61W.
OCCASIONALLY HEAVY SHOWERS HAVE BEEN AFFECTING PARTS OF THE
LESSER ANTILLES. ALSO...THE ABOVE MENTIONED UPPER LOW WILL
COMBINE WITH THE LOCAL EFFECTS TO PRODUCE SOME SHOWER ACTIVITY
OVER THE UK/US VIRGIN ISLANDS...PUERTO RICO AND HISPANIOLA OVER
THE NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...
A RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE FORECAST AREA. THE
WRN ATLC RIDGE IS CENTERED JUST E OF THE NW BAHAMAS NEAR 26N75W.
A VERY LARGE TROUGH LIES TO THE E OF RIDGE ENTERING THE REGION
NEAR 31N48W THEN CONTINUES SW TO THE AFOREMENTIONED CUT-OFF LOW.
THIS UPPER TROUGH SUPPORTS A SFC TROUGH...REMNANTS OF A FRONTAL
BOUNDARY THAT RUNS FROM 31N38W TO 24N50W. SCATTERED SHOWERS ARE
RELATED TO THIS FEATURE. AN UPPER RIDGE ANCHORED ON A HIGH OVER
THE DEEP TROPICS COVERS THE REMAINDER OF THE ATLC. THE RIDGE
AXIS EXTENDS NE BEYOND 32N22W. THE SFC PATTERN IN THE CENTRAL
AND E ATLC IS MOSTLY CONTROLLED BY WEAK HIGH PRES RIDGING
ANCHORED BY A 1021 MB HIGH SITUATED NEAR 26N32W. THIS IS
PRODUCING MAINLY LIGHT WINDS OVER THE SUBTROPICAL ATLC...WHILE
MODERATE TRADES PERSIST IN THE TROPICS ESPECIALLY NEAR THE
TROPICAL WAVE WHERE A RECENTLY ASCAT PASS SHOWS WINDS OF 15 TO
20 KT.

$$
GR






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