[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN JAN 20 2008

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

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 4N8W 4N30W EQ50W. SCATTERED MODERATE
CONVECTION IS WITHIN 60-80 NM EITHER SIDE OF AXIS WEST OF 30W.
UPPER DIFFLUENCE IS ENHANCING THIS CONVECTIVE ACTIVITY...AND IS
ALSO HELPING THE DEVELOPMENT OF STRONG CONVECTION NE BRAZIL.

...DISCUSSION...

THE GULF OF MEXICO...
STRONG HIGH PRES OVER THE EASTERN CONUS EXTENDS A RIDGE OVER THE
ENTIRE GULF OF MEXICO USHERING A COLD AIR MASS. THIS FEATURE
WILL MOVE EWD ACROSS THE SE U.S. THROUGH MONDAY. BROKEN TO
OVERCAST COLD AIR STRATOCUMULUS CLOUDS COVERS MOST OF THE AREA
WITH PATCHES OF SCATTERED SHOWERS OVER SOUTH-CENTRAL FLORIDA AND
THE SE PORTION OF THE GULF. AN EARLIER ASCAT PASS SHOWED NLY
WINDS OF 20 TO 30 KT OVER THE EASTERN GULF. SOME OBSERVATIONS
ACROSS SOUTH FLORIDA INDICATE SUSTAINED WINDS OF 25-30 KNOTS.
THE WESTERN GULF HAS 15-20 KT NE TO E WINDS. IN THE UPPER
LEVELS...A SHORT-WAVE TROUGH IS OVER THE E GULF WITH AXIS ALONG
85W. SIGNIFICANT UPPER LEVEL MOISTURE IS AHEAD OF THIS TROUGH
AFFECTING FLORIDA AND WEST-CENTRAL CUBA. AS HIGH PRES MOVES
EWD...RETURN FLOW WILL DEVELOP ACROSS THE WESTERN GULF
INCREASING THE CHANCES OF SHOWERS ALONG THE COASTS OF TEXAS AND
NE MEXICO.

THE CARIBBEAN SEA...
AS OF 2100 UTC...A COLD FRONT FROM THE WESTERN ATLC ENTERS THE
CARIBBEAN SEA THROUGH CENTRAL CUBA...THEN CONTINUES SW AND SOUTH
ACROSS THE GULF OF HONDURAS INTO HONDURAS. LIGHTNING DATA
REVEALS SOME TSTM ACTIVITY OVER CENTRAL CUBA WITH SCATTERED
SHOWERS ALONG THE FRONTAL BOUNDARY OVER THE BASIN. AN ASCAT PASS
FROM AROUND 16Z SHOWED NLY WINDS OF 20-25 KT OVER THE NW
CARIBBEAN JUST BEHIND THE COLD FRONT. ELSEWHERE...MODERATE TO
STRONG TRADEWINDS ARE BLOWING ACROSS THE AREA WITH THE STRONGEST
WINDS ALONG THE COAST OF N COLOMBIA. PATCHES OF BROKEN TO
OVERCAST LOW CLOUDS WITH EMBEDDED SHOWERS ARE AFFECTING FROM
WESTERN PANAMA TO HONDURAS LIKELY RELATED TO LOW LEVEL
CONVERGENCE. AN OLD FRONTAL BOUNDARY IS PRODUCING A BAND OF
CLOUDS AND SHOWERS FROM THE N LEEWARD ISLANDS TO DOMINICAN
REPUBLIC. IN FACT...THE SAN JUAN DOPPLER RADAR SHOWERS SCATTERED
SHOWERS AND ISOLATED TSTMS OVER THOSE ISLANDS AND COASTAL
WATERS...INCLUDING THE ANEGADA AND MONA PASSAGES. THE GFS MODEL
HAS MOISTURE FROM THIS OLD FRONT AFFECTING THE NE CARIBBEAN
DURING THE NEXT 24 HOURS OR SO. IN THE UPPER LEVELS...A RIDGE IS
OVER THE CARIBBEAN WITH AXIS ALONG 75W. VERY STRONG SUBSIDENCE
COVERS THE BASIN EXCEPT OVER THE YUCATAN CHANNEL AND W CUBA
WHERE CONSIDERABLE MOISTURE IS NOTE DUE TO THE PRESENCE OF THE
ABOVE MENTIONED COLD FRONT. ACCORDING TO THE GFS MODEL...THIS
FRONTAL SYSTEM AND ITS ASSOCIATED MOISTURE FIELD WILL SURGE
BACK NORTH ACROSS SOUTH FLORIDA TOMORROW KEEPING THE RISK OF
SHOWERS...PARTICULARLY ON MONDAY NIGHT.

THE ATLANTIC OCEAN...
AS OF 21Z...A COLD FRONT IS OVER THE W ATLANTIC FROM 31N68W
TO CENTRAL CUBA NEAR 23N80W. LATEST VIS IMAGERY FROM THE DAY
SHOWS A WELL-DEFINED BAND OF CLOUDS WITH EMBEDDED SHOWERS AND
ISOLATED TSTMS ASSOCIATED WITH THE FRONT. BROKEN TO OVERCAST
COLD AIR STRATOCUMULUS CLOUDS ARE W OF THE FRONT. A 1027 MB HIGH
IS OVER THE CENTRAL ATLANTIC NEAR 32N44W. THIS SYSTEM IS
FORECAST TO MOVE INTO THE FORECAST REGION DURING THE NEXT 6-12
HOURS THEN WILL BE ABSORBED BY ANOTHER HIGH PRES CENTER EXITING
THE EASTERN COAST OF THE UNITED STATES ON MONDAY EVENING. THE
LEADING EDGE OF THIS HIGH IS A COLD FRONT WHICH EXTENDS S THEN W
FROM A 1009 MB SFC LOW LOCATED NEAR 34N28W TO THE NE CARIBBEAN.
SATELLITE PHOTOS ALSO SHOW A WELL-DEFINED BAND OF CLOUDS AND
SHOWERS RELATED TO THE FRONT. ALOFT...A TROUGH/RIDGE/TROUGH
PATTERN DOMINATES THE DISCUSSION AREA. A DEEP-LAYERED TROUGH
OVER THE EASTERN SEABOARD MAINLY N OF 30N SUPPORTS THE FRONT
THAT LIES OVER THE W ATLC. A RIDGE CENTERED ON A HIGH NEAR
24N56W COVERS MOST OF THE W-CENTRAL ATLC BUT MAINLY BETWEEN 45W
AND 70W. ANOTHER UPPER-LEVEL TROUGH IS OVER THE E ATLANTIC AND
EXTENDS SW FROM A CUT-OFF LOW LOCATED NEAR 32N28W TO NEAR
17N53W. AROUND THE BASE OF THIS TROUGH...A STRONG JET STREAM
BRANCH WITH CORE WINDS OF 90-110 KT IS TRANSPORTING ABUNDANT
UPPER-LEVEL MOISTURE/ HIGH CLOUDS FROM NORTHERN SOUTH AMERICA
ALL THE WAY NE TO THE WEST COAST OF AFRICA...PASSING THROUGH THE
CAPE VERDE ISLANDS.

$$
GR





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