[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 132341
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE MAR 13 2007

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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

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

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N10W 2N25W 3N40W EQ50W. WIDELY
SCATTERED MODERATE CONVECTION IS FROM 3N-6N E OF 16W. SIMILAR
CONVECTION IS S OF 3N BETWEEN 35W-50W. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE OVER NE BRAZIL AND
SOUTHERN LIBERIA.

...DISCUSSION...

GULF OF MEXICO...
A RATHER VIGOROUS MID/UPPER LEVEL CUT-OFF LOW IS SPINNING OVER
THE TEXAS PANHANDLE WHILE A BROAD UPPER RIDGE DOMINATES THE
ENTIRE GULF... WITH THE AXIS ALONG THE FAR E GULF/FLORIDA
PENINSULA. UPPER LEVEL DIFFLUENCE BETWEEN THESE TWO FEATURES IS
PRODUCING AN AREA OF SHOWERS AND PROBABLY ISOLATED TSTMS IN THE
NW CORNER OF THE GULF. A SFC TROUGH IS ANALYZED THERE AND GOES
FROM 29N93W TO 23N95W. DOPPLER RADAR SHOWS AN AREA OF SHOWERS
AND TSTMS OVER EASTERN TEXAS JUST AHEAD OF THE MID/UPPER LOW
MENTIONED ABOVE. A PLUME OF HIGH CLOUDS IS CROSSING THE S
PORTION OF THE REGION AND IS ASSOCIATED WITH A SUBTROPICAL
JETSTREAM THAT CROSSES SOUTH-CENTRAL MEXICO INTO THE GULF. A
SURFACE RIDGE FROM THE W ATLC COVERS THE SE US AND THE GULF
ANCHORED BY A 1027 SFC HIGH LOCATED NEAR 31N73W. ACCORDING TO
THE COMPUTER MODEL...THE UPPER LOW IS EXPECTED TO WEAKEN DURING
THE NEXT DAY OR SO...BUT A SHORTWAVE TROUGH WILL REMAIN MOVING E
ACROSS THE GULF. MEANWHILE...THE SFC RIDGE WILL ALSO RETREAT
ALLOWING LOW-LEVEL RETURN FLOW TO DEVELOP ACROSS MUCH OF THE
AREA. A COLD FRONT IS FORECAST TO MOVE OFF THE TEXAS COAST THU
NIGHT.

CARIBBEAN...
BROAD UPPER RIDGE COVERS THE ENTIRE CARIBBEAN SEA WITH TWO
HIGHS. ONE IS CENTERED IN THE TROPICAL EPAC NEAR 7N88W...THE
SECOND ONE IS OVER N SOUTH AMERICA. IN BETWEEN...THERE IS A WEAK
TROUGH THAT EXTENDS FROM E CUBA/JAMAICA TO COSTA RICA. DRY AND
STABLE AIR ALOFT EXISTS OVER MUCH OF THE BASIN WITH SOME UPPER
LEVEL MOISTURE MOVING INTO THE NW CORNER OF THE AREA FROM THE
GULF. IN THE LOWER LEVELS...PATCHES OF LOW TO MID LEVEL CLOUDS
ARE BEING STEERED BY MODERATE TO FRESH NELY TRADES ACROSS THE
SEA. A SFC TROUGH FROM THE CENTRAL ATLC DIGS INTO THE NE
CARIBBEAN AND IS AFFECTING THE LEEWARD/VIRGIN ISLANDS. THE SAN
JUAN DOPPLER RADAR IS SHOWING LINES OF SHOWERS AND ISOLATED
TSTMS CROSSING THE ISLANDS. HIGH PRES OVER THE SE U.S. AND W
ATLC WILL KEEP STRONG TRADE WINDS OVER THE CENTRAL AND WRN
CARIBBEAN AT LEAST DURING THE NEXT 24 HOURS.


WESTERN AND CENTRAL ATLANTIC...
A TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE FORECAST AREA. AN
AMPLIFYING UPPER LEVEL TROUGH IS OVER THE W-CENTRAL ATLC
COVERING THE AREA W OF 50W. THE ASSOCIATED FRONTAL BOUNDARY
ENTERS THE AREA NEAR 32N50W AND EXTENDS SSW TO A 1014 MB FRONTAL
WAVE NEAR 28N53W. A SFC TROUGH CONTINUES SW FROM THE LOW TO THE
LEEWARD ISLANDS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS JUST AHEAD OF THE LOW/FRONTAL SYSTEM FROM 24N TO BEYOND 31N.
SFC HIGH PRES DOMINATES THE WRN ATLC BEHIND THE FRONT. UNDER A
NELY WINDS FLOW...FRAGMENTS OF LOW-LEVEL CLOUDS WITH EMBEDDED
WEAK SHOWERS ARE MOVING ACROSS THE SOUTHERN BAHAMAS. OVER THE
NEXT DAY OR SO...NWP MODELS SHOW THE FRONTAL BOUNDARY MOVING
SLOWLY E KEEPING SOME LOW LEVEL MOISTURE OVER THE NE CARIBBEAN.

EASTERN ATLANTIC...
A STRONG CUT-OFF LOW IS OVER THE MADEIRA ISLANDS WITH A TROUGH
EXTENDING SWWD TO NEAR 15N35W. DRY AND STABLE AIR ALOFT IS
ALONG THE TROUGH AXIS WHILE ABUNDANT UPPER LEVEL MOISTURE IS
SEEN SE OF THE TROUGH AXIS RELATED TO A TROPICAL JETSTREAM WITH
CORE WINDS OF AROUND 75 KT. AT THE SURFACE...A WELL-DEFINED
OCCLUDED 1013 MB LOW IS DRIFTING S BETWEEN THE MADEIRA AND THE
CANARY ISLANDS. A PRE-FRONTAL TROUGH LIES ALONG THE COAST OF
WESTERN SAHARA. THE PRESSURE DIFFERENCE BETWEEN THE OCCLUDED LOW
AND STRONG SFC RIDGE OVER THE E ATLC IS GENERATING A LARGE AREA
OF STRONG NLY WINDS N OF 20N BETWEEN 18W-29W.

$$
GR




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