[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 152355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU MAR 15 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 7N12W 3N20W THEN BECOMES ALIGNED
WITH THE EQUATOR W TO S AMERICA AT 48W. THE AXIS IS MUCH LESS
ACTIVE THAN 24 HRS AGO WITH MOST OF THE ACTIVITY CONCENTRATED
OVER THE FAR WRN PORTION WHERE SCATTERED STRONG IS OCCURRING
WITHIN 60 NM N OF THE AXIS W OF 45W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE ELSEWHERE WITHIN 180 NM N OF THE AXIS
BETWEEN 22W-40W.

...DISCUSSION...

GULF OF MEXICO...
A WELL PRONOUNCED MID/UPPER LEVEL LOW MOVING E 20-25 KT IS
LOCATED OVER THE EXTREME SRN PORTION OF MISSISSIPPI. THE LOW
IS EMBEDDED IN A DEEP LAYERED TROUGH THAT EXTENDS FROM THE
UPPER GREAT LAKES SWD ACROSS ALABAMA AND ACROSS THE E GULF
THROUGH 27N86W TO THE NE YUCATAN PENINSULA. ITS ASSOCIATED
SURFACE LOW WAS ANALYZED JUST SW OF MOBILE BAY AT 2100 UTC.
AN ATTENDED TROUGH EXTENDS SW FROM THE LOW THROUGH 27N90W TO
NEAR 26N97W. THE COMBINATION OF THE SURFACE TROUGH ALONG
WITH UPPER LEVEL DIFFLUENCE FOUND AHEAD OF THE LOW AND
A VERY MOIST SLY FLOW PRESENT E OF THE TROUGH CONTINUES
TO RESULT IN SCATTERED TO NUMEROUS TSTMS OVER THE NE GULF...
WITH THE ACTIVITY PRIMARILY TIED TO A VIGOROUS FAST MOVING
SQUALL LINE THAT EXTENDS FROM APALACHEE BAY SW TO NEAR 27N88W.
THE REMAINDER OF THE GULF IS FAIRLY TRANQUIL UNDER MODERATE
TO STRONG SUBSIDENCE AND ASSOCIATED DRY AIR ALOFT. OVER
THE NEXT COUPLE OF DAYS...THE UPPER LOW WILL MOVE ESE AND
WEAKEN. NWP MODELS SHOW A RATHER QUICK MOVING UPPER TROUGH
DEVELOPING AND SWINGING THROUGH THE REGION ON FRI AND INTO
EARLY SAT. THIS UPPER FEATURE IS FORECAST TO QUICKLY SWING
A SFC FRONT ACROSS THAT WILL MOST LIKELY BE ACCOMPANIED BY
A LINE OF SCATTERED TO NUMEROUS SHOWERS AND TSTMS.

CARIBBEAN...
BROAD FLAT RIDGING HAS SETTLED IN ACROSS MUCH OF THE CENTRAL
AND ERN PORTIONS OF THE CARIBBEAN WITH UPPER LEVEL SW-W WINDS
NOTED ON SATELLITE DERIVED UPPER AIR DATA. MODERATE SUBSIDENCE
AND ASSOCIATED DRY AIR IS EVIDENT ACROSS JUST ABOUT THE ENTIRE
SEA. IN THE LOWER LEVELS...THE TAIL END OF A STUBBORN TROUGH
EXTENDS SW FROM THE ATLANTIC TO EXTREME NE PART OF THE SEA
IN THE VICINITY OF THE LEEWARD ISLANDS. SLIGHT LOW-LEVEL
CONVERGENCE NEAR THIS SLOWLY WEAKENING BOUNDARY IS PRODUCING
PATCHES OF SHALLOW CLOUDS WITH ISOLATED SHOWERS MOSTLY WITHIN
120 NM N OF THE SFC TROUGH. RESIDUAL LOW LEVEL CLOUDINESS FROM
THIS TROUGH IS MOVING WSW IN MODERATE TO FRESH NE-E TRADES
PRODUCED BY STRONG SFC HIGH PRES LOCATED N OF THE DISCUSSION
AREA. ISOLATED SHOWERS ARE EMBEDDED WITHIN THESE CLOUDS FROM
15N-17N E OF 76W. OVER THE NEXT COUPLE OF DAYS...THE STRONG SFC
RIDGE AND TROUGH WILL SHIFT SLIGHTLY TO THE E. THIS WILL ALLOW
THE TRADE WINDS TO SLACKEN AND GRADUALLY THIN THE FETCH OF
MOISTURE ACROSS THE ERN CARIB. MEANWHILE...A COLD FRONT IS
FORECAST TO ENTER THE NW CARIBBEAN LATE FRI INTO SAT WITH
INCREASING MOISTURE ALONG AND TO ITS E. THE FRONT IS THEN
EXPECTED TO WEAKEN IN THE VICINITY OF THE WINDWARD PASSAGE SUN.

WESTERN ATLANTIC...
THE PATTERN HERE HAS NOT CHANGED MUCH SINCE YESTERDAY WITH A
MID AND UPPER LEVEL RIDGE/TROUGH PATTERN MOVING SLOWLY E ACROSS
THE ATLC. THE MID/UPPER LEVEL RIDGE IS ALIGNED FAIRLY N-S ALONG
70W. A THINNING PLUME OF HIGH LEVEL CLOUDS IS FOUND IN THE RIDGE
AXIS...CURRENTLY N OF 22N BETWEEN 60W-77W. THIS UPPER MOISTURE
QUICKLY DRIES OUT E OF 60W AS THE MID/UPPER LEVEL FLOW VEERS
NWLY IN RESPONSE TO A WELL-DEFINED VERTICALLY STACKED OCCLUDED
LOW N OF THE AREA NEAR 34N50W. IN FACT...THE AIR ALOFT IS VERY
DRY BETWEEN 50W-61W WHERE UPPER CONFLUENCE IS QUITE STRONG. THIS
LOW PRES SYSTEM HAS AN ASSOCIATED SLOW MOVING COLD FRONT THAT
ENTERS THE AREA NEAR 32N47W AND EXTENDS SW TO 24N51W...WHERE IT
THEN CONTINUES AS A WEAKENING SFC TROUGH TO THE NRN LEEWARD
ISLANDS. SCATTERED SHOWERS AND TSTMS ARE WITHIN 180 NM AHEAD
OF THE FRONT N OF 25N...AND ISOLATED TO SCATTERED SHOWERS AND
ISOLATED WEAK TSTMS ARE WITHIN 120 NM ELSEWHERE EITHER SIDE
FRONT/TROUGH. LOOKING AHEAD A DAY OR TWO...THE FRONT WILL SLOWLY
BECOME DIFFUSE IN THE REGION AS THE STACKED LOW PRES
SYSTEM...ITS SUPPORT...PULLS NE. AT THE SAME TIME THE NEXT COLD
FRONT IS EXPECTED TO MOVE OFF THE U.S. EAST COAST FRI NIGHT.

EASTERN ATLANTIC...
BROAD DEEP RIDGING COVERS THE MAJORITY OF THE ATLC BETWEEN 30W-
55W...WITH A RIDGE AXIS ROUGHLY RUNNING THROUGH 8N55W 6N45W TO
A MID/UPPER LEVEL ANTICYCLONE NEAR 5N36W AND TO 2N30W. DEBRIS
MOISTURE FROM THE FRONT IN THE CENTRAL ATLC CONTINUES TO
STREAM AROUND THE RIDGE TO 30W. THIS UPPER MOISTURE QUICKLY
DRIES OUT E OF 30W AS THE MID/UPPER LEVEL FLOW VEERS NWLY IN
RESPONSE TO A WEAKENING DEEP TROUGH STRETCHING FROM SPAIN
THROUGH THE CANARY ISLANDS. A STRONG SFC HIGH CENTERED NEAR THE
AZORES  CONTINUES TO GENERATE A LARGE AREA OF MODERATE TO
STRONG WINDS ACROSS THE REGION.

IN THE DEEP TROPICS...THE UPPER LEVEL JETSTREAM BRANCH IS BEING
SUPPRESSED SE EXTENDING FROM NEAR 6N30W TO 13N19W...AND NE
TO INLAND ACROSS AFRICA. ABUNDANT MOISTURE EXISTS TO THE S AND E
OF THE JET AXIS WHILE STRONG CONFLUENCE ALOFT ATTRIBUTED TO
THE WEAKENING DEEP TROUGH MENTIONED ABOVE SIGNIFICANTLY DRIES
THE AIR TO ITS N. OVER THE NEXT COUPLE OF DAYS...THE SFC HIGH
WILL SLOWLY RETREAT NWD BUT SHOULD REMAIN IN CONTROL MAINTAINING
THE WIDESPREAD FAIR WEATHER.

$$
AGUIRRE



This weather bulletin was brought to you by:
www.nashvilleweather.net