[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151756
TWDAT

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

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N11W 3N20W THEN BECOMING RATHER
HORIZONTAL ALONG THE EQUATOR FROM 27W-45W TO 1S51W. THE AXIS IS
MUCH LESS ACTIVE THAN YESTERDAY WITH MOST OF THE ACTIVITY ACROSS
THE WRN PORTION WHERE SCATTERED MODERATE CONVECTION IS FROM
2S-4N W OF 43W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN
180 NM EITHER SIDE OF THE AXIS BETWEEN 23W-28W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG CUT OFF LOW CONTINUES ITS ESE PROGRESSION NOW CENTERED
OVER SRN MISSISSIPPI. THIS SYSTEM DOES SHOW SOME SFC CONNECTION.
AS OF 15 UTC...A SFC LOW WAS ANALYZED UNDERNEATH THE UPPER LOW
OVER SE LOUISIANA WITH A TROUGH EXTENDING SW ALONG 28N90W 27N95W
TO JUST S OF BRO. ANOTHER WEAK SFC TROUGH LIES AHEAD OF THE MAIN
ONE ALONG 27N89W 25N94W. LOW-LEVEL LIFT NEAR THE LOW AND
BOUNDARIES ALONG WITH STRONG UPPER LEVEL DIFFLUENCE IS SPARKING
STORMY WEATHER ACROSS THE NE GULF. NUMEROUS SHOWERS AND TSTMS
ARE N OF 27N BETWEEN 85W-89W. THE REMAINDER OF THE GULF IS
FAIRLY QUIET WITH ABUNDANT DRY AIR ALOFT KEEPING SKIES FAIR TO
MOSTLY CLEAR. 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
EARLY SAT. THIS UPPER FEATURE IS FORECAST TO HAVE AN ASSOCIATED
SFC FRONT WHICH WILL INCREASE THE CHANCE OF RAIN AS IT TRACKS SE
ACROSS THE GULF.

CARIBBEAN...
THE TAIL END OF THE UPPER TROUGH HAS NOW PULLED E OF THE LESSER
ANTILLES ALLOWING BROAD FLAT RIDGING TO CONTROL THE UPPER
PATTERN. MOST OF THE CARIB LIES ON THE NW SIDE OF THIS RIDGE SO
SW-WLY UPPER LEVEL FLOW IS COMMON WITH MODERATE DRY AIR NOTED ON
WV IMAGES. IN THE LOWER LEVELS...THE TAIL END OF A STUBBORN
TROUGH REMAINS IN THE NE PART OF THE AREA EXTENDING ACROSS THE
NRN LEEWARD ISLANDS TO 16N64W. SLIGHT LOW-LEVEL CONVERGENCE NEAR
THIS SLOWLY WEAKENING BOUNDARY IS PRODUCING PATCHES OF SHALLOW
CLOUDS MOSTLY WITHIN 120 NM N OF THE SFC TROUGH. DOPPLER RADAR
FROM SAN JUAN SHOWS VERY LITTLE SHOWER ACTIVITY NEAR OR OVER THE
ISLAND...BUT THERE IS SOME ECHOES BEING DETECTING IN THE FAR SE
RANGE WHERE VIS IMAGERY SHOWS THE AREA OF CLOUDS. STRONG SFC
HIGH PRES LOCATED N OF THE REGION IS PRODUCING MODERATE TO FRESH
NE-ELY TRADES. THESE WINDS ARE STEERING SOME PATCHES OF DEBRIS
SHALLOW MOISTURE FROM THE TROUGH ACROSS THE SEA...THICKEST
BETWEEN 14N-17N BETWEEN 65W-74W. 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 WILL ENTER THE NW CARIB LATE FRI/SAT INCREASING THE
CHANCE OF SHOWERS NEAR IT.

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/71W. A THINNING PLUME OF HIGH LEVEL CLOUDS ARE EMBEDDED IN
THE RIDGE AXIS...CURRENTLY N OF 22N BETWEEN 66W-78W. THIS UPPER
MOISTURE QUICKLY DRIES OUT E OF 66W AS THE MID/UPPER LEVEL FLOW
VEERS NWLY IN RESPONSE TO A WELL-DEFINED VERTICALLY STACKED
OCCLUDED LOW NEAR 34N53W. 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 32N48W AND EXTENDS SW TO 25N52W....IT THEN
CONTINUES AS A SFC TROUGH ACROSS THE NRN LEEWARD ISLANDS.
SCATTERED SHOWERS AND TSTMS ARE WITHIN 240 NM AHEAD OF THE FRONT
N OF 25N AND ISOLATED TO SCATTERED SHOWERS WITHIN 120 NM EITHER
SIDE S OF THERE. LOOKING AHEAD A DAY OR TWO...THE FRONT WILL
SLOWLY FALL APART IN THE REGION AS THE STACKED LOW PRES
SYSTEM...ITS SUPPORT...PULLS NE. AT THE SAME TIME ANOTHER COLD
FRONT WILL PUSH OFF THE U.S. EAST COAST LATE FRI/EARLY SAT.

EASTERN ATLANTIC...
A DEEP LAYER RIDGE COVERS THE MAJORITY OF THE ATLC E OF 45W. THE
UPPER LEVEL PART OF THIS RIDGE RUNS ALONG 10N41W 23N36W TO
BEYOND 32N34W. DEBRIS MOISTURE FROM THE FRONT IN THE CENTRAL
ATLC IS STREAMING 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. THE WEAK ASSOCIATED SFC
LOW...ANALYZED AT 1014 MB JUST OFF THE COAST OF AFRICA NEAR
24N17W HAS NOW DISSIPATED BASED ON THE LATEST VISIBLE IMAGES. A
STRONG SFC HIGH CENTERED NEAR THE AZORES IS GENERATING A LARGE
AREA OF MODERATE TO STRONG WINDS ACROSS THE REGION. IN THE DEEP
TROPICS...THE UPPER LEVEL JETSTREAM BRANCH IS BEING SUPPRESSED
SE RACING FROM 7N30W TO 15N16W AND THEN INLAND ACROSS AFRICA.
ABUNDANT MOISTURE EXISTS TO THE S AND E OF THE JET AXIS WHILE
STRONG CONFLUENCE ALOFT IS SIGNIFICANTLY DRYING THE AIR TO THE N
AND W. OVER THE NEXT COUPLE OF DAYS...THE SFC HIGH WILL SLOWLY
RETREAT NWD BUT SHOULD REMAIN IN CONTROL MAINTAINING THE
WIDESPREAD FAIR WEATHER.

$$
CANGIALOSI


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