[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131658
TWDAT

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

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 6N10W 4N21W 2N36W EQ46W EQ52W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 3S TO 3N W OF 43W TO INLAND OVER SOUTH AMERICA. ELSEWHERE
SCATTERED SHOWERS ARE WITHIN 90 NM EITHER SIDE OF THE AXIS
BETWEEN 17W-43W.

...DISCUSSION...

GULF OF MEXICO...
A RATHER VIGOROUS MID TO UPPER LEVEL LOW IS PULLING SLOWLY ESE
NOW CENTERED OVER THE TEXAS PANHANDLE. UPPER LEVEL DIFFLUENCE
BETWEEN THIS SYSTEM AND AMPLIFIED RIDGING ALIGNED ALONG 86W IS
PRODUCING A SWATH OF SCATTERED SHOWERS AND TSTMS IN THE WRN GULF
FROM 25N-28N BETWEEN 94W-97W. AVAILABLE DOPPLER RADAR INDICATES
THAT THE PREVIOUS SQUALL LINE ANALYZED ON THE 12 Z MAP IS
BREAKING UP. ANOTHER BATCH OF CLOUDS HAS DEEPENED SOME IN THE
MIDDLE GULF N OF 25N BETWEEN 89W-92W. EMBEDDED ISOLATED SHOWERS
ARE POSSIBLE IN THAT DIFFLUENT ZONE. THE REMAINDER OF THE GULF
IS RELATIVELY QUIET DOMINATED BY STRONG SFC HIGH PRES CENTERED
IN THE WRN ATLC. MODERATE ELY WINDS AND MOSTLY FAIR
WEATHER...ONLY SCATTERED HIGH LEVEL CLOUDS...IS THE RULE IN THE
AREAS NOT OUTLINED. LOOKING AHEAD A DAY OR TWO...THE UPPER LOW
IS EXPECTED TO WEAKEN AS IT MOVES A LITTLE FASTER ON THE ESE
TRACK. MEANWHILE THE SFC RIDGE WILL ALSO RETREAT ALLOWING
LOW-LEVEL RETURN FLOW TO DEVELOP ACROSS MUCH OF THE AREA. THE
COMBINATION OF THIS MOIST LOW-LEVEL FLOW AND UPPER DIFFLUENCE
WITH LIKELY AID IN THE CONTINUATION OF SHOWERS AND
TSTMS...ESPECIALLY IN THE UPPER DIFFLUENT ZONE.

CARIBBEAN...
TWO UPPER LEVEL HIGHS CENTERED S OF THE REGION COVER MUCH OF THE
CARIB. THE WRN-MOST ONE IS IN THE TROPICAL EPAC NEAR 7N90W. THE
OTHER IS MUCH BROADER IN NATURE LOCATED OVER NE SOUTH AMERICA. A
SLIGHT WEAKNESS BETWEEN THESE UPPER HIGHS IS AIDING INT THE
DEVELOPMENT OF A FEW CLUSTERS OF MODERATE CONVECTION OVER
WRN COLOMBIA AND ERN PANAMA PUSHING W INTO THE EPAC. ELSEWHERE
DRY SUBSIDENT FLOW IS WIDESPREAD PROVIDING A STABLE ENVIRONMENT.
IN THE LOWER LEVELS...PATCHES OF LOW TO MID LEVEL CLOUDS ARE
BEING STEERED BY MODERATE TO FRESH NELY TRADES ACROSS THE SEA.
THESE PATCHES ARE THICKEST E OF 75W...PARTICULARLY OVER THE NRN
LEEWARD ISLANDS AND PUERTO RICO WHERE THERE IS WEAK LOW-LEVEL
CONVERGENCE NEAR THE TAIL END OF A CENTRAL ATLC TROUGH. SAN
JUAN'S 88-D DEPICTS SCATTERED SHOWERS EMBEDDED IN THESE POCKETS
OF CLOUDS. LITTLE CHANGE IS ANTICIPATED OVER THE NEXT COUPLE OF
DAYS AS A STRONG SFC RIDGE REMAINS N OF THE REGION.

WESTERN AND CENTRAL ATLANTIC...
BROAD MID TO UPPER LEVEL TROUGHING COVERS THE BULK OF THE ATLC W
OF 40W. A SERIES OF WEAK SHORTWAVE ARE ROTATING THROUGH THE
TROUGH HELPING TO SUSTAIN AND DEEPEN IT. AN ASSOCIATED COLD
FRONT ENTERS THE DISCUSSION AREA NEAR 32N50W AND EXTENDS SSW TO
A 1016 MB FRONTAL WAVE NEAR 24N57W. A SFC TROUGH CONTINUES SW
FROM THE LOW TO THE NRN LEEWARD ISLANDS. LOW-LEVEL LIFT AND
UPPER DIFFLUENCE IS GENERATING A SWATH OF SCATTERED SHOWERS AND
TSTMS WITHIN 240 NM AHEAD OF THE FRONT N OF 28N AND ISOLATED
SHOWERS WITHIN 180 NM AHEAD OF THE FRONT/TROUGH S OF THERE.
STRONG SFC HIGH PRES DOMINATES THE WRN ATLC BEHIND THE FRONT.
MODERATE ANTICYCLONIC LOW-LEVEL FLOW IS STIRRING UP AND STEERING
PATCHES OF LOW-LEVEL CLOUDS WITH EMBEDDED WEAK SHOWERS ACROSS
THE AREA W OF 60W. BASED ON THE LATEST VISIBLE IMAGES...THERE
MAY BE A VERY INVERTED SFC TROUGH DEVELOPING E OF BERMUDA ALONG
63W N OF 29N...THIS WILL LIKELY BE ADDED TO THE 18Z ANALYSIS.
OVER THE NEXT DAY OR SO...NWP MODELS SHOW THE FRONTAL BOUNDARY
SLOWING MOVING E AND GAINING SOME STRENGTH AS A SHORTWAVE CUTS
OFF AND PROVIDES UPPER SUPPORT FOR THE WEAK LOW AND FRONT.

EASTERN ATLANTIC...
A VERTICALLY STACKED RIDGE/TROUGH PATTERN EXISTS ACROSS THE ATLC
E OF 40W-45W. THE UPPER LEVEL RIDGE AXIS IS TITLED RUNNING FROM
17N44W TO BEYOND 32N35W. THIS RIDGE HAS BEEN ERODED IN THE FAR E
ATLC WHERE A WELL-DEFINED OCCLUDED 1013 MB LOW IS DRIFTING S
BETWEEN THE CANARY AND MADEIRA ISLANDS NEAR 32N17W. A COLD FRONT
AND PRE-FRONTAL TROUGH ARE ASSOCIATED WITH THE LOW AIDING IN THE
DEVELOPMENT OF SCATTERED SHOWERS N OF 29N BETWEEN 14W-20W.
WIDESPREAD DRY STABLE AIR ALOFT COVERS MUCH OF THE REMAINDER OF
THE AREA ESPECIALLY E OF 30N N OF 17N WHERE UPPER CONFLUENCE IS
QUITE STRONG. IN THE DEEP TROPICS...A WSWLY JET CUTS ACROSS THE
REGION N OF THE ITCZ ALONG 10N40W 14N28W 16N16W. THESE STRONG
UPPER LEVEL WINDS ARE ADVECTING PATCHES OF MID-HIGH LEVEL CLOUDS
E OF THE AXIS...WITH DRY AIR ENHANCED W OF THE JET AXIS. AT THE
SFC...THE TIGHT PRES GRADIENT BETWEEN THE STRONG HIGH AND LOW
PRES IN THE FAR E ATLC IS GENERATING A LARGE AREA OF STRONG
WINDS N OF 20N BETWEEN 27W-36W. THE CORE OF THE WINDS ARE ALONG
AND JUST N OF THE AREA WHERE A STORM WARNING IS IN EFFECT.

$$
CANGIALOSI



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