[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201048
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN MAY 20 2007

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1030 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 6N20W 4N35W 4N45W 3N52W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM
EITHER SIDE OF THE AXIS BETWEEN 19W-25W. A LOW LATITUDE TROPICAL
WAVE MAY BE ENHANCING THIS ACTIVITY...ALTHOUGH DID NOT ADD THIS
TO THE SFC MAP YET BECAUSE TRACKING BACK OVER AFRICA WAS
DIFFICULT TO DISCERN. A CLUSTER OF SCATTERED MODERATE IS MOVING
OFF THE AFRICAN COAST E OF 15W FROM 8N-10N. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE WITHIN 180 NM N OF THE AXIS W OF 28W.

...DISCUSSION...
GULF OF MEXICO...
SURFACE HIGH PRES OVER THE SOUTHEAST U.S. IS PROVIDING MOSTLY
FAIR WEATHER ACROSS THE MAJORITY OF THE GULF AND MODERATE NE
WINDS IN THE ERN AND MID GULF N OF 26N. A WEAK SFC TROUGH HAS
BEEN ADDED TO THE ANALYSIS FROM THE FL STRAITS TO SRN LOUISIANA
ALONG 25N80W 25N89W 30N91W. THIS WEAK BOUNDARY LIKELY BROKE
OFF FROM THE MAIN FRONTAL TROUGH IN THE W ATLC AND IS GETTING
PULLED W BY THE LOW-LEVEL FLOW. A BAND OF LOW CLOUDS AND A
POSSIBLE SHOWERS MARK THE TROUGH AXIS ALONG WITH AN INCREASE IN
WINDS BEHIND IT. THE UPPER FLOW IS FAIRLY UNIFORM WNWLY BETWEEN
RIDGING OVER THE S CENTRAL U.S. AND LARGE SCALE TROUGHING OFF
THE U.S. EASTERN SEABOARD. THIS PATTERN IS PRODUCING MODEST
STABLE AIR ALOFT AIDING IN THE TRANQUIL CONDITIONS. DEBRIS HIGH
CLOUDS...WHICH ARE ADVECTED E FROM FIZZLING BURSTS OF CONVECTIVE
ACTIVITY OVER MEXICO...IS MOISTENING THE ATMOSPHERE SLIGHTLY W
OF 92W. LITTLE CHANGE IN THE OVERALL WEATHER IS EXPECTED OVER
THE NEXT DAY OR TWO THOUGH MID-HIGH CLOUDINESS MAY SPREAD
FURTHER E AS THE UPPER FLOW VEERS TO THE WSW.

CARIBBEAN SEA...
A SFC TROUGH EXTENDS FROM PANAMA NWD TO CUBA ROUGHLY ALONG
79W/80W. THIS FEATURE WAS WELL DEPICTED BY LAST EVENING'S QSCAT
PASS WHICH SHOWS MODERATE ELY TRADES E OF THE TROUGH AXIS AND
LIGHT NELY WINDS TO THE W. ALOFT...A SPRAWLING RIDGE IS CENTERED
OVER NRN VENEZUELA. S-SWLY FLOW ON THE WRN PERIPHERY OF THE
RIDGE IS TAPPING MOISTURE FROM THE ITCZ AND SPREADING IT
ANTICYCLONICALLY AROUND ITS CIRCULATION...ALMOST ENTIRELY
CONTAINED W OF 68W. MOST OF THE MOISTURE IS ONLY IN THE FORM OF
A MID-HIGH LEVEL CLOUD DECK...ALTHOUGH THERE COULD BE ISOLATED
SHOWERS EMBEDDED ESPECIALLY S OF 15N W OF 78W CLOSER TO THE DEEP
MOISTURE SOURCE AND N OF 18N BETWEEN 74W-79W IN A WEAK UPPER
DIFFLUENT ZONE. THE ERN CARIB IS EXPERIENCING TRANQUIL
CONDITIONS UNDER A SUBSIDENT ENVIRONMENT. MOST OF THE GLOBAL
MODELS SHOW THE WEAK SFC TROUGH BEING PUSHED VERY SLOWLY W BY
THE LOW-LEVEL ELY FLOW AND THE MOISTURE SWATH GENERALLY BECOMING
LESS DENSE OVER THE NEXT COUPLE DAYS.

ATLANTIC OCEAN...
THE SYNOPTIC PICTURE SHOWS A HIGHLY AMPLIFIED
TROUGH/RIDGE/TROUGH PATTERN COVERING THE ATLC DISCUSSION AREA
THIS MORNING. BEGINNING IN THE W ATLC...THE UPPER TROUGH EXTENDS
FROM A VIGOROUS UPPER LOW OVER RHODE ISLAND TO THE WRN BAHAMAS
WITH A FAINT INFLUENCE IN THE WINDS ALOFT EXTENDING INTO THE NW
CARIB. THIS UPPER SYSTEM IS SUPPORTING A SFC TROUGH WHICH RUNS
FROM NEAR 29N65W TO THE CENTRAL BAHAMAS.  ANOTHER WEAK BOUNDARY
IS EVIDENT ON NIGHT CHANNEL VIS IMAGES EXTENDING FROM JUST W OF
BERMUDA TO THE FL STRAITS. THIS WESTERN BOUNDARY...REMNANTS OF
AN OLD FRONT...APPEARS TO HAVE STALLED AND ISENTROPIC LIFT IS
PRODUCING A FEED OF SHOWERS AND TSTMS ACROSS SE FLORIDA.
SCATTERED SHOWERS ARE ALSO OCCURRING BETWEEN 62W-75W NEAR THE
SFC TROUGH MENTIONED ABOVE AND IN AN UPPER DIFFLUENT ZONE.

IN THE CENTRAL ATLC...WATER VAPOR IMAGERY SHOWS AN AMPLIFIED
RIDGE CENTERED WELL N OF THE AREA NEAR 42N44W. AN UPPER LOW IS
EMBEDDED IN THE RIDGE NEAR 28N47W BUT IS DOING VERY LITTLE IN
GENERATING MUCH WEATHER. MODERATE DRY STABLE AIR EXISTS BETWEEN
40W-60W. THE RIDGE MENTIONED N OF THE AREA IS VERTICALLY STACKED
WITH AN ASSOCIATED 1037 MB HIGH CENTERED NEAR 41N42W. THIS HIGH
PRES IS AIDING IN THE WIDESPREAD FAIR WEATHER AND PRODUCING
MODERATE ELY TRADES ACROSS THE REGION.

THE E ATLC IS AN AREA OF UPPER CONVERGENCE BETWEEN A TROUGH
WHICH DIGS SWD TO 23N AND UPPER RIDING POKING NWD TOWARD THE
TROUGH. AN STRONG SW-WLY JET LIES BETWEEN THESE UPPER FEATURES
EXTENDING FROM 17N42W TO W AFRICA NEAR 22N17W. CORE WINDS ALONG
THIS JET AXIS ARE BETWEEN 110-130 KT BASED ON SATELLITE DERIVED
WINDS. PATCHES OF MID-HIGH LEVEL CLOUDS AND ISOLATED SHOWERS ARE
DRAWN NEWD FROM THE ITCZ TO THE JET AXIS...WHILE ABUNDANT
SINKING AIR ALOFT IS STABILIZING THE ATMOSPHERE N OF THE JET. IN
THE LOWER LEVELS...MODERATE TO STRONG NELY TRADES COVER MUCH OF
THE AREA BETWEEN STRONG HIGH PRES IN THE CENTRAL ATLC AND LOWER
PRES OVER AFRICA.

$$
CANGIALOSI




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