[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211042
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON MAY 21 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.

...TROPICAL WAVES...

TROPICAL WAVE...THE FIRST TRACKED ON OUR SFC MAP IN 2007...IS
LOCATED ALONG 21W/22W S OF 10N MOVING W ABOUT 15 KT. THIS WAVE
APPEARS TO HAVE MOVED OFF THE AFRICAN COAST AROUND 06Z ON SAT
BASED ON SATELLITE AND SFC DATA OVER THE PAST FEW DAYS. THE WAVE
PLACEMENT WAS BASED ON LOW TO MID LEVEL CURVATURE SEEN ON NIGHT
CHANNEL VIS IMAGES WHICH ALSO SEEMED TO MESH WELL WITH A SHIP
AND BUOY REPORT SURROUNDING THE FEATURE. THE BUOY...CALL SIGN
31006...HAS BEEN PARTICULARLY HELPFUL SHOWING THE WIND VEER MORE
TOWARD THE E POSSIBLY INDICATING THE APPROACH OF THE WAVE AXIS.
HOWEVER...EARLY MORNING'S VIS IMAGERY SUGGESTS THAT THE WAVE
AXIS COULD BE FURTHER W BASED ON THE SHAPE OF THE LOW-MID LEVEL
CLOUD FIELD...SO THE FORWARD SPEED OF THE WAVE MIGHT BE CLOSER
TO 20 KT. THIS WEAK FEATURE IS LOW-LATITUDE AND IT'S MAIN
FUNCTION IS PERTURBING THE ITCZ SLIGHTLY. SCATTERED MODERATE
CONVECTION IS WITHIN 180 NM E OF THE WAVE AXIS.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N10W 4N24W 5N38W 3N52W. ISOLATED
MODERATE CONVECTION IS WITHIN 180 NM N OF THE AXIS W OF 24W.
CLUSTERS OF SCATTERED MODERATE TO STRONG ARE ALONG A SPEED
GRADIENT BOUNDARY FROM THE EQ-3N E OF 10W. SCATTERED STRONG IS
MOVING INTO THE FAR E ATLC WATERS N OF 2N E OF 2W.

...DISCUSSION...
GULF OF MEXICO...
FAIR WEATHER IS THE RULE ACROSS THE GULF OF MEXICO THIS MORNING
WITH A SFC HIGH PRES RIDGE IN CONTROL RUNNING E-W ALONG 30N.
SHIPS/BUOYS ARE REPORTING LIGHT WINDS ACROSS THE N GULF NEAR THE
RIDGE AXIS. HOWEVER...MODERATE TO FRESH NE TO E WINDS EXIST
ACROSS THE CENTRAL AND E GULF AS THE PRES GRADIENT REMAINS
TIGHTENED BETWEEN HIGH PRES TO THE N AND A TROUGH OF LOW PRES TO
THE E. THIS STRONG NE BREEZE AND SOME INFLUENCE FROM A FIZZLING
OLD FRONTAL BOUNDARY IS PRODUCING LOW CLOUD STREAMERS WITH
EMBEDDED ISOLATED SHOWERS MOVING FROM THE ATLC ACROSS THE FL
STRAITS AND INTO THE SE GULF. THE UPPER PATTERN REMAINS ZONAL OR
WNWLY PROVIDING A MODESTLY STABLE ENVIRONMENT...AIDING IN THE
TRANQUIL CONDITIONS. PATCHES OF HIGH CLOUDS LIE OVER THE W GULF
THINNING AS THEY PUSH E OF 92W. LOOKING AHEAD A COUPLE
DAYS...HIGH PRES IS EXPECTED TO SHIFT EWD INTO THE W ATLC. THIS
WILL ALLOW THE WINDS TO SHIFT MORE TO THE E TO SE AND REMAIN
BRISK.

CARIBBEAN SEA...
SFC OBS AND NIGHT CHANNEL VIS IMAGERY CONTINUE TO SHOW THAT THE
SFC TROUGH ALONG 81W REMAINS WEAK YET EVIDENT IN THE
LOW-LEVEL WINDS AS IT SLOWLY DRIFTS W. A QSCAT PASS AROUND 00Z
CONFIRMS THIS WITH MODERATE TO FRESH ELY TRADES E OF THE AXIS
AND LIGHT N TO NE WINDS TO THE W OF THE AXIS. THE UPPER PATTERN
IS BROADLY WLY AROUND THE NRN PERIPHERY OF A FLAT RIDGE CENTERED
OVER NRN SOUTH AMERICA. LARGE CLUSTERS OF MODERATE CONVECTION
ARE SCATTERED TO NUMEROUS ALONG THE ITCZ WITH ONE CLUSTER BEING
ENHANCED BY CONVERGENCE ALONG THE TROUGH STRETCHING WITHIN 150
NM E OF THE AXIS S OF 16N. SMALLER PATCHES OF LOW TOPPED SHOWERS
AND TSTMS...ASSOCIATED WITH THE TAIL END OF A W ATLC
TROUGH...ARE OBSERVED BETWEEN JAMAICA AND CUBA AND FURTHER NE IN
THE SE BAHAMAS. THIS ACTIVITY HAS BEEN FAIRLY PERSISTENT OVER
THE PAST DAY OR TWO. IN FACT...A 24-H PRECIP REPORT FROM MONTEGO
BAY JAMAICA SHOWS 2.22 IN. HAS FALLEN BETWEEN 8 PM SAT AND 8 PM
SUN. THE ERN CARIB REMAINS FAIRLY TRANQUIL UNDER NWLY FLOW AND
MODERATE DRY AIR ALOFT. NOT MUCH CHANGE IN THE PATTERN IS
EXPECTED OVER THE NEXT DAY OR TWO WITH THE WEAK TROUGH EDGING W
STEERED BY THE LOW-LEVEL FLOW.

ATLANTIC OCEAN...
BROAD UPPER TROUGHING COVERS MUCH OF THE W ATLC ANCHORED BY A
VIGOROUS LOW OVER NOVA SCOTIA. THIS UPPER SYSTEM IS SUPPORTING
A SFC TROUGH/OLD FRONTAL BOUNDARY WHICH EXTENDS FROM A 1014 MB
LOW 250 NM NE OF BERMUDA ALONG 34N60W 25N67W TO HAITI. LOW-LEVEL
LIFT ALONG THE BOUNDARY ALONG WITH UPPER DIFFLUENCE BETWEEN THE
TROUGH AND RIDGE TO THE E IS PRODUCING SCATTERED SHOWERS WITHIN
150 NM EITHER SIDE OF THE TROUGH AXIS AND N OF 30N BETWEEN
57W-59W. THE SFC FLOW IS QUITE BRISK IN THIS REGION AS A
TIGHTENED PRES GRADIENT HAS SET UP BETWEEN THE TROUGH AND HIGH
PRES NEAR THE SE CONUS. THIS STRONG FLOW IS ADVECTING SCATTERED
SHOWERS ACROSS THE W ATLC WATERS TO THE BAHAMAS AND EXTREME S
FLA. HOWEVER...MOISTURE IN THAT AREA IS SIGNIFICANTLY LESS THAN
YESTERDAY WHEN UP TO 8 IN OF RAIN FELL IN ISOLATED SPOTS NEAR A
STALLED SFC TROUGH.

AN UPPER LOW HAS BEEN NEARLY STATIONARY IN THE CENTRAL ATLC NEAR
27N46W WITH ITS ASSOCIATED TROUGHING STRETCHING SWD TO 7N48W.
THIS UPPER LOW IS PRODUCING VERY LITTLE WEATHER AS IT LIES IN A
STABLE ENVIRONMENT EMBEDDED TO THE S OF AN AMPLIFIED RIDGE. THE
E ATLC IS AN AREA OF UPPER CONVERGENCE BETWEEN A TROUGH WHICH
DIGS SWD ACROSS THE CANARY ISLANDS TO 23N AND UPPER RIDING
POKING NWD FROM ITCZ TOWARD THE TROUGH. AN STRONG SW-WLY JET
LIES BETWEEN THESE UPPER FEATURES EXTENDING FROM 15N43W TO W
AFRICA NEAR 23N16W. CORE WINDS ALONG THIS JET AXIS ARE BETWEEN
100-120 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...VERY HEALTHY 1036 MB HIGH PRES IN THE CENTRAL ATLC NEAR
41N36W IS AIDING IN THE FAIR WEATHER AND PRODUCING A LARGE AREA
OF MODERATE TO FRESH TRADES.

$$
CANGIALOSI





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