[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101144
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SAT NOV 10 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
1115 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 51W S OF 13N MOVING W 15-20 KT. THE MIMIC
TPW ANIMATION CLEARLY SHOWS A LARGE DRY SURGE...ASSOCIATED AT
LEAST IN PART WITH SAHARAN DUST...QUICKLY SPREADING WWD TO ABOUT
55W. THIS LOW AMPLITUDE WAVE IS NEAR THE SW EDGE OF THE
SURGE...MARKED BY A SUBTLE MOISTURE BUMP ON THE PRODUCT AND IN
SATELLITE IMAGES. AT 06Z...SHIP C6UG4 REPORTED 20 KT SE WINDS
JUST E OF THE WAVE AXIS. SCATTERED SHOWERS AND ISOLATED TSTMS
ARE WITHIN 120 NM EITHER SIDE OF THE AXIS.

TROPICAL WAVE IS ALONG 64W S OF 13N MOVING W NEAR 15 KT. MUCH OF
THIS WAVE IS INLAND OVER S AMERICA WITH VERY LITTLE SIGNATURE
APPARENT IN ANY OF THE AVAILABLE DATA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 7N12W 6N25W 4N40W 4N49W 5N58W.
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM N OF THE AXIS
BETWEEN 26W-34W. ISOLATED MODERATE IS FROM 6N-8N BETWEEN 42W-48W.

DISCUSSION...

GULF OF MEXICO...
MID TO UPPER LEVEL NWLY FLOW AND DRY STABLE AIR DOMINATES THE
GULF THIS MORNING. THE AIR IS DRIEST OVER THE SE PORTION WHERE
THE FLOW BECOMES HIGHLY CONFLUENT ALOFT TOWARD THE BASE OF AN
ATLC TROUGH. THIS STABLE AIRMASS IS SUPPRESSING DEEP CLOUD
FORMATION ACROSS THE REGION. IN THE LOWER LEVELS...WEAK 1020 MB
HIGH PRES AREA NEAR 29N87W IS IN CONTROL. THIS HAS ALLOWED
WINDS TO BE LIGHT TO MODERATE AND ANTICYCLONIC ACROSS THE
REGION. BROKEN STRATOCUMULUS CLOUDS ARE EVIDENT OVER THE S
CENTRAL PORTION...INDICATIVE OF THE COOL AIRMASS. THERE COULD BE
A BRIEF SHALLOW ISOLATED SHOWER IN THE W GULF ASSOCIATED WITH
THE LOW-LEVEL RETURN FLOW BUT NOT MUCH MORE AS DOPPLER RADARS
REMAIN ECHO-FREE ACROSS THE GULF COAST. THIS TRANQUIL PATTERN IS
EXPECTED TO PERSIST THRU THE DAY ALLOWING THE PLEASANT FALL
WEATHER TO CONTINUE.

CARIBBEAN SEA...
ACTIVE WEATHER PERSISTS IN THE SW CARIB ASSOCIATED WITH A NEARLY
STATIONARY LOW-LEVEL TROUGH...ANALYZED ALONG 76W/77W S OF 16N.
SFC OBSERVATIONS AND NIGHT CHANNEL VIS IMAGES REVEAL A BROAD
ENVELOPE OF LOW TO MID LEVEL CYCLONIC TURNING SUGGESTING AN
ILL-DEFINED 1009 MB LOW CENTERED JUST N OF PANAMA. IR IMAGERY
AND LIGHTNING DATA INDICATE SCATTERED MODERATE TO STRONG
CONVECTION S OF 16N BETWEEN 72W-84W. IN ADDITION TO LOW-LEVEL
CONVERGENCE NEAR THE LOW/TROUGH...AN UPPER DIFFLUENT PATTERN IS
AIDING IN THE INSTABILITY AND SPREADING HIGH LEVEL CLOUDINESS
TOWARD PUERTO RICO AND HISPANIOLA. THESE STRONG UPPER-LEVEL
WINDS ARE UNFAVORABLE FOR SIGNIFICANT TROPICAL DEVELOPMENT. A
QSCAT PASS AROUND 00Z SHOWED STRONG NLY WINDS IN THIS
AREA...ESPECIALLY TO THE W OF THE TROUGH AXIS. THE NW
CARIB...LIKE THE GULF OF MEXICO...IS EXPERIENCING RATHER
PLEASANT WEATHER UNDER THE INFLUENCE OF ABUNDANT SUBSIDENCE AND
LOW-LEVEL NLY FLOW. THE REMAINDER OF THE CENTRAL AND ERN CARIB
IS FAIRLY TRANQUIL WITH LIGHT TO MODERATE TRADES AND MODEST DRY
AIR EVIDENT ON WATER VAPOR IMAGES UNDER MID TO UPPER RIDGING.

ATLANTIC OCEAN...
LARGE MID AND UPPER TROUGH OVER THE W ATLC IS SUPPORTING A FEW
WEAK FRONTAL TROUGHS. ONE OF THESE IS A COLD FRONT WHICH EXTENDS
SW INTO THE AREA ALONG 32N71W 29N76W. A PREFRONTAL TROUGH LIES
AHEAD OF THIS FEATURE ALONG 32N63W 26N70W. BOTH OF THESE ARE
ONLY PRODUCING A THIN LINE OF LOW CLOUDS...LIKELY SUPPRESSED BY
THE VERY DRY ATMOSPHERE THEY ARE EMBEDDED IN. THE ERN-MOST
BOUNDARY...ANALYZED AS A TROUGH...ENTERS THE AREA NEAR 32N54W
AND EXTENDS SW TO A 1011 MB LOW 150 NM NNW OF PUERTO RICO NEAR
21N67W. WIDESPREAD MID TO HIGH LEVEL CLOUDINESS AND LIKELY
EMBEDDED SHOWERS AND ISOLATED TSTMS LIE OVER THIS BOUNDARY
ADVECTED BY SWLY UPPER FLOW FROM THE CARIB. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE CONFINED TO N OF 26N BETWEEN 48W-53W...IN
AN UPPER DIFFLUENT ZONE BETWEEN THE AFOREMENTIONED TROUGH AND
UPPER RIDGING TO THE E. THIS BROAD LOW-LEVEL TROUGHING PATTERN
IS CREATING LIGHT AND SOMEWHAT VARIABLE WINDS ACROSS MUCH OF THE
W ATLC.

IN THE CENTRAL AND E ATLC...THE UPPER PATTERN CONSISTS OF A
RIDGE/TROUGH. THE RIDGE IS HIGHLY ELONGATED FROM A HIGH CENTER
OVER THE LESSER ANTILLES EXTENDING NE TO 32N41W. AN UPPER LOW
APPEARS TO HAVE OPENED INTO A SHARP TROUGH FROM 20N39W 4N48W.
STRONG SW TO WLY FLOW IS GENERATING AND TRANSPORTING A BROKEN
MID TO HIGH LEVEL CLOUD DECK S OF 18N E OF 43W. A LARGE DEEP
LAYER LOW PRES SYSTEM...ANALYZED 1007 MB AT THE SFC...IS
CENTERED N OF THE AREA OVER THE WRN AZORES. A TRAILING SFC
TROUGH EXTENDS FROM 32N18W TO 22N27W. THIS LARGE LOW PRES TROUGH
IS ALLOWING WINDS TO BE LIGHT TO MODERATE ACROSS MUCH OF THE
CENTRAL AND E ATLC AS NOTED IN RECENT SCATTEROMETER PASSES.

$$
CANGIALOSI


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