[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 100517
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 50W S OF 12N MOVING W NEAR 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 53W. THIS LOW AMPLITUDE WAVE IS NEAR THE SW EDGE OF THE
SURGE...MARKED BY A FAINT MOISTURE BUMP ON THE PRODUCT AND IN
SATELLITE IMAGES. 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 10N14W 5N30W 7N42W 6N49W 5N54W.
SCATTERED MODERATE CONVECTION IS WITHIN 45 NM OF THE AXIS
BETWEEN 27W-33W. WIDELY SCATTERED MODERATE IS WITHIN 30 NM OF
THE AXIS BETWEEN 41W-44W.

DISCUSSION...

GULF OF MEXICO...
MID TO UPPER LEVEL NWLY FLOW AND DRY STABLE AIR DOMINATES THE
GULF TONIGHT. THE AIR IS DRIEST OVER THE SE PORTION WHERE THE
FLOW BECOMES HIGHLY CONFLUENT ALOFT. THIS STABLE AIRMASS IS
SUPPRESSING DEEP CLOUD FORMATION ACROSS THE REGION. IN THE LOWER
LEVELS...WEAK HIGH PRES RIDGE ALONG 29N 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 FEW QUICK MOVING SHALLOW SHOWERS IN THE W GULF ASSOCIATED WITH
THE LOW-LEVEL RETURN FLOW BUT THE DOPPLER RADARS ARE ECHO-FREE
ACROSS THE GULF COAST. THIS TRANQUIL PATTERN SHOULD PERSIST THRU
SATURDAY 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 17N.
IR IMAGERY AND LIGHTNING DATA REVEAL DEEPENING AND EXPANDING
CONVECTION S OF 15N BETWEEN 72W-83W. IN ADDITION TO LOW-LEVEL
CONVERGENCE...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 PAIR
OF WEAK FRONTAL TROUGHS. THE ERN BOUNDARY ENTERS THE AREA NEAR
32N54W AND EXTENDS SW TO A 1011 MB LOW NEAR 21N68W. THE OTHER
FEATURE STRETCHES FROM A 1012 MB LOW N OF THE AREA ALONG 32N73W
TO THE NW BAHAMAS. THERE IS MINIMAL SHOWER ACTIVITY NEAR THE WRN
BOUNDARY DUE TO THE VERY DRY ATMOSPHERE IT IS EMBEDDED IN.
WIDESPREAD MID TO HIGH LEVEL CLOUDINESS AND LIKELY EMBEDDED
SHOWERS AND ISOLATED TSTMS LIE OVER THE ERN BOUNDARY N OF 24N
BETWEEN 50W-60W...IN AN UPPER DIFFLUENT ZONE BETWEEN THE
AFOREMENTIONED TROUGH AND UPPER RIDGING TO THE E.

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 32N43W. AN UPPER LOW
APPEARS TO HAVE OPENED INTO A SHARP TROUGH FROM 21N39W 4N47W.
STRONG SW TO WLY FLOW IS GENERATING AND TRANSPORTING A BROKEN
MID TO HIGH LEVEL CLOUD DECK S OF 17N E OF 42W. A LARGE DEEP
LAYER LOW PRES SYSTEM...ANALYZED 1006 MB AT THE SFC...IS
CENTERED N OF THE AREA OVER THE AZORES. A TRAILING SFC TROUGH
EXTENDS FROM 32N23W TO 25N31W. THIS LARGE LOW PRES TROUGH IS
ALLOWING WINDS TO BE LIGHT TO MODERATE ACROSS MUCH OF THE
CENTRAL AND E ATLC.

$$
CANGIALOSI




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