[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191747
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI OCT 19 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 50W S OF 16N MOVING W 10-15 KT. FOR THE
PAST FEW DAYS THERE HAS BEEN SOME CONFLICTING EVIDENCE ON THE
POSITION OF THIS WAVE. WE HAVE MAINTAINED CONTINUITY FOR THE
PAST COUPLE OF DAYS FOLLOWING A FAINT LOW-LEVEL INVERTED V-SHAPE
IN THE LOW CLOUDS WELL AHEAD OF DENSER CLOUDINESS. HOWEVER...
THAT WEAK LOW-LEVEL SIGNATURE HAS JUST ABOUT DISSIPATED AND THE
DENSER CLOUDINESS HAS BECOME MORE PRONOUNCED WITH SOME WAVE LIKE
STRUCTURE EVIDENT. A LONG-TERM SATELLITE LOOP AND THE MIMIC TPW
ANIMATION ALSO SHOWS WWD PROPAGATION OF THIS CLOUD MASS.
THEREFORE...THIS WAVE WILL LIKELY BE RELOCATED BACK FIVE DEGREES
OR SO TO AGREE WITH THE SATELLITE SIGNATURE. SCATTERED MODERATE
CONVECTION IS FROM 5N-13N BETWEEN 39W-47W.

WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 72W S OF
17N MOVING W 10-15 KT. THIS WAVE HAS BEEN CHALLENGING TO TRACK
OVER THE PAST COUPLE OF DAYS WITH THE CURRENT POSITION SOLELY
BASED ON FORWARD CONTINUITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 6N30W 8N46W 6N56W. THERE IS NO
SIGNIFICANT CONVECTION BESIDES FOR THE ACTIVITY ASSOCIATED WITH
THE TROPICAL WAVE.

DISCUSSION...

GULF OF MEXICO...
A COLD FRONT...SUPPORTED BY A UPPER TROUGH OVER THE PLAINS...IS
MOVING ACROSS THE GULF WATERS. AS OF 15Z...THE FRONT WAS
ANALYZED FROM THE WRN FL PANHANDLE TO JUST N OF BROWNSVILLE
TEXAS ALONG 31N87W 28N90W 27N98W. A PREFRONTAL TROUGH OR BROKEN
SQUALL LINES LIE ABOUT 60 NM AHEAD OF THE FRONT. MOSAIC DOPPLER
RADAR DATA DEPICTS NUMEROUS SHOWERS AND TSTMS MOSTLY ALONG AND
TO THE E OF THE FRONT WITHIN 90 NM. THIS RAINFALL HAS PRODUCED
SOME FLOODING ACROSS THE FL PANHANDLE. FOR DETAILS REFER TO
PRODUCTS FROM YOUR LOCAL WEATHER OFFICE. BEHIND THE FRONT...MUCH
DRIER AND SLIGHTLY COOLER AIR IS FILTERING IN WITH DEWPOINTS
DROPPING INTO THE 40'S AND 50'S F. WELL AHEAD OF THE
FRONT...DEEP LAYER SLY FLOW IS CREATING A WARM HUMID AIRMASS
WITH A FAIR AMOUNT OF CLOUDINESS BUT ONLY ISOLATED SHOWERS AT
THE MOMENT. MODEL GUIDANCE SHOWS THIS FRONT CONTINUING SE THRU
TONIGHT THEN SLOWLY AND BEGINNING TO WASH OUT OVER THE WEEKEND.
THE NEXT FRONT...WHICH WILL LIKELY BE STRONGER...SHOULD ENTER
THE REGION EARLY NEXT WEEK.

CARIBBEAN SEA...
AN UPPER LOW IS TRACKING NW ACROSS THE CARIBBEAN CENTERED VERY
NEAR COZUMEL MEXICO. S TO SE FLOW ALOFT...BETWEEN THIS UPPER LOW
AND A RIDGE OVER THE SW ATLC...IS DRAWING ABUNDANT TROPICAL
MOISTURE NWD FROM THE ITCZ BETWEEN 76W-83W. THIS MOISTURE PLUME
HAS BEEN PERSISTENT AND SHIFTING W WITH THE UPPER LOW OVER THE
PAST FEW DAYS. THERE ALSO HAS BEEN SOME EVIDENCE OF LOW-LEVEL
TROUGHING LIKELY ASSOCIATED WITH A TROPICAL WAVE WHICH HAS BEEN
MOVING IN TANDEM WITH THE UPPER LOW. IR IMAGES SHOW A NARROW
SWATH OF SCATTERED SHOWERS AND TSTMS FROM 11N-20N BETWEEN
77W-82W. MUCH DRIER MID TO UPPER LEVEL AIR IS OVER THE CARIB
WATERS E OF 73W ADVECTED BY NLY UPPER FLOW AROUND THE
AFOREMENTIONED RIDGE. SCATTERED CLOUDINESS AND SHOWER ACTIVITY
IS OVER PORTIONS OF THE LESSER ANTILLES ASSOCIATED WITH
DIFFLUENT AREAS BETWEEN A DEVELOPING CUT OFF JUST N OF THE AREA
AND THE SW PERIPHERY OF A HIGH JUST TO THE E. THE FAR NW CARIB
IS FAIRLY TRANQUIL WITH LITTLE SIGNIFICANT MOISTURE DIRECTLY
UNDERNEATH THE UPPER LOW.

ATLANTIC OCEAN...
AN AMPLIFIED LONG WAVE RIDGE/TROUGH/RIDGE PATTERN IS
WELL ESTABLISHED ACROSS THE SUBTROPICAL ATLC. THE WRN ATLC RIDGE
IS CENTERED ABOUT 90 NM NE OF THE NRN BAHAMAS NEAR 28N76W. A
VERY LARGE SHARPENING TROUGH LIES TO THE E OF THERE COVERING THE
AREA BETWEEN 40W-63W N OF 20N. A LOW APPEARS TO BE TRYING TO CUT
OFF NEAR THE BASE OF THE TROUGH JUST N OF THE LESSER ANTILLES.
THIS TROUGH IS PROVIDING SOME SUPPORT FOR A SLOWLY DYING
STATIONARY FRONTAL BOUNDARY WHICH ENTERS THE AREA NEAR 32N30W
AND STRETCHES SW TO A 1016 MB LOW NEAR 29N43W CONTINUING TO
24N57W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE GENERALLY
WITHIN 180 NM W OF THIS BOUNDARY SUPPORTED BY DIFFLUENCE ALOFT.
MODERATE SFC RIDGING DOMINATES THE AREA TO THE W OF THE FRONT.

THE SFC PATTERN IN THE CENTRAL AND E ATLC IS MOSTLY CONTROLLED
BY WEAK HIGH PRES RIDGING ANCHORED BY A 1020 MB HIGH SITUATED
NEAR 26N31W. THIS IS PRODUCING MAINLY LIGHT WINDS OVER THE
SUBTROPICAL ATLC...WHILE MODERATE TRADES PERSIST IN THE TROPICS
ESPECIALLY NEAR THE TROPICAL WAVE. THE UPPER PATTERN OVER THE E
ATLC CONSISTS OF A LARGE SCALE RIDGE EXTENDING NWD FROM A HIGH
CENTER NEAR 10N32W. THE STRONG CUT OFF LOW FROM A FEW DAYS AGO
HAS RACED NE AND OPENED INTO A TROUGH BUT IS STILL INTERRUPTING
RIDGING SLIGHTLY ALONG 27W/28W N OF 18N. CONVECTION IS MOSTLY
CONFINED TO THE ITCZ SUPPORTED BY DIFFLUENCE ALOFT NEAR THE W
PERIPHERY OF THE RIDGE. SEE ABOVE FOR DETAILS.

$$
CANGIALOSI


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