[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151747
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 15 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 31W/32W S OF 19N MOVING W 10-15 KT.
VISIBLE IMAGERY REVEALS A FAIR AMOUNT OF LOW-LEVEL TURNING IN
THE CLOUD FIELD. HOWEVER...VERY STRONG UPPER LEVEL SOUTHWESTERLY
WINDS ARE LIMITING ORGANIZING SHEARING MUCH OF THE DENSER
CLOUDINESS TO THE E OF THE ANALYZED AXIS. SCATTERED SHOWERS AND
TSTMS ARE VERY DISORGANIZED WITHIN 300 NM E OF THE AXIS N OF 12N
AND WITHIN 150 NM EITHER SIDE NEAR THE INTERSECTION OF THE ITCZ
FROM 9N-11N.

LOW AMPLITUDE TROPICAL WAVE IS ALONG 51W S OF 14N MOVING W 10-15
KT. THIS WAVE WAS VERY CONVECTIVE A COUPLE OF DAYS AGO WHEN
INTERACTING WITH ENERGY FROM AN UPPER JET BRANCH. HOWEVER
..SINCE THEN THE WAVE HAS MOVED INTO A MORE STABLE ENVIRONMENT.
CONSEQUENTLY...CONVECTION HAS DIMINISHED WITH ONLY A SWIRL OF
LOW CLOUDS LEFT OVER.

TROPICAL WAVE IS IN THE WESTERN CARIBBEAN ALONG 80W S OF 19N
MOVING W 10-15 KT. A 1007 MB LOW IS ANALYZED ALONG THE WAVE AXIS
NEAR 13.5N. THIS LOW HAS BECOME INCREASINGLY DISORGANIZED THIS
AFTERNOON AND IS NOW TOUGH TO LOCATE THE CENTER ON THE LATEST
VIS IMAGES. ASSOCIATED SCATTERED SHOWERS AND TSTMS ARE SHEARED
OFF TO THE W OF THE WAVE BY STRONG UPPER NELY WINDS ON THE BACK
SIDE OF AN UPPER LOW. WHILE FURTHER DEVELOPMENT IS NOT
ANTICIPATED THIS SYSTEM COULD STILL CAUSE LOCALLY HEAVY RAINS
OVER PORTIONS OF CENTRAL AMERICA TODAY AND TOMORROW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 5N21W 10N34W 8N44W 9N61W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...A SMALL AREA OF SCATTERED MODERATE IS WITHIN 60 NM OF
THE AXIS E OF 14W.

DISCUSSION...

GULF OF MEXICO...
THE MAIN WEATHER PRODUCING FEATURE IN THE AREA IS A 1006 MB LOW
CENTERED JUST OFF THE W COAST OF THE YUCATAN PENINSULA NEAR
21N91W. THIS LOW LIES AT THE BASE OF A SFC TROUGH WHICH EXTENDS
NE INTO THE CENTRAL GULF REACHING 26N87W. IR IMAGERY AND
LIGHTNING DATA SUGGEST THAT THE MORE ORGANIZED SHOWER AND TSTM
ACTIVITY IS TO THE N OF THE LOW WITHIN 60 NM EITHER SIDE OF THE
TROUGH. SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE DURING THE
NEXT DAY OR TWO AS IT MOVES GENERALLY NORTHWESTWARD. THE
REMAINDER OF THE GULF IS EXPERIENCING A FAIRLY NICE DAY UNDER
MODERATE TO STRONG SUBSIDENCE EMBEDDED WITHIN AN UPPER HIGH
CENTERED OVER THE SW GULF. SFC WINDS ARE ON THE STRONG
SIDE...20-25 KT...E OF THE SFC TROUGH AS THE GRADIENT IS
TIGHTENED BETWEEN IT AND HIGH PRES OVER THE MID-ATLANTIC
STATES.

CARIBBEAN SEA...
THE AREA OF LOW PRES ASSOCIATED WITH A TROPICAL WAVE ALONG 80W
HAS BECOME ILL-DEFINED TODAY LIKELY FEELING THE EFFECTS OF NELY
SHEAR. FOR MORE INFORMATION REFER TO THE TROPICAL WAVES SECTION
ABOVE. ELSEWHERE...A WWD MOVING UPPER LOW IS CURRENTLY CENTERED
OFF THE N COAST OF COLOMBIA NEAR 13N73W. S TO SELY FLOW ON THE E
SIDE OF THIS UPPER SYSTEM IS DRAWING MOISTURE NWD FROM THE DEEP
TROPICS BASICALLY COVERING THE AREA E OF 70W. MOST OF THIS
MOISTURE IS IN THE FORM OF MID-HIGH LEVEL CLOUDINESS...THOUGH AN
AREA OF SCATTERED SHOWERS AND TSTMS HAVE FORMED OVER THE PAST
FEW HOURS FROM 13N-16N BETWEEN 62W-68W. THE WRN CARIB...MAINLY W
OF THE TROPICAL WAVE...IS EXPERIENCING SIMILAR WEATHER THOUGH
MOST OF THE SHOWERS AND TSTMS ARE NOW INLAND OVER PORTIONS OF
CENTRAL AMERICA. THE ATMOSPHERE IS SLIGHTLY DRIER IN THE CENTRAL
CARIB...BETWEEN 70W-76W...UNDERNEATH THE UPPER LOW. TRADE WINDS
ARE MAINLY MODERATE AND ARE EXPECTED TO REMAIN THAT WAY OVER THE
NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...
A STALLED FRONTAL BOUNDARY ENTERS THE REGION NEAR 32N58W AND
EXTENDS SW TOWARD THE CENTRAL BAHAMAS WHERE IT IS BEGINNING TO
DISSIPATE. SCATTERED SHOWERS AND ISOLATED TSTMS ARE GENERALLY
WITHIN 75 NM OF THE BOUNDARY. DIFFLUENT FLOW ALOFT BETWEEN
TROUGHING OFF THE U.S. EAST COAST AND AN UPPER HIGH NEAR 24N53W
IS ALSO SUPPORTING THIS ACTIVITY. WIDESPREAD STRONG SUBSIDENCE
DOMINATES ALONG AND TO THE W OF THE TROUGH OVER FLORIDA...THE NW
BAHAMAS AND THE NEARBY ATLANTIC WATERS LIMITING SIGNIFICANT
SHOWER ACTIVITY. THE TIGHTENED PRES GRADIENT BETWEEN THE
FRONT...LOW PRES IN THE CARIB AND HIGH PRES OVER THE
MID-ATLANTIC STATES IS PRODUCING MODERATE TO FRESH NE-E WINDS
ACROSS PORTIONS OF THE SW NORTH ATLC. THESE WINDS ARE EXPECTED
TO DECREASE SLIGHTLY OVER THE NEXT DAY OR TWO.

CONDITIONS ARE FAIRLY TRANQUIL ACROSS MUCH OF THE REMAINDER OF
THE CENTRAL AND E ATLC. THE SFC PATTERN IS MOSTLY CONTROLLED BY
RIDGING EXTENDING S/SW FROM A 1022 MB HIGH SITUATED OVER THE
AZORES NEAR 38N25W. THIS IS PRODUCING MAINLY LIGHT WINDS OVER
THE SUBTROPICAL E AND CENTRAL ATLC...WHILE MODERATE TRADES
PERSIST IN THE TROPICS. THE UPPER PATTERN OVER THE E ATLC
CONSISTS OF A LARGE SCALE HIGHLY AMPLIFIED UPPER RIDGE/TROUGH
PATTERN. A SWLY JET BRANCH ORIGINATES JUST AHEAD OF THE BASE OF
THE TROUGH OVER THE TROPICAL ATLC AND EXTENDS NE TO AFRICA NEAR
23N16W. THIS JET IS SHEARING THE TROPICAL WAVE ALONG 31W AND
SPREADING HIGH LEVEL CLOUDINESS ACROSS THE TROPICAL E ATLC.

$$
CANGIALOSI




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