[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192242
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2215 UTC.

...SPECIAL FEATURE...
A WEAK 1008 MB SURFACE LOW PRESSURE AREA ALONG THE COAST OF
FLORIDA NEAR 28N80W AND AN UPPER LEVEL LOW IN THE EASTERN GULF
NEAR 27N84W ARE PRODUCING A LARGE AREA OF DISTURBED WEATHER OVER
THE WESTERN ATLANTIC...THE CENTRAL AND NORTHWESTERN
BAHAMAS...PORTIONS OF THE FLORIDA PENINSULA...AND THE EASTERN
GULF MEXICO. THIS SYSTEM WILL LIKELY BRING SHOWERS...SQUALLS...
AND LOCALLY HEAVY RAINS OVER PORTIONS OF FLORIDA DURING THE NEXT
DAY OR TWO. THE SURFACE LOW IS A LITTLE BETTER DEFINED AT THE
MOMENT AS SEEN ON RADAR...BUT IS EXPECTED TO MOVE INTO OR
REDEVELOP OVER THE EASTERN GULF OF MEXICO DURING THE NEXT DAY OR
SO...WHERE A SUBTROPICAL OR TROPICAL CYCLONE COULD FORM. THE
SURFACE WINDS IN THE IMMEDIATE VICINITY OF THE LOW ARE NOT VERY
STRONG...MOSTLY 15 KT OR LESS. STRONGER WINDS ARE DISPLACED
FURTHER N OF THE LOW WHERE THE INTERACTION BETWEEN THE LOW
ITSELF...STRONG CONTINENTAL HIGH PRESSURE CENTERED OVER NEW
ENGLAND...AND A SLOW MOVING COASTAL WARM FRONT ARE PRODUCING
20-25 KT NE TO E WINDS OFF THE COAST OF SOUTH CAROLINA AND
GEORGIA.

...TROPICAL WAVES...
A LOW AMPLITUDE TROPICAL WAVE IS OVER THE E ATLC ALONG 30W/31W S
OF 15N MOVING W 10-15 KT. THIS WAVE STILL SHOWS UP WELL IN LOW
LEVEL SATELLITE DERIVED WINDS AND VORTICITY...AND THE UW CIMSS
TPW PRODUCTS. HOWEVER...THE WAVE REMAINS DISORGANIZED WITH
LIMITED SHOWER ACTIVITY...WHICH IS GENERALLY ISOLATED WITHIN 210
NM OF THE ITCZ AXIS.

TROPICAL WAVE IS ALONG 55W/56W S OF 21N MOVING W NEAR 15 KT.
THIS WAVE ALSO IS NOT VERY WELL ORGANIZED. SOME OF THE
ENERGY/MOISTURE ASSOCIATED WITH THE NRN PORTION OF THE WAVE
APPEARS TO BE ROUNDING THE E ATLC RIDGE AND MOVING TOWARDS THE
FRONTAL TROUGH IN THE CENTRAL ATLC. CLUSTERS OF SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 150/180 NM OF LINE FROM 17N54W
TO 25N48W. MINIMAL SHOWER ACTIVITY IS NOTED FURTHER S.

TROPICAL WAVE IS ALONG 87W S OF 21W MOVING W 10-15 KT. SHOWER
ACTIVITY REMAINS LIMITED IN ASSOCIATION WITH THIS WAVE. STRONG
UPPER WLY FLOW IS OVER THIS PORTION OF THE CARIBBEAN BETWEEN THE
STRONG UPPER LOW IN THE ERN GULF AND RIDGING OVER CENTRAL
AMERICA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N16W 11N26W 7N32W 5N41W 10N55W
7N63W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION ARE FROM 6N-13N BETWEEN 15W-30W AND FROM 2N-11N
BETWEEN 30W-41W.

DISCUSSION...

GULF OF MEXICO...
A WELL DEFINED UPPER-LEVEL LOW IS OVER THE ERN GULF NEAR 27N84W.
A SWATH OF VERY DRY MID TO UPPER AIR CONTINUES TO WRAP AROUND
THE PERIPHERY OF THIS FEATURE THROUGH THE MIDDLE GULF THEN SE TO
FAR WRN CUBA AND NE ACROSS THE FLORIDA PENINSULA.
HOWEVER...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
ASSOCIATED WITH THE SYSTEM ARE NOW AFFECTING THE ERN GULF FROM
24N-28N E OF 87W. A 1008 MB SURFACE LOW NEAR THE COAST OF E
FLORIDA IS INTERACTING WITH THE UPPER LOW. THE SURFACE LOW IS
EXPECTED TO MOVE INTO OR REDEVELOP OVER THE ERN GULF OVER THE
NEXT DAY OR SO...SEE SPECIAL FEATURE SECTION ABOVE FOR MORE
DETAILS. UPPER RIDGING DOMINATES THE FAR NW AND SW PORTIONS OF
THE GULF WHILE ANOTHER UPPER LOW CONTINUES TO MOVE SLOWLY W
ACROSS MEXICO. UPPER DIFFLUENCE BETWEEN THESE FEATURES IS
HELPING SUPPORT SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF
28N W OF 94W TO THE COAST OF TEXAS AND MEXICO. ELSEWHERE AT THE
SURFACE RIDGING DOMINATES N OF 25N FROM THE LARGE FALL-LIKE
SURFACE HIGH EXTENDING FROM NEW ENGLAND JUST TO THE W OF THE
APPALACHIAN MOUNTAINS. THIS IS PRODUCING MODERATE NE TO E WINDS
OVER THE N GULF...WHILE LIGHTER MORE VARIABLE WINDS PERSIST
FURTHER S AROUND TROUGHING.

CARIBBEAN SEA...
THE ITCZ AXIS EXTENDS ACROSS N PORTION OF SOUTH AMERICA...
PANAMA...AND COSTA RICA GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 13N TO INLAND OVER SOUTH AND CENTRAL AMERICA.
OTHERWISE...AFTERNOON THUNDERSTORMS HAVE BEEN GENERATED OVER THE
ISLANDS OF THE GREATER ANTILLES AND JAMAICA COUPLED WITH THE
EXTENSIVE WLY FLOW ALOFT IS PUSHING THE STORM TOPS TO THE E. THE
SURFACE PRES GRADIENT REMAINS FAIRLY RELAXED ACROSS THE AREA.
THIS IS KEEPING TRADES MOSTLY LIGHT AGAIN TODAY...EXCEPT
SLIGHTLY STRONGER NEAR THE COAST OF COLOMBIA. SIMILAR CONDITIONS
EXPECTED OVER THE NEXT DAY OR SO.

ATLANTIC OCEAN...
SHOWERS AND THUNDERSTORM ACTIVITY CONTINUES OVER THE WRN ATLC
ASSOCIATED WITH THE SPECIAL FEATURE...SEE ABOVE. THE MOST
CONCENTRATED SHOWER AND THUNDERSTORM ACTIVITY IS N OF THE BAHAMA
ISLANDS TO BEYOND 32N BETWEEN 70W-78W...WHICH IS IN A REGION OF
PRONOUNCED UPPER DIFFLUENCE BETWEEN THE UPPER LOW OVER THE ERN
GULF AND THE UPPER HIGH NEAR 26N73W. THE NEXT WEATHER PRODUCER
IS THE REMNANTS OF INGRID...ANALYZED AS A 1012 MB LOW NEAR
22N65W WITH A WEAK SURFACE TROUGH EXTENDING FROM 26N63W TO
20N65W. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR REDEVELOPMENT OF
THIS SYSTEM. THIS ALONG WITH AN UPPER LOW NEAR 24N66W ARE
PRODUCING DISORGANIZED SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
FROM 17N-22N BETWEEN 60W-64W. A WEAK 1016 MB SURFACE LOW IS NEAR
30N50W THAT HAS A TRAILING TROUGH EXTENDING SW TO NEAR 25N58W.
SCATTERED SHOWER ACTIVITY IS TO THE E OF THE SURFACE TROUGH
WITHIN 120 NM OF LINE FROM 26N47W TO 31N45W. E OF THE
TROUGH...WHICH IS ALSO BEING SUPPORTED BY ANOTHER UPPER LOW NEAR
32N51W. AN UPPER RIDGE EXTENDS N THROUGH THE CENTRAL ATLC ALONG
45W...WITH AN UPPER TROUGH EXTENDING FROM AN UPPER LOW ALONG THE
COAST OF PORTUGAL TO A SECOND NEAR 31N24W TO NEAR 25N30W. UPPER
RIDGING DOMINATES THE REMAINDER OF THE E ATLC FROM ITS ORIGIN
OVER W AFRICA. THE E ATLC SURFACE PATTERN CONTINUES TO BE
DOMINATED BY RIDGING S OF A 1031 MB HIGH N OF THE AZORES THROUGH
32N33W TO 18N43W. THIS IS PRODUCING MODERATE NE TRADES E OF
35W...EXCEPT SLIGHTLY STRONG NEAR THE COAST OF NW AFRICA WHERE
THE USUAL STRONGER GRADIENT EXISTS.

$$
WALLACE


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