[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191805
TWDAT

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

...SPECIAL FEATURE...
A WEAK 1010 MB SURFACE LOW PRESSURE AREA ALONG THE COAST OF
FLORIDA NEAR 27N80W AND AN UPPER LEVEL LOW IN THE EASTERN GULF
NEAR 26N83W 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 NOT WELL
DEFINED AT THE MOMENT...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 CAROLINAS THROUGH NORTH FLORIDA.

...TROPICAL WAVES...
A LOW AMPLITUDE TROPICAL WAVE IS OVER THE E ATLC ALONG 29W/30W 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 AXIS.

TROPICAL WAVE IS ALONG 54W/55W S OF 20N 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. SCATTERED SHOWERS ARE WITHIN
180NM E/60NM W OF THE AXIS N OF 16N WITH WLY SHEAR OVER THE
AREA. MINIMAL SHOWER ACTIVITY IS NOTED FURTHER S.

TROPICAL WAVE IS ALONG 86W 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 6N35W 8N52W 7N62W.
SCATTERED MODERATE CONVECTION IS NEAR THE COAST OF W AFRICA
MOVING W WITHIN 240 NM S/180 NM N OF THE AXIS. THIS ACTIVITY MAY
BE ASSOCIATED WITH THE NEXT TROPICAL WAVE BASED ON RECENT
SOUNDING DATA UPSTREAM. SCATTERED MODERATE CONVECTION IS FROM
3N-9N BETWEEN 32W-39W. SIMILAR ACTIVITY IS WITHIN 250NM N OF THE
AXIS BETWEEN 46W-52W.

DISCUSSION...

GULF OF MEXICO...
A WELL DEFINED UPPER-LEVEL LOW IS OVER THE ERN GULF NEAR 26N83W.
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
WRN CUBA AND NE INTO S FLORIDA. HOWEVER...SCATTERED SHOWERS AND
ISOLATED TSTMS ASSOCIATED WITH THE SYSTEM ARE NOW AFFECTING THE
ERN GULF FROM 24N-29N E OF 86W. A 1010 MB SFC LOW NEAR THE COAST
OF S FLORIDA IS INTERACTING WITH THE UPPER LOW. THE SFC 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 AN UPPER LOW CONTINUES TO MOVE SLOWLY OVER MEXICO
NEAR 22N101W. UPPER DIFFLUENCE BETWEEN THESE FEATURES IS HELPING
SUPPORT SCATTERED SHOWERS/ISOLATED TSTMS S OF 24N W OF 95W TO
THE COAST OF MEXICO. ANOTHER SIMILAR AREA OF SHOWERS IS OVER THE
CENTRAL GULF WATERS FROM 23N-27N BETWEEN 88W-92W. WEAK SFC
TROUGHING IS ALSO AFFECTING THESE AREAS GIVING FURTHER SUPPORT.
ELSEWHERE AT THE SFC RIDGING DOMINATES N OF 26N FROM THE LARGE
FALL-LIKE ANTICYCLONE CENTERED OVER NEW ENGLAND. 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 MOST ACTIVE WEATHER IN THE CARIBBEAN THIS AFTERNOON IS IN
THE SW PORTION OFF THE COAST OF COLOMBIA AND PANAMA. SCATTERED
MODERATE CONVECTION IS GENERALLY S OF 12N. THIS IS ASSOCIATED
WITH THE ITCZ AND DIFFLUENCE ALOFT. OTHERWISE...SHOWER ACTIVITY
IS LIMITED AND ISOLATED AT BEST. EXTENSIVE WLY FLOW ALOFT IS
OVER THE MAJORITY OF CARIBBEAN TODAY WHICH IS STRETCHING THE
HIGH CLOUDS OVER THE LIMITED SHOWER ACTIVITY TO THE E. THE SFC
PRES GRADIENT REMAINS FAIRLY RELAXED S OF THE PAIR OF WEAK LOWS
IN THE WRN ATLC. THIS IS KEEPING TRADES MOSTLY LIGHT IN THE 5-15
KT RANGE AGAIN TODAY...EXCEPT SLIGHTLY STRONGER NEAR THE COAST
OF COLOMBIA. SIMILAR CONDITIONS EXPECTED OVER THE NEXT DAY OR
SO.

ATLANTIC OCEAN...
MESSY WEATHER CONTINUES OVER THE WRN ATLC ASSOCIATED WITH THE
SPECIAL FEATURE...SEE ABOVE. THE MOST CONCENTRATED SHOWER AND
TSTM ACTIVITY IS N OF 22N BETWEEN 72W-79W...WHICH IS IN A REGION
OF PRONOUNCED UPPER DIFFLUENCE BETWEEN THE UPPER LOW OVER THE
ERN GULF AND THE UPPER HIGH NEAR 29N69W. THE NEXT WEATHER
PRODUCER IS THE REMNANTS OF INGRID...ANALYZED AS A 1012 MB LOW
NEAR 22N64W. 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
TSTMS FROM 19N-24N BETWEEN 59W-64W. A WEAK 1017 MB SFC LOW IS
NEAR 31N50W THAT HAS A TRAILING TROUGH EXTENDING SW TO NEAR
25N59W. SCATTERED SHOWER ACTIVITY IS WITHIN 150 NM E OF THE
TROUGH...WHICH IS ALSO BEING SUPPORTED BY ANOTHER UPPER LOW NEAR
32N52W. AN UPPER RIDGE EXTENDS N THROUGH THE CENTRAL ATLC ALONG
44W...WITH AN UPPER TROUGH ALONG 30W N OF 20N. UPPER RIDGING
DOMINATES THE REMAINDER OF THE E ATLC FROM ITS ORIGIN OVER W
AFRICA.  THESE FEATURES CONTINUE TO PRODUCE AN ABUNDANCE OF WLY
FLOW ALOFT N OF 16N E OF 55W. THE E ATLC SFC PATTERN CONTINUES
TO BE DOMINATED BY RIDGING S OF A 1032 MB HIGH N OF THE AZORES
NEAR 42N25W. THIS IS PRODUCING MODERATE NE TRADES E OF
35W...EXCEPT SLIGHTLY STRONG NEAR THE COAST OF NW AFRICA WHERE
THE USUAL STRONGER GRADIENT EXISTS.

$$
WILLIS


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