[Tropical] Tropical Weather Discussion

Tue Apr 8 18:51:10 CDT 2008

AXNT20 KNHC 082348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE APR 08 2008

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
2345 UTC.

...ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 04N08W 3N19W CROSSING THE
EQUATOR AT 29N THEN TO NE COAST OF BRAZIL NEAR 3N39W. SCATTERED
MODERATE CONVECTION IS WITHIN 300 NM N OF AXIS BETWEEN 20W AND
31W.

...DISCUSSION...
GULF OF MEXICO...
A POSITIVELY-TITLED SHORTWAVE TROUGH EXTENDING FROM EAST CENTRAL
FLORIDA TO THE GULF OF HONDURAS CONTINUES TO GRADUALLY EXIT THE
EASTERN GULF THIS EVENING...LEAVING BEHIND WEAK SHORTWAVE
RIDGING ALOFT FROM THE NE TO THE SW GULF. AN ASSOCIATED
STATIONARY FRONT LIES ACROSS THE FLORIDA STRAITS THROUGH THE
EXTREME SOUTHEASTERN GULF OF MEXICO...THOUGH THE BOUNDARY IS NOT
PARTICULARLY WELL-DEFINED. WATER VAPOR INDICATES AN EMBEDDED
CYCLONIC CIRCULATION ALONG THE SHORTWAVE TROUGH OVER THE FLORIDA
STRAITS APPROACHING THE CENTRAL KEYS...A FEATURE WHICH MOST OF
THE SHORT-TERM GUIDANCE INITIALIZES.  A PATTERN OF WEAK
UPPER-LEVEL DIVERGENCE AND LIFT AHEAD OF THE CIRCULATION HAS
SPARKED A ROUND OF LATE AFTERNOON CONVECTION OVER THE FLORIDA
STRAITS...WHILE OVERRUNNING RAINS ARE OCCURRING N OF THE
BOUNDARY OVER S FLORIDA AND PARTS OF THE KEYS.  W OF THE TROUGH
AXIS...WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE
OVERTAKING NEARLY ALL THE GULF...WITH THE STRONGEST DRYING NOTED
IN THE STRONGEST UPPER-LEVEL CONVERGENCE JUST W OF THE BASE OF
THE TROUGH IN THE VICINITY OF THE YUCATAN.  OTHERWISE...WEAK
SURFACE RIDGING BULGES SOUTHWESTWARD FROM N FLORIDA INTO THE SW
GULF...KEEPING A GENERALLY LIGHT E TO SE WIND FLOW ACROSS THE
REGION AND 2 TO 5 FT SEAS.

MODELS SHOW A BROAD MID- TO UPPER-LEVEL RIDGE BUBBLING
NORTHEASTWARD FROM SOUTHERN MEXICO THE NEXT FEW DAYS...IN
RESPONSE TO A PARTICULARLY STRONG DISTURBANCE ROLLS INTO THE FAR
WEST. AS THIS OCCURS...BROAD SURFACE LOW PRESSURE IS FORECAST TO
FORM ACROSS THE SOUTHERN PLAINS...WHICH SHOULD RESULT IN A
HEALTHY RETURN FLOW AND SEAS BUILDING TO 5 TO 8 FT OVER THE
WESTERN HALF OF THE GULF JUST BEYOND MID-WEEK.  WITH SURFACE
HIGH PRESSURE STILL NOSING INTO THE EASTERN GULF...LIGHT WINDS
AND SEAS OF 2 TO 4 FT SHOULD CONTINUE TO PREVAIL.  OTHERWISE
...BROAD MID- TO UPPER-LEVEL RIDGING ACROSS THE REGION SHOULD
KEEP A TRANQUIL WEATHER PATTERN ACROSS THE AREA THROUGH LATE
WEEK.

CARIBBEAN SEA...
THE MID- TO UPPER-LEVEL SHORTWAVE EXITING THE GULF EXTENDS FROM
FLORIDA THROUGH THE GULF OF HONDURAS AND SW TO AROUND 10N88W...
WHILE WEAK MID- TO UPPER-LEVEL RIDGING LIES FARTHER E OVER THE
EASTERN AND CENTRAL PART OF THE BASIN. RECENT WATER VAPOR
IMAGERY AND CLOUD-TRACKED WINDS REVEAL A WEAK CYCLONIC
CIRCULATION IN THE BASE OF THE TROUGH JUST W OF COSTA RICA. A
DIFFLUENT UPPER-LEVEL FLOW...DAYTIME HEATING...AND SURFACE LOW
PRESSURE AND CONVERGENCE E OF THIS FEATURE HAS LED TO SCATTERED
TO LOCALLY NUMEROUS TSTMS OVER COSTA RICA... PANAMA ...AND NW
COLOMBIA.  A PLUME OF MOISTURE STREAKING NE FROM THE CONVECTION
CONTINUES INTO THE CENTRAL AND EASTERN CARIBBEAN TO NEAR
65W...WHISKED EASTWARD BY A WEAK WESTERLY FLOW ALOFT.  LATE
AFTERNOON CONVECTION WAS ALSO NOTED OVER MOST OF CUBA...ENHANCED
BY THE SHORTWAVE TROUGH AND EMBEDDED CYCLONIC CIRCULATION MOVING
THROUGH THE AREA...NOT TO MENTION LOCAL SEA BREEZE CIRCULATIONS.

OTHERWISE...WEAK SURFACE RIDGING NE OF THE AREA HAS AN EXTENSION
INTO THE CARIBBEAN SEA...WHICH IS KEEPING TRADES AT OR JUST
BELOW CLIMATOLOGICAL LEVELS. SEAS RANGE FROM 4 TO 7 FT OVER MOST
OF THE REGION...EXCEPT 1 TO 3 FT NEAR THE CUBAN COAST AND 6 TO 9
FT NW OF THE COLOMBIA COAST.

AS THE SHORTWAVE TROUGH CURRENTLY MOVING INTO THE SW ATLANTIC
DIGS INTO THE NORTHERN CARIBBEAN THE NEXT FEW DAYS...EXPECT THE
SURFACE RIDGE NE OF THE AREA TO WEAKEN FURTHER ALONG WITH THE
TRADES.  A DIFFLUENT UPPER-LEVEL FLOW MAINLY N OF 15N AND E OF
HISPANIOLA COULD RESULT IN A NOMINAL INCREASE IN RAIN CHANCES
ACROSS THESE AREAS...PARTICULARLY AROUND PEAK HEATING.

ATLANTIC OCEAN...
THE SHORTWAVE TROUGH DEPARTING THE EASTERN GULF THIS EVENING
EXTENDS FROM 31N77W THROUGH THE E CENTRAL FLORIDA COAST AND INTO
THE FLORIDA STRAITS. AN ASSOCIATED...WEAK FRONTAL BOUNDARY LIES
FROM 31N72W TO A 1013 MB SURFACE WAVE NEAR 29N75W...WITH THE
FRONT CONTINUING SW ACROSS THE WESTERN BAHAMAS AND ULTIMATELY
INTO THE STRAITS OF FLORIDA. LATE AFTERNOON VISIBLE IMAGERY
REVEALS A BROAD CYCLONIC ENVELOPE NEAR THE MAIN SURFACE WAVE
ALONG THE FRONT...WITH SEVERAL DISTINCT LOW-LEVEL SWIRLS
ATTEMPTING TO ROTATE AROUND EACH OTHER.  WITH FEW SURFACE
OBSERVATIONS ACROSS THIS REGION AND NO RECENT MICROWAVE
PASSES...DETERMINING THE EXACT FRONTAL LOCATION HAS PROVEN
RATHER DIFFICULT.  FARTHER W...WATER VAPOR IMAGERY REVEALS A
COMMA HEAD OF HIGHER MOISTURE CROSSING THE FLORIDA STRAITS LATE
THIS AFTERNOON...WHICH SEEMS TO BE A DISTINCT AND TIGHT MID- TO
UPPER-LEVEL CIRCULATION NEAR 24.5N80W...MOVING NE AT 10 TO 15
KT. AS NOTED PREVIOUSLY...UPPER-LEVEL DIVERGENCE AND LIFT AHEAD
OF THIS FEATURE HAS RESULTED IN SPOTTY CONVECTION FROM THE
FLORIDA STRAITS...WHICH IS NOW BEGINNING TO MOVE INTO THE SW
BAHAMAS.  N OF THE BOUNDARY IN THE COLD SECTOR...OVERRUNNING
LATE AFTERNOON RAINS HAVE DEVELOPED ACROSS THE SOUTHERN FLORIDA
PENINSULA AND ARE SPREADING NE INTO THE E FL COASTAL WATERS.
FINALLY...W OF THE BOUNDARY...WEAK SURFACE RIDGING ALONG THE SE
U.S. COAST EXTENDS INTO THE FLORIDA PENINSULA...WHICH HAS HELPED
KEEP NE 15 TO 20 KT WINDS AND 7 TO 10 FT SEAS ACTIVE FROM N OF
THE BAHAMAS TO THE NE FLORIDA COAST.

AS MID- TO UPPER-LEVEL RIDGING BUILDS ACROSS THE GULF THE NEXT
FEW DAYS...MODELS DIG THE SHORTWAVE CURRENTLY ACROSS FLORIDA AND
THE SW ATLANTIC DOWN THE E SIDE OF THE RIDGE INTO THE WESTERN
ATLANTIC AND THE NORTHERN CARIBBEAN. THIS SHOULD HELP DRIVE THE
STATIONARY FRONT SE OF FLORIDA DEEPER INTO THE WESTERN ATLANTIC
...WHILE WEAK LOW PRESSURE MOVES NE ALONG THE FRONT TO NEAR
29N56W BY EARLY FRI.  WHILE SCATTERED SHOWERS AND TSTMS ERUPT
ALONG THE BOUNDARY...ESPECIALLY NEAR THE MAIN SURFACE
WAVE...HIGH PRESSURE SHOULD CONTINUE BUILDING SW BEHIND THE
BOUNDARY...MAINTAINING LIGHT NE TO E WINDS ACROSS THE SW
ATLANTIC.

ELSEWHERE...A BROAD CYCLONIC CIRCULATION AT MID- AND UPPER-
LEVELS DOMINATES THE AREA N OF 15N AND E OF 60W....WITH THE TAIL
OF AN ASSOCIATED COLD FRONT STILL TO 22N39W. THIS PATTERN HAS
RESULTED IN A DISTINCT BREAK IN THE ATLANTIC SUBTROPICAL RIDGE
...WITH THE RESULT BEING WEAKER-THAN-NORMAL TRADES ACROSS THE
TROPICAL AND SUBTROPICAL ATLANTIC. IN FACT...LATEST REAL-TIME
NCEP RE-ANALYSIS DATA SUGGESTS WESTERLY WIND ANOMALIES OF 5 TO
10 KT S OF 20N AND E OF 60W...WITH MUCH LARGER ANOMALIES OF 15
TO 30 KT N OF 20N W OF 60W. NO IMPORTANT CHANGES TO THIS PATTERN
ARE EXPECTED THE NEXT FEW DAYS.

FINALLY...A NARROW MID- TO UPPER-LEVEL RIDGE LIES S OF 12N OVER
THE TROPICAL ATLANTIC WITH A RIDGE AXIS GENERALLY ALONG 8N.
DEEP EASTERLIES ARE PRESENT S OF THE AXIS...WITH REAL-TIME NCEP
RE-ANALYSIS DATA INDICATING EASTERLY WIND ANOMALIES OF UP TO 20
KT.  OTHERWISE...SPORADIC BUT ENHANCED CONVECTION CONTINUES FROM
THE GULF OF GUINEA TO EITHER SIDE OF THE EQUATOR AS FAR W AS
30W. SATELLITE IMAGERY REVEALS A WELL-DEFINED MID-LEVEL CYCLONIC
CIRCULATION EMBEDDED WITHIN THE DYING CONVECTION CENTERED CLOSE
TO 5N21W...WITH ANOTHER ONE CLOSE TO 9N35W.  THOUGH ENHANCED...
THE CONVECTION IS SUBSTANTIALLY LESS THAN WHAT WAS OCCURRING
LATE LAST WEEK INTO THIS PAST WEEKEND...WHEN AN ATMOSPHERIC
DISTURBANCE KNOWN AS KELVIN WAVE WAS MOVING THROUGH THE REGION.

$$
KIMBERLAIN

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