[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 141803
TWDAT

TROPICAL WEATHER DISCUSSION...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON APR 14 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N08W 2N19W EQ30W TO NE
BRAZIL NEAR 1S46W. A LARGE CLUSTER OF MODERATE TO STRONG
CONVECTION IS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 14W AND
20W. SCATTERED MODERATE ISOLATED/STRONG CONVECTION IS WITHIN 150
NM N OF AXIS AND 60 NM S OF AXIS BETWEEN 27W AND 37W.  SCATTERED
MODERATE CONVECTION LIES BETWEEN 01N AND 04 BETWEEN 42W AND 50W.

...DISCUSSION...

THE GULF OF MEXICO...
A STRONG SHORTWAVE TROUGH DIGGING INTO THE SE U.S. DROVE A COLD
FRONT THROUGH THE GULF YESTERDAY AND LAST NIGHT...BUT SURFACE
ANALYSES INDICATE A SECOND...STRONGER SURGE EXTENDING FROM NEAR
TAMPA WSW THROUGH NE MEXICO SWEEPING S AND E ACROSS THE REGION
AS OF 1500 UTC. AN 1132 UTC QUIKSCAT PASS PROVIDED SOME PROOF AS
TO THE LOCATION OF THE SECOND FRONT...GIVEN BY A BROAD CYCLONIC
SHEAR AND A MARGINAL INCREASE IN WINDS N OF THE BOUNDARY.
MOREOVER...VISIBLE SATELLITE IMAGERY SHOWS A DISTINCT ROPE-LIKE
BAND OF CLOUDS AT THE LEADING EDGE OF THE FRONT JUXTAPOSED WITH
NEARLY CLEAR SKIES OVER THE SOUTHERN GULF SAVE FOR LOW CLOUDS
BANKED UP THE HIGHER TERRAIN OF THE SIERRA MADRE ORIENTAL.
INTERESTINGLY...DESPITE THE HIGHER MID-APRIL SUN ANGLE ...COLD
AIR ADVECTION BEHIND THE FRONT IS ENOUGH TO KEEP TEMPERATURES
THE SAME OR FALLING AT THIS HOUR OF THE DAY. MOSTLY NW TO N
WINDS OF 15 TO 20 KT COVER MOST OF THE CENTRAL AND WESTERN
GULF...WITH A MINOR MINIMUM IN WINDS IMMEDIATELY N OF THE
SECONDARY BOUNDARY.  FULLY DEVELOPED SEAS OF 6 TO 10 FT ARE
COMMON OVER MOST OF THE GULF EXCEPT 4 TO 7 FT OVER THE EASTERN
GULF...WITH SEAS GRADUALLY SUBSIDING AFTER PEAKING LATE
YESTERDAY.

MODELS SHOW THE SHORTWAVE OVER THE SE U.S. CUTTING OFF OVER THE
WESTERN ATLANTIC EARLY THIS WEEK AND PERSISTING OVER THE
REGION.  THIS SHOULD KEEP THE POLAR BOUNDARY WELL S AND E OF THE
AREA... WITH HIGH PRESSURE...FAIR SKIES...AND DRY WEATHER
REIGNING ACROSS THE GULF THROUGH LATE WEEK. A NW TO N FLOW TODAY
SHOULD DECREASE AND BECOME E TO SE OVER THE CENTRAL AND WESTERN
GULF BY MID-WEEK...WHICH SHOULD LED TO AN INCREASE IN LOW-LEVEL
MOISTURE OVER THE WESTERN GULF BY WED.

THE CARIBBEAN SEA...
THE SAME VIGOROUS SHORTWAVE DIGGING INTO THE SOUTHEASTERN STATES
HAS HELPED DRAG THE FRONT WHICH SWEPT ACROSS THE GULF YESTERDAY
INTO THE NW CARIBBEAN...LYING FROM 21N78W TO 17N88W AS OF 1500
UTC.  AS THE SECONDARY FRONT DESCENDS WELL INTO THE GULF...THE
PRIMARY BOUNDARY HAS NOTICEABLY SLOWED DOWN BUT IS STILL ON THE
MOVE...ALBEIT IT BARELY. VISIBLE SATELLITE IMAGERY REVEALS
SCATTERED LOW CLOUDS LINING THIS FEATURE...FOLLOWED BY A NEARLY
SOLID AREA OF STRATUS HOVERING OVER THE YUCATAN CHANNEL...NE TIP
OF THE YUCATAN...AND THE WESTERN CUBA. SHIP REPORTS AND AN
EARLIER QUIKSCAT PASS SHOWED INCREASING N TO NE WINDS OF 15 TO
20 KT ARE N OF THE FIRST FRONT...WITH THE HIGHEST WINDS NOTED IN
THE VICINITY OF THE YUCATAN CHANNEL.

AS THE SHORTWAVE MOVING OFFSHORE THE SE U.S. DIGS INTO THE
WESTERN ATLANTIC AND CUTS OFF TUE...THE SECONDARY FRONT SHOULD
CATCH UP TO THE FIRST. THE CONSOLIDATED FRONTAL BOUNDARY SHOULD
PUSH AS FAR SE AS A WINDWARD PASSAGE-CAPE GRACIAS A DIOS
NICARAGUA LINE BY LATE TUE...WHERE IT IS FORECAST TO BECOME
STATIONARY AND THEN DISSIPATE BY FRI. A BRISK NE FLOW N OF THE
FRONT SHOULD CAUSE SEAS TO BUILD TO 5 TO 8 FT IN N SWELL...WITH
SCATTERED LOW CLOUDS ALONG THE BOUNDARY AND A FEW SHOWERS
DECREASING AS THE BOUNDARY LOSES ITS IDENTITY.

ELSEWHERE...WEAK LOW- TO MID-LEVEL HIGH PRESSURE EXTENDS FROM
THE CENTRAL ATLANTIC SW INTO THE CENTRAL CARIBBEAN AND IS
KEEPING TRADES NEAR OR BELOW CLIMATOLOGICAL AVERAGES FOR THE
TIME BEING.  THIS IS ESPECIALLY TRUE WITHIN ABOUT 400 NM SE OF
THE NW CARIBBEAN FRONT TODAY...WHERE QUIKSCAT DATA INDICATE N TO
NE WINDS OF ONLY 5 TO 10 KT EXCEPT S OF JAMAICA.  VISIBLE
SATELLITE IMAGERY AND SURFACE OBSERVATIONS ALSO SUGGEST THE
PRESENCE OF WHAT COULD BE A WEAK LOW-LEVEL TROUGH EXTENDING FROM
14N72W TO PUERTO RICO AND THE U.S. VIRGIN ISLANDS. TIME SERIES
DATA FROM SAN JUAN AND OTHER SURROUNDING SITES CORROBORATE THE
EXISTENCE OF THIS FEATURE...BUT AS WITH MOST OTHER METRICS...
THESE DATA SUGGEST A FAIRLY WEAK SIGNATURE. STILL THOUGH...
LOW-LEVEL MOISTURE E OF THE BOUNDARY HAS INCREASED AS REVEALED
IN THE MOST RECENT SAN JUAN SOUNDING...WHERE 70-90 PER CENT
RELATIVE HUMIDITY HAS GONE FROM AT OR BELOW 850MB TWO DAYS AGO
TO 700 MB TODAY.

WITH HEIGHTS COLLAPSING OVER THE NW CARIBBEAN W ATLANTIC EARLY
THIS WEEK...TRADES SHOULD CONTINUE WEAK THROUGH MIDDLE AND LATE
WEEK AND SEAS CONTINUING TO RUN FROM 4 TO 7 FT EXCEPT LOCALLY
HIGHER IMMEDIATELY OFFSHORE THE COLOMBIAN COAST.  THE WEAK
LOW-LEVEL TROUGH SHOULD CONTINUE WESTWARD AT 10 TO 15 KT AND
EVENTUALLY MERGE WITH THE STATIONARY FRONTAL BOUNDARY BY LATE
TUE.

THE ATLANTIC OCEAN...
THE SAME SHORTWAVE TROUGH DIGGING INTO THE SE U.S. TODAY IS
RESPONSIBLE FOR CARRYING A FRONTAL BOUNDARY ACROSS FL LAST NIGHT
...WITH THE FRONT EXTENDING FROM 31N69W TO EAST CENTRAL CUBA AS
OF 1500 UTC. VISIBLE SATELLITE IMAGERY CONFIRMS WHAT MODELS HAVE
BEEN FORECASTING...THAT IS...THE DEVELOPMENT OF A 1012 MB
FRONTAL WAVE LOCATED NEAR 27N74W...MOVING NE AT 15 TO 20 KT.
NOT TOO FAR BEHIND...A STRONGER SECONDARY BOUNDARY HAS MOVED
OFFSHORE THE NE FL COAST AND IS ON THE VERGE OF DESCENDING
THROUGH THE NW BAHAMAS. AS THE SE U.S. SHORTWATE CUTS OFF
TUE...EXPECT THE DEVELOPING FRONT WAVE TO SLOW DOWN...STRENGTHEN
...AND MOVE N OF THE AREA TO A POSITION OFFSHORE THE MID-
ATLANTIC COAST. AS IT DOES SO...IT SHOULD DRAG A CONSOLIDATED
COLD FRONT THROUGH THE REMAINDER OF THE BAHAMAS AND THE SW
ATLANTIC...WITH THE FRONT LYING FROM 31N66W TO CENTRAL
HISPANIOLA LATE WED. A BRISK NW FLOW BEHIND THE FRONT SHOULD
VEER MORE NE...AS LOW PRESSURE RAPIDLY GATHERS STEAM OFF THE
CAROLINA COAST AND RESULT IN SEAS BUILDING TO 9 TO 15 FT
GENERALLY N OF 27N W OF 70W IN NE SWELL.  LARGE BREAKERS SHOULD
BEGIN ARRIVING OVER THE NW BAHAMAS AS WELL AS THE NE AND EAST
CENTRAL FL COASTS LATE TUE AND WED.

OTHERWISE...AN ANOMALOUS MID- TO UPPER-LEVEL RIDGE SHOULD SET UP
SHOP N OF 17N E OF ABOUT 65W EARLY AND MID-WEEK. THIS SHOULD
FAVOR A STRONGER SUBTROPICAL RIDGE OVER THE EASTERN AND CENTRAL
ATLANTIC...WHICH SHOULD IN TURN LEAD TO A TRADE WIND FLOW CLOSER
TO CLIMATOLOGY...COMPARED TO THE WEAK TO NON-EXISTENT TRADES
FROM LAST WEEK.  ALREADY EARLY MORNING QUIKSCAT PASSES ARE
HINTING AT AN INCREASED NE FLOW BETWEEN 15N AND 20N E OF 45W...
AND THESE WINDS SHOULD EXPAND FURTHER THROUGH MID-WEEK.


$$
KIMBERLAIN


This weather bulletin was brought to you by:
www.nashvilleweather.net