000
AXPZ20 KNHC 131613 CCA
TWDEP 

TROPICAL WEATHER DISCUSSION...CORRECTED 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN APR 13 2008  

...CORRECTED FOR SPELLING...

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...

ITCZ AXIS ALONG 7N77W 6.5N100W 6N110W 4N130W 4N140W. SCATTERED 
MODERATE WITHIN 60 NM S OF AXIS BETWEEN 77W AND 79W. SCATTERED 
MODERATE ISOLATED STRONG WITHIN 300 NM S AND 60 N OF AXIS 
BETWEEN 82W AND 100W. SCATTERED MODERATE WITHIN 300 NM S OF AXIS 
BETWEEN 104W AND 112W. SCATTERED MODERATE WITHIN 150 NM S OF 
AXIS BETWEEN 113W AND 118W. SCATTERED MODERATE WITHIN 90 NM N OF 
AXIS BETWEEN 135W AND 140W.

SCATTERED MODERATE CONVECTION IS SURGING OUT OF THE GULF OF 
TEHUANTEPEC AND WEAKENING CONSIDERABLY. THE CONVECTION LIES IN 
THE AREA FROM 10N TO 14N BETWEEN 93W AND 100W.

...DISCUSSION...

W OF 110W...
A PROGRESSIVE MID-LATITUDE SHORTWAVE EXTENDING FROM THE SOUTHERN 
GULF OF ALASKA TO 39N141W AND THEN TO 33N157W IS BEING BLOCKED 
FROM DIGGING FARTHER SOUTH OVER THE EASTERN PACIFIC BY A NEARLY 
STATIONARY MID- TO UPPER-LEVEL RIDGE CENTERED NEAR 28N132W. THE 
SHORTWAVE WAS CARRYING A WEAK COLD FRONT FROM THE CENTRAL N 
PACIFIC INTO THE FAR NW WATERS...BUT THIS FEATURE IS LOSING ITS 
IDENTITY AS A 1046 MB SURFACE RIDGE BUILDS WELL N OF HAWAII. AS 
THE RIDGE SLIDES E THE NEXT FEW DAYS...AN INCREASING PRESSURE 
GRADIENT OVER THE FAR NW WILL ULTIMATELY SPILL FARTHER SE INTO 
THE LOWER LATITUDES...WHICH SHOULD RESULT IN INCREASING TRADES. 
AT THEIR HIGHEST...NE WINDS OF 20 TO 25 KT SHOULD BE CONFINED NW 
OF A LINE FROM 30N130W TO ABOUT 20N140W...WITH SEAS BUILDING TO 
8 TO 13 FT IN NW SWELL. THE SWELL SHOULD PROPAGATE AS FAR S AS 
19N BETWEEN 130W AND 140W AND AS FAR E AS 125W N OF 24N BY TUE.

AS THE SAME SHORTWAVE REACHES THE W COAST AND DIGS INTO THE FAR 
W EARLY THIS WEEK...A BROAD CYCLONIC LOW-LEVEL FLOW WITH WINDS 
TO GALE FORCE ARE FORECAST OFFSHORE THE CA COAST. THESE WINDS 
SHOULD EXPAND INTO THE REGION N OF 25N AND E OF 125W WITHIN 
ABOUT 48 HOURS...WITH SEAS BUILDING TO 8 TO 12 FT IN NW SWELL.

E OF 110W...
A BROAD AND FAIRLY DEEP TROUGH COMING OUT OF THE CENTRAL U.S. 
HAS DRIVEN A WELL-DEFINED COLD FRONT WELL SOUTH INTO THE GULF OF 
MEXICO AND RECENTLY THROUGH THE GULF OF TEHUANTEPEC.  STRONG 
PRESSURE RISES AND A TIGHTENING PRESSURE GRADIENT ASSOCIATED 
WITH A 1033 MB RIDGE BUILDING SOUTH-WARD W OF THE FRONT HAS LED 
TO NEAR GALE FORCE WINDS IN THE SW GULF THIS MORNING...WITH 
INCREASING WINDS NOW NOTED IN THE GULF OF TEHUANTEPEC.  IN 
FACT...A FORTUITOUSLY-TIMED QUIKSCAT PASS AT 1156 UTC REVEALS A 
NARROW SWATH OF N TO NE WINDS OF 20 TO 30 KT WITHIN 30 NM EITHER 
SIDE OF LINE FROM 16.5N94.5W TO 14.5N95W. IN ADDITION...THE SAME 
QUIKSCAT PASS SHOWS SCATTERED STRONG WINDS IN THE WAKE OF 
DISORGANIZED COMPLEX OF TSTMS SURGING OUT OF THE GULF OF 
TEHUANTEPEC. SEVERAL NON-FLAGGED DATA SUGGESTED NE WINDS OF UP 
TO 25 KT...BUT LOCALLY STRONGER WINDS SEEM POSSIBLE ALONG THE 
LEADING EDGE OF THE CONVECTIVE LINE.

MODEL GUIDANCE INDICATES THAT GAP WINDS IN THE GULF OF 
TEHUANTEPEC SHOULD CONTINUE MATURING AND SPREADING SW TODAY 
...WITH GALE CONDITIONS DEVELOPING BY TONIGHT AND PEAK 
CONDITIONS EXPECTED LATE MON INTO EARLY TUE. A FAIRLY CONSTANT 
FETCH AND MORE THAN 24 HOURS OF GALE FORCE WINDS SHOULD SUPPORT 
SEAS BUILDING TO 10 TO 15 FT BY MON NIGHT...AS THE GAP WIND 
EVENT LEAVES A FOOTPRINT AS FAR SW AS 12N98W. SST ANALYSES SHOW 
WATERS AS WARM AS 29C IN THE GULF OF TEHUANTEPEC...WHICH COULD 
INCREASE THE ATMOSPHERIC INSTABILITY DURING THIS EVENT AND HELP 
TRANSFER HIGH WINDS JUST ABOVE THE SURFACE TO THE OCEAN. BY 
EARLY WED...WINDS SHOULD GRADUALLY DROP BELOW GALE FORCE...AND 
SEAS SHOULD BEGIN TO SUBSIDE BY THU. A RECENT QUIKSCAT PASS ALSO 
INDICATES NE TO E WINDS OF 20 TO 25 KT IN AND NEAR THE GULF OF 
PAPAGAYO ...BUT MODELS SUGGEST THAT THESE WINDS SHOULD ABATE 
LATER TODAY OR TONIGHT. HOWEVER...A SIGNIFICANT INCREASE IN 
WINDS SHOULD OCCUR TUE AS HIGH PRESSURE BEHIND THE SAME COLD 
FRONT BUILDS INTO THE WESTERN CARIBBEAN...EXCITING GULF OF 
PAPAGAYO GAP WINDS. 

ELSEWHERE...SATELLITE IMAGERY AND QUIKSCAT DATA REVEAL AN 
ELONGATED AREA OF LOW PRESSURE ALONG THE ITCZ NEAR 6.5N91.8W 
...DRIFTING SW TO W. ALTHOUGH POORLY-ORGANIZED...THERE IS SOME 
CONTINUITY WITH THIS FEATURE...AS MICROWAVE DATA AND SATELLITE 
IMAGERY HAVE INDICATED ITS PRESENCE NOW FOR AT LEAST 36 HOURS. 
THE ORIGINS OF THIS SYSTEM ARE NOT APPARENT...THOUGH IT MAY BE 
ONE OF THE SEASONS FIRST AFRICAN EASTERLY WAVES EMERGING INTO 
THE EAST PACIFIC OR MAY HAVE FORMED IN SITU AS A RESULT OF 
PREVIOUS CONVECTIVE ACTIVITY.  NONETHELESS...A DIFFLUENT FLOW 
ALOFT RELATED TO A MID- TO UPPER-LEVEL RIDGE CENTERED OVER 
PANAMA AND COSTA RICA IS ENCOURAGING THE DEVELOPMENT OF 
ADDITIONAL CONVECTIVE NEAR AND S OF THE WEAK SURFACE LOW...WITH 
THE MOST CONCENTRATED WITHIN 300 NM OF THE SOUTH SEMICIRCLE.  

$$
KIMBERLAIN