000
AXPZ20 KNHC 300931
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI MAY 30 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY 
THROUGH 0915 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION ALMA IS NOW WELL INLAND OVER HONDURAS NEAR 
14.6N 87.6W AT 0900 UTC MOVING NNW 10 KT WITH AN ESTIMATED 
SURFACE PRESSURE OF 1004 MB. MAXIMUM SUSTAINED WINDS ARE 
ESTIMATED AT 25 KT WITH GUSTS TO 35 KT.  FRAGMENTS OF 
DISORGANIZED CONVECTION ARE STILL OCCURRING NEAR SOUTH OF THE 
CENTER WITHIN 60 NM EITHER SIDE OF A LINE FROM 13N92W TO 
14N87W.  HOWEVER...LITTLE...IF ANY...STRONG WINDS REMAIN...WITH 
AN EARLIER QUIKSCAT PASS INDICATING WINDS OF NO MORE THAN 10 TO 
15 KT ALONG THE EL SALVADOR AND GUATEMALAN COASTS.  ALMA SHOULD 
CONTINUE ON A NNW TO NW TRACK TODAY INITIALLY OVER THE MORE 
RUGGED TERRAIN OF CENTRAL AMERICA AND DISSIPATE BY TONIGHT.  
HOWEVER...MODEL GUIDANCE IS INSISTING ON BROAD SURFACE LOW 
PRESSURE REFORMING OVER THE GULF OF HONDURAS TODAY...WHICH MAY 
OR MAY NOT BE ASSOCIATED WITH THE REMAINS OF ALMA.  WHETHER THIS 
OCCURS OR NOT IS AN OPEN QUESTION...BUT WHAT IS MORE CLEAR IS 
THAT HEAVY OROGRAPHIC RAINS ARE LIKELY TO PLAGUE PARTS OF 
CENTRAL AMERICA...SPREADING SLOWLY NW INTO THE WEEKEND.

...TROPICAL WAVES...

A TROPICAL WAVE MARCHING ACROSS THE CARIBBEAN EARLIER IN THE 
WEEK HAS NOW REACHED THE NW CARIBBEAN AND IS INTERACTING WITH 
THE CIRCULATION AROUND ALMA.  THIS FEATURE IS NOW BEING ANALYZED 
AS A TROUGH OVER THE GULF OF HONDURAS AND IS ACCOMPANIED BY 
SCATTERED STRONG CONVECTION FROM SAN ANDRES AND NE HONDURAS INTO 
THE OPEN WATERS OF THE NW CARIBBEAN SEA.

...ITCZ...

INTERTROPICAL CONVERGENCE ZONE AXIS FROM 12N88W TO 07N100W TO 
06N115W TO 03N130W TO 06N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION WITHIN 60 NM S OF AXIS BETWEEN 110W AND 116W. 
NUMEROUS STRONG CONVECTION WITHIN 30 NM EITHER SIDE OF LINE FROM 
15.5N95.5W TO 13N96W. 

...DISCUSSION...

WATER VAPOR IMAGERY...CLOUD-TRACKED WINDS...AND OTHER UPPER-AIR 
DATA INDICATE THE PRESENCE OF A LOW AMPLITUDE BUT BROAD TROUGH 
EXTENDING FROM JUST OFFSHORE THE U.S. WEST COAST THROUGH THE 
WATERS W OF 120W...WITH AN AXIS ALONG 30N130W TO 23N130W TO 
18N140W.  THE TROUGH HAS ACCENTUATED THE NORMAL CONFIGURATION 
OF HIGH PRESSURE OVER THE NE PACIFIC AND RELATIVE LOW PRESSURE 
OVER THE SOUTHWEST CONUS THE PAST FEW DAYS. AS A RESULT...NW TO
N WINDS TO 20 KT HAVE BEEN FAIRLY STEADY GENERALLY N OF 25N AND 
E OF 120W TO THE BAJA CALIFORNIA COAST.  THE NLY FLOW HAS BEEN 
ACTIVE LONG ENOUGH SO THAT SEAS HAVE BUILT TO 6 TO POSSIBLY 8 FT 
IN ISOLATED SPOTS IN A MIXTURE LONG PERIOD NW SWELL COMING OUT 
OF THE NORTH PACIFIC AND NEWLY-FORMED N WIND WAVES.  AS A 
SHORTWAVE LIFTS OUT OF THE LONGWAVE TROUGH OFFSHORE THE WEST 
COAST LATER TODAY THROUGH EARLY SAT...MODELS SHOW THE AREA OF 20 
KT WINDS SHRINKING AND EVENTUALLY GROWING LESS INTENSE.  HOWEVER 
...ANOTHER VIGOROUS SHORTWAVE IS FORECAST TO DIG INTO THE SAME 
POSITION SUN...REINFORCING THE LONGWAVE TROUGH WHICH HAS BEEN IN 
THE SAME POSITION FOR SOME TIME. INTERESTINGLY...THE PERSISTENCE 
OF THIS FEATURE AND SEVERAL SPRING GALE WIND EVENTS ACROSS THIS 
REGION HAVE LED TO ANOMALOUSLY COLD SEA SURFACE TEMPERATURES IN 
A STRIPE EXTENDING FROM THE U.S. WEST COAST SW TO THE CENTRAL 
NORTH PACIFIC.

IN ANY EVENT...AS THE NEXT SHORTWAVE BEGINS TO EXERT ITS 
INFLUENCE OVER THE FAR WEST...NW TO N WINDS SHOULD BECOME 
REINVIGORATED.  IN FACT...THE NLY FLOW SHOULD REACH 2O TO 25 KT 
BEGINNING SAT EVENING...WITH SEAS FORECAST TO BUILD TO OVER 8 FT 
OVER AN INCREASING AREA N OF 23N E OF 118W IN A MIXTURE OF N 
WIND WAVES AND SW SWELL FROM THE SOUTHERN HEMISPHERE.

ELSEWHERE...THE DIFFERENCE BETWEEN DEEP LOW PRESSURE ASSOCIATED 
WITH TROPICAL DEPRESSION AL,A AND RELATIVE HIGH PRESSURE OVER 
THE GULF OF MEXICO LED TO AN UNUSUAL LATE SPRING GAP WIND EVENT 
IN THE GULF OF TEHUANTEPEC YESTERDAY.  PRELIMINARY DATA INDICATE 
THAT WINDS OF UP TO GALE FORCE MAY HAVE OCCURRED NEAR AND 
DOWNWIND OF THIS AREA YESTERDAY MORNING...WITH QUIKSCAT DATA 
FROM YESTERDAY EVENING STILL INDICATING A WIDE SWATH OF NLY 25 
TO 30 KT WINDS. SEAS OF 8 TO 10 FT HAVE BUILT WITHIN A FEW 
HUNDRED MILES SOUTH OF THE GULF OF TEHUANTEPEC IN N WIND WAVES 
AND SW SWELL.  NOW THAT ALMA HAS DIMINISHED IN STRENGTH...EXPECT 
THE STRONG PRESSURE GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC 
TO WEAKEN SUBSTANTIALLY OVER THE NEXT 6 TO 12 HOURS. 
CONSEQUENTLY...WINDS SHOULD GRADUALLY ABATE TODAY WITH SEAS 
FOLLOWING SUIT TODAY THROUGH SAT.

FINALLY...WEAKLY ENHANCED SUBTROPICAL RIDGING OVER THE EASTERN 
PACIFIC W OF 120W HAS LED TO SLIGHTLY ABOVE AVERAGE TRADES N OF 
A LINE FROM 08N140W TO 13N121W TO 19N.  LITTLE CHANGE TO THESE 
CONDITIONS ARE EXPECTED TODAY...WITH THE COVERAGE DECREASING 
LATER IN THE WEEKEND.  SEAS TO 8 FT IN NE WIND WAVES AND SW 
SWELL ARE POSSIBLE OVER THE FAR SW PART OF THIS AREA TODAY...BUT 
SEAS SHOULD GRADUALLY SUBSIDE AREA WIDE THROUGH SUN.

$$
KIMBERLAIN