000
AXPZ20 KNHC 180928
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED JUN 18 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 
0900 UTC.

...ITCZ...
INTERTROPICAL CONVERGENCE ZONE 07N78W TO 07N90W TO 10N100W TO 
09N113W TO 07N120W TO 06N140W. SCATTERED MODERATE CONVECTION IS 
WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 78W AND 82W. SCATTERED 
MODERATE CONVECTION IS WITHIN 300 NM N OF AXIS FROM 99W TO 109W. 
ISOLATED MODERATE CONVECTION IS ALSO WITHIN 300 NM N AND 150 NM 
S OF AXIS BETWEEN 130W AND 135W. SCATTERED MODERATE CONVECTION 
FROM 09N TO 11N BETWEEN 115W AND 117W. SCATTERED STRONG 
CONVECTION N OF 14N BETWEEN 93W AND 96W.

...DISCUSSION...
A STRONG PRESSURE GRADIENT BETWEEN CLIMATOLOGICAL LOW PRESSURE 
OVER THE DESERT SW AND A 1030 MB SURFACE HIGH NEAR 39N134W HAS 
BEEN GENERATING NEAR-CONSTANT GALE CONDITIONS OFFSHORE THE 
CALIFORNIA AND OREGON COASTS SINCE LATE LAST WEEK. IN SPITE OF 
THE GALE CONDITIONS STILL OCCURRING OFFSHORE THE CENTRAL WEST 
COAST...THE CURRENT WIND EVENT APPEARS TO BE NEARING AN END. IN 
FACT...QUIKSCAT DATA FROM LATE YESTERDAY AND RECENT SHIP REPORTS 
CONFIRM THAT THE AREAL EXTENT OF STRONG WINDS HAS BEEN SHRINKING 
AND INDICATE THAT N TO NE WINDS OF UP TO 20 KT HAVE FULLY 
RETREATED FROM THE FAR NORTHERN WATERS. HOWEVER...THE ASSOCIATED 
N TO NE SWELL CONTINUES TO CREEP AS FAR S AS 26N BETWEEN 119W 
AND 133W AND IS MIXING WITH LONG PERIOD SW SWELL NOW WELL AWAY 
FROM ITS ORIGIN IN THE MID-LATITUDES OF THE SOUTHERN HEMISPHERE. 
MODEL GUIDANCE SUGGESTS THAT THE NORTHERLY SWELL IS EITHER 
PEAKING OR HAS ALREADY PEAKED AND SEAS SHOULD SLOWLY SUBSIDE 
TODAY THROUGH FRI. 

OVER THE SOUTHERN WATERS WELL-DEFINED LONG PERIOD SW SWELL 
PROPAGATING OUT OF THE SOUTHERN HEMISPHERE CONTINUES TO CROSS 
THE EQUATOR. AS A RESULT...A RATHER LARGE AREA OF 8 TO 10 FT 
SEAS PERSISTS...GENERALLY S OF 14N W OF 94W. IN ADDITION TO THE 
SWELL...PAST MICROWAVE DATA SHOWED A NARROW REGION OF ENHANCED 
NERLY TRADES TO 20 KT ROUGHLY FROM 10N TO 17N W OF 132W...WHICH 
MEANS THAT NE WIND WAVES ARE COMBINING WITH SW SWELL OVER THIS 
REGION. OVER THE NEXT FEW DAYS...NOAA WAVEWATCH III GUIDANCE 
SHOWS THIS PARTICULAR BATCH OF SOUTHWESTERLY SWELL GREATLY 
SUBSIDING...WITH THE AREA OF 8 FT SEAS LIKELY CONFINED TO S 
0F 7N BETWEEN 96W AND 129W BY FRI EVENING. NEWER SOUTHEASTERLY 
SWELL ALREADY PASSING THROUGH THE TROPICAL SOUTH PACIFIC IS 
EXPECTED TO HAVE LITTLE IMPACT ON SEAS TO THE N THROUGH LATE 
WEEK.

ELSEWHERE...MICROWAVE DATA INDICATE THE PRESENCE OF A WEAK AREA 
OF LOW PRESSURE EMBEDDED WITHIN THE ITCZ NEAR 9N113W...WHICH IS 
DRIFTING W TO WNW AROUND THE SW PERIPHERY OF A LARGE MID- TO 
UPPER-LEVEL ANTICYCLONE CENTERED OVER NORTHERN MEXICO. SATELLITE 
IMAGERY HAD EARLIER REVEALED SOME MINOR ORGANIZATION TO THIS 
FEATURE...BUT MORE RECENT PICTURES SHOW WARMING CLOUD TOPS AND A 
CHAOTIC PATTERN TO THE CONVECTION THAT STILL EXISTS.  WITH A 
FAIRLY CONVERGENT UPPER-LEVEL FLOW TO THE W AND STRONG WESTERLY 
SHEAR W OF 125W...IT SEEMS DOUBTFUL THAT THIS SYSTEM WILL 
ACQUIRE ADDITIONAL ORGANIZATION IN THE NEXT FEW DAYS. 
NEVERTHELESS...SOME OF THE GLOBAL MODELS DO PERSIST THIS FEATURE 
THROUGH THE REMAINDER OF THE WEEK AND INTO WEEKEND...SUGGESTING 
THAT IT SHOULD BE MONITORED.

FINALLY...STRONG TRADES IN THE CENTRAL AND EASTERN CARIBBEAN 
SHOULD EVENTUALLY SPREAD FARTHER WEST INTO THE WESTERN CARIBBEAN 
LATE THIS WEEK AND COULD SPARK A GAP WIND EVENT IN THE GULF OF 
PAPAGAYO. ALTHOUGH MODEL GUIDANCE SHOWS NO THREAT OF GAP WINDS 
DEVELOPING BEFORE ABOUT THU...THERE IS STILL SOME CHANCE OF 
INTERMITTENT NE TO E 20 KT WINDS DOWNSTREAM OF THE GULF REGION.  
BY FRI...INDICATIONS ARE THAT A STEADY STREAM OF 20 TO PERHAPS 
25 KT WINDS SHOULD LIE FROM 10N TO 12N AND AS FAR W AS 90W. ONCE 
WINDS BECOME ESTABLISHED...EXPECT SEAS TO THEN FOLLOW SUIT BY 
BUILDING TO 8 OR 9 FT BY LATE FRI.

$$
KIMBERLAIN