000
AXPZ20 KNHC 010925
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN JUN 01 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...

ITCZ AXIS ALONG 10N86W TO 11N91W TO 04N110W TO 06N130W TO 
05N140W. SCATTERED MODERATE CONVECTION WITHIN 150 NM N OF AXIS 
BETWEEN 96W AND 105W. ELSEWHERE...SCATTERED MODERATE ISOLATED 
STRONG CONVECTION N OF 12N BETWEEN 90W AND 99W.

...DISCUSSION...

W OF 110W...
A BROAD MID- TO UPPER-LEVEL TROUGH EXTENDING FROM JUST OFFSHORE 
THE U.S. WEST COAST THROUGH THE WATERS W OF 125W...WITH AN AXIS 
ALONG 30N132W TO 21N140W. THE PRESENCE OF THE TROUGH OFFSHORE 
THE WEST COAST HAS ACCENTUATED THE NORMAL CONFIGURATION OF HIGH 
PRESSURE OVER THE NE PACIFIC AND RELATIVE LOW PRESSURE OVER THE 
SOUTHWEST CONUS FOR MUCH OF THIS LAST WEEK. 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. ALTHOUGH THE NLY FLOW 
HAS FLUCTUATED SOME THE LAST FEW DAYS...THE NLY FLOW HAS BEEN 
PERSISTENT LONG ENOUGH SO THAT SEAS STILL RANGE FROM 6 TO 8 FT 
IN MIXED N SWELL COMING OUT OF THE NE PACIFIC AND SW SWELL WITH 
ORIGINS FROM THE SOUTHERN HEMISPHERE.

A NEW AND VIGOROUS SHORTWAVE IS FORECAST TO DIG OFFSHORE THE 
CALIFORNIA COAST LATER TODAY AND MON...REINFORCING THE CURRENT 
LONGWAVE TROUGH. ALTHOUGH NLY WINDS W OF THE BAJA PENINSULA WERE 
IN A TEMPORARY LULL SAT...THE ARRIVAL OF THIS NEXT SHORTWAVE 
SHOULD REINVIGORATE THE NLY FLOW. IN FACT...THE NLY FLOW SHOULD 
REACH 2O TO 25 KT OVER AND EXPANDING AREA GENERALLY N OF 24N AND 
WITHIN A FEW HUNDRED MILES W OF THE BAJA PENINSULA SUN AND MON 
...WITH SEAS BUILDING TO 8 TO 10 FT IN MIXED N AND SW SWELL BY 
MON AFTERNOON.

E OF 110W...
ANOMALOUSLY STRONG MID- TO UPPER-LEVEL RIDGING EXTENDING FROM 
THE BAJA CALIFORNIA PENINSULA EASTWARD INTO THE GULF OF MEXICO 
SHOULD REMAIN IN PLACE THE NEXT FEW DAYS. THE PATTERN SHOULD 
STEER TROPICAL STORM ARTHUR...NOW OVER THE SOUTHERN YUCATAN 
PENINSULA...ON A SLOW WESTWARD COURSE THIS WEEKEND.  WITH THE 
CENTER EXPECTED TO REMAIN NEAR OR OVER LAND...ARTHUR SHOULD 
GRADUALLY WEAKEN TO A TROPICAL DEPRESSION AND ULTIMATELY A 
REMNANT LOW OVER THE ISTHMUS OF TEHUANTEPEC BY SUN.  HOWEVER 
...ANY DEVIATION RIGHT OF THE FORECAST TRACK COULD ALLOW THE 
WEAKENING STORM TO MOVE INTO THE SOUTHERN BAY OF CAMPECHE... 
POSSIBLY RESULTING IN SOME REGENERATION. WHETHER THIS OCCURS OR 
NOT...THE PRESENCE OF BROAD LOW PRESSURE UNDERNEATH A STRONGLY 
DIFFLUENT FLOW ALOFT IN A CONDITIONALLY UNSTABLE ATMOSPHERE 
SHOULD LEAD TO SCATTERED TO WIDESPREAD CONVECTION EACH DAY 
...ESPECIALLY AROUND PEAK HEATING. EXPECT THE HIGHEST RAINFALL 
TO BE COLLOCATED WITH PEAK OROGRAPHIC FEATURES.

OTHERWISE...IT APPEARS THAT AN UNUSUALLY LATE GAP WIND EVENT 
OVER THE TEHUANTEPEC THE PAST FEW DAYS IS FINALLY COMING TO A 
CLOSE. THE JUXTAPOSITION OF DEEP SURFACE LOW PRESSURE EAST OF 
THE AREA AND RELATIVE HIGH PRESSURE OVER THE WESTERN GULF OF 
MEXICO HELPED INDUCE THE STRONG NORTHERLY FLOW TO GALE FORCE 48 
HOURS AGO.  HOWEVER...WITH THE APPROACH OF ARTHUR...PRESSURES 
ARE FALLING NORTH OF ISTHMUS OF TEHUANTEPEC...WHICH HAS LED TO A 
WEAKENING PRESSURE GRADIENT ACROSS THE GAP AND HENCE REDUCED 
WINDS.  STILL THOUGH...A 0408 UTC ASCAT PASS DID SHOW NORTHERLY 
15 KT WINDS WITHIN ABOUT 60 NM OF THE COAST.  GIVEN THE LOW BIAS 
OF ASCAT WIND DATA...IT IS ASSUMED THAT A SMALL AREA MAY STILL 
BE EXPERIENCING UP TO 20 KT WINDS. SEAS DOWNWIND OF THE GULF OF 
TEHUANTEPEC MAY STILL BE UP TO 8 FT LOCALLY BUT SHOULD SUBSIDE 
FAIRLY QUICKLY SUNDAY.

$$
KIMBERLAIN