000
AXPZ20 KNHC 070335
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN SEP 07 2008

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LOWELL CENTERED NEAR 15.7N 106.4W OR 385 NM WSW 
OF ACAPULCO MEXICO AT 07/0000 UTC MOVING WNW OR 295 DEGREES AT 
10 KT. ESTIMATED CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED 
WINDS 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC PUBLIC ADVISORY 
UNDER AWIPS/WMO HEADERS OF MIATCPEP3/WTPZ33 KNHC AND THE FULL 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMEP3/ WTPZ23 KNHC 
FOR MORE DETAILS. THE BROAD AREA OF LOW PRESSURE WITHIN THE 
WESTERN END OF THE STRONG MONSOON TROUGH...WHICH HAS PERSISTED 
OFFSHORE THE SOUTHERN MEXICAN COAST THE LAST FEW DAYS...HAS 
FINALLY COALESCED INTO A TROPICAL CYCLONE. SATELLITE PICTURES 
INDICATE TWO MAIN BANDING FEATURES...ONE FEEDING IN FROM THE 
SOUTHWEST AND ANOTHER MORE PROMINENT ONE RUNNING PARALLEL BUT 
OFFSHORE COASTAL MEXICO INTO THE NW QUADRANT. NIGHTTIME VISIBLE 
IMAGERY SHOWS LOW CLOUDS SWIRLING AROUND WHAT APPEARS TO BE THE 
LOW-LEVEL CENTER...WHICH LIES ON THE NE SIDE AND NEAR THE EDGE 
OF THE DEEPEST CONVECTIVE TOPS. THE CENTER DISPLACED FROM THE 
DEEPEST CONVECTION SEEMS TO BE A CONSEQUENCE OF MODERATE TO 
STRONG ENE TO NE SHEAR OVER THE STORM. NUMEROUS MODERATE/ 
SCATTERED STRONG CONVECTION WITHIN 180 NM W SEMICIRCLE.

...ITCZ...

ITCZ LIES ALONG 09N83W TO 13N96W TO 16N106W TO 09N116W TO 
10N133W TO 08N140W. NUMEROUS MODERATE ISOLATED STRONG CONVECTION 
BETWEEN 10 AND 16N BETWEEN 92W AND 104W. ISOLATED MODERATE 
CONVECTION WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN 128W AND 
140W.

...DISCUSSION...

THE SAME...STRONG MONSOON TROUGH FROM WHICH LOWELL DEVELOPED 
CONTINUES E AND THEN SE ALONG THE COAST OF MEXICO TO OFFSHORE 
CENTRAL AMERICA. WITHIN THE TROUGH ANOTHER POORLY-DEFINED AREA 
OF BROAD CYCLONIC TURNING IS NOTED JUST W OF THE GULF OF 
TEHUANTEPEC NEAR 15.5N96.5W AND IS MOVING LITTLE. A 0032 UTC 
QUIKSCAT PASS OVER THE REGION REVEALED NOTHING BUT UNIFORM SW TO 
W FLOW AND NO INCIPIENT LOW PRESSURE FOR THE MOMENT. NONE OF THE 
GLOBAL MODELS FAVOR DEVELOPMENT IN THIS AREA EITHER AND SUGGEST 
THAT WHATEVER IS TRYING TO TAKE SHAPE THERE NOW SHOULD NOT 
PERSIST. APART FROM THIS FEATURE...QUIKSCAT DATA ALSO INDICATED 
WIDESPREAD...ENHANCED SW TO W FLOW WITHIN ABOUT 10 DEGREES S OF 
THE TROUGH AXIS BETWEEN 87W AND 115W. THE COMBINATION OF LOW- 
LEVEL SPEED CONVERGENCE AND CYCLONIC SHEAR ALONG THE TROUGH 
AXIS...NOT TO MENTION A PATTERN OF DIFFLUENCE ALOFT...IS 
FAVORING A BROAD AREA OF CLOUDINESS AND SCATTERED TO NUMEROUS 
CONVECTION FROM ABOUT 10N-16N BETWEEN 92W AND 104W.

ELSEWHERE...A NEW GROUP OF LONG PERIOD SW SWELL IS NOW ARRIVING 
OVER MUCH OF THE SOUTHERN HALF OF THE TROPICAL EAST PACIFIC... 
WITH WAVE HEIGHTS OF 8 TO 11 FT PREVAILING S OF 14N W OF A LINE 
FROM 00N92W TO 13N87W. HIGHEST WAVE HEIGHTS ACROSS THIS AREA 
GENERALLY COINCIDE WITH THE STRONG WINDS WITHIN THE MONSOON 
TROUGH AS WELL AS OVER THE SOUTHWESTERN WATERS. MODELS INDICATE 
THE SWELL HANGING AROUND THROUGH AT LEAST EARLY NEXT WEEK BEFORE 
GRADUALLY SUBSIDING.

FINALLY...LONG PERIOD N TO NE SWELL PROPAGATING AWAY FROM 
PERSISTENT GALE CONDITIONS OFF THE U.S. WEST COAST CONTINUE TO 
ARRIVE OVER THE NW WATERS. A NEW BATCH OF NE SWELL IS ALREADY 
ARRIVING OVER THIS AREA AND SHOULD CAUSE WAVE HEIGHTS TO REBUILD 
TO 9 TO 10 FT OVER THE FAR NW WATERS TODAY.

$$
KIMBERLAIN