000
AXPZ20 KNHC 021604
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 02 2009

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.

...SPECIAL FEATURE...

TROPICAL STORM OLAF...WAS CENTERED NEAR 23.1N 117.5W AT 02/1500 
UTC OR ABOUT 420 NM...780 KM...WEST OF THE SOUTHERN TIP OF BAJA 
CALIFORNIA...WITH MAXIMUM SUSTAINED WINDS OF 40 KT WITH GUSTS TO 
50 KT. OLAF WAS MOVING N OR 360 DEG AT 9 KT WITH AN ESTIMATED 
MINIMUM CENTRAL PRESSURE OF 1000 MB. IT APPEARS SOUTHERLY SHEAR 
IS BEGINNING TO IMPACT OLAF WITH THE DEEP CONVECTION CONFINED TO 
THE N SEMICIRCLE OF THE STORM. A BAND OF NUMEROUS STRONG 
THUNDERSTORMS WERE NOTED WITHIN 60-90 NM EITHER SIDE OF A BAND 
THROUGH 23N119W 25N117W 24N115W TO 22N115W. LITTLE OR NO 
CONVECTION WAS NOTED IN THE S SEMICIRCLE. IN ADDITION RECENT 
MICROWAVE OVERPASSES FROM THE NRL TC WEBSITE INDICATE THAT OLAF 
IS BECOMING MORE VERTICALLY TILTED TOWARD THE NORTH DUE TO THE
INCREASING SOUTH-SOUTHWESTERLY SHEAR.  OLAF IS EXPECTED TO 
SLOWLY WEAKEN LATER TODAY AND TONIGHT...AND MAY BECOME A 
TROPICAL DEPRESSION BY LATE SUN. ADDITIONAL INFORMATION CAN BE 
FOUND  UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC.

...ITCZ...

AXIS WAS CENTERED ALONG 09N84W TO 09N100W TO 11N119W THEN 
RESUMES AT 13N125W TO 09N140W. CLUSTER OF MODERATE TO ISOLATED 
STRONG IS FROM 07N TO 10N BETWEEN 84W AND 86W. SIMILAR 
CONVECTION IS NOTED FROM 07N TO 12N W OF 128W.

...DISCUSSION...

AMPLIFIED POSITIVELY TILTED UPPER PATTERN REMAINS IN PLACE S OF 
30N WITH SHEAR AXIS EXTENDING FROM A CYCLONIC CIRCULATION SW OF 
SOUTHERN CALIFORNIA NEAR 33N122W SOUTHWESTWARD TO A CYCLONIC 
CIRCULATION JUST W OF THE AREA NEAR 27N143W. A POSITIVELY TILTED 
MID TO UPPER TROUGH CONTINUED FROM THE CIRCULATION TO A BASE 
NEAR 13N146W. SATELLITE DERIVED WINDS INDICATED A 65-85 KT JET 
SE OF THE TROUGH WHICH EXTENDED FROM 17N140W TO 28N130W THEN 
CURVED EWD ACROSS NORTHERN BAJA CALIFORNIA AND THE SW CONUS.
 MODERATE TO STRONG SUBSIDENCE WITH DRY STABLE AIR IN THE MIDDLE 
AND UPPER LEVELS OF THE ATMOSPHERE WAS NOTED NEAR THE 
CIRCULATION OFF CALIFORNIA...AND SWEEPING AROUND THE SOUTHERN
END OF THE POSITIVELY TILTED TROUGH GENERALLY S OF 18N W OF 
125W. DOWNSTREAM...AN UPPER LEVEL BROAD BLOCKING ANTICYCLONIC 
CIRCULATION IS CENTERED NEAR 22N111W...WITH RIDGE N TO THE 
NORTHERN COAST OF THE BAJA PENINSULA. THIS SAME AREA OF 
ANTICYCLONIC BUT DIFFLUENT FLOW IS ALSO SUPPORTING OLAF'S 
DEEP CONVECTION. 

AN INVERTED TROUGH IN THE DEEP TROPICS WITH AXIS FROM THE 
EQUATOR AT 98W TO 10N90W WAS NEARLY STATIONARY. MODERATE TO 
STRONG SUBSIDENCE IS WITH THE TROUGH S OF 7N E OF 100W.

AT THE SURFACE...
STRONG RIDGE OF HIGH PRES EXTENDED SE FROM A 1036 MB HIGH NEAR 
41N142W AND COVERED THE DISCUSSION AREA N OF 18N W OF 120W. THE 
RIDGE COMBINED WITH THE LOWER PRESSURES IN THE TROPICS AND IN 
THE VICINITY OF TROPICAL STORM OLAF HAS RESULTED IN A LARGE AREA 
OF NE TRADES OF 20-25 KT W OF A LINE FROM 30N116W TO 20N120W TO 
11N140W. AS NOTED EARLIER THE WIND FIELD ASSOCIATED WITH OLAF IN 
THE W SEMICIRCLE HAS MERGED INTO THE LARGER AREA OF TRADES WITH 
A LARGE AREA OF 8-13 FT SEAS NOTED. 

SEAS OVER THE FAR SRN WATERS S OF ABOUT 8N ARE UP TO 9 OR 10 FT 
DUE TO LONG PERIOD SRN HEMISPHERIC SWELLS. THESE CONDITIONS ARE
FORECAST BY WAVE MODEL GUIDANCE TO GRADUALLY BECOME DIFFUSE 
THROUGH THE NEXT 48 HOURS OR SHORTLY THEREAFTER.

$$

COBB