000
AXPZ20 KNHC 082159
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED JUL 08 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2000 UTC.

...SPECIAL FEATURE...
AT 2100 UTC TROPICAL DEPRESSION BLANCA WAS NEAR 21.2N 121.0W OR 
ABOUT 625 NM...1160 KM...WEST OF THE SOUTHERN TIP OF BAJA 
CALIFORNIA MOVING WNW OR 290 DEG AT 9 KT. THIS MOTION IS 
EXPECTED TO CONTINUE AS BLANCA DIMINISHES TO A REMNANT LOW THIS 
EVENING AND FINALLY DISSIPATES LATE THU. MAXIMUM SUSTAINED WIND 
SPEED IS 25 KT WITH GUSTS TO 35 KT. MINIMUM PRESSURE IS 1006 MB. 
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP3/WTPZ33 KNHC FOR MORE DETAILS. SOME WEAK CONVECTION HAS 
AGAIN BEGUN TO APPEAR NEAR THE CENTER OF BLANCA...BUT THIS 
CONVECTION IS LIKELY ASSOCIATED WITH THE NORMAL DIURNAL MAXIMUM 
SEEN THIS TIME OF THE DAY AND IS EXPECTED TO DIMINISH OVERNIGHT.

...TROPICAL WAVES...
TROPICAL WAVE N OF 08N TO THE COAST OF GUATEMALA ALONG 91W 
MOVING W 15 KT. ISOLATED STRONG CONVECTION LIES OVER SOUTHERN 
MEXICO...BELIZE...GUATEMALA...AND EL SALVADOR ASSOCIATED WITH 
THE TROPICAL WAVE. 

TROPICAL WAVE FROM 05N TO 13N ALONG 108W MOVING W 20 KT. 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION CAN BE FOUND 
WITHIN 180 NM E OF THE TROPICAL WAVE FROM 07N TO 13N.

TROPICAL WAVE FROM 05N TO 13N ALONG 120W. SCATTERED MODERATE 
CONVECTION CAN BE FOUND WITHIN 150 NM E OF THE TROPICAL WAVE  
FROM 07N TO 11N.

...ITCZ...
THE ITCZ AXIS IS ALONG 08N77W TO 10N90W TO 10N106W TO 09N110W TO 
09N140W. ISOLATED MODERATE CONVECTION LIES E OF 88W WITHIN 210 
NM S OF THE ITCZ AXIS AND N OF THE AXIS TO COAST AND OVER 
PORTIONS OF NICARAGUA...COSTA RICA...AND PANAMA. SCATTERED 
MODERATE CONVECTION CAN ALSO BE FOUND WITHIN 90 NM N OF THE AXIS 
BETWEEN 114W AND 116W.

...DISCUSSION...
THE UPPER-LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER NW MEXICO 
NEAR 30N108W WILL BE FORCED EASTWARD INTO THE SOUTHERN PLAINS OF 
THE U.S. OVER THE NEXT TWO DAYS BY THE UPPER LEVEL TROUGH 
CURRENTLY MOVING INTO NW WATERS. THIS TROUGH IS PICKING UP THE 
UPPER LOW CENTERED NEAR 20N130W INTO ITS LEADING EDGE...HELPING 
TO AMPLIFY THE TROUGH. ANOTHER UPPER LEVEL LOW CAN BE FOUND NEAR 
17N108W. DIFFLUENT FLOW IS FOUND BETWEEN THE TWO LOWS ON THE SW 
SIDE OF THE ANTICYCLONE AND OVER T.D. BLANCA. AS THE UPPER 
TROUGH AMPLIFIES AND NUDGES EASTWARD...WHAT REMAINS OF BLANCA 
WILL MOVE INTO A REGION OF INCREASING VERTICAL SHEAR. AT THE 
SURFACE...THE SE EDGE OF THE RIDGE OVER NW WATERS WILL WEAKEN 
SLIGHTLY IN RESPONSE TO THE INCREASED TROUGHING ALOFT...ALLOWING 
BLANCA TO MOVE NW AS IT DISSIPATES. THE SURFACE RIDGE CURRENTLY 
LIES FROM 30N140W TO 27N116W. BROKEN TO OVERCAST STRATOCUMULUS 
CLOUDS BLANKET THE AREA N OF 19N W OF 128W AND APPROACHING THE 
SW QUADRANT OF BLANCA. THE PRESSURE GRADIENT BETWEEN THIS RIDGE 
AND THE REMNANT CIRCULATION OF BLANCA WILL KEEP WINDS TO 20 KT 
OVER N CENTRAL WATERS TOMORROW.

CROSS-EQUATORIAL SOUTHWEST SWELL WITH PERIODS IN THE 13-15 
SECOND RANGE CAN BE FOUND OVER MUCH OF THE N EASTERN PACIFIC E 
OF 118W. THIS SW SWELL EVENT IS EXPECTED TO CONTINUE ALONG THE 
ENTIRE COASTLINE OF THE FORECAST AREA FOR THE NEXT FEW 
DAYS...WITH SIGNIFICANT WAVE HEIGHTS GRADUALLY DECREASING OVER 
THAT TIME PERIOD.

$$
SCHAUER CLARK