000
AXPZ20 KNHC 090313
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU JUL 09 2009

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 
0100 UTC.

...SPECIAL FEATURE...
AT 0300 UTC TROPICAL DEPRESSION BLANCA WAS NEAR 21.5N 121.9W OR 
ABOUT 660 NM...1245 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 DIMINISHES OVER THE NEXT FEW DAYS. MAXIMUM SUSTAINED 
WIND SPEED IS 25 KT WITH GUSTS TO 35 KT. MINIMUM PRESSURE IS 
1006 MB. SEE THE FINAL NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADERS MIATCMEP3/WTPZ33 KNHC FOR MORE DETAILS. AS 
EXPECTED...THE WEAK CONVECTION THAT HAD FLARED 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 SOUTHERN MEXICO ALONG 93W 
TO 94W MOVING W 15 KT. SCATTERED MODERATE CONVECTION CAN BE 
FOUND WITHIN 150 NM EITHER SIDE OF THE TROPICAL WAVE OVER 
SOUTHERN MEXICO AND GUATEMALA S OF 18N TO NEAR THE COAST. 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION CAN BE FOUND 
TO THE E OF THE WAVE OVER WESTERN HONDURAS/NICARAGUA IN A REGION 
OF MODERATE UPPER LEVEL DIFFLUENCE ON THE SW SIDE OF A WEAK 
ANTICYCLONE CENTERED OVER THE YUCATAN.

TROPICAL WAVE EMBEDDED IN THE ITCZ CAN BE FOUND FROM 05N TO 13N 
ALONG 109W MOVING W 15 KT. SCATTERED MODERATE WITH ISOLATED 
STRONG CONVECTION CAN BE FOUND WITHIN 150 NM EITHER SIDE OF THE 
TROPICAL WAVE FROM 05N TO 10N AND SCATTERED MODERATE CONVECTION 
LIES WITHIN 60 NM W AND 210 NM E OF THE WAVE AXIS FROM 10N TO 
13N. THERE IS MODERATE UPPER LEVEL DIFFLUENCE IN THE VICINITY OF 
THE WAVE AROUND 10N THAT IS EXPECTED TO CONTINUE TO PROMOTE THE 
DEVELOPMENT OF CONVECTION THE NEXT FEW DAYS.

ANOTHER TROPICAL WAVE IS EMBEDDED IN THE ITCZ ALONG 121W FROM 
05N TO 14N. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 75 
NM W AND 240 NM E OF THE TROPICAL WAVE AXIS FROM 06N TO 
10N.

...ITCZ...
THE ITCZ AXIS IS ALONG 06N78W TO 10N91W TO 10N107W TO 06N115W TO 
09N140W. ASIDE FROM THE AFOREMENTIONED TROPICAL 
WAVES...SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 210 NM 
S OF THE ITCZ AXIS BETWEEN 86W AND 100W AND N OF THE ITCZ AXIS 
TO THE COAST OF HONDURAS...NICARAGUA...COSTA 
RICA...PANAMA...AND NORTHERN ECUADOR E OF 88W.

...DISCUSSION...
THE MID TO 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. THE EASTERLY FLOW TO THE 
SOUTH OF THE ANTICYCLONE IS FORCING THE THUNDERSTORMS THAT HAD 
FORMED OVER THE SIERRA MADRE OCCIDENTAL THIS EVENING TOWARD THE 
COAST...WITH SCATTERED MODERATE CONVECTION FOUND WITHIN 60 NM OF 
MAINLAND MEXICO COAST FROM 20N TO 27N. MEANWHILE...THE TROUGH 
OVER NW WATERS IS LIFTING UPPER LOW CENTERED NEAR 21N130W INTO 
ITS LEADING EDGE...HELPING TO AMPLIFY THE MEAN TROUGHING ALOFT. 
ANOTHER UPPER LEVEL LOW CAN BE FOUND NEAR 17N109W. DIFFLUENT 
FLOW BETWEEN THE TWO LOWS ON THE SW SIDE OF THE ANTICYCLONE AND 
OVER T.D. BLANCA IS WEAKENING. AS THE UPPER TROUGH AMPLIFIES AND 
NUDGES EASTWARD...WHAT REMAINS OF BLANCA WILL MOVE INTO A REGION 
OF INCREASING SOUTHERLY FLOW ALOFT. AT THE SURFACE...THE RIDGE 
OVER N WATERS WILL WEAKEN IN RESPONSE TO THE INCREASED TROUGHING 
ALOFT...ALLOWING BLANCA TO MOVE NW AS IT DISSIPATES. THE SURFACE 
RIDGE CURRENTLY LIES FROM 30N125W TO 25N115W. BROKEN TO OVERCAST 
STRATOCUMULUS CLOUDS BLANKET THE AREA N OF 19N W OF 129W 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