000
AXPZ20 KNHC 080311
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED JUL 08 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 
0145 UTC.

...SPECIAL FEATURE...
TROPICAL STORM BLANCA CENTERED NEAR 20.3N 117.8W AT 0300 UTC OR 
OR ABOUT 450 NM...865 KM...WEST-SOUTHWEST OF THE SOUTHERN TIP OF 
BAJA CALIFORNIA MOVING WES-NORTHWEST OR 300 DEG AT 10 KT. 
MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. 
MINIMUM PRESSURE IS 1002 MB. SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ33 KNHC FOR MORE DETAILS. 
BLANCA HAD A BURST OF DEEP CONVECTION NEAR THE CENTER AROUND 
2200 UTC THAT IS NOW BEGINNING TO WEAKEN.  BLANCA IS FORECAST TO 
MOVE OVER COOLER WATERS OVER THE NEXT 24 HOURS WITH THE FORECAST 
CALLING FOR THE STORM TO WEAKEN TO A REMNANT LOW BY WED EVENING.

...TROPICAL WAVES...
TROPICAL WAVE WITH AN AXIS ALONG 100-101W FROM 05N TO 16N IS 
MOVING W AT 20 KT. THIS WAVE IS EMBEDDED IN THE ITCZ. THERE IS 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WITHIN 450 NM 
W OF THE TROPICAL WAVE ALONG 101W FROM 05N TO 13N.

TROPICAL WAVE WITH AN AXIS ALONG 85-86W N OF 05N IS MOVING W AT 
20 KT. THIS WAVE IS CURRENTLY PASSING THROUGH EASTERN 
HONDURAS...CENTRAL NICARAGUA...AND NW COSTA RICA. THIS WAVE IS 
EMBEDDED IN THE ITCZ. THERE NO SIGNIFICANT DEEP CONVECTION 
ASSOCIATED WITH THE WAVE OVER THE FORECAST AREA...WITH ONLY SOME 
SCATTERED TSTMS WITHIN 30 NM OF THE COAST OF COSTA RICA E OF THE 
WAVE AND WITHIN 120 NM E OF THE WAVE BETWEEN 05N AND 06.5N.

...ITCZ...
THE ITCZ AXIS IS ALONG 06N77W TO 10N98W TO 08N108W TO 10N118W TO 
09N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 90 NM 
OF AXIS W OF 137W.

...DISCUSSION...
A STATIONARY UPPER-LEVEL ANTICYCLONIC CIRCULATION IS CENTERED 
OVER NW MEXICO NEAR 29N112W WITH A RIDGE AXIS EXTENDING W ALONG 
29N TO 130W AND THEN SW TO 15N140W AND A RIDGE AXIS EXTENDING SE 
FROM THE ANTICYCLONIC CENTER TO BROWNSVILLE TX AND E ACROSS THE 
GULF OF MEXICO ALONG 25N/26N. THE UPPER PATTERN IS HIGHLY 
AMPLIFIED OVER THE FORECAST AREA TO THE S OF THIS RIDGE 
AXIS...WITH UPPER LOWS CENTERED NEAR 20N130W AND 17N104W. 
BETWEEN THESE LOWS LIES T.S. BLANCA UNDER A REGION OF WEAK UPPER 
LEVEL DIFFLUENCE. THE UPPER RIDGE AXIS TO THE N OF BLANCA IS 
EXPECTED TO BREAKDOWN AS A TROUGH MOVES INTO NW WATERS...FORCING 
THE UPPER LOW FROM 20N130W NORTHWARD ALONG 130W ON ITS LEADING 
EDGE AND TURNING THE MID TO UPPER LEVEL STEERING FLOW SOUTHERLY 
IN THE VICINITY OF BLANCA. AT THE SURFACE...THE RIDGE OVER NW 
WATERS WILL WEAKEN IN RESPONSE TO THE INCREASED TROUGHING 
ALOFT...SENDING T.S. BLANCA NW AS IT GRADUALLY WEAKENS TO A 
REMNANT LOW OVER THE NEXT FEW DAYS.

SURFACE RIDGE EXTENDS FROM 30N130N TO 25N112W. BROKEN TO 
OVERCAST STRATOCUMULUS CLOUDS BLANKET THE AREA N OF 15N W OF 
123W AND APPROACHING THE SW QUADRANT OF BLANCA. THE PRESSURE 
GRADIENT BETWEEN THIS RIDGE AND THE SURFACE TROUGH ALONG 141W 
FROM 06N TO 12N IS RESULTING IN AN AREA OF NE-E TRADES OF 20 TO 
25 KT FROM 11N TO 16N W OF 137W AS SEEN IN THE 1822 UTC ASCAT 
PASS. THESE TRADE WINDS ARE FORECAST TO GRADUALLY DIMINISH IN 
AREAL COVERAGE DURING THE NEXT 24 HOURS. SCATTERED MODERATE 
CONVECTION CAN BE CURRENTLY FOUND E OF THE SURFACE TROUGH WITHIN 
90 NM OF THE ITCZ AXIS W OF 137W.

THE TROPICAL WAVE ALONG 100W-101W FROM 05N TO 16N LIES UNDER A 
REGION OF UPPER LEVEL DIFFLUENCE TO THE S OF THE UPPER LOW NEAR 
17N103W. THE LOW LEVEL MOISTURE CONVERGENCE NEAR THIS WAVE 
COUPLED WITH THIS DIFFLUENCE ALOFT IS SUPPORTING A LARGE AREA OF 
CONVECTION TO THE W OF THE WAVE AXIS. THE UPPER LEVEL LOW IS 
EXPECTED TO CONTINUE TRACKING W WITH THE WAVE TOMORROW...BUT 
WILL BE OVERTAKEN BY THE INCREASED MID TO UPPER LEVEL TROUGHING 
TO ITS NW ON THU. STRONG EASTERLY FLOW ALOFT BETWEEN THIS LOW 
AND THE ANTICYCLONE OVER NW MEXICO IS INHIBITING DEEP CONVECTION 
OVER SOUTHERN MEXICO.

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