000
AXPZ20 KNHC 212205
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED JUL 21 2010

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 
2145 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED ALONG 16N98W TO 
13N110W TO 07N123W TO 10N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION WAS NOTED WITHIN 120 NM EITHER SIDE OF AXIS E 
OF 128W. 

...DISCUSSION...

AN UPPER LEVEL RIDGE EXTENDED ACROSS FAR W PORTIONS OF THE 
AREA...FROM A CENTER LOCATED SE OF THE BIG ISLAND OF HAWAII NE 
TO NEAR 31N135W. A SECOND HIGH WAS CENTERED OVER THE SUB TROPICS 
NEAR 20N119W. A NARROW AND ELONGATED MID TO UPPER TROUGH 
SEPARATED THESE HIGHS EXTENDING INTO THE AREA FROM A FILLING LOW 
NEAR 30.5N126W TO A MID LEVEL LOW NEAR 19N136W. STABLE 
ATMOSPHERIC CONDITIONS PREVAILED ACROSS MOST OF THIS 
AREA...EXCEPT NEAR THE SOUTHERN LOW PRESSURE ALOFT...WHERE 
SHALLOW STRATIFORM PRECIP WAS OCCURRING. THE N PORTION OF THIS 
TROUGH IS FORECAST TO MOVE E-NE AND INLAND ACROSS SRN CALIFORNIA 
DURING THE NEXT 36 HOURS WHILE THE SOUTHERN PORTIONS CONTINUES 
TO DRIFT W...WITH THE FRACTURING TROUGH IN BETWEEN EXPECTED TO 
BECOME INVIGORATED AS UPSTREAM ENERGY DROPS INTO THE BACKSIDE OF 
THE TROUGH AND ENHANCES IT BETWEEN 135W AND 140W. RIDGING TO THE 
E WILL EXPAND SOMEWHAT W TO E. 

E AND SE OF THESE FEATURES...UPPER LEVEL EASTERLIES PREVAIL AND 
ARE PRODUCING A SHEARED ENVIRONMENT THAT IS ENHANCING CONVECTION 
NEAR THE ITCZ AND ACROSS THE FAR TROPICAL EPAC N TO THE SW COAST 
OF MEXICO AND CENTRAL AMERICA. AS THE HIGH TO THE N EXPANDS W 
DURING THE NEXT FEW DAYS...THIS BROADENING UPPER ELY JET WILL 
SPREAD W ACROSS THE TROPICS AND REACH TO NEAR 130W BY FRI 
EVENING WITH CORE SPEEDS ALOFT FORECAST TO 55 KT. 

A 1034 MB HIGH PRES AT THE SURFACE IS CENTERED WELL NW OF THE 
DISCUSSION AREA NEAR 45N148W WITH A RIDGE AXIS EXTENDING THROUGH 
30N131W TO 18N114W. THE RIDGE AXIS IS MARKED BY STABLE AIR AND 
STRATOCUMULUS...ESPECIALLY N OF 17N. ANTICYCLONIC FLOW DOMINATED 
THE FAR EPAC S OF THE ITCZ EXTENDING W TO 125W WITH SELY WINDS 
TO 20 KT EXPECTED TO EXPAND ACROSS THIS ZONE IN THE NEXT 48 
HOURS. 

GALE FORCE WINDS ALONG THE PACIFIC NW COAST OF THE U.S. CONTINUE 
TO GENERATE NORTHERLY SWELL IN THE 8 TO 11 FT RANGE OVER
THE DISCUSSION AREA N OF 24N BETWEEN 119W AND 135W. THIS SWELL 
WILL GRADUALLY SUBSIDE TO 8 FT THU NIGHT AND BELOW 8 FT BY FRI 
MORNING.

LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELL OF 8 TO 9 FT LIES 
ACROSS THE S CENTRAL PORTION OF THE FORECAST AREA GENERALLY S OF 
10N BETWEEN 95W AND 130W. THIS SWELL WILL GRADUALLY DECAY OVER 
THE NEXT TWO DAYS...BUT A NEW SURGE OF SE SWELL IS EXPECTED TO 
MOVE ACROSS THE EQUATOR THU NIGHT. IN ADDITION...SE TO S WINDS 
ARE EXPECTED TO INCREASE TO 20 KT TONIGHT THROUGH FRI IN S 
CENTRAL WATERS. THIS WILL HELP KEEP SEAS ABOVE 8 FT IN MUCH OF 
THE REGION S OF 10N THROUGH FRI MORNING.

$$
STRIPLING