000
AXPZ20 KNHC 282155
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT AUG 28 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.

...TROPICAL LOW...

THE REMNANT LOW OF FORMER TROPICAL DEPRESSION FRANK WAS CENTERED 
NEAR 21N112.5W AND CONSISTED A SWIRL OF LOW CLOUDS WITH AN 
INTERMITTENT BURST OF THUNDERSTORM ACTIVITY OVER THE PAST FEW 
HOURS. AS THE LOW DRIFTS NNW FURTHER WEAKENING IS ANTICIPATED.
THE EDGE OF A 1750 UTC ASCAT PASS INDICATED 20 KT WINDS AROUND 
THE PERIPHERAL CIRCULATION OF THE LOW.   

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 95W N OF 08N MOVING W NEAR 10 KT WITH AN 
ASSOCIATED 1008 MB LOW ALONG THE WAVE AXIS NEAR 13N. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS WITHIN 120 NM EITHER SIDE 
OF THE WAVE AXIS FROM 13N TO 15.5N. 

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 09N83W 
TO 08N104W THEN RESUMES FROM 14N110W TO 11N127W TO 08N140W. 
SCATTERED MODERATE WITHIN 120 NM S OF AXIS E OF 91W AND WITHIN 
60 NM N OF AXIS BETWEEN 86W AND 91W. SCATTERED MODERATE WITHIN 
75 NM N AND 30 NM S OF AXIS BETWEEN 128W AND 130W.

...DISCUSSION...

WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE AND DRY 
AIR ALOFT OVER A LARGE PORTION OF THE AREA NW OF A LINE FROM 
30N110W TO 15N140W. THE AREA N OF 20N IS DOMINATED BY A PAIR OF 
ANTICYCLONES...THE FIRST OVER EASTERN MEXICO NEAR 23N100W AND A 
LARGER ONE OVER THE PACIFIC NEAR 24N134W. A NARROW RIDGE AXIS 
CONNECTS THE TWO ANTICYCLONES. UPPER LEVEL DIFFLUENT FLOW TO THE 
S AND E OF THE ANTICYCLONE OVER MEXICO IS ENHANCING CONVECTION 
OVER THE EAST PACIFIC FROM 06N TO 14N BETWEEN 96W AND 105W.

THE SOUTHERN EXTENT OF AN AMPLIFYING BROAD UPPER LEVEL TROUGH
OFF THE CALIFORNIA COAST SPLITS THE TWO ANTICYCLONES NOTED ABOVE 
ALONG 122W WITH A COL NEAR 23N122W. MID AND UPPER LEVEL DEBRIS 
MOISTURE FROM THE REMNANT LOW OF FORMER T.D. FRANK WAS BEING 
ADVECTED TO THE NE OVER BAJA CALIFORNIA AND NW MEXICO AS NEW 
CONVECTION WAS DEVELOPING ALONG THE SIERRA MADRE MOUNTAINS OF 
MEXICO.

STRONG SURFACE RIDGE COVERS THE AREA N OF 18N W OF 120W. THE 
PRES GRADIENT IS FORECAST TO TIGHTEN THUS INCREASING WINDS TO 20 
KT AND BUILDING SEAS TO 9 FT OVER THE NEXT 24 HOURS MAINLY N OF 
25N E OF 120W. THE RIDGE WILL THEN RELAX WITH ONLY 20 KT WINDS 
CONFINED TO THE BAJA COASTLINE BY 48 HOURS.  

SURFACE TROUGHING WILL BUILD OVER WESTERN NORTH AMERICA AS THE 
REMNANT LOW OF FRANK MOVES NORTHWARD AND THE TROPICAL WAVE/LOW 
PRES CURRENTLY ALONG 95W PROGRESSES WESTWARD. IN TURN...THE 
SURFACE PRES GRADIENT BETWEEN THIS MEAN TROUGHING AND HIGHER 
PRES S OF THE ITCZ WILL BUILD INCREASING SW WINDS 20 TO 25 KT IN 
THE REGION S OF 11N BETWEEN 90W AND 105W TONIGHT THROUGH MON.
THESE WINDS ARE EXPECTED TO FEED INTO THE TROPICAL WAVE AND AREA 
OF LOW PRES.

A NEW SURGE OF CROSS-EQUATORIAL SWELL OF 15 TO 17 SECONDS IS 
MOVING NWD ACROSS THE FORECAST WATERS S OF 10N E OF 115W. THESE 
SWELLS WILL ARRIVE ON THE COAST OF MEXICO AND CENTRAL AMERICA 
SUN AND SPREAD NWD TO BAJA CALIFORNIA SUN NIGHT AND MON. 

$$
COBB