000
AXPZ20 KNHC 122115
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 12 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 
1900 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 09N84W 
TO 08N88W TO 1011 MB LOW PRES NEAR 12N113W TO LOW PRES NEAR 
11N125W TO LOW PRES NEAR 13N134W THEN TO 12N140W. SCATTERED 
MODERATE CONVECTION LIES WITHIN 150 NM EITHER SIDE OF THE ITCZ 
AXIS E OF 94W AND WITHIN 75 NM EITHER SIDE OF THE ITCZ AXIS 
BETWEEN 98W AND 105W. SCATTERED MODERATE CONVECTION LIES WITHIN 
60 NM N AND 150 NM S OF LOW PRES NEAR 12N113W AND ELSEWHERE 
WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 109W AND 118W. 
SCATTERED MODERATE CONVECTION ALSO LIES WITHIN 150 NM NW 
SEMICIRCLE OF LOW NEAR 11N125W AND ELSEWHERE WITHIN 120 NM S OF 
THE ITCZ AXIS BETWEEN 127W AND 131W.

...DISCUSSION...

AN EXPANSIVE ANTICYCLONE CENTERED OVER SE TEXAS EXTENDS A RIDGE 
SOUTHWEST TO 15N112W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH 
THIS RIDGE IS ENHANCING THE SCATTERED MODERATE CONVECTION FOUND 
WITHIN 150 NM OF THE COAST OF MEXICO FROM 18N TO 21N. BROAD 
UPPER LEVEL DIFFLUENCE CAN ALSO BE FOUND BETWEEN THE E TO SE 
FLOW ON THE FAR SW SIDE OF THE ANTICYCLONE AND CYCLONIC FLOW 
ALOFT BETWEEN TWO UPPER LOWS CENTERED NEAR 00N96W AND 03N114W. 
THIS DIFFLUENCE IS ENHANCING CONVECTION ON THE EASTERN EDGE OF 
THE ITCZ. N WINDS FUNNELING THROUGH THE ISTHMUS OF TEHAUNTEPEC 
ARE EXPECTED TO BE AROUND 20 KT FOR THE NEXT FEW DAYS AS A 
SURFACE TROUGH LINGERS FROM THE SW GULF OF MEXICO INTO THE 
ISTHMUS...DIRECTING NORTHERLY FLOW ON ITS W SIDE FROM HIGHER 
PRES OVER THE NORTHERN GULF COASTAL PLAIN SOUTHWARD INTO THE 
EASTERN PACIFIC.

A NEGATIVELY TILTED UPPER TROUGH EXTENDING FROM N OF AREA 
THROUGH 32N123W TO 25N117W IS ATTEMPTING TO PICK UP A WEAK UPPER 
LOW LOCATED NEAR 18N125W. HOWEVER...THE FORECAST CALLS FOR THE 
LEADING EDGE OF THE TROUGH TO MOVE NE INTO CALIFORNIA 
OVERNIGHT...LEAVING THIS LOW BEHIND. A REINFORCING SHOT OF 
SHORTWAVE ENERGY WILL MEET UP WITH THIS TROUGH OFF THE 
CALIFORNIA COAST BY MON...MAINTAINING THE MEAN TROUGH THERE AND 
TURNING THE FLOW ALOFT MORE ZONAL TO THE W OF THE TROUGH AXIS. A 
WESTERLY UPPER JET IS ALREADY MOVING INTO FAR NW WATERS BEHIND 
THIS TROUGH. THE REFLECTION OF THIS TROUGHING AT THE SURFACE IS 
EXPANDING THE USUAL TROUGHING OVER THE GULF OF CALIFORNIA 
NORTHWARD INTO CALIFORNIA AND OFFSHORE. THE PRES GRADIENT 
BETWEEN THIS TROUGHING AND THE SUBTROPICAL RIDGE...WHICH LIES 
FROM A 1024 MB HIGH NEAR 36N139W THROUGH 32N133W TO 18N113W...IS 
YIELDING NW TO N WINDS TO 15 KT WITHIN 90 NM OF THE COAST OF 
NORTHERN BAJA CALIFORNIA ACCORDING TO THE 1348 UTC WINDSAT PASS. 

FARTHER SW...THE SAME WINDSAT PASS SHOWS SOUTHWESTERLY WINDS TO 
20 KT FEEDING INTO THE LOW PRES SYSTEM NEAR 12N113W. THESE WINDS 
ARE EXPECTED TO EXPAND ALONG THE SOUTHERN SIDE OF THE ITCZ OVER 
THE NEXT FEW DAYS AS THIS LOW DIMINISHES. SEAS IN THIS AREA ARE 
ALSO EXPECTED TO REMAIN AROUND 8 FT AS A NEW SURGE OF SW SWELL 
PUSHES INTO THIS AREA ON MON. AN ASCAT PASS BEFORE DAWN THIS 
MORNING SHOWED 20 TO 25 KT NORTHERLY WINDS FEEDING INTO THE LOW 
PRES SYSTEM NEAR 13N134W. THESE CONDITIONS ARE EXPECTED TO 
CONTINUE AS THIS LOW REMAINS RELATIVELY STATIONARY AND BUTTED 
AGAINST THE SOUTHERN EDGE OF SUBTROPICAL HIGH PRESSURE.

$$
SCHAUER