000
AXPZ20 KNHC 272121
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON SEP 27 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 
2100 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ANALYZED FROM 13N110W TO 
11N123W TO 12N122W TO 11N140W. ONLY ISOLATED MODERATE CONVECTION 
LIES WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 116W AND 134W. AN 
INCREASE IN POOLED MOISTURE ALONG THE ITCZ AND DIFFLUENT FLOW 
ALOFT OVER THE ITCZ BETWEEN A RIDGE AXIS TO THE NE AND AN UPPER 
LOW CENTERED NEAR 00N129W HAS MADE CONDITIONS SLIGHTLY MORE 
CONDUCIVE FOR CONVECTIVE ACTIVITY HERE COMPARED TO THIS TIME 
YESTERDAY.

...DISCUSSION...

AN UPPER LEVEL RIDGE LIES BETWEEN AN ANTICYCLONE NEAR 21N103W 
AND ANOTHER ANTICYCLONE NEAR 30N128W. AN UPPER LOW OVER THE 
CENTRAL GULF OF CALIFORNIA NEAR 29N112W LIES TO THE N OF THIS 
RIDGE AXIS. THIS LOW IS SIPHONING DEEP LAYER TROPICAL MOISTURE 
AWAY FROM THE 1008 MB SURFACE LOW NEAR 17N107W AND INTO THE GULF 
OF CALIFORNIA. IN ADDITION...SOUTH-SOUTHEASTERLY UPPER LEVEL 
WINDS ON THE SOUTH SIDE OF THE RIDGE AXIS OVER THIS SURFACE LOW 
CONTINUE TO BE AROUND 20-25 KT. AS A RESULT....SCATTERED 
MODERATE CONVECTION IS DISPLACED BETWEEN 90 NM AND 270 NM OF THE 
NW QUADRANT OF THIS SURFACE LOW. THE SHEAR OVER THIS NEARLY 
STATIONARY LOW IS EXPECTED TO SLACKEN TOMORROW AS THE EASTERN 
ANTICYCLONE SHIFTS SW OVER IT AND CONSOLIDATES WITH THE WESTERN 
ANTICYCLONE ALOFT WHICH IS EXPECTED TO BE FORCED SOUTHWARD BY 
THE WESTWARD MIGRATING UPPER LOW PASSING OVER THE CENTRAL BAJA 
PENINSULA. THIS WILL MAKE FOR A MORE DIFFLUENT PATTERN ALOFT 
OVER THE SURFACE LOW AND POSSIBLY ALLOW FOR SOME BRIEF 
DEVELOPMENT OF THE LOW. HOWEVER...NORTHERLY SHEAR SHOULD 
INCREASE BY WED AFTERNOON ON THE EAST SIDE OF THE ANTICYCLONE 
AND AGAIN INHIBIT ANY DEVELOPMENT.

BUOY DATA AND THE ASCAT PASS FROM AROUND 1552 UTC SHOW SW WINDS 
OFF THE COAST OF CENTRAL AMERICA AROUND 20-25 KT WHILE SHIP 
ZCDF4 TRAVELING S APPROXIMATELY 100 NM OFF THE COAST OF 
NICARAGUA REPORTED SLIGHTLY STRONGER SW WINDS AND SEAS TO 10 FT 
BETWEEN 1200 UTC AND 1800 UTC. THESE SW WINDS ARE FEEDING INTO A 
BROAD CYCLONIC GYRE OVER CENTRAL AMERICA THAT IS ASSOCIATED BOTH 
WITH THE REMNANTS OF MATTHEW OVER SOUTHERN MEXICO AND AN AREA OF 
LOW PRES OVER THE NW CARIBBEAN. THE FORECAST OFF THE PACIFIC 
COAST OF CENTRAL AMERICA IS HIGHLY DEPENDENT ON THE EVOLUTION OF 
THE PATTERN OVER THE NORTHWESTERN CARIBBEAN AND GULF OF MEXICO 
OVER THE NEXT FEW DAYS. THE CURRENT FORECAST CALLS FOR THE 
DEVELOPMENT OF A SURFACE LOW OVER THE NW CARIBBEAN THAT WILL 
LIFT NE AHEAD OF A COLD FRONT STRADDLING THE GULF OF MEXICO FROM 
NE TO SW. NORTHERLY WIND BEHIND THE COLD FRONT IS EXPECTED TO 
FUNNEL THROUGH THE ISTHMUS OF TEHUANTEPEC ON TUE AND SHIFT THE 
SURFACE WINDS MORE NORTHERLY THERE WHILE THE DOMINANT FLOW S OF 
14N AND E OF ABOUT 100W REMAINS SOUTHWESTERLY.

FURTHER TO THE N...15-17 SECOND PERIOD SWELL HAS PUSHED SE FROM 
THE N CENTRAL PACIFIC...WITH THE LEADING EDGE FOUND FROM THE 
CENTRAL BAJA PENINSULA TO THE WEST-CENTRAL PORTION OF THE 
FORECAST AREA. SEAS HAVE BEGUN TO SUBSIDE FROM A MAX OF 13 FT 
OVER NW WATERS WITH THIS SWELL TRAIN. THE FORECAST CALLS FOR 
THIS INITIAL SWELL TRAIN TO CONTINUE TO SPREAD SE THROUGH THE 
AREA AND GRADUALLY SUBSIDE...WITH THE LEADING EDGE OF THIS SWELL 
REACHING FROM THE CENTRAL MEXICAN COAST TO THE EQUATOR NEAR 120W 
WED AFTERNOON. A SECOND SURGE OF NW SWELL WILL REACH NW WATERS 
TUE AND BRING THE SEAS BACK TO THE 10 TO 13 FT RANGE TUE 
AFTERNOON AND EVENING OVER NW WATERS.

$$
SCHAUER