000
AXPZ20 KNHC 220927
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE OCT 21 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0745 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 09N84W TO 11N100W TO 09N111W TO 
10N116W TO 09N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND 
WITHIN 180 NM N OF AXIS FROM 91W TO 94W...WITHIN 210 NM N AND 
150 NM S OF AXIS FROM 99W TO 118W....AND WITHIN 90 NM S OF AXIS 
W OF 135W.

...DISCUSSION...

A HIGHLY AMPLIFIED MID LEVEL PATTERN IS TAKING SHAPE N OF 
20N...WITH TROUGHING BUILDING OVER NW WATERS AND MUCH OF 
NORTHERN MEXICO WHILE RIDGING HOLDS STRONG IN BETWEEN ALONG 
125W.  A COLD FRONT ASSOCIATED WITH THE AMPLIFYING TROUGHING 
OVER MEXICO WILL SURGE SOUTHWARD THROUGH THE GULF OF MEXICO AND 
BRING STRONG NORTHERLY FLOW THROUGH CHIVELA PASS INTO THE GULF 
OF TEHUANTEPEC BY THU AFTERNOON/EVENING.  THE CURRENT FORECAST 
CALLS FOR THESE WINDS TO REMAIN BELOW GALE FORCE.  IN 
ADDITION...HIGH PRESSURE SPILLING SOUTHEASTWARD THROUGH THE 
SOUTHWESTERN CONUS BEHIND THIS COLD FRONT WILL INDUCE A STRONG 
PRESSURE GRADIENT OVER THE GULF OF CALIFORNIA.  NW WINDS ARE 
EXPECTED TO BUILD TO 30 KT IN THE GULF OF CALIFORNIA N OF 26N ON 
THU.

THE WEAK UPPER LOW OVER NW WATERS AT THE MOMENT IS BEING 
OVERTAKEN BY THE AMPLIFIED TROUGH APPROACHING THE FORECAST AREA 
FROM THE NORTHWEST.  THE COLD FRONT ASSOCIATED WITH THIS TROUGH 
WILL MOVE INTO NW WATERS TODAY...STALL...AND WEAKEN WHILE THE 
MID LEVEL TROUGH PINCHES OFF A CUT OFF LOW ALONG 140W THAT WILL 
GRAZE THE AREA.  THE SURFACE REFLECTION OF THIS ACTIVITY 
ALOFT...A TROUGH ON THE SOUTHEASTERN EDGE OF THE SUBTROPICAL 
RIDGE...WILL LINGER FOR THE NEXT FEW DAYS DISRUPTING THE 
NORTHEASTERLY FLOW.  NW SWELL INDUCED BY THE COLD FRONT WILL 
PUSH INTO THE FORECAST AREA THU...ELEVATING SEAS TO THE 8 TO 11 
FT RANGE.  MEANWHILE...THE 20 TO 25 KT EASTERLY TRADE WINDS 
FOUND BETWEEN 10N AND 20N W OF 125W WILL WEAKEN TO 20 KT DUE TO 
THE DISRUPTION IN THE DEEP LAYER ANTICYCLONIC FLOW.

A LOW PRESSURE SYSTEM CURRENTLY NEAR 11N104W IS EXPECTED TO 
CONTINUE ON A WNW PATH OVER THE NEXT FEW DAYS TOWARD THE 
AMPLIFYING MID TO UPPER LEVEL TROUGHING JUST S OF BAJA 
CALIFORNIA.  THE SYSTEM WILL ENCOUNTER STRONG SW UPPER LEVEL 
FLOW ON THE LEADING EDGE OF THE AMPLIFYING TROUGH BY THU.  THIS 
WILL LIMIT THE DEVELOPMENT OF DEEP CONVECTION NEAR THE LOW. 
WHATEVER IS LEFT OF THE SYSTEM AS IT MOVES INTO AN ENVIRONMENT 
OF STRONG VERTICAL WIND SHEAR WILL BE PULLED NORTH TO 
NORTHEASTWARD INTO THE LEADING EDGE OF THE TROUGH FRI.

$$
SCHAUER CLARK