000
AXPZ20 KNHC 221539
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 22 2010

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

AXIS ANALYZED FROM 10N85W TO 08N100W TO 11N122W TO 09N140W. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 06N TO 
13N E OF 91W...AND WITHIN 150 NM S OF THE AXIS BETWEEN 91W AND 
96W.

...DISCUSSION...

A DEEP LAYERED UPPER LEVEL TROUGH IS MOVING QUICKLY ACROSS THE 
THE WESTERN U.S. AND ENTERS THE FAR NE PORTION OF THE AREA 
THROUGH 32N115W...AND STRETCHES SW TO 24N123W. ANOTHER UPPER 
LEVEL TROUGH LINGERS FARTHER WEST WITH AXIS FROM 25N132W SW TO 
22N140W THEN TO SOUTH OF THE HAWAIIAN ISLANDS NEAR 18N160W. THE 
ASSOCIATED SURFACE COLD FRONT HAS SLOWED EASTWARD PROGRESSION 
OVER THE LAST 24-36 HOURS AND REMAINS MOVING E AT 10 KT WHILE 
CONTINUING TO WEAKEN. THE DISSIPATING COLD FRONT ENTERS THE AREA 
NEAR 32N124W AND EXTENDS TO 26N132W WITH WINDS LESS THAN 20 KT 
ON EITHER SIDE OF THE FRONT. HOWEVER...NW OF THE FRONT SEAS 
REMAIN IN THE 9 TO 10 FT RANGE IN NW SWELL WHILE SEAS GREATER 
THAN 8 FT REMAIN OVER A LARGE AREA IN THE NW QUARTER OF THE 
DISCUSSION ZONE. AS THE UPPER LEVEL TROUGH CONTINUES RACING 
EASTWARD LEAVING THE SURFACE FRONT BEHIND BY THIS EVENING...THE 
BOUNDARY WILL BECOME DIFFUSE BY EARLY SAT BEFORE REACHING N 
PORTIONS OF THE BAJA. SEAS ARE EXPECTED TO BE UP TO 8 FT IN 
SUBSIDING NW SWELLS FROM 10N TO 26N BETWEEN 108W AND 120W.

S OF THE UPPER LEVEL TROUGH...A VERY PRONOUNCED SUBTROPICAL JET 
STREAM BRANCH ENTERS THE REGION THROUGH 20N140W...AND EXTENDS 
E-NE TO 22N120W WHERE IT BEGINS TO ROUND THE BASE OF THE UPPER 
LEVEL TROUGH OVER THE WESTERN CONUS. JET CORE WINDS ARE IN THE 
RANGE OF 50-80 KT. A PLUME OF UPPER LEVEL MOISTURE DERIVED FROM 
THE DEEP CENTRAL TROPICAL PACIFIC IS PRESENT WITHIN 300 NM S OF 
THE JET STREAM BRANCH AS NOTED ON SATELLITE WATER VAPOR IMAGERY. 

AN ELONGATED MIDDLE TO UPPER LEVEL RIDGE IS LOCATED S AND SE OF 
THIS TROUGH BETWEEN 08N AND 22N BETWEEN 90W AND 142W...THAT 
SEPARATES UPPER LEVEL WESTERLIES FROM UPPER LEVEL EASTERLIES 
ACROSS THE TROPICS. PRESENTLY...SCATTERED MODERATE CONVECTION 
FOCUSED WEST OF A SURFACE TROUGH EMBEDDED WITHIN THE ITCZ ALONG 
130W IS CONTINUING TO BE ENHANCED BY AMPLE UPPER LEVEL 
DIVERGENCE W OF 130W...WITHIN THE WESTERN PERIPHERY OF THE 
RIDGE. THE AFOREMENTIONED UPPER LEVEL TROUGH WILL MOVE INTO THE 
CENTRAL U.S. OVER THE WEEKEND...WITH THE TRAILING JETSTREAM 
FORECAST TO ERODE THIS UPPER RIDGE...AND WEAKEN IT AS IT SHIFTS 
E OF 125W. 

WITHIN THE LOW LEVELS...A MONSOONAL TROUGH EXTENDS FROM THE 
TROPICAL EPAC E OF 90W NE ACROSS CENTRAL AMERICA TO TROPICAL 
STORM RICHARD...WHICH IS EMBEDDED IN THE NE END OF THIS TROUGH. 
AN UPPER LEVEL ANTICYCLONE HAS BECOME ESTABLISHED OVER THE 
CENTRAL CORE CONVECTION OVER RICHARD. SW MONSOONAL FLOW TO NEAR 
20 KT WAS OCCURRING ACROSS THE E PACIFIC TO THE S OF THIS 
TROUGH...WITH ACTIVE CONVECTION IN THE VICINITY OF THE TROUGH E 
OF 92W INDUCING DIVERGENCE IN THE UPPER LEVEL EASTERLIES. 
RICHARD IS FORECAST TO MOVE SLOWLY W TO W-NW DURING THE NEXT 48 
HOURS...WHICH WILL SHIFT THIS MONSOONAL TROUGH SLOWLY WESTWARD 
AS WELL. THIS WILL RESULT IN THE EXPANSION OF THE SW MONSOONAL 
FLOW W TO 110W BY SUN. ABUNDANT TROPICAL MOISTURE LOCATED S OF 
THE TROUGH AXIS WILL ADVECT NE ACROSS PORTIONS OF PANAMA...COSTA 
RICA...AND NICARAGUA DURING THIS TIME LEADING TO VERY ACTIVE 
CONVECTION AND PERIODS OF VERY HEAVY RAINFALL.

ELSEWHERE AT THE SURFACE...A 1021 MB HIGH IS CENTERED WEST OF 
THE COLD FRONT NEAR 26N138W DRIFTING EASTWARD OVER THE NEXT 24 
HOURS ACROSS NORTHERN PORTIONS OF THE AREA. THE PRESSURE 
GRADIENT TO THE S OF THIS HIGH PRODUCING A SMALL AREA OF FRESH 
NE TRADES FROM 12N TO 18N W OF 133W...WITH SEAS 10 FT. AS THE 
FRONT MOVES FURTHER E OVER THE NEXT 24 HOURS...THE HIGH WILL 
ESTABLISH AN EAST TO WEST RIDGE AXIS ALONG 26N AND ACT TO EXPAND 
THE FRESH NE TRADES EASTWARD TO 126W...WITH SEAS EXPECTED TO 
REMAIN IN THE 8 TO 9 FT RANGE. 

THIS REALIGNING RIDGE WILL ALSO WILL INDUCE A STRONGER PRESSURE 
GRADIENT ALONG THE BAJA CALIFORNIA COAST BY EARLY SATURDAY WITH 
NW TO N WINDS NEAR 20 KT EXPECTED WITHIN 90 NM OF THE COAST N OF 
25N...WITH SEAS TO 8 FT.

OTHERWISE...MERGING NW AND SOUTHERN HEMISPHERE SW LONG PERIOD 
SWELL WILL AFFECT THE AREA WATERS AND MAINTAIN SEAS NEAR 7 FT 
ACROSS THE EQUATORIAL WATERS...IN THE ABSENCE OF 20 KT TRADES.

$$
HUFFMAN