000
AXPZ20 KNHC 120942
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI OCT 12 2007

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 0845 UTC.

...ITCZ...

INTERTROPICAL CONVERGENCE ZONE...AXIS ALONG 14N89W 11N105W 
10N122W 12N134W 11N140W. ISOLATED MODERATE CONVECTION NEAR 
10N105W AND 10N138W. 

SCATTERED MODERATE WITHIN 90 NM OF 7N79W. SCATTERED STRONG NEAR 
THE COAST FROM 13N88W TO 14N93W AND FROM 14N96W TO 16N99W.

SCATTERED STRONG CONVECTION WITHIN 120 NM W QUADRANT OF A LOW 
PRES CENTER NEAR 14N102W.

...DISCUSSION...

TWO STRONG FEATURES DOMINATE THE MID LEVELS TONIGHT. THE FIRST 
IS A UPPER TROUGH ALONG 125W WITH A POLAR JET DIVING SE TO 
30N127W. THE OTHER IS A RIDGE CENTERED NEAR 25N114W WITH AN AXIS 
NE OVER THE CENTRAL CONUS. REST OF THE MID LEVEL AREA FLAT HIGH 
PRES. ON THE SURFACE TONIGHT A COLD FRONT WAS MOVING SE TO THE 
EXTREME NW CORNER OF THE REGION SUPPORTED BY THE UPPER TROUGH. 
AN AREA OF DISTURBED WEATHER WAS LOCATED NEAR 14N106W AND THE 
LATEST SATELLITE PICTURES SHOW GOOD ANTICYCLONIC FLOW ALOFT OVER 
THE DISTURBANCE. THE GFS MODEL LIKES THIS AREA BUT DOESN'T 
DEVELOP A LOW CENTER TIL ABOUT 18Z LATER TODAY. A WEAK PACIFIC 
RIDGE ALONG 25N PRESSES E AND NE AGAINST THE COAST TONIGHT AND 
GRADIENT BETWEEN THE RIDGE AND LOW PRES OVER THE SEA OF CORTEZ 
IS PRODUCING NW WINDS 15 TO 20 KT ALONG THE BAJA COAST ACCORDING 
TO SSMI. NO PASS FROM QUIKSCAT IN THIS AREA. GAP WINDS MOSTLY 
LIGHT. SOME LIGHT DRAINAGE FLOW THROUGH TEHUANTEPEC OTHERWISE 
OTHER GAP AREAS MOSTLY ONSHORE FLOW. LOWER SURFACE PRES OVER 
CENTRAL AMERICA KEEPS SWLY WINDS 20 TO 25 KT BETWEEN 5N AND 12N 
E OF 110W ACCORDING TO SSMI AND QUIKSCAT AND THE GFS CONCURS. 
OTHER CROSS EQUATORIAL SLY WINDS S OF 10N W OF 110W MOSTLY 15 TO 
20 KT ACCORDING TO SSMI IMAGERY. 

LATER DAY 1 THE STRONG UPPER TROUGH WILL CONTINUE MOVING EWD TO 
ALONG 120W WHILE THE MID LEVEL RIDGE CENTER REMAINS STATIONARY 
OVER SRN BAJA. ON THE SURFACE LATER TODAY THE COLD FRONT ENTERS 
THE REGION BUT CONTINUES TO WEAKEN WITH WINDS TO 20 KT AND NW 
SWELL 8 TO 9 FT. LITTLE CHANGE ELSEWHERE.

FOR DAY 2 THE GFS MODEL SHOWS A NEW SURGE OF COLD AIR SPILLING 
RAPIDLY SWD OVER THE SW CONUS IN THE STRONG TROUGH. THIS WILL 
FORCE THE MID LEVEL RIDGE TO SHIFT EWD AND WEAKEN. THE MID LEVEL 
FLOW BECOMES MORE ZONAL W OF THE TROUGH WITH A WEAK SHORTWAVE 
MOVING EWD TO 140W. ON THE SURFACE DAY 2 THE PACIFIC RIDGE WITH 
LITTLE SUPPORT ALOFT WILL REMAIN WEAK WITH A 1019 MB CENTER NEAR 
23N135W. NE TRADES WILL REMAIN MOSTLY 10 TO 15 KT ABOUT THE SAME 
AS NWLY WINDS ALONG THE BAJA COAST. THE GFS MODEL CONTINUES SLOW 
DEVELOPMENT OF THE LOW CENTER MOVING IT WWD TO NEAR 14N108W WITH 
WINDS TO 20 KT. CROSS EQUATORIAL SLY WINDS WILL CONTINUE TO 
ACCELERATE AS THEY MOVE SWLY BETWEEN 5N AND 11N E OF 110W. 
LITTLE CHANGE IN SPEED FROM DAY 1. GAP WINDS WILL REMAIN LIGHT. 

$$
RRG