000
AXPZ20 KNHC 150326
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU OCT 15 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0200 UTC.

...SPECIAL FEATURE... 

AT 0000 UTC A BROAD AREA OF LOW PRESSURE WAS CENTERED NEAR 
09N94W.  OVER THE LAST SEVERAL HOURS...SCATTERED MODERATE 
CONVECTION HAS FORMED WITHIN 180 NM NORTH OF THE LOW.  WHILE THE 
CONVECTION HAS NOT YET BEEN IN PLACE FOR THE 12 HOURS NECESSARY 
FOR DVORAK CLASSIFICATIONS TO BEGIN...THE ROBUST SPIN-UP IN ALL 
FOUR GLOBAL MODELS IS ONE OF THE REASONS FOR CONSIDERING THIS TO 
BE A POSSIBLE TROPICAL CYCLONE WITHIN THE NEXT 48 HOURS.  GIVEN 
THE LOW SHEAR...ABUNDANT MOISTURE...AND WARMER THAN NORMAL SSTS 
IN THE AREA...IT IS NOT SURPRISING THAT THE MODELS ARE CALLING 
FOR GENESIS.

AT 0000 UTC THE 1009 MB REMNANT LOW OF PATRICIA WAS LOCATED NEAR 
23N112W OR ABOUT 120 NM WSW OF THE SOUTHERN TIP OF BAJA 
CALIFORNIA.  THE LOW WAS MOVING W AROUND 10 KT.  NO DEEP 
CONVECTION REMAINS NEAR THE CENTER OF PATRICIA. THE REMNANTS OF 
PATRICIA ARE EXPECTED TO GRADUALLY WEAKEN AND FOLLOW A W TRACK 
FOR THE NEXT FEW DAYS...DISSIPATING FRI MORNING AFTER IT CROSSES 
115W. 

...TROPICAL WAVES...

A TROPICAL WAVE WAS ANALYZED ALONG 105W FROM 04N TO 13N.  THE 
WAVE WAS MOVING W AT 10-15 KT. THIS WAVE IS ON THE WESTERN EDGE 
OF AN AREA OF BROAD CYCLONIC TURNING THAT EXTENDS EAST TO THE 
COAST.  AN EARLIER ASCAT PASS SHOWED THAT THE TROPICAL WAVE WAS 
BEGINNING TO BREAK AWAY FROM THE LARGER SCALE CYCLONIC 
GYRE...WHICH IS NOW THE LOW DESCRIBED ABOVE. SCATTERED MODERATE 
CONVECTION CAN BE FOUND WITHIN 240 NM W OF THE TROPICAL WAVE 
FROM 06N TO 12N.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS ALONG 08N78W TO 09N93W TO 
08N100W TO 11N115W TO 14N140W. SCATTERED MODERATE CONVECTION IS 
OCCURRING WITHIN 180 NM EITHER SIDE OF AXIS BETWEEN 105W AND 
115W.

A TROUGH INTERSECTS THE ITCZ ALONG 139W...THOUGH THERE IS NO 
SIGNIFICANT CONVECTION ASSOCIATED WITH THE TROUGH. 

...DISCUSSION...

1017 MB HIGH PRES CURRENTLY NEAR 27N126W WILL MIGRATE NW OVER 
THE NEXT TWO DAYS AS THE NEGATIVELY TILTED DEEP LAYER TROUGH 
OVER THE EASTERN PACIFIC N OF THE FORECAST AREA PASSES INTO 
THE WESTERN U.S. THIS WILL MAKE WAY FOR DEEP LAYER RIDGING TO 
BUILD ACROSS N WATERS. STEERING FLOW FOR THE REMNANTS OF 
PATRICIA WILL BE DOMINATED BY THIS RIDGE TO ITS NW THE REMAINDER 
OF THE PERIOD. THE TIGHT PRES GRADIENT ALONG THE COAST OF THE 
BAJA PENINSULA BETWEEN THIS RIDGE AND PATRICIA IS GENERATING 20 
KT N TO NW WINDS ALONG THE WESTERN BAJA COAST N OF PATRICIA THAT 
WILL CONTINUE FOR ABOUT ONE MORE DAY. THE WESTWARD BUILDING 
SURFACE RIDGE HAS ALLOWED EASTERLY FLOW TO INCREASE W OF 122W 
BETWEEN THE RIDGE AXIS AND THE TROUGHS OVER W WATERS EMBEDDED IN 
THE ITCZ. THIS RIDGE WILL PREVENT THE NEXT COLD FRONT...EXPECTED 
TO APPROACH THE FORECAST AREA THU...FROM MOVING INTO NW WATERS. 
THE AFOREMENTIONED DEEP LAYER TROUGHING WELL NORTH OF THE AREA 
IS PRODUCING NW SWELL THAT IS MOVING SOUTH THROUGH NORTHERN 
FORECAST WATERS.

A STRONG COLD FRONT IS PROJECTED TO MOVE ACROSS THE GULF OF 
MEXICO AND INDUCE A TEHUANTEPEC GAP WIND EVENT.  THIS IS LIKELY 
TO COMMENCE IN ABOUT THREE DAYS.  GIVEN THE WARMER THAN NORMAL 
WATERS SOUTH OF MEXICO FOR THIS TIME OF YEAR...THIS MAY CAUSE 
STRONGER WINDS IN THE EVENT THEN PERHAPS OTHERWISE ANTICIPATED.  
IT IS...HOWEVER...TOO EARLY TO STATE WHETHER THIS GAP EVENT WILL 
REACH GALE FORCE.

$$
LANDSEA/SCHAUER