000
AXPZ20 KNHC 120255
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE SEP 11 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURE...
A BROAD AREA OF LOW PRESSURE CENTERED NEAR 16N104W MOVING W-NW 
AT ABOUT 10 KT IS EMBEDDED ALONG THE MONSOON TROUGH. EASTERLY 
WINDS TO 25 KT ARE IN THE NE SEMICIRCLE OF THE LOW ALONG THE 
SOUTHERN COAST OF MEXICO BETWEEN 98W AND 103W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION EXISTS WITHIN 180 NM OF THE 
LOW. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR TROPICAL 
CYCLOGENESIS DURING THE NEXT TWO DAYS AS THE VERTICAL SHEAR 
SHOULD REMAIN MODERATE OUT OF THE NORTHEAST AND THE SYSTEM WILL 
STAY OVER WARM WATERS. THE DISTURBANCE IS EXPECTED TO INTENSIFY 
AS IT MOVES NORTHWEST OFFSHORE OF THE MEXICAN COAST.  THE 18 UTC 
GFS...18 UTC NOGAPS...AND 12 UTC UKMET GLOBAL MODELS ARE MORE 
AGGRESSIVE WITH ITS INTENSIFICATION...WHILE THE 12 UTC ECMWF 
SHOWS ONLY A SMALL AMOUNT OF DEVELOPMENT.  SOMEWHAT COMPLICATING 
THE PREDICTION IS THAT A SEPARATE LOW IS SUGGESTED TO OCCUR 
ALONG THE MONSOON TROUGH SOUTHWEST OF THE CURRENT LOW.  THIS 
COULD...IF IT OCCURS...AFFECT THE EVENTUAL TRACK AND INTENSITY 
OF THE EXISTING LOW. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 08N78W TO 08N96W TO LOW PRES NEAR 
16N104W TO 12N121W. ITCZ THEN BEGINS AND EXTENDS TO 13N126W. 
ITCZ BEGINS AGAIN AT 10N134W TO BEYOND 08N140W.  SCATTERED 
MODERATE CONVECTION EXISTS WITHIN 60 NM OF AXIS EAST OF 83W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION EXISTS WITHIN 180 
NM OF THE LOW.  SCATTERED MODERATE CONVECTION EXISTS WITHIN 180 
NM N OF AXIS BETWEEN 110W AND 115W. SCATTERED MODERATE 
CONVECTION EXISTS WITHIN 120 NM S OF AXIS BETWEEN 120W AND 128W.

...DISCUSSION...
THE SUBTROPICAL HIGH IS CENTERED WELL N OF THE AREA WITH RIDGING 
EXTENDING SOUTHEAST FROM THE HIGH ALONG THE NORTHERN PORTION OF 
THE DISCUSSION AREA.  THE PRESSURE GRADIENT FROM THE RIDGE 
EQUATORWARD TO THE MONSOON TROUGH IS MODEST AND THUS THE 
TRADEWINDS ARE WEAK AND BELOW OUR 25 KT CRITERION FOR THE HIGH 
SEAS.  SW WINDS ON THE EQUATORWARD SIDE OF THE MONSOON TROUGH 
ARE ALSO RELATIVELY WEAK FOR THIS TIME OF YEAR.  A WEAK GULF OF 
PAPAGAYO GAP WIND EVENT IS OCCURRING...BUT NE-E WINDS AS SEEN IN 
AN EARLIER ASCAT SCATTEROMETER PASS ARE AT 20 KT.  THESE SHOULD 
NOT REACH THE 25 KT HIGH SEAS CRITERION BUT MAY CONTINUE AROUND 
20 KT THROUGH FRIDAY.

$$
CHRIS LANDSEA