000
AXPZ20 KNHC 210925
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI SEP 21 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...SPECIAL FEATURES...
A 1006 MB SURFACE LOW PRES IS EMBEDDED IN MONSOON TROUGH NEAR 
13.5N104.5W AT 21/0600 UTC. ALTHOUGH THUNDERSTORM ACTIVITY 
REMAINS LIMITED NEAR THE CENTER...SOME BANDING FEATURES ARE 
NOTED SPINNING AROUND THE LOW LEVEL CENTER. SCATTERED MODERATE 
TO ISOLATED STRONG CONVECTION COVERS THE AREA FROM 10N TO 16N 
BETWEEN 100W AND 107W. ENVIRONMENTAL CONDITIONS APPEAR TO BE 
CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT 
COUPLE OF DAYS. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD 
TO WEST-NORTHWESTWARD AT 5 TO 10 KT. GLOBAL MODELS ARE IN PRETTY 
GOOD AGREEMENT SHOWING THE DEVELOPMENT OF THIS SYSTEM. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 11N85W TO 10N93W TO 1006 MB LOW PRES 
NEAR 13.5N104.5W TO 1008 MB LOW PRES NEAR 15N112W TO 11N124W 
THEN THE ITCZ CONTINUES TO 10N133W TO BEYOND 06N140W. CLUSTERS 
OF SCATTERED MODERATE TO STRONG CONVECTION ARE NOTED NEAR THE 
PACIFIC COAST OF PANAMA FROM 04N TO 08N BETWEEN 78W AND 81W AND 
N OF 06N BETWEEN 81W AND 86W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS FROM 07N TO 10N BETWEEN 128W AND 138W. 

...DISCUSSION...
AN UPPER ANTICYCLONE CENTERED NEAR 13N139W EXTENDS A RIDGE NE 
ACROSS THE FORECAST WATERS TO BEYOND 30N120W. STRONG SWLY WINDS 
OF 50-70 KT ARE TRANSPORTING ABUNDANT MID TO UPPER LEVEL 
MOISTURE ACROSS THE NW CORNER OF THE AREA. THESE WINDS ARE 
ASSOCIATED WITH A LONG WAVE TROUGH THAT CROSSES 30N140W. A 
SECOND ANTICYCLONE ALOFT NEAR 15N104W IS PRODUCING A LOW SHEAR 
ENVIRONMENT AND GOOD OUTFLOW OVER THE SURFACE LOW PRES LOCATED 
NEAR 13.5N104.5W. NWLY FLOW AND MODERATE TO STRONG SUBSIDENCE IS 
SEEN ON WATER VAPOR IMAGERY N OF 21N E OF 120W...INCLUDING THE 
BAJA CALIFORNIA PENINSULA. AN INVERTED TROUGH EXTENDS FROM NE 
HONDURAS AND NICARAGUA INTO THE EPAC ALONG 12N85W 07N87W 
09N85W.  

A SURFACE TROUGH...RELATED TO THE REMNANTS OF LANE...EXTENDS 
FROM 24N138W TO 18N137W. THE TROUGH IS FORECAST TO MOVE W OF THE 
FORECAST AREA TODAY. THE MOST RECENT SCATTEROMETER DATA SHOWED 
AN AREA OF FRESH WINDS...IN ASSOCIATION WITH THIS TROUGH...FROM 
21N TO 25N W OF 134W. PRES GRADIENT BETWEEN HIGH PRES LOCATED N 
OF THE FORECAST REGION NEAR 33N137W AND LOWER PRES ALONG THE 
ITCZ WILL RESULT IN A SMALL AREA OF 20 KT TRADE WINDS FROM 11N 
TO 16N W OF 135W. THESE WINDS WILL RAISE SEAS TO 8 FT TONIGHT 
AND SAT. NLY WINDS OF 20-25 KT CAN BE FOUND N OF 26N BETWEEN 
120W AND 125W. THESE WINDS ARE THE RESULT OF A TIGHT PRES 
GRADIENT BETWEEN THE AFOREMENTIONED HIGH PRES AND A SURFACE 
TROUGH ALONG BAJA CALIFORNIA. THESE WINDS ARE EXPECTED TO 
DIMINISH BELOW 20 KT BY SAT. 

ANOTHER LOW PRES WITHIN THE MONSOON TROUGH IS SITUATED NEAR 
15N112W. A TROUGH EXTENDS FROM THE LOW CENTER TO NEAR 18N112W. 
THIS SYSTEM IS FORECAST TO DISSIPATE IN ABOUT 24 HOURS.  

GAP WINDS...BUILDING HIGH PRESSURE ACROSS EASTERN MEXICO AND THE 
SW GULF OF MEXICO IS SUPPORTING A GAP WIND EVENT THROUGH THE 
GULF OF TEHUANTEPEC. THE MOST RECENT ASCAT PASS PROVIDED 
OBSERVATIONS OF 20-25 KT WINDS ACROSS THIS REGION. THIS WEATHER 
PATTERN IS FORECAST TO PERSIST THROUGH THE WEEKEND WITH THE 
STRONGEST WINDS OCCURRING LATE AT NIGHT TILL THE EARLY MORNING 
HOURS. 
 
$$
GR