000
AXPZ20 KNHC 132205
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU SEP 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...SPECIAL FEATURE...

TROPICAL STORM KRISTY CENTERED NEAR 19.3N 110.2W AT 2100 UTC 
MOVING WNW AT 9 KT WITH MAXIMUM SUSTAINED WINDS OF 45 KT WITH 
GUSTS TO 55 KT AND MINIMUM PRESSURE OF 1002 MB. SATELLITE IMAGES
DURING THE DAY SHOW THAT THE CYCLONE CENTER IS PARTIALLY EXPOSED
UNDER N-NW UPPER SHEAR. THE DENSEST OF THE CLOUD SHEAR PATTERN 
TO THE E AND SE OF THE CENTER. SCATTERED STRONG CONVECTION IS 
NOTED WITHIN 90 NM OF THE CENTER IN THE SE QUADRANT. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION IS ELSEWHERE WITHIN 150 NM 
SE OF THE CYCLONE. KRISTY IS FORECAST TO TRACK IN A GENERAL NW
DIRECTION OVER COOLER SEA SURFACE TEMPERATURES DURING THE
NEXT 48 HRS CAUSING KRISTY TO UNDERGO GRADUAL WEAKENING. SEE 
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM 09N84W TO 07N96W TO 07N107W TO 
10N115W WHERE IT ENDS. IT THEN RESUMES AT 14N119W TO 11N129W. 
THE ITCZ BEGINS AT 10N138W AND CONTINUES TO BEYOND 09N140W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N 
OF THE MONSOON TROUGH E OF 88W.

...DISCUSSION...

IN THE MID/UPPER LEVELS...A HIGHLY AMPLIFIED PATTERN IS DEPICTED 
BY A LARGE ANTICYLONE OVER THE CENTRAL PORTION OF THE DISCUSSION
AREA WITH ITS MEAN AXIS ROUGHLY ALONG 123W WITH A CREST TO WELL 
NNE OF THE REGION. TO ITS W OVER THE CENTRAL PACIFIC IS A LARGE 
TROUGH THAT STRETCHES FROM 32N143W SSW TO NEAR 19N144W. MODERATE 
SUBSIDENCE RESULTING IN RATHER DRY AND STABLE ENVIRONMENTAL 
CONDITIONS DEPICTED BY BROKEN STRATOCUMULUS CLOUDS MOVING WSW 
COVERS THE REGION UNDER THE SUBSIDENCE AREA TO THE N AND NW OF 
THE TROPICAL ZONE. THE MID/UPPER LEVEL RIDGE FEATURE IS FORECAST
TO HOLD THROUGH THE NEXT 48 HRS...WITH THE TROUGH DEVELOPING
A LOW JUST NW OF THE AREA.

AT THE SURFACE...A 1011 MB LOW IS SW OF TROPICAL STORM KRISTY
NEAR 15N117W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
WITHIN 150 NM OF THE LOW IN THE NW QUADRANT. THE LOW IS EXPECTED 
TO MOVE SLOWLY W THEN NNW WITH LITTLE DEVELOPMENT THROUGH THE 
WEEKEND. AN ELONGATED A AREA OF LOW PRES HAS FORMED OVER THE
WESTERN PORTION OF THE AREA FROM 10N TO 16N BETWEEN 130W-135W
WHERE CLUSTERS OF SCATTERED MODERATE TO STRONG CONVECTION ARE
NOTED. THE GLOBAL MODELS HAVE BEEN HINTING THAT A LOW PRES WOULD
FORM AND MOVE SLOWLY W TO W TO NW THROUGH THE NEXT 48 HOURS. THE
GFS HAS BEEN MORE AGGRESSIVE IN FORECASTING WINDS AND SEAS WITH 
THIS FEATURE. WILL LEAN TOWARDS THE LESS AGGRESSIVE MODEL 
CONSENSUS FOR NOW...AND WAIT FOR UPDATED MODEL RUNS BEFORE 
MAKING A MORE DEFINITIVE FORECAST WITH RESPECT TO WINDS AND SEAS 
RELATED TO THIS LOW PRES SYSTEM.

A 1027 MB HIGH N OF THE DISCUSSION AREA AT 39N143W EXTENDS A
RIDGE SE THROUGH 32N134W AND TO NEAR 24N115W. LIGHT TO MODERATE 
WINDS PREVAIL OVER MOST OF THE REGION...EXCEPT WITHIN 300 NM N 
OF THE CONVERGENCE ZONE W OF 130W IN ENHANCED NE TRADE WIND 
FLOW...AND JUST W OF THE GULF OF PAPAGAYO IN FRESH E-NE GAP 
WINDS FUNNELING FROM THE W CARIBBEAN THROUGH CENTRAL 
AMERICA...BUILDING SEAS DOWNWIND FROM THE GULF OF PAPAGAYO TO 
AROUND 7 FT.

FRESH NE WINDS WITH SEAS AROUND 7 FT ARE EXPECTED TO PERSIST N 
OF THE CONVERGENCE ZONE W OF 130W THROUGH FRI. FRESH WINDS AND 
HIGHER SEAS ARE EXPECTED TO PERSIST DOWNSTREAM OF THE GULF OF 
PAPAGAYO THROUGH FRI EVENING. GFS AND ECMWF MODELS CONTINUE
TO INDICATE DIURNAL PULSES OF NORTHERLY DRAINAGE FLOW INTO THE 
GULF OF TEHUANTEPEC BEGINNING EARLY FRI... AND CONTINUING INTO
SAT WITH N-NE WINDS TO 20-25 KT PRIMARILY AROUND DAYBREAK. SEAS
THERE SHOULD REMAIN 8 FT OR LESS DOWNWIND FROM THE GULF OF 
TEHUANTEPEC.

$$
AGUIRRE