000
AXPZ20 KNHC 101513
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC FRI MAY 10 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

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

A MONSOON TROUGH EXTENDS FROM 09N85W TO 10N93W THEN TRANSITIONS 
TO A ITCZ TO 11N104W...THEN CONTINUES FROM 10N110W TO 07N125W TO 
07N140W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION NOTED 
WITHIN 120 NM S OF MONSOON TROUGH AXIS BETWEEN 78W AND 85W. 
SCATTERED MODERATE CONVECTION NOTED WITHIN 150 NM S OF ITCZ AXIS 
BETWEEN 115W AND 125W...AND WITHIN 120 NM N OF ITCZ AXIS W OF 
130W.

...DISCUSSION...

W OF 110W...1025 MB HIGH PRES IS CENTERED NEAR 
34N130W...MAINTAINING FAIRLY LIGHT WINDS OVER MOST OF THE AREA W 
OF 110W. SHIP AND SCATTEROMETER DATA INDICATE NW WINDS TO 20 KT 
OFF THE COAST OF NORTHERN BAJA ON THE EASTERN EDGE OF THE HIGH 
PRES. SCATTEROMETER DATA ALSO SHOWS 15 TO 20 KT TRADE WINDS FROM 
10N TO 20N W OF 120W...SUPPORTING SCATTERED CONVECTION ALONG THE 
ITCZ. THE MID/UPPER PATTERNS WILL BECOME MORE AMPLIFIED THROUGH 
SUN...AS LOW PRES CUTS OFF OVER NW MEXICO AHEAD OF RIDGING 
BUILDING ALONG 130W...AS A DEEP LAYER TROUGH SHIFTS EASTWARD 
THROUGH THE N CENTRAL PACIFIC WELL N OF HAWAII. A WEAK LATE 
SEASON FRONTAL BOUNDARY ASSOCIATED WITH THE SYSTEM IN THE N 
CENTRAL PACIFIC WILL REACH AS FAR AS 30N140W LATE SAT BEFORE 
BECOMING DIFFUSE AND LIFTING NE. THE RIDGE AND ASSOCIATED 
SURFACE HIGH PRES WILL WEAKEN SAT INTO SUN AS THIS BOUNDARY 
APPROACHES...THEN BECOME ABSORBED INTO A STRONGER RIDGE BUILDING 
BEHIND THE TROUGH/FRONT NE OF HAWAII. LOOKING AHEAD TO EARLY 
NEXT WEEK...THE GFS AND ECMWF BOTH INDICATE AN ARC OF N TO NE 
FLOW AROUND THE SE PERIPHERY OF THE NEW HIGH PRES AS IT SLOWLY 
SHIFTS E TO THE N OF THE AREA.

E OF 110W...SURFACE OBSERVATIONS AND OSCAT DATA SHOW W TO SW 
FLOW ACROSS PANAMA AND THE GULF OF PANAMA...INDICATING THE 
MONSOON TROUGH AXIS IS LIKELY N OF THE ISTHMUS. PRECIPITABLE 
WATER VALUES REMAIN QUITE HIGH IN THIS AREA...PROLIFIC 
CONVECTION PERSISTS BOTH OVER THE SW CARIBBEAN AND IN THE 
PACIFIC FROM COASTAL COLOMBIA TO COSTA RICA. GLOBAL MODELS 
REMAIN IN GOOD AGREEMENT SHOWING A SURFACE LOW SHIFTING W ALONG 
THE MONSOON TROUGH REACHING THE PACIFIC COAST OF COSTA RICA BY 
LATE SAT. FOR EARLY NEXT WEEK...GAP WINDS FUNNELING THROUGH THE 
GULF OF PAPAGAYO WILL INTERACT WITH THE MONSOON TROUGH AND HELP 
TO INCREASE LOW LEVEL VORTICITY WITHIN THE MONSOON TROUGH. GAP 
WINDS THROUGH THE GULF OF TEHUANTEPEC WILL BE INDUCED MON AND 
TUE BY THE LOW PRES AS IT SHIFTS FARTHER WEST AND FURTHER 
INCREASE LOW LEVEL VORTICITY WITHIN THE MONSOON TROUGH TUE AND 
WED. BOTH GFS AND ECMWF INDICATE A WEAK NEGATIVELY TILTED TROUGH 
ALOFT WILL SHIFT E OF 110W MON INTO TUE. WHILE THIS MAY AID 
CONVECTION SOMEWHAT...IT COULD ALSO APPLY WESTERLY SHEAR AS 
DEPICTED PRIMARILY BY THE GFS. THIS MAY BE SHORT LIVED HOWEVER 
AS BOTH MODELS SHOW THE MID/UPPER RIDGE SHIFTING S BY MIDWEEK. 
STILL SOME UNCERTAINTY THEREFORE IN HOW ACTIVE THE LOW WILL BE 
AS IT PUSHES W EARLY NEXT WEEK.
  
$$
CHRISTENSEN