000
AXPZ20 KNHC 170327
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT OCT 17 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... 

HURRICANE RICK WAS CENTERED NEAR 13.3N 101.0W AT 0300 UTC OR 
ABOUT 260 MILES...415 KM S-SW OF ACAPULCO MEXICO MOVING WNW AT 9 
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 975 MB. MAXIMUM 
SUSTAINED WINDS HAVE INCREASED TO 85 KT WITH GUSTS TO 105 KT. 
SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. A LARGE BURST OF 
CONVECTION ON THE NE SIDE OF RICK AROUND SUNSET HAS WRAPPED 
AROUND THE CENTER OF THE SYSTEM AND AN EYE APPEARS TO BE 
FORMING. NUMEROUS STRONG CONVECTION CAN BE FOUND WITHIN 120 NM N 
QUADRANT AND NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION 
LIES ELSEWHERE WITHIN 330 NM S AND 210 NM N SEMICIRCLES OF RICK.
ATMOSPHERIC CONDITIONS APPEAR FAVORABLE FOR RICK TO CONTINUE TO 
UNDERGO INTENSIFICATION UNDER A LOW SHEAR ENVIRONMENT ALONG WITH 
VERY CONDUCIVE SEA SURFACE TEMPERATURES THROUGH THE NEXT 48 
HOURS AS IT TRACKS W-NW.

...TROPICAL WAVE...

A TROPICAL WAVE ALONG 116W FROM 08N TO 15N IS MOVING W AT ABOUT 
13 KT. ISOLATED MODERATE CONVECTION CAN BE FOUND WITHIN 210 NM E 
OF WAVE FROM 08N TO 10N...SOUTH OF WHERE IT CROSSES THE ITCZ.

...ITCZ...

THE AXIS OF THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 
AXIS 09N78W TO 12N95W TO 10N107W TO 10N135W TO LOW PRES 12N139W. 
SCATTERED MODERATE CONVECTION LIES WITHIN 90 NM EITHER SIDE OF 
THE ITCZ AXIS BETWEEN 105W AND 110W.

...DISCUSSION...

THE DEEP LAYER RIDGE WILL HOLD OVER N WATERS THROUGH THE 
FORECAST PERIOD DESPITE BEING CHALLENGED BY A TROUGH CURRENTLY 
BRUSHING NW WATERS. THE MID TO UPPER LEVEL TROUGH WILL LIFT NE 
SAT AND THE NW SWELL ASSOCIATED WITH THIS TROUGH...WHICH IS 
CURRENTLY BRINGING SIGNIFICANT WAVE HEIGHTS TO 12 FT IN N 
WATERS...WILL SUBSIDE AS IT MOVES SOUTH. THE WEAKENING COLD 
FRONT AT THE SURFACE WILL ENTER NW WATERS LATE TONIGHT AND 
DISSIPATE SAT. HIGH PRES BEHIND THE FRONT WILL APPROACH NW 
WATERS SAT NIGHT. AS A RESULT...THE MEAN SURFACE RIDGE WILL 
SHIFT W OVER THE NEXT FEW DAYS. THE PRES GRADIENT BETWEEN THE 
RIDGE AND THE 1006 MB SURFACE LOW NEAR 12N139W WILL KEEP WINDS 
IN THE NE QUADRANT OF THE LOW IN THE 20 TO 25 KT RANGE AS IT 
MOVES OUT OF THE FORECAST AREA OVERNIGHT. THE 1834 UTC ASCAT 
PASS CONFIRMS THESE 20 TO 25 KT WINDS. EASTERLY FLOW ATTRIBUTED 
TO THIS PRES GRADIENT WILL SLOWLY DIMINISH TO 20 KT OVER THE 
NEXT FEW DAYS OVER W WATERS BETWEEN 14N AND 22N. ON THE EASTERN 
EDGE OF THE RIDGE...THE 1830 UTC ASCAT PASS SHOWS N WINDS IN THE 
TO 20 KT OFF THE W COAST OF THE BAJA PENINSULA WHERE THE PRES 
GRADIENT IS TIGHT BETWEEN LOW PRES OVER THE GULF OF CALIFORNIA 
AND THE RIDGE. THESE WINDS SHOULD SHIFT N AND DIMINISH BY SUN 
MORNING.

GAP WINDS...A COLD FRONT CURRENTLY LIES OVER THE GULF OF MEXICO 
FROM TAMPA BAY TO NE MEXICO. THE DEEP LAYER MID LATITUDE TROUGH 
SUPPORTING THIS COLD FRONT WILL AMPLIFY OVER THE GULF OF MEXICO 
SAT AND SEND THE STRONG COLD FRONT THROUGH THE BAY OF CAMPECHE. 
THE NORTHERLY FLOW WILL BEGIN FUNNELING THROUGH THE ISTHMUS OF 
TEHUANTEPEC BY SAT MORNING...MAKING ITS WAY OVER SEA SURFACE 
TEMPERATURES NEAR 30 CELSIUS. STRONG WINDS ALOFT WILL QUICKLY 
MIX TO THE SURFACE. WINDS ARE EXPECTED TO REACH GALE FORCE BY 
SAT EVENING AND STORM FORCE BY SUN EVENING...WITH SIGNIFICANT 
WAVE HEIGHTS REACHING 15 FT.

$$
SCHAUER