NANMADOL Prognosis

[Jeb]

WDPN31 PGTW 010300

MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//

SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W

/WARNING NR 10//

RMKS/

1. FOR METEOROLOGISTS.

2. PROGNOSTIC REASONING FOR 010000Z1 DEC TO 060000Z6 DEC 2004.

A. TYPHOON (TY) 30W (NANMADOL), LOCATED APPROXIMATELY 340 NM

WEST-NORTHWEST OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT

24 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS

BASED ON 292330Z9 MULTISPECTRAL SATELLITE IMAGERY. THE

WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY

ESTIMATES OF 102 AND 115 KNOTS.

B. TY 30W IS FORECAST TO CONTINUE TO TRACK RAPIDLY WEST-

NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL

RIDGE CENTRED TO THE NORTHEAST. TY 30W IS FORECAST TO MAKE LANDFALL

ALONG THE EAST COAST OF THE NORTHERN PHILIPPINES AT APPROXIMATELY

TAU 36. TY 30W WILL TRACK ACROSS THE NORTHERN PHILIPPINES

INTO THE SOUTH CHINA SEA WHERE IT WILL TURN POLEWARD IN RESPONSE

TO A DEVELOPING WEAKNESS IN THE STEERING RIDGE CENTERED TO THE

NORTHEAST OF THE SYSTEM. THE AVAILABLE DYNAMIC AIDS CONSISTING OF

NOGAPS, COAMPS, GFDN, NCEP GFS, JGSM, JTYM, TCLAPS, UKMET, AND

WBAR ARE IN FAIR AGREEMENT WITH THIS SCENARIO. THE TIMING OF THE

ONSET OF RECURVATURE VARIES AMONG DYNAMIC AIDS BEYOND

APPROXIMATELY TAU 48. NCEP AVN DEPICTS A STRONGER MID-LATITUDE

TROUGH AND MORE MERIDIONAL DEVELOPMENT OF THE STEERING RIDGE TO THE

NORTHEAST AND THEREFORE TRACKS TY 30W POLEWARD FASTER AS COMPARED

TO OTHER AIDS. THIS FORECAST IS BASED ON A CONSENSUS OF ALL

AVAILABLE DYNAMIC AIDS.

C. THE INTENSITY OF TY 30W IS FORECAST TO INCREASE AT AN

APPROXIMATELY CLIMATOLOGICAL RATE THROUGH TAU 36 IN AN ENVIRONMENT

OF LOW TO MODERATE VERTICAL WIND SHEAR BALANCED BY GOOD RADIAL

OUTFLOW. THE INTENSITY IS FORECAST TO DECREASE SLOWLY AFTER TAU 36

AS THE SYSTEM INTERACTS WITH LAND AND ENTERS AN ENVIRONMENT OF

STRONGER VERTICAL WIND SHEAR.

D. CURRENT WIND RADII ARE BASED ON A 300902Z4 QUIKSCAT PASS AND

A 302132Z1 SSMI MICROWAVE PASS. FORECAST WIND RADII ARE BASED ON

CLIMATOLOGY FOR A LARGE SIZED SYSTEM.

E. THE MID-LATITUDE TROUGH PROPGATING EASTWARD OVER CHINA WILL

PROVIDE A WEAKNESS IN THE STEERING RIDGE LATER IN THE FORECAST PERIOD

THAT WILL ALLOW TY 30W TO TURN POLEWARD AFTER TAU 48. TY 30W WILL

WEAKEN IN INTENSITY AFTER TAU 72 AS IT ENCOUNTERS INCREASED VERTICAL

WIND SHEAR IN THE SOUTH CHINA SEA. TY 30W IS FORECAST TO BEGIN THE

INITIAL STAGES OF EXTRATROPICAL TRANSITION BEYOND TAU 72 AS IT TRACKS

NORTHEASTWARD AND BECOMES EMBEDDED IN THE MID-LATITUDE WESTERLIES.

3. FORECAST TEAM: DIXON/FJELD/SCHULTZ//