Tropical Storm LIONROCK Advisory Thu Aug 25

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 26//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 269 NM EAST-
SOUTHEAST OF KADENA AB, JAPAN, HAS TRACKED SOUTH-SOUTHWESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. TY 12W HAS RAPIDLY INTENSIFIED OVER
THE PAST 24 HOURS FROM 55 KNOTS TO THE CURRENT INTENSITY OF 100
KNOTS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A COMPACT
SYSTEM WITH A 12NM EYE AND NEAR-RADIAL OUTFLOW. A 240731Z GPM 89GHZ
IMAGE DEPICTS A SMALL CORE, APPROXIMATELY 30NM DIAMETER, WITH A
PINHOLE EYE AND BANDING FEATURE. RECENT ANIMATED WATER VAPOR IMAGERY
INDICATES THAT TY 12W HAS BEEN ABLE TO INSULATE ITSELF AND MAINTAIN
RADIAL OUTFLOW DESPITE WEAKENING POLEWARD OUTFLOW AND CONVERGENT
FLOW ASSOCIATED WITH THE BUILDING RIDGE TO THE NORTH. THE CURRENT
INTENSITY IS ASSESSED AT 100 KNOTS BASED ON DVORAK INTENSITY
ESTIMATES RANGING FROM T5.0 (90 KNOTS) TO T5.5 (102 KNOTS).
ADDITIONALLY, THE 24/0630Z SATCON ESTIMATE HAS JUMPED TO 104 KNOTS.
TY 12W IS TRACKING SLOWLY SOUTHWESTWARD ALONG THE EASTERN PERIPHERY
OF THE WESTERN SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. HOWEVER, THE INTENSITY FORECAST HAS
BEEN INCREASED SIGNIFICANTLY BASED ON THE RECENT PERIOD OF RAPID
INTENSIFICATION.
   B. TY 12W WILL REMAIN TRAPPED WITHIN THIS COMPETING STEERING
ENVIRONMENT WHILE DRIFTING SOUTHWESTWARD TO WESTWARD THROUGH
TAU 36. THE WESTERN STR IS EXPECTED TO REMAIN ENTRENCHED OVER THE
EAST CHINA SEA AND OKINAWA PROVIDING A BARRIER TO ANY SIGNIFICANT
WESTWARD MOVEMENT. IN FACT, ALL DYNAMIC MODELS SHOW A SLOW, QUASI-
STATIONARY MOTION THROUGH TAU 48 AND SHOW NO POSITION WEST OF 131E
LONGITUDE. TY 12W IS FORECAST TO GRADUALLY INTENSIFY UNDER FAVORABLE
CONDITIONS TO A PEAK OF 120 KNOTS BY TAU 24.
   C. IN THE EXTENDED TAUS, THE NEAR-EQUATORIAL RIDGE (NER) IS
FORECAST TO BUILD TO THE SOUTH OF TY 12W WHILE A DEEP MIDLATITUDE
TROUGH DEEPENS OVER JAPAN, ALLOWING THE SYSTEM TO ACCELERATE
NORTHEASTWARD. WHILE THE MODEL VORTEX TRACKERS DIFFER ON THE EXACT
NATURE OF THE TURN EASTWARD, THE TRACKERS ALL SHOW AN EASTWARD TURN
WITH DIFFERENT TRACK SPEEDS. DUE TO THE COMPLEXITY OF THE STEERING
ENVIRONMENT AND UNCERTAINTY IN THE EASTWARD TURN, THERE IS LOW
CONFIDENCE IN JTWC FORECAST TRACK.//
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