Tropical Storm LIONROCK Advisory Wed Aug 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 251 NM EAST-
SOUTHEAST OF KADENA AB, HAS TRACKED SOUTHWESTWARD AT 07 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
CONTINUES TO DEPICT A COMPACT SYSTEM WITH A CLOUD-FILLED EYE AND
NEAR-RADIAL OUTFLOW. A 241000Z SSMIS 91GHZ IMAGE DEPICTS A SMALL
CORE, APPROXIMATELY 60NM DIAMETER, WITH A BANDING FEATURE OVER THE
WESTERN SEMI-CIRCLE. 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 CURRENT INTENSITY
ESTIMATES RANGING FROM 5.0 (90 KNOTS) TO 5.5 (102 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.
   B. TY 12W WILL REMAIN TRAPPED WITHIN THIS WEAK 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 36 AND SHOW NO POSITION WEST OF 131E
LONGITUDE. TY 12W IS FORECAST TO GRADUALLY INTENSIFY UNDER FAVORABLE
CONDITIONS TO A PEAK OF 115 KNOTS BY TAU 12 BUT IS EXPECTED TO
WEAKEN THROUGH TAU 36, AS IT BECOMES QUASI-STATIONARY, DUE TO
UPWELLING COOLER WATER.
   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 A NORTHEASTWARD
TURN WITH DIFFERENT TRACK SPEEDS. SLIGHT INTENSIFICATION IS FORECAST
DUE TO INCREASING POLEWARD OUTFLOW ASSOCIATED WITH THE APPROACHING
DEEP SHORTWAVE TROUGH EXPECTED TO DIG OVER CENTRAL JAPAN. DUE TO THE
COMPLEXITY OF THE STEERING ENVIRONMENT AND UNCERTAINTY IN BOTH THE
EARLY PHASE OF THE TRACK AND LATER PHASE OF THE TRACK, THERE IS LOW
CONFIDENCE IN JTWC FORECAST TRACK.//
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