Tropical Storm LIONROCK Advisory Sun Aug 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 38//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 742 NM SOUTH-
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH A 23-NM ROUND EYE, WHICH PROVIDES GOOD CONFIDENCE IN THE
CURRENT POSITION. A 270634Z SSMIS 91GHZ IMAGE SHOWS FRAGMENTED
SPIRAL BANDING WRAPPING INTO THE COMPACT CORE. ANIMATED WATER VAPOR
IMAGERY INDICATES NEAR-RADIAL OUTFLOW ENHANCED BY AN UPPER LOW NEAR
33N 150E. THE CURRENT INTENSITY IS ASSESSED AT 115 KNOTS BASED ON A
PGTW DVORAK CURRENT INTENSITY ESTIMATE OF 6.0 (115 KNOTS). TY 12W IS
TRACKING EAST-NORTHEASTWARD ALONG THE NORTHERN PERIPHERY OF THE NEAR-
EQUATORIAL RIDGE (NER). THE 500MB ANALYSIS INDICATES BROAD TROUGHING
TO THE NORTH, WHICH HAS WEAKENED THE SUBTROPICAL RIDGE (STR), AND
ALLOWED THE NER TO REMAIN THE DOMINANT STEERING INFLUENCE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 12W WILL CONTINUE TO TRACK ALONG THE NORTHERN PERIPHERY OF
THE NER THROUGH TAU 48. TY LIONROCK IS FORECAST TO MAINTAIN
INTENSITY NEAR 115 KNOTS THROUGH THIS PERIOD DUE TO FAVORABLE
ENVIRONMENTAL CONDITIONS. DYNAMIC MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PHASE OF THE
JTWC FORECAST TRACK. AFTER TAU 48, THE DYNAMIC MODEL TRACKERS
DIVERGE WITH MAJOR DIFFERENCES IN TRACK DESPITE CONSISTENT DEPICTION
OF THE MAJOR SYNOPTIC FEATURES (MAJOR SHORTWAVE TROUGH AND THE
POSITION OF THE STRONG RIDGE NORTHEAST OF JAPAN).
   C. AFTER TAU 72, TY 12W IS FORECAST TO RE-CURVE OVER NORTHERN
JAPAN AND TO WEAKEN AS IT ENCOUNTERS INCREASING VERTICAL WIND SHEAR
(VWS) AND COOLER SST. FURTHER WEAKENING IS EXPECTED AS THE SYSTEM
CROSSES NORTHERN HONSHU AND ENCOUNTERS STRONGER VWS. THE DYNAMIC
MODEL TRACKERS ARE IN VERY POOR AGREEMENT WITH THREE DISCRETE
CLUSTERS OF TRACKERS. THE FIRST CLUSTER DEPICTS A RAPID RE-CURVE
TRACK OVER CENTRAL JAPAN AND THEN INTO NORTHEAST ASIA, AND INCLUDES
THE JENS, ECMWF AND UKMET TRACKERS. IN GENERAL, THESE TRACKERS DRIVE
THE SYSTEM DIRECTLY INTO THE MAJOR SHORTWAVE TROUGH AND MERGE THE
SYSTEM AS AN EXTRA-TROPICAL LOW INTO A STRONG OCCLUDED LOW. THE
SECOND CLUSTER INDICATES A SLOWER RE-CURVE OVER OR NEAR NORTHERN
JAPAN AND INCLUDES NAVGEM, EEMN AND COAMPS-TC. THESE MODELS PROVIDE
A SOLUTION THAT SEEMS MORE REALISTIC CONSIDERING THE RE-CURVE POINT
FURTHER NORTH ALONG THE LEADING EDGE OF THE MAJOR SHORTWAVE TROUGH
RATHER THAN DIRECTLY INTO THE TROUGH DEEPENING OVER CENTRAL JAPAN.
THE THIRD CLUSTER INDICATES A NORTHEAST TO EAST-NORTHEAST TRACK AND
QUASI-STATIONARY TRACK MOTION WELL TO THE SOUTHEAST OF NORTHERN
JAPAN AND INCLUDES GFDN, GFS AND HWRF. THESE MODELS APPEAR TO STALL
THE SYSTEM AS IT ENTERS A WEAK STEERING ENVIRONMENT BETWEEN THE
MAJOR TROUGH OVER JAPAN AND ANOTHER DEEP TROUGH TO THE NORTHEAST.
THE JTWC TRACK PHILOSOPHY FAVORS THE SECOND CLUSTER OF MODEL
TRACKERS, WHICH PRESENT A REALISTIC SCENARIO, HOWEVER, ERRATIC
PERFORMANCE OF SEVERAL MODELS IS ALSO CREATING MUCH UNCERTAINTY IN
THE TRACK FORECAST. DUE TO THE HIGH DEGREE OF UNCERTAINTY, BEYOND
TAU 48, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.//
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