Tropical Storm TRAMI Advisory Sun Sep 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (TRAMI)
WARNING NR 10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 28W (TRAMI), LOCATED APPROXIMATELY 705 NM SOUTHEAST
OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
A DEEP AND PERSISTENT CORE OF CONVECTION WITH SPIRAL BANDS EXTENDING
FROM THE SOUTHWEST TO THE NORTHEAST. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE AND IS BASED ON A 230017Z METOP-B ASCAT
AMBIGUITY IMAGE SHOWING A WELL DEFINED LOW LEVEL CIRCULATION CENTER
(LLCC). THE INITIAL INTENSITY OF 75 KNOTS IS HEDGED BETWEEN DVORAK
INTENSITY ESTIMATES OF T4.0 (65 KNOTS) FROM PGTW AND RJTD, AND AN
ESTIMATE OF T4.5 (77 KNOTS) FROM KNES AND ADT ALONG WITH A 222213Z
SATCON ESTIMATE OF 82 KNOTS. ENVIRONMENTAL ANALYSIS SHOWS THAT TY 28W
IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (10 TO 15 KNOTS) ALONG
WITH GOOD EQUATORWARD OUTFLOW AND EXCELLENT POLEWARD OUTFLOW. SEA
SURFACE TEMPERATURES ARE ALSO CONDUCIVE FOR DEVELOPMENT, BETWEEN 29
TO 30 DEGREES CELSIUS. TY 28W IS TRACKING WESTWARD ALONG THE SOUTHERN
PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE
NORTH.
 3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, TY 28W WILL TRACK NORTHWESTWARD WHILE UNDER THE
INFLUENCE OF THE AFOREMENTIONED STR. FAVORABLE ENVIRONMENTAL
CONDITIONS (LOW VERTICAL WIND SHEAR, FAVORABLE OUTFLOW, AND WARM SEA
SURFACE TEMPERATURES) WILL CONTINUE TO RAPIDLY INTENSIFY TY 28W.
RAPID INTENSIFICATION IS STILL BEING INDICATED BY MODEL GUIDANCE.
TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH TAU 48 WITH A
SPREAD OF 90NM. HOWEVER, BY TAU 72 THE SPREAD IN MODEL GUIDANCE
INCREASES TO 220NM. THEREFORE, THERE IS LOW CONFIDENCE IN THIS
PORTION OF THE JTWC FORECAST TRACK. THE JTWC FORECAST TRACK IS PLACED
NEAR BUT JUST SOUTH OF THE MULTI-MODEL CONSENSUS.
   C. AFTER TAU 72, A MIDLATITUDE SHORTWAVE TROUGH WILL DEEPEN OVER
THE EAST CHINA SEA AND WESTERN JAPAN CREATING A BROAD, PERSISTENT
BREAK IN THE STR. STRS TO THE WEST AND NORTHEAST WILL COMPETE TO
BECOME THE DOMINANT STEERING FEATURE. AS A RESULT, TY 28W WILL SLOW
IN FORWARD SPEED AND MAY BECOME QUASI-STATIONARY FOR A SHORT TIME.
MODEL GUIDANCE IS IN POOR AGREEMENT WITH A SIGNIFICANT SPREAD OF
570NM BY TAU 120. GFS SHOWS A MORE NORTH-NORTHWESTWARD TRACK AFTER
TAU 72 WHILE NAVGEM, JGSM, AN AFUM INDICATE A MORE WESTWARD TRACK.
THE JTWC FORECAST TRACK IS PLACED SLIGHTLY SOUTH OF THE MULTI-MODEL
CONSENSUS, FAVORING A MORE WESTWARD TRACK AND NEAR THE ECMWF TRACK.
DUE TO THE CONTINUED WIDE SPREAD IN MODEL GUIDANCE, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
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