Tropical Storm TRAMI Advisory 9月23日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (TRAMI)
WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 28W (TRAMI), LOCATED APPROXIMATELY 727 NM SOUTHEAST
OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 15 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS AN AREA OF DEEP AND PERSISTENT CONVECTION LOCATED ABOVE THE
LOW LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TY 28W. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE AND IS BASED ON A
221608Z 89GHZ AMSR2 MICROWAVE IMAGE SHOWING A FORMATIVE EYE
FEATURE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON A DVORAK
INTENSITY ESTIMATE OF T4.0 (65 KNOTS) FROM RJTD. THE INTENSITY IS
HEDGED BETWEEN AN ADT ESTIMATE OF T4.4 (75 KNOTS), A 221641Z SATCON
ESTIMATE OF 78 KNOTS AND A DVORAK INTENSITY ESTIMATE OF T3.5 (55
KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS SHOWS THAT TY 28W IS
EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (5 TO 10 KNOTS) ALONG
WITH EXCELLENT RADIAL OUTFLOW WHICH CONTINUES TO TAP INTO THE
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL LOCATED TO THE EAST.
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 WEST-NORTHWEST WHILE UNDER
THE INFLUENCE OF THE AFOREMENTIONED STR. FAVORABLE ENVIRONMENTAL
CONDITIONS (LOW VERTICAL WIND SHEAR, FAVORABLE OUTFLOW, AND WARM
SEA SURFACE TEMPERATURES) WILL LEAD TO RAPID INTENSIFICATION WHICH
HAS BEEN CAPTURED BY MODEL GUIDANCE. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT. TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH TAU
48 WITH A SPREAD OF 150NM. HOWEVER, BY TAU 72 THE SPREAD IN MODEL
GUIDANCE INCREASES TO 230NM. THEREFORE, THERE IS LOW CONFIDENCE IN
THIS PORTION OF THE JTWC FORECAST TRACK.
   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
500NM BY TAU 120. MODELS ARE BEGINNING TO SHOW A BIFURCATION WITH
GFS AND COAMPS SHOWING A NORTHWESTWARD TRACK AFTER TAU 72 WHILE
NAVGEM, JGSM, AN AFUM INDICATING 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.
THEREFORE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.//
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