Tropical Storm MALAKAS Advisory Fri Sep 16

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 18W (MALAKAS), LOCATED APPROXIMATELY 534 NM SOUTH OF
KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A
SLIGHTLY IMPROVED CONVECTIVE STRUCTURE IN THE LAST SIX HOURS. THE
INITIAL POSITION IS BASED ON SATELLITE FIXES FROM PGTW AND RJTD AS
WELL AS A 150335Z AMSR2 89GHZ IMAGE WITH GOOD CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 80 KNOTS AND IS BASED ON THE RISING
SUBJECTIVE DVORAK ESTIMATE FROM PGTW, NOW REPORTING T4.5/4.5 (77
KNOTS), AND IS REPRESENTATIVE OF THE IMPROVEMENT SEEN IN THE
CONVECTIVE STRUCTURE. UPPER-LEVEL ANALYSIS SHOWS IMPROVING POLEWARD
OUTFLOW AND VERTICAL WIND SHEAR BEING OFFSET BY A FORMING UPPER-
LEVEL LOW JUST TO THE EAST CREATING A REGION OF SUBSIDENCE. SEA
SURFACE TEMPERATURES ARE VERY FAVORABLE NEAR 30 CELSIUS. CURRENTLY
TY MALAKAS IS TRACKING WEST-NORTHWEST ALONG THE PERIPHERY OF A DEEP-
LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM FORECAST TY MALAKAS WILL CONTINUE TO
TRACK NORTHWEST ALONG THE STEERING RIDGE UNDER FAVORABLE CONDITIONS.
THE UPPER-LEVEL LOW IS EXPECTED TO PERSIST AND INFLUENCE OUTFLOW ON
THE EASTERN PERIPHERY, HOWEVER ENHANCED POLEWARD FLOW IS ALSO
EXPECTED TO IMPROVE GIVING AN OPPORTUNITY FOR INTENSIFICATION
THROUGH TAU 36 REACHING A PEAK INTENSITY OF 110 KNOTS. FROM TAU 36
TO 72, TY MALAKAS WILL BEGIN TO SLOW DOWN AS IT ROUNDS THE RIDGE
AXIS NEAR NORTHEASTERN TAIWAN. SLIGHT LAND INTERACTION IS EXPECTED
DURING THIS TIME LEADING TO A GRADUAL WEAKENING.
   C. IN THE EXTENDED TAUS BEYOND TAU 72, TY MALAKAS WILL TRACK
NORTHEASTWARD ALONG THE NORTHERN PERIPHERY OF THE SUBTROPICAL RIDGE
INTO THE WESTERLY JET. VERTICAL WIND SHEAR WILL INCREASE
SIGNIFICANTLY LEADING TO RAPID WEAKENING OF THE SYSTEM BY TAU 120.
DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE FORECAST
PHILOSOPHY AND SHOWS RELATIVELY TIGHT GROUPING IN TRACK SOLUTIONS,
PARTICULARLY IN THE EARLY PERIOD AND EXTENDED TRACK AS IT GETS
ABSORBED INTO THE WESTERLY JET. HOWEVER THE NUMERICAL MODELS SHOW A
DEGREE OF UNCERTAINTY IN THE SPEED, POSITION, AND TIMING OF THE TURN
TO THE NORTHEAST AS IT ROUNDS THE RIDGE AXIS. DUE TO THIS
UNCERTAINTY, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK. //
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