Tropical Storm ONE Advisory Tue Jul 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (HALOLA)
WARNING NR 41//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TROPICAL STORM (TS) 01C (HALOLA), LOCATED APPROXIMATELY 400 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS TIGHT CURVED BANDING WRAPPING INTO A WELL-DEFINED LOW
LEVEL CIRCULATION CENTER WITH SHALLOW CONVECTIVE BANDING ALONG ALL
QUADRANTS. A 200351Z GPM 89GHZ MICROWAVE IMAGE SHOWS A COMPACT
CONVECTIVE SIGNATURE WITH A DEVELOPING MICROWAVE EYE FEATURE THAT,
ALONG WITH THE MSI LOOP, SUPPORTS THE INITIAL POSITION WITH HIGH
CONFIDENCE. THE INITIAL INTENSITY HAS BEEN INCREASED TO 40 KNOTS
BASED ON AN ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL
AGENCIES AND SUPPORTED BY A RECENT RSCAT PASS SHOWING 40 KNOT WINDS
ALONG THE NORTHEASTERN PERIPHERY. ANIMATED WATER VAPOR IMAGERY SHOWS
ENHANCED EQUATORWARD OUTFLOW DUE TO AN UPPER LEVEL TROUGH POSITIONED
TO THE EAST. TS HALOLA IS ENCOUNTERING LOW TO MODERATE (5-15 KNOT)
VERTICAL WIND SHEAR (VWS) AND SEA SURFACE TEMPERATURES (SSTS) NEAR
30 CELSIUS WHICH IS SUPPORTING THE CURRENT INTENSIFICATION. TS 01C
IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED
STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS HALOLA WILL CONTINUE TRACKING ON A WEST-NORTHWESTWARD
TRAJECTORY UNDER THE STEERING INFLUENCE OF THE DOMINANT STR THROUGH
TAU 72. THE SYSTEM IS FORECAST TO INTENSIFY THROUGH TAU 48 DUE TO A
FAVORABLE ENVIRONMENT WITH GOOD OUTFLOW, LOW VWS, AND SSTS ABOVE 28
CELSIUS. BEYOND TAU 48, VWS WILL INCREASE ABOVE 20 KNOTS WHICH WILL
CAUSE THE RATE OF INTENSIFICATION TO DECREASE. DYNAMIC MODEL
GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72 WITH A 90 NM SPREAD AT
TAU 72, LENDING TO HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST.
   C. IN THE EXTENDED TAUS, THE SYSTEM WILL BEGIN TO TURN POLEWARD
AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STEERING STR. TS
HALOLA SHOULD BEGIN TO WEAKEN DUE TO INCREASING VERTICAL WIND SHEAR,
ASSOCIATED WITH A BUILDING MID-LATITUDE RIDGE TO THE NORTHWEST
PRODUCING STRONG NORTHERLY FLOW OVER THE CYCLONE, AND SSTS DROPPING
BELOW 26 CELSIUS. DYNAMIC MODEL GUIDANCE SPREADS OUT AFTER TAU 72
DUE TO VARYING DEGREES IN THE TIMING OF THE RE-CURVE. THIS SPREAD
LEADS TO AN OVERALL LOW CONFIDENCE IN THE JTWC FORECAST. AT THIS
TIME, TS HALOLA IS NOT EXPECTED TO UNDERGO EXTRA-TROPICAL TRANSITION
SOUTH OF JAPAN DUE TO THE BAROCLINIC ZONE FORECASTED TO BE SITUATED
NEAR 40 DEGREES LATITUDE.//
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