Advisories

WDPN33 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 135.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 233 NM NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A LOOSELY
ORGANIZED AND ASYMMETRIC SYSTEM, WITH DEEP CONVECTION ALONG THE
WESTERN FLANK. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS OBSCURED,
BUT AN EARLIER 221201Z ASCAT-B PASS REVEALED A COMPACT LLCC WITH
20-25 KNOT WINDS, POSITIONED EAST OF THE CONVECTIVE ENVELOPE. LATE
RECEIPT OF A 221625Z AMSR3 37GHZ MICROWAVE IMAGE SUGGESTS THE LLCC
IS POSITIONED A BIT FURTHER NORTHWEST THAN THE 1800Z POSITION,
WHICH WILL BE REPOSITIONED PRIOR TO THE NEXT FORECAST. THE AMSR3
IMAGE ALSO REVEALS THE ASYMMETRIC NATURE OF THE SYSTEM, WITH DEEP
CONVECTION CONFINED TO THE WESTERN PORTION OF THE CIRCULATION,
WHILE DRY AIR AND EASTERLY SHEAR LIMIT CONVECTIVE DEVELOPMENT ON
THE EASTERN PERIMETER. THE INITIAL POSITION IS ASSESSED WITH LOW
CONFIDENCE USING AN EXTRAPOLATION OF THE EARLIER ASCAT DATA AND
ANIMATED SHORTWAVE INFRARED (SWIR) IMAGERY. THE INITIAL INTENSITY
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGREEMENT OF THE BULK
OF SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW AND
EXTRAPOLATION OF THE EARLIER ASCAT DATA.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A LOW- TO
MID-LEVEL NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 31 KTS AT 221910Z
   CIMSS ADT: 31 KTS AT 221800Z
   CIMSS AIDT: 30 KTS AT 221800Z
   CIMSS D-MINT: 34 KTS AT 221708Z
   CIMSS D-PRINT: 29 KTS AT 221800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 19W IS POSITIONED IN
THE FAR SOUTHWESTERN END OF A AN AREA OF TROUGHING EXTENDING
SOUTHWESTWARD FROM TY 17W (SAUDEL), AND ALONG THE NORTHERN EDGE OF
A BROAD REGION OF MONSOON CROSS-EQUATORIAL SOUTHERLY FLOW, WHICH IS
PUSHING THE SYSTEM SLOWLY NORTHWARD AT THE CURRENT TIME. OVER THE
NEXT 12 HOURS, THE LOW- TO MID-LEVEL NEAR EQUATORIAL RIDGE (NER) TO
THE SOUTHEAST WILL BUILD, RESULTING IN TD 19W BEGINNING A SLOW TURN
NORTHEASTWARD. BY TAU 24, TY 17W WILL BE POSITIONED DUE NORTH OF TD
19W, AND BEGIN TO EXERT A POLEWARD PULL ON TD 19W. SIMULTANEOUSLY,
THE NER TO THE SOUTHEAST CONTINUES TO BUILD, STRENGTHENING THE
STEERING GRADIENT, DRIVING TD 19W EVEN FASTER NORTHWARD. THE SYSTEM
SLOWS AND CURVES NORTHWESTWARD BY THE END OF THE FORECAST, AS THE
PRIMARY STEERING INFLUENCE IS HANDED OFF FROM THE NER TO THE
SOUTHEAST TO A STR TO THE NORTHEAST. REGARDING INTENSITY, THE
SYSTEM HAS A BRIEF WINDOW OF OPPORTUNITY, WITH RELATIVELY LIGHTER
SHEAR EXPECTED, WHEREIN TO INTENSIFY UP TO MINIMAL TROPICAL STORM
(TS) STRENGTH. HOWEVER, BY TAU 24 SHEAR IS FORECAST TO INCREASE
SHARPLY AND STAY ELEVATED THROUGH THE REMAINDER OF THE FORECAST
PERIOD, LEADING TO DISSIPATION BY TAU 60. 

MODEL DISCUSSION: TRACK GUIDANCE, WITH THE EXCEPTION OF NAVGEM, IS
IN GOOD AGREEMENT, WITH LESS THAN 120NM OF CROSS-TRACK SPREAD,
THROUGH THE FORECAST PERIOD. THE JTWC FORECAST IS PLACED NEAR THE
ECMWF TRACKER WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT AS WELL, WITH THE BULK OF MODELS INDICATING A BRIEF
PERIOD OF INTENSIFICATION UP TO 35 KNOTS BY TAU 12, FOLLOWED BY A
SLOW BUT STEADY WEAKENING TREND THROUGH THE END OF THE FORECAST
PERIOD. THE ONLY EXCEPTION IS COAMPS-TC WHICH DEPICTS RAPID
INTENSIFICATION THROUGH TAU 36, UP TO 55 KNOTS, FOLLOWED BY RAPID
WEAKENING THEREAFTER. THE JTWC FORECAST IS PLACED NEAR THE
CONSENSUS MEAN, WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
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