Advisories

WDPN33 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (ATSANI) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7N 138.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 514 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 19W (ATSANI) WITH A NEARLY FULLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH A RECENT CONVECTIVE FLARE-UP ALONG THE
SOUTHWESTERN PERIPHERY. THE SYSTEM HAS SLOWED DOWN OVER THE LAST 6
HOURS, WHILE A SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST 
ASSUMED PRIMARY STEERING. CONSEQUENTLY, A NORTHWARD TRANSLATION VECTOR 
IS INITIATING TO DOMINATE THE DIRECTION OF MOTION. A BINARY FUJIWHARA 
INTERACTION REMAINS ACTIVE AS THE DISTANCE BETWEEN TD 19W AND TYPHOON 
(TY) 17W REMAINS WITHIN THE CRITICAL DISTANCE THRESHOLD. HIGH 
CONFIDENCE ENVELOPS THE INITIAL POSITION COORDINATES, DEDUCED VIA 
SHORTWAVE INFRARED IMAGERY DEPICTING THE NEARLY FULLY UNVEILED LLCC. 
THE METEOROLOGICAL ENVIRONMENT REMAINS MARGINALLY UNFAVORABLE FOR 
FURTHER INTENSIFICATION. ALTHOUGH SEA SURFACE TEMPERATURES (SST) 
REMAIN VERY WARM (29-30 C), THE EQUATORWARD OUTFLOW CHANNEL PROVIDES 
MINIMAL ASSISTANCE. SIMULTANEOUSLY, HIGH (25-30 KTS) NORTHEASTERLY 
VERTICAL WIND SHEAR (VWS) ARRESTS ANY CENTRAL CONVECTIVE STRUCTURING. 
MOREOVER, ALTHOUGH TROPOSPHERIC MOISTURE PERSISTS TO THE WEST, 
UNFAVORABLE MID-LEVEL DRY-AIR ADVECTION CONTINUES TO WRAP AROUND AND 
INTO THE INNER VORTEX CORE. THE INITIAL INTENSITY OF 30 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON A 241144Z METOP-C ASCAT PASS 
SHOWING WIND SPEED MAXIMA OF 25 KTS, WITH VERY FEW 30 KTS WIND BARBS. 
ADDITIONALLY, AGENCY DVORAK ESTIMATES ARE IN PERFECT T2.0 AGREEMENT.

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

CURRENT STEERING MECHANISM: SOUTHEASTWARD EXTENSION OF A SUBTROPICAL 
RIDGE CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 31 KTS AT 241210Z
   CIMSS AIDT: 34 KTS AT 241210Z
   CIMSS D-MINT: 33 KTS AT 241133Z
   CIMSS D-PRINT: 26 KTS AT 241210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: PERSISTENT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TD 19W IS FORECAST TO BEGIN TURNING NORTHWARD
AND EVENTUALLY NORTHWESTWARD OVER THE NEXT 12 TO 24 HOURS, ULTIMATELY 
RETREATING INTO THE HIGHLY SHEARED WAKE OF TYPHOON 17W. THIS EVOLUTION 
MARKS THE ONSET OF THE TERMINAL WEAKENING OF TD ATSANI, DICTATED BY 
INCREASINGLY HOSTILE NORTHEASTERLY VWS AND RELENTLESS CORE DRY-AIR 
ENTRAINMENT. CONSEQUENTLY, THE SYSTEM WILL SUSTAIN 30 KTS ONLY 
TRANSIENTLY. STRUCTURAL DEGRADATION WILL BE RAPID AS THE LLCC LOSES 
ITS SYMMETRIC DYNAMICS AND OPENS UP, PARTICULARLY ACROSS THE WESTERN 
SEMICIRCLE. COMPLETE DISSIPATION OVER WATER IS PROJECTED BY TAU 36.

MODEL DISCUSSION: NUMERICAL MODEL TRACK PREDICTION SPREAD EXHIBITS 
HIGH CONSISTENCY, DEPICTING A TIGHT 90 NM CROSS-TRACK DISPERSION 
ENVELOPE THROUGH TAU 36. ALONG-TRACK UNCERTAINTY IS MODERATE, 
CONSTRAINED TO A 190 NM SPREAD SEPARATING THE FASTEST JGSM AND 
DETERMINISTIC ECMWF TRACKERS AND THE SLOWEST UKMET AND ECMWF ENSEMBLE 
PREDICTIONS. THE OFFICIAL JTWC TRACK FORECAST IS POSITIONED ALONG THE 
EASTERN BOUNDARY OF THE MULTI-MODEL ENVELOPE WITH HIGH CONFIDENCE, 
OFFSETTING THE SLOWEST UKMET SOLUTION. INTENSITY FORECAST CONSENSUS 
REMAINS ALIGNED ON CONTINUOUS DECAY AND DISSIPATION BETWEEN TAU 24 AND 
TAU 36. PREVIOUS COAMPS-TC SOLUTIONS PROJECTION OF AN ANOMALOUS 
INTENSIFICATION TO 50-55 KTS HAS DISSIPATED, SOLIDIFYING HIGH 
CONFIDENCE IN THE TERMINAL WEAKENING OUTLOOK.

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