Advisories

WDPN33 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (ATSANI) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.2N 137.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 346 NM NORTH OF YAP
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WHICH PUSHED RAPIDLY
NORTHEASTWARD FROM 1900Z-2300Z BUT HAS ONCE AGAIN BEGUN TO
DECELERATE AND WOBBLE. WHILE THE SYSTEM IS OVERALL BEING STEERED BY
THE NER TO THE SOUTHEAST, TY 17W, POSITIONED APPROXIMATELY 530NM TO
THE NORTH, IS EXERTING A SLIGHT TUG ON TD 19W AS THE TWO SYSTEMS
ARE ON THE EDGE OF THE CAPTURE DISTANCE FOR BINARY INTERACTION. A
240012Z ASCAT-B PASS SHOWS A COMPACT BUT ASYMMETRIC WIND FIELD,
WITH LIGHT WINDS ALONG THE NORTHERN PERIPHERY, AND A REGION OF 30
KNOT WINDS ACROSS MOST OF THE SOUTHERN HEMISPHERE OF THE
CIRCULATION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE EXPOSED LLCC IN THE MSI AND THE ASCAT DATA. THE
INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
ASCAT DATA, SUPPORTING THE OBJECTIVE AND SUBJECTIVE INTENSITY
ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE,
WITH THE STRONG NORTHEASTERLY SHEAR OFFSETTING THE OTHERWISE
FAVORABLE OCEANIC CONDITIONS AND UPPER-LEVEL OUTFLOW PATTERN.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 240000Z
   CIMSS AIDT: 33 KTS AT 240000Z
   CIMSS D-MINT: 30 KTS AT 232054Z
   CIMSS D-PRINT: 29 KTS AT 240000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30+ KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY MID-LEVEL AIR ALONG THE EASTERN FLANK. 

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: WITH TY 17W AND TD 19W NOW WITHIN RANGE OF
REMOTE INTERACTION (APPROXIMATELY 530-600NM), THE TRACK TD 19W
ULTIMATELY TAKES WILL IN LARGE PART BE DRIVEN BY THIS BINARY
INTERACTION. TD 19W WILL CONTINUE NORTHEASTWARD FOR ANOTHER 12
HOURS OR SO BEFORE TURNING NORTHWARD. AFTER TAU 24, THE SYSTEM
TURNS NORTHWESTWARD AS IT FOLLOWS IN THE WAKE OF TY 17W AND IS
DRIVEN ALONG THE SOUTHWESTERN FLANK OF A SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST. REGARDING INTENSITY, THE SYSTEM IS ALREADY SEEING
THE EFFECTS OF THE EQUATORWARD EDGE OF THE OUTFLOW ASSOCIATED WITH
TY 17W, ENHANCING THE ENVIRONMENTAL NORTHEASTERLY FLOW ALOFT,
CREATED HIGH DEEP-LAYER SHEAR AND UPPER-LEVEL CONVERGENCE ALONG THE
NORTHEASTERN FLANK OF THE SYSTEM. ADDITIONALLY, LARGE AMOUNTS OF
MID-LEVEL DRY AIR IS PRESENT TO THE EAST OF TD 19W, AND BOTH
FACTORS ARE SERVING TO INHIBIT CONVECTIVE DEVELOPMENT AND
CONSOLIDATION. GOING FORWARD, BOTH THE HIGH SHEAR AND DRY AIR WILL
PERSIST, AND TD 19W WILL SLOWLY DECAY AND ULTIMATELY DISSIPATE
WITHIN THE NEXT 48 HOURS. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT, DEPICTING A
SMALL (100NM) AMOUNT OF CROSS-TRACK SPREAD THROUGH TAU 48.
ALONG-TRACK UNCERTAINTY REMAINS MODEST, SITTING AT APPROXIMATELY
250NM BETWEEN THE GFS (FAST) AND ECMWF ENSEMBLE MEAN (SLOW). THE
JTWC FORECAST IS PLACED NEAR THE EXPERIMENTAL GOOGLE DEEPMIND
TRACKER WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD
AGREEMENT, DEPICTING A GRADUAL WEAKENING TREND THROUGH DISSIPATION
BETWEEN TAUS 36 AND 48.  

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