Advisories

WDPN31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.8N 163.2E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 1014 NM EAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
30W AS A MUCH-IMPROVED SYSTEM WHEN COMPARED TO 6 HOURS AGO. THE UPPER-
LEVEL CONVECTION IS FINALLY MAINTAINING PATCHES OF SUB-NEGATIVE 80 C 
CLOUD TOP TEMPERATURES, WHICH ARE WRAPPED AROUND THE CENTRAL AXIS. A 
NASCENT RAGGED EYE FEATURE IS FORMING IN THE ANIMATED BRIGHTNESS 
TEMPERATURES, WITH A CORRELATING DIMPLE IN THE ANIMATED MSI. THE 
252230Z ASCAT PASS REVEALS A VERY COMPACT WIND FIELD, WITH TYPHOON-
FORCE WINDS CONFINED TO WITHIN APPROXIMATELY 20 NM OF THE CORE. 
ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY FAVORABLE ENVIRONMENT, 
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-
30 C) SEA SURFACE TEMPERATURES (SST), GOOD (100-125 KJ PER CM SQUARED) 
OCEAN HEAT CONTENT (OHC), AND STRONG POLEWARD OUTFLOW. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE NASCENT RAGGED 
EYE FORMING IN ANIMATED MSI. THE INITIAL INTENSITY OF 80 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND 
AUTOMATED CIMMS INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 262230Z ASCAT DATA

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN THE NORTHWESTERN FLANK OF A DEEP-LAYER NEAR-EQUATORIAL
RIDGE (NER) TO THE SOUTHEAST AND A SUBTROPICAL RIDGE (STR) CENTERED
TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   PHFO: T5.0 - 90 KTS
   CIMSS SATCON: 65 KTS AT 252200Z
   CIMSS ADT: 74 KTS AT 252330Z
   CIMSS AIDT: 73 KTS AT 260030Z
   CIMSS D-MINT: 70 KTS AT 252228Z
   CIMSS D-PRINT: 80 KTS AT 260000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 30W (IN-FA) IS FORECAST TO CONTINUE TRACKING 
FOR THE NEXT 12 HOURS WHILE IT REMAINS ON THE NORTHWESTERN PERIPHERY 
OF THE NER CENTERED TO ITS SOUTHEAST. THE SUBTROPICAL RIDGE (STR) TO 
THE NORTHWEST HAS STRETCHED EASTWARD, WHICH CREATED A COMPETING 
STEERING ENVIRONMENT, INDUCING A SLIGHT SLOWDOWN IN IN-FA'S 
NORTHWESTWARD TRACK. THE STR IS EXPECTED TO BUILD AND GAIN STEERING 
AUTHORITY BY TAU 24, WHICH IS EXPECTED TO CAUSE 30W TO ACCELERATE 
WEST-NORTHWESTWARD THROUGH THE TAU 72. BETWEEN TAU 48-60, AN UPPER-
LEVEL TROUGH IS EXPECTED TO PASS NORTH OF THE STR, FORCING THE RIDGE 
TO RETREAT EASTWARD AND INDUCING A NORTHWESTWARD TRACK FOR 30W BETWEEN 
TAU 96-120 AS IT BEGINS TO CURL AROUND THE RIDGE'S SOUTHEASTERN 
PERIPHERY. REGARDING INTENSITY, 30W IS ASSESSED TO BE RAPIDLY 
INTENSIFYING, AND IS FORECAST TO CONTINUE RI THROUGH TAU 12. AT AROUND 
TAU 12, THE COMPETING STEERING ENVIRONMENT IS ANTICIPATED TO 
TEMPORARILY HALT INTENSIFICATION AS THE PROBABILITY FOR ADVERSE 
IMPACTS OF UPWELLING INCREASES. ONCE 30W TRANSITIONS STEERING 
ENVIRONMENTS AND BEGINS TRACKING WEST-NORTHWESTWARD, THE ENVIRONMENT 
WILL REMAIN FAVORABLE, SUPPORTING A SECOND ROUND OF INTENSIFICATION. 
AS 30W GAINS INTENSITY, IT MAY UNDERGO AN EYEWALL REPLACEMENT CYCLE 
(ERC), WHICH WOULD INDUCE TEMPORARY WEAKENING AND EXPAND THE WIND 
FIELD. AT LEAST ONE ERC IS DEPICTED IN THE HAFS-A MODEL GUIDANCE 
BETWEEN TAU 24-60, BUT MORE ARE LIKELY THE LONGER 30W MAINTAINS 
INTENSITY. 30W IS EXPECTED TO PEAK AT TAU 96, THEN BEGIN WEAKENING AS 
SHEAR IS ANTICIPATED TO INCREASE SLIGHTLY, AND OHC VALUES DECREASE.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 120, WITH NO SIGNIFICANT OUTLIERS. AS A RESULT, 
THE JTWC TRACK FORECAST LIES WITH THE BULK OF PHYSICS-BASED MODEL 
GUIDANCE AND EXPERIMENTAL AI MEMBERS WITH OVERALL HIGH CONFIDENCE. 
RELIABLE INTENSITY MEMBERS ARE IN POOR AGREEMENT THROUGHOUT THE 
FORECAST PERIOD. SEVERAL JTWC RI AIDS MEET CRITERIA, STRONGLY 
SUPPORTING RI FOR THE NEXT 12-36 HOURS. UNCERTAINTY EMERGES REGARDING 
THE INTENSITY FOLLOWING RI AND THE INTENSITY AS 30W CHANGES STEERING 
INFLUENCES. THE INTENSITY SPREAD REGARDING PEAK INTENSITY IS 45 KTS, 
BETWEEN GFS PEAKING AT 85 KTS AND COAMPS-TC PEAKING AROUND 135 KTS. 
CONSEQUENTLY, THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120. THE JTWC 
INTENSITY FORECAST IS IN GOOD AGREEMENT WITH THE HAFS-A SOLUTION AND 
GOOGLE DEEPMIND.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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