WDPN31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (NOKAEN) 
WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 128.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 434 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAGGED, EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH MULTIPLE
MESOSCALE VORTICES CYCLONICALLY ROTATING ABOUT A MEAN CENTROID. 
MODERATE CONVECTIVE ACTIVITY HAS PERSISTED OVER THE PAST FEW HOURS, 
COALESCING ALONG A CONVERGENCE LINE COINCIDENT WITH THE LEADING EDGE 
OF A LOW-LEVEL NORTHEASTERLY COLD SURGE. EARLIER ASCAT DATA DEPICTED
A HIGHLY ASYMMETRIC WIND FIELD, WITH GRADIENT-REINFORCED WINDS ALONG 
THE NORTHWESTERN FLANK OF 30-35 KNOTS, CONTRASTED BY LESS THAN 20 
KNOTS IN THE SOUTHEASTERN SECTOR. A 191723Z AMSR2 36GHZ
IMAGE SHOWS A RELATIVELY LARGE LOW EMISSIVITY REGION (LER) MARKING
THE CENTROID OF THE LLCC, WITH AT LEAST THREE SMALLER VORTICES
ALONG THE PERIPHERY OF THE LER. THE INITIAL POSITION IS PLACED IN
THE CENTROID OF THE BROAD ROTATION, DISCOUNTING A TRANSIENT VORTEX ON 
THE SOUTHEASTERN PERIPHERY OF THE CIRCULATION. THE INITIAL INTENSITY 
IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON A CONSENSUS OF THE
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW.
ENVIRONMENTAL CONDITIONS ARE MARGINALLY UNFAVORABLE, WITH LOW VWS,
AND WARM SSTS OFFSET BY WEAK POLEWARD OUTFLOW ALOFT AND COPIOUS
AMOUNTS OF ENTRAINED DRY MID-LEVEL AIR SUPPRESSING THE SHALLOW 
VORTEX.

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

CURRENT STEERING MECHANISM: COMPLEX INTERACTION BETWEEN A
SUBTROPICAL RIDGE (STR) TO THE EAST AND LEADING EDGE OF A COLD
SURGE EVENT. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   CIMSS SATCON: 35 KTS AT 191732Z
   CIMSS ADT: 37 KTS AT 191730Z
   CIMSS AIDT: 34 KTS AT 191730Z
   CIMSS D-MINT: 25 KTS AT 191732Z
   CIMSS D-PRINT: 31 KTS AT 191730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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) 01W (NOKAEN) IS 
CURRENTLY MOVING GENERALLY EASTWARD, INDEPENDENT OF A RECENT 
SOUTHEASTWARD TRACK AS THE VORTEX WOBBLES, AFTER CROSSING THE AXIS OF 
THE LOW- TO MID-LEVEL STR TO THE EAST. A CONTINUED TRACK TOWARDS THE 
EAST IS EXPECTED FOR THE NEXT 12 HOURS OR SO, THEN THE SYSTEM WILL 
TURN SHARPLY SOUTHWARD, PUSHED ALONG THE LEADING EDGE OF A STRONG 
SURGE IN THE NORTHEASTERLY FLOW, CONNECTED WITH A STRENGTHENING COLD
SURGE. IN TERMS OF INTENSITY, THE SYSTEM WILL SLOWLY SPIN DOWN AND
WEAKEN, WITH THE LLCC REMAINING UNDER VERY DRY MID-LEVEL AIR AND
INFLUENCED BY INCREASING DEEP LAYER SHEAR. WHILE THE CORE CONVECTIVE 
WINDS WILL STEADILY DECREASE, GALE-FORCE WINDS WILL PERSIST IN THE 
NORTHWESTERN QUADRANT DUE TO TIGHT PRESSURE GRADIENTS ASSOCIATED WITH 
THE COLD SURGE. THE SYSTEM IS FORECAST TO DISSIPATE AS A SIGNIFICANT 
TROPICAL CYCLONE NORTHWEST OF YAP BETWEEN TAU 36 AND TAU 48.

MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE AND ARTIFICIAL
INTELLIGENCE (AI) TRACK GUIDANCE IS IN GENERAL AGREEMENT ON THE
OVERALL TRACK SCENARIO, WITH DIFFERENCES IN THE TIMING AND STRENGTH
OF THE TURN TO THE SOUTH. THE NAVGEM AND JGSM MODELS DEPICT A MORE 
ABRUPT EQUATORWARD TURN, WHILE THE GALWEM AND FGN3 MODELS SUGGEST A 
DELAYED TRAJECTORY, TAKING THE SYSTEM FURTHER EAST. THE REMAINDER OF 
THE MODEL PACKAGE IS CONSISTENT WITH THE JTWC FORECAST, WHICH IS 
PLACED NEAR THE MULTI-MODEL CONSENSUS MEAN WITH MEDIUM CONFIDENCE. 
INTENSITY GUIDANCE IS MIXED, WITH THE HWRF AND COAMPS-TC MODELS 
SUPPORTING INTENSIFICATION IN THE NEAR-TERM, THOUGH LIKELY THESE 
MODELS ARE PICKING UP ON THE COLD-SURGE ASSOCIATED WINDS VICE THOSE 
DIRECTLY ASSOCIATED WITH THE LLCC. THE HAFS-A AND DECAY-SHIPS 
GUIDANCE MEANWHILE DEPICT A STEADY WEAKENING TREND THROUGH THE ENTIRE 
FORECAST PERIOD. THE JTWC FORECAST IS POSITIONED CLOSE TO THE HAFS-A 
GUIDANCE, WITH HIGH CONFIDENCE. 

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