WPAC: ATSANI - Post-Tropical

[euro6208]

WDPN32 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 31//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 237 NM EAST-
NORTHEAST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS A WEAKENING CONVECTIVE STRUCTURE WITH DRY AIR
PENETRATING THE NORTHWESTERN EYEWALL. THE SYSTEM HAS MAINTAINED A 12
NM EYE, WHICH SUPPORTS THE CURRENT POSITION WITH HIGH CONFIDENCE.
MOST OF THE REMAINING CONVECTION IS CONFINED TO THE SOUTHERN
PERIPHERY WHICH IS BEING AIDED BY A ROBUST EQUATORWARD OUTFLOW. A
211738Z SSMI 85GHZ MICROWAVE IMAGE SHOWS A MUCH LARGER MICROWAVE EYE
FEATURE WITH AN ERODING EYEWALL. THE CURRENT INTENSITY HAS BEEN
LOWERED TO 90 KNOTS BASED ON DECREASING DVORAK INTENSITY ESTIMATES
FROM ALL AGENCIES AND REFLECTS THE WEAKENING CONVECTIVE STRUCTURE.
ENVIRONMENTAL CONDITIONS ARE MARGINAL DUE TO THE STRONG SUBSIDENCE
AND DRY AIR ALONG THE NORTHERN AND WESTERN PERIPHERIES; HOWEVER, SEA
SURFACE TEMPERATURES REMAIN FAVORABLE. TY 17W IS ROUNDING THE
SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR)
LOCATED TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL CONTINUE TO ROUND THE WESTERN PERIPHERY OF THE
DEEP LAYERED STR AND TURN POLEWARD. BY TAU 36, TY ATSANI WILL BEGIN
TO ACCELERATE NORTHEASTWARD IN FRONT OF AN APPROACHING MID-LATITUDE
TROUGH. ENVIRONMENTAL CONDITIONS WILL REMAIN MOSTLY UNCHANGED
THROUGH TAU 72, CREATING A SLOW WEAKENING TREND. BY TAU 72, SEA
SURFACE TEMPERATURES WILL DROP BELOW 26 CELSIUS AND THE SYSTEM WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT).
C. IN THE EXTENDED FORECAST, TY 17W WILL CONTINUE TO ACCELERATE
NORTHEASTWARD AND EMBED FURTHER INTO THE WEAK BAROCLINIC ZONE. BY
THE END OF THE FORECAST PERIOD, TY ATSANI WILL SLOW AS IT GETS
ENVELOPED BY THE MID-LATITUDE TROUGH AND IS FORECAST TO COMPLETE ETT
AS A STRONG COLD-CORE LOW. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[1900hurricane]

Atsani's eye temp has been measured to be over 10*C by infrared for over three consecutive days and still counting.

[dexterlabio]

I wonder how much it will affect the northern regions of America as it transitions to ET...

[WeatherGuesser]

Despite moving further away from the tropics (about to cross 25*N now) and the general waning of the coldest cloudtops, Atsani has managed to maintain the prominent eye that has highlighted the system for the past few days. Pretty impressive if you ask me.

Dang, that even looks like a Human eye if you orient from the ESE, eyelashes, eyebrow and all.

[euro6208]

WDPN32 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 35//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 192 NM SOUTHEAST
OF CHICHI JIMA, HAS TRACKED NORTH-NORTHEASTWARD AT 06 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR)
DEPICTS A VERY LARGE SYSTEM WITH SPIRAL BANDING WRAPPING INTO A 38-
NM EYE. A 221114Z ASCAT PASS PROVIDES A GOOD ESTIMATE OF THE
EXTENSIVE 35-KNOT WIND FIELD. THE INITIAL POSITION IS BASED ON THE
EYE FEATURE IN THE EIR AS WELL AS IN A 221721Z SSMI 37GHZ IMAGE WITH
HIGH CONFIDENCE. THE INITIAL INTENSITY OF 80 KNOTS IS BASED ON AN
OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM ALL REPORTING AGENCIES.
UPPER LEVEL ANALYSIS SHOWS A MARGINAL ENVIRONMENT WITH MODERATE (20
KNOT) NORTHEASTERLY VERTICAL WIND SHEAR AND GOOD EQUATORWARD
OUTFLOW; HOWEVER, DRY AIR ENTRAINMENT ALONG THE WESTERN PERIPHERY IS
INHIBITING INTENSIFICATION. TY 17W IS NOW TRACKING ALONG THE NORTH
WESTERN PERIPHERY OF THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR)
LOCATED TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL ACCELERATE TO THE NORTHEAST AS IT BECOMES EMBEDDED
IN THE MIDLATITUDE WESTERLIES, AHEAD OF AN APPROACHING MID-LATITUDE
TROUGH.
ENVIRONMENTAL CONDITIONS WILL REMAIN MOSTLY UNCHANGED THROUGH TAU 72,
CREATING A SLOW WEAKENING TREND. BY TAU 48, SEA SURFACE TEMPERATURES
WILL DROP BELOW 26 CELSIUS AND THE SYSTEM WILL BEGIN EXTRA-TROPICAL
TRANSITION (ETT).
C. TY 17W WILL COMPLETE ETT, BECOMING A STRONG COLD CORE LOW BY
TAU 96 AND POSSIBLY SOONER. AFTER TAU 72, THE STEERING FLOW IS
FORECAST TO BREAK DOWN LEADING TO A SLOW AND POSSIBLY ERRATIC TRACK
AS DEPICTED IN THE MAJORITY OF DYNAMICAL MODELS. THE REASONABLY GOOD
AREEMENT AMONG TRACK GUIDANDE AIDS LENDS HIGH CONFIDENCE TO THE JTWC
FORECAST TRACK.//
NNNN

[euro6208]

Atsani's eye temp has been measured to be over 10*C by infrared for over three consecutive days and still counting.

Amazing storm...

[1900hurricane]

Atsani is just keeping on keeping on. About to cross 30*N now.

[euro6208]

WDPN32 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 37//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 445 NM SOUTHEAST OF
YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 07 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A
VERY LARGE SYSTEM THAT HAS MAINTAINED SPIRAL BANDING WRAPPING INTO A
27-NM EYE. THE INITIAL POSITION IS BASED ON THE EYE FEATURE IN THE
MSI AND ON THE 230461Z GPM MICROWAVE PASS. THE INITIAL INTENSITY OF
80 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM
ALL REPORTING AGENCIES. UPPER LEVEL ANALYSIS SHOWS A FAIR ENVIRONMENT
WITH MODERATE (10-15 KNOT) NORTHEASTERLY VERTICAL WIND SHEAR AND
EXCELLENT EQUATORWARD OUTFLOW; HOWEVER, PERSISTENT DRY AIR
ENTRAINMENT ALONG THE WESTERN PERIPHERY REMAINS IN PLACE. TY 17W IS
TRACKING ALONG THE NORTHWESTERN PERIPHERY OF THE DEEP-LAYERED
SUB-TROPICAL RIDGE (STR) LOCATED TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL ACCELERATE TO THE NORTHEAST IN THE MID-LATITUDE
WESTERLY FLOW, AHEAD OF AN APPROACHING MID-LATITUDE TROUGH. BY TAU
36, SEA SURFACE TEMPERATURES WILL DROP BELOW 26 CELSIUS AND THE
SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT). STEADY
ENVIRONMENTAL CONDITIONS WILL ALLOW FOR A SLOW WEAKENING TREND. TY
17W IS THEREFORE EXPECTED TO BE A STRONG GALE-FORCE COLD CORE LOW BY
THE END OF THE FORECAST PERIOD.//
NNNN

[euro6208]

[1900hurricane]

Atsani's eyewall opened up and I don't think it's going to repair itself this time. It's been a great run.

[euro6208]

WDPN32 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 39//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 367 NM NORTHEAST
OF CHICHI JIMA, HAS TRACKED NORTHEASTWARD AT 09 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY (EIR) DEPICTS A VERY
LARGE AND SLOWLY WEAKENING SYSTEM, WITH SPIRAL BANDING ALONG THE
WESTERN PERIPHERY BECOMING MORE SHALLOW AS COOL DRY AIR WRAPS IN
FROM THE NORTH. THE INITIAL POSITION IS BASED ON THE ANIMATED EIR AS
WELL AS CURVED BANDING IN A 231756Z GPM MICROWAVE IMAGE WITH GOOD
CONFIDENCE. THE INITIAL INTENSITY OF 75 KNOTS IS CONSISTENT WITH
DVORAK ESTIMATES FROM ALL REPORTING AGENCIES. A 231056Z ASCAT PASS
PROVIDED AN EXCELLENT ESTIMATE OF THE WIND STRUCTURE, REVEALING 50
KNOT WINDS IN THE EASTERN SEMI-CIRCLE EXTENDING OUT NEARLY 150 NM
FROM THE CENTER. UPPER LEVEL ANALYSIS INDICATES LOW 5-10 KNOT
VERTICAL WIND SHEAR (VWS) OVER THE CENTER AND GOOD RADIAL OUTFLOW.
THE NORTHERN EXTENT OF THIS EXPANSIVE SYSTEM HOWEVER IS UNDER
CONSIDERABLY HIGHER VWS AND IS ALREADY INTERACTING WITH THE MID-
LATITUDE BAROCLINIC ZONE. TY 17W IS TRACKING ALONG THE NORTHWESTERN
PERIPHERY OF THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR) LOCATED TO
THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL CONTINUE TO TRACK NORTHEASTWARD DEEPER IN THE
MID-LATITUDE WESTERLY FLOW. BY TAU 36, SEA SURFACE TEMPERATURES WILL
DROP BELOW 26 CELSIUS AND THE SYSTEM WILL BEGIN EXTRA-TROPICAL
TRANSITION (ETT). THE FORECAST CALLS FOR ETT TO COMPLETE BY TAU 72,
HOWEVER, THAT TRANSITION MAY BE COMPLETE BY TAU 48. GOOD OUTFLOW
AND LOW VWS WILL SOMEWHAT OFFSET COLDER SSTS, LEADING TO A GRADUAL
WEAKENING TREND. TY 17W IS THEREFORE EXPECTED TO BECOME A STRONG
GALE-FORCE COLD CORE LOW BY THE END OF THE FORECAST PERIOD.//
NNNN

[euro6208]

WDPN32 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 41//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 500 NM
EAST-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 11
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULSPECTRAL SATELLITE IMAGERY
(MSI) SHOWS SPIRAL BANDING HAVE MAINTAINED THEIR DEGREE OF WRAP
AROUND A RAGGED, ALBEIT WELL-DEFINED LOW LEVEL CIRCULATION. THE
INITIAL POSITION IS BASED ON THE ANIMATED MSI WITH GOOD CONFIDENCE.
THE INITIAL INTENSITY OF 65 KNOTS IS CONSISTENT WITH DVORAK ESTIMATES
FROM ALL REPORTING AGENCIES. UPPER LEVEL ANALYSIS INDICATES LOW TO
MODERATE (10-15 KNOT) VWS THAT IS MOSTLY OFFSET BY GOOD RADIAL
OUTFLOW. THE NORTHERN EXTENT OF THIS EXPANSIVE SYSTEM HOWEVER IS
UNDER CONSIDERABLY HIGHER VWS AND IS INTERACTING WITH THE
MID-LATITUDE BAROCLINIC ZONE. TY 17W IS TRACKING ALONG THE
NORTHWESTERN PERIPHERY OF THE DEEP-
LAYERED SUB-TROPICAL RIDGE (STR) LOCATED TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL CONTINUE NORTHEASTWARD IN THE MID-LATITUDE
WESTERLY FLOW. SEA SURFACE TEMPERATURES WILL DROP BELOW 26 CELSIUS
OVER THE NEXT 12-24 HOURS AND THE SYSTEM WILL BEGIN EXTRA-TROPICAL
TRANSITION (ETT). THE ETT WILL BE COMPLETE BY TAU 48. GOOD OUTFLOW
AND LOW VWS WILL SOMEWHAT OFFSET COLDER SSTS, RESULTING IN A GRADUAL
WEAKENING TREND. TY 17W IS THEREFORE EXPECTED TO BECOME A STRONG
GALE-FORCE COLD CORE LOW BY THE END OF THE FORECAST PERIOD.//
NNNN

[euro6208]

WDPN32 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (ATSANI) WARNING NR
43//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 626 NM EAST OF
NARITA AIRPORT, HAS TRACKED EAST-NORTHEASTWARD AT 20 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS SOME SPIRAL BANDING WRAPPING INTO A RAGGED LOW LEVEL
CIRCULATION. THE INITIAL POSITION IS BASED ON THE AFOREMENTIONED IR
IMAGERY AS WELL AS A 241647Z SSMI IMAGE, SHOWING AN ELONGATED EYE
AND DEEP CONVECTION CONCENTRATED ON THE SOUTHEASTERN QUADRANT OF THE
LLCC. THE INITIAL INTENSITY OF 60 KNOTS IS BASED ON AN OVERALL
ASSESSMENT OF DVORAK ESTIMATES FROM PGTW AND RJTD. UPPER LEVEL
ANALYSIS INDICATES MODERATE (20-30 KNOT) IN-PHASE VWS THAT IS OFFSET
BY DUAL CHANNEL OUTFLOW. THE NORTHERN PORTION OF THE SYSTEM IS
CURRENTLY INTERACTING WITH THE MID-LATITUDE BAROCLINIC ZONE. TY 17W
IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL CONTINUE NORTHEASTWARD IN THE MID-LATITUDE
WESTERLY FLOW. AS THE SYSTEM TRACKS TO THE NORTH, IT WILL CONTINUE
TO BECOME ENTRENCHED IN THE WESTERLIES, INTERACTING WITH THE
BAROCLINIC ZONE. ADDITIONALLY, VWS WILL INCREASE AND SSTS AND OHC
WILL DECREASE, CAUSING A GRADUAL WEAKENING OF THE SYSTEM. BY TAU 36,
TY ATSANI WILL BECOME FULLY ENVELOPED INTO THE BAROCLINIC ZONE,
HAVING COMPLETED ETT. MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT
THROUGH TAU 36 GIVEN HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[euro6208]

WTPN32 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL STORM 17W (ATSANI) WARNING NR 044
02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
250000Z --- NEAR 35.2N 155.8E
MOVEMENT PAST SIX HOURS - 060 DEGREES AT 28 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
RADIUS OF 050 KT WINDS - 045 NM NORTHEAST QUADRANT
045 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 180 NM NORTHEAST QUADRANT
200 NM SOUTHEAST QUADRANT
200 NM SOUTHWEST QUADRANT
105 NM NORTHWEST QUADRANT
REPEAT POSIT: 35.2N 155.8E
---
FORECASTS:
12 HRS, VALID AT:
251200Z --- 38.1N 160.2E
MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
RADIUS OF 050 KT WINDS - 035 NM NORTHEAST QUADRANT
035 NM SOUTHEAST QUADRANT
030 NM SOUTHWEST QUADRANT
025 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 150 NM NORTHEAST QUADRANT
160 NM SOUTHEAST QUADRANT
165 NM SOUTHWEST QUADRANT
100 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 050 DEG/ 16 KTS
---
24 HRS, VALID AT:
260000Z --- 40.0N 163.4E
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
250300Z POSITION NEAR 35.9N 156.9E.
TROPICAL STORM (TS) 17W (ATSANI), LOCATED APPROXIMATELY 1065 NM
SOUTH OF PETROPAVLOVSK, HAS TRACKED EAST-NORTHEASTWARD AT 20 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MSI SHOWS MINIMAL SPIRAL BANDING
WRAPPING INTO AN ELONGATED RAGGED CIRCULATION. THE INITIAL POSITION
IS BASED ON THE AFOREMENTIONED MSI AND A 242036Z SSMIS IMAGE WITH
MODERATE CONFIDENCE. THE NORTHERN PORTION OF THE SYSTEM IS
CURRENTLY INTERACTING WITH THE MID-LATITUDE BAROCLINIC ZONE AS THE
SYSTEM TRACKS ALONG THE NORTHERN PORTION OF THE STR. FINALLY, A
241933Z AMSU-B CROSS SECTION ANALYSIS SHOWS THAT THE SYSTEM HAS
MAINTAINED A DEEP WARM CORE, HOWEVER WINDS ARE PLACED SIGNIFICANTLY
FAR FROM THE LLCC, SPECIFICALLY IN THE SOUTHEASTERN QUADRANT,
INDICATING THE SYSTEM HAS BEGUN ETT. TS 17W WILL CONTINUE
NORTHEASTWARD IN THE MID-LATITUDE WESTERLY FLOW AND CONTINUE
INTERACTING WITH THE BAROCLINIC ZONE. BY TAU 24, TY ATSANI
WILL BECOME FULLY ENVELOPED INTO THE BAROCLINIC ZONE, HAVING
COMPLETED ETT. MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT THROUGH
TAU 24 GIVEN HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON
WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR
SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 250000Z
IS 22 FEET. REFER TO TYPHOON 16W (GONI) WARNINGS (WTPN31 PGTW)
FOR SIX-HOURLY UPDATES.//
NNNN

[1900hurricane]

Talk about textbook extratropical transition.