WPAC: ATSANI - Post-Tropical

[1900hurricane]

I wonder what the pressure must be in this. It's quite a large system with a large eye, so it has to be down there.

[euro6208]

I'm thinking 150 knots right now. Agree that it looks similiar to Katrina...

[Yellow Evan]

I'm thinking 150 knots right now. Agree that it looks similiar to Katrina...

A Dvorak technique analysis would only yield T6.0 or T6.5. It's hard to say without Recon, but I'd estimate this at 135 knts, which is still higher than Dvorak anyhow and much higher than ADT.

[Yellow Evan]

I wonder what the pressure must be in this. It's quite a large system with a large eye, so it has to be down there.

I'd say somewhere around 905 mbar.

[1900hurricane]

I wonder what the pressure must be in this. It's quite a large system with a large eye, so it has to be down there.

I'd say somewhere around 905 mbar.

Seems reasonable to me. I wouldn't be surprised if it was flirting with pressures just on the other side of 900 mb a few hours ago, but it's really all guesswork unfortunately. The dataset of large-eyed storms this well formed with direct pressure measurements is fairly small.

[euro6208]

WDPN32 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 17W (ATSANI) WARNING NR
24//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON 17W (ATSANI), LOCATED APPROXIMATELY 502 NM EAST-
SOUTHEAST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A 47-NM ROUND EYE WITH DEEP CONVECTION LOCATED PRIMARILY
OVER THE SOUTHERN SEMI-CIRCLE. A 192358Z METOP-B 89GHZ IMAGE SHOWS A
SYMMETRIC EYEWALL AND TIGHTLY-CURVED BANDING. OVERALL, THERE IS GOOD
CONFIDENCE IN THE CURRENT POSITION. ANIMATED WATER VAPOR IMAGERY
REVEALS RADIAL OUTFLOW, ENHANCED BY A TUTT CELL TO THE EAST-
SOUTHEAST. THE CURRENT INTENSITY IS ASSESSED AT 135 KNOTS BASED ON
AN AVERAGE OF DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 127 TO
140 KNOTS. STY 17W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF
THE DEEP-LAYERED STR TO THE NORTHEAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. STY 17W WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU
72 UNDER THE STEERING INFLUENCE OF THE STR. FAVORABLE UPPER-
LEVEL CONDITIONS ARE EXPECTED TO PERSIST ALLOWING THE SYSTEM TO
MAINTAIN STY STRENGTH THROUGH TAU 24. AFTER TAU 24, GRADUAL
WEAKENING IS FORECAST AS SST AND OCEAN HEAT CONTENT VALUES DECREASE
TO MARGINAL LEVELS.
C. IN THE EXTENDED PERIOD, THE STR IS FORECAST TO ERODE DUE TO
INCREASING WESTERLY FLOW ACROSS JAPAN, WHICH WILL ALLOW THE STR TO
RE-ORIENT EAST OF THE SYSTEM. STY 17W WILL THEN TURN NORTHEASTWARD
ALONG THE NORTHWESTERN PERIPHERY OF THE STR. STY 17W SHOULD BEGIN TO
INTERACT WITH A WEAK BAROCLINIC ZONE NEAR TAU 120; HOWEVER, EXTRA-
TROPICAL TRANSITION IS NOT EXPECTED TO ACCELERATE THE SYSTEM DUE TO
THE LACK OF STRONG MIDLATITUDE WESTERLIES AT THIS TIME. THE SYSTEM
SHOULD REMAIN AT STORM-FORCE STRENGTH AFTER TAU 120. AVAILABLE MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK.//
NNNN

[1900hurricane]

I'm thinking 150 knots right now. Agree that it looks similiar to Katrina...

A Dvorak technique analysis would only yield T6.0 or T6.5. It's hard to say without Recon, but I'd estimate this at 135 knts, which is still higher than Dvorak anyhow and much higher than ADT.

If you put it @905hpa then it's a 180 mph peak sustained system.

If a standard pressure/wind relationship is used, then sure. However, because of Atsani's sheer size, this is likely one of those times where just getting a pressure output from the standard relationship isn't going to give you the best pressure estimate.

[Yellow Evan]

I'm thinking 150 knots right now. Agree that it looks similiar to Katrina...

A Dvorak technique analysis would only yield T6.0 or T6.5. It's hard to say without Recon, but I'd estimate this at 135 knts, which is still higher than Dvorak anyhow and much higher than ADT.

If you put it @905hpa then it's a 180 mph peak sustained system.

For a small EPAC or ATL storm, sure. Not in this basin with a storm of this size and this eye size.

[euro6208]

Deep convection again strengthening around the well defined eye...

[euro6208]

Eye is on the warming trend now at +18C and tops continuing to cool now at -67.7C...

[euro6208]

Atsani has such long life...According to EURO, we haven't seen the last of this monster yet as a secondary peak much stronger will commence in 96 hours with a bombing low of 894 mb as it slowly recurves southeast of Tokyo...

[euro6208]

WDPN32 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 17W (ATSANI) WARNING NR
25//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON 17W (ATSANI), LOCATED APPROXIMATELY 436 NM EAST-
SOUTHEAST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MSI SATELLITE IMAGERY DEPICTS A 45-NM
ROUND EYE WITH DEEP CONVECTION LOCATED PRIMARILY OVER THE SOUTHERN
SEMI-CIRCLE. A 200536Z GPM IMAGE SHOWS A HIGHLY SYMMETRIC EYEWALL
AND TIGHTLY-CURVED BANDING WITH DEEPEST CONVECTION IN THE SOUTHERN
PORTION. OVERALL, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION.
UPPER-LEVEL ANALYSIS REVEALS RADIAL OUTFLOW, ENHANCED BY A TUTT CELL
TO THE EAST- SOUTHEAST AND LOW VWS. THE CURRENT INTENSITY IS
MAINTAINED AT 135 KNOTS BASED ON AN AVERAGE OF DVORAK CURRENT
INTENSITY FROM ALL AGENCIES. STY 17W IS TRACKING ALONG THE WESTERN
PERIPHERY OF THE DEEP-LAYERED NORTH-SOUTH ORIENTED STR.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. STY 17W WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 72
UNDER THE STEERING INFLUENCE OF THE STR AS IT CONTINUES TO BUILD.
FAVORABLE UPPER- LEVEL CONDITIONS ARE EXPECTED TO PERSIST ALLOWING
THE SYSTEM TO MAINTAIN STY STRENGTH THROUGH TAU 24. HOWEVER, AFTER
TAU 24, GRADUAL WEAKENING IS FORECAST AS SST AND OCEAN HEAT CONTENT
VALUES DECREASE TO MARGINAL LEVELS NORTH OF 25 DEGREES LATITUDE. BY
TAU 72, STY ATSANI WILL CROSS THE AXIS OF THE STR.
C. IN THE EXTENDED PERIOD, STY 17W WILL CONTINUE TO ROUND THE STR
AXIS AND TRACK TO THE NORTHEAST. STY 17W WILL BEGIN TO INTERACT WITH
A WEAK BAROCLINIC ZONE NEAR TAU 120 STARTING EXTRA-TROPICAL
TRANSITION. HOWEVER, THE SYSTEM SHOULD REMAIN AT STORM-FORCE
STRENGTH AFTER TAU 120. AVAILABLE MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[euro6208]

Underestimated...

[euro6208]

What amazes me is that Atsani has managed to maintained a very well defined stable eye for over 24 hours...Still think it's a Cat 5 likely in the neighborhood of 140-155 knots...

[galaxy401]

Looks very impressive but I don't think it's a cat 5. There isn't a full ring of red around the eye and the northern wall is getting thinner. Probably a cat 4 for sure.

[1900hurricane]

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.

[I-wall]

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.

I agree - beautiful, and massive sized storm. Amazing.

[euro6208]

000
WTPQ32 PGUM 210926
TCPPQ2

BULLETIN
TYPHOON ATSANI (17W) ADVISORY NUMBER 29
NATIONAL WEATHER SERVICE TIYAN GU WP172015
800 PM CHST FRI AUG 21 2015

...ATSANI WELL TO THE NORTH OF THE MARIANA ISLANDS...

CHANGES WITH THIS ADVISORY
--------------------------
NONE.

WATCHES AND WARNINGS
--------------------
NONE.

SUMMARY OF 700 PM CHST...0900 UTC...INFORMATION
-----------------------------------------------
LOCATION...25.2N 145.9E

ABOUT 440 MILES NORTH OF AGRIHAN
ABOUT 490 MILES NORTH OF PAGAN
ABOUT 520 MILES NORTH OF ALAMAGAN
ABOUT 695 MILES NORTH OF SAIPAN
ABOUT 705 MILES NORTH OF TINIAN
ABOUT 815 MILES NORTH OF GUAM.

MAXIMUM SUSTAINED WINDS...125 MPH
PRESENT MOVEMENT...NORTH-NORTHWEST...335 DEGREES AT 10 MPH.

DISCUSSION AND OUTLOOK
----------------------
AT 700 PM CHST...0900 UTC...TYPHOON ATSANI WAS CENTERED AT LATITUDE
25.2 NORTH AND LONGITUDE 145.9 EAST...MOVING NORTH-NORTHWEST AT 10
MPH. ATSANI IS EXPECTED TO GRADUALLY TURN TOWARD NORTH TONIGHT AND
RECURVE TOWARD NORTHEAST OVER THE WEEKEND.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 125 MPH. ATSANI IS
EXPECTED TO SLOWLY WEAKEN THROUGH SATURDAY...THEN BEGIN A MORE RAPID
WEAKENING TREND SUNDAY.

TYPHOON FORCE WINDS EXTEND OUTWARD UP TO 75 MILES FROM THE CENTER.
TROPICAL STORM FORCE WINDS EXTEND OUT UP TO 225 MILES NORTH OF THE
CENTER...AND UP TO 250 MILES SOUTH OF THE CENTER.

NEXT ADVISORY
-------------
THIS WILL BE THE LAST SCHEDULED ADVISORY ISSUED BY THE NATIONAL
WEATHER SERVICE ON TYPHOON ATSANI.

$$

WILLIAMS

[euro6208]

000
WWMY80 PGUM 210920
SPSMY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TIYAN GU
800 PM CHST FRI AUG 21 2015

GUZ003>005-PMZ153>154-220200-
TINIAN-SAIPAN-NORTHERN MARIANAS-MARIANAS COASTAL WATERS-
800 PM CHST FRI AUG 21 2015

...TYPHOON ATSANI MOVING AWAY FROM AGRIHAN...PAGAN...AND ALAMAGAN...

AT 700 PM CHST THE EYE OF TYPHOON ATSANI WAS NEAR NEAR 25 DEGREES
NORTH LATITUDE AND 146 DEGREES EAST LONGITUDE...MOVING NORTH-NORTHWEST AT
10 MPH.

THIS IS ABOUT...

ABOUT 440 MILES NORTH OF AGRIHAN
ABOUT 490 MILES NORTH OF PAGAN
ABOUT 520 MILES NORTH OF ALAMAGAN
ABOUT 695 MILES NORTH OF SAIPAN AND
ABOUT 815 MILES NORTH OF GUAM.

TYPHOON ATSANI IS EXPECTED TO MAINTAIN A NORTHWESTWARD TRACK TONIGHT
...THEN GRADUALLY TURN TOWARD THE NORTH SATURDAY. SATELLITE
SCATTEROMETER DATA SHOWS DAMAGING WINDS OF 35 KNOTS SUSTAINED ARE
OFFSHORE TO THE NORTH OF AGRIHAN.

FOR AGRIHAN...PAGAN...AND ALAMAGAN ISLANDS...
MONSOON WINDS FLOWING TOWARD ATSANI WILL BE WEST TO SOUTHWEST AT 25
TO 35 MPH WITH GUSTS TO 40 MPH TONIGHT. WINDS WILL GRADUALLY TAPER
OFF OVER THE WEEKEND. HAZARDOUS SEAS WILL RANGE FROM 15 TO 20 FEET
TONIGHT THROUGH SATURDAY...THEN SLOWLY SUBSIDE. RAINFALL WILL ALSO
BE HEAVY AT TIMES WITH 1 TO 3 INCHES POSSIBLE THROUGH SATURDAY.

BE PREPARED FOR RAINY AND WINDY CONDITIONS THROUGH SATURDAY. DO NOT
NOT ATTEMPT ANY TRAVEL BY BOAT.

FOR SAIPAN AND TINIAN...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITH SOUTHWEST WINDS OF
20 TO 30 MPH WITH GUSTS TO 40 MPH WILL CONTINUE ACROSS TINIAN AND
SAIPAN THROUGH SATURDAY.

A SMALL CRAFT ADVISORY REMAINS IS IN EFFECT UNTIL 600 PM MONDAY.
WINDS OF 20 TO 30 KNOTS WITH COMBINED SEAS OF 12 TO 16 FEET ARE
EXPECTED THROUGH SATURDAY. CONDITIONS SHOULD SLOWLY IMPROVE SUNDAY
THROUGH MONDAY.

STAY INFORMED ON THE PROGRESS OF TYPHOON ATSANI BY FOLLOWING THE
LATEST STATEMENTS ISSUED BY THE NATIONAL WEATHER SERVICE ON GUAM.
THESE ARE POSTED ON THE WFO GUAM WEB PAGE AT http://WWW.PRH.NOAA.GOV/GUAM/
(ALL LOWER CASE).

$$

ZIOBRO

[euro6208]

TPPN12 PGTW 210938

A. TYPHOON 17W (ATSANI)

B. 21/0832Z

C. 25.33N

D. 145.64E

E. FIVE/MTSAT

F. T4.5/5.5/W1.5/24HRS STT: W0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 36A/PBO LARGE EYE/ANMTN. WMG EYE SURROUNDED BY OW
YIELDS AN E# AND DT (NO EYE ADJUSTMENT) OF 4.0. MET YIELDS A
5.0, WHILE PT YIELDS A 4.5. DBO PT.

I. ADDITIONAL POSITIONS: NONE


CHAPPOTIN