WPAC: JEBI - Post-Tropical

[xtyphooncyclonex]

JEBI 25W T6.0/6.0 30/0830Z West Pacific

[NotoSans]

Starting to give me vibes of Meranti’16.

[mrbagyo]

Eye temp is now on the positive double digit

2018AUG30 113000 5.8 949.3 109.8 5.8 6.1 6.1 NO LIMIT OFF OFF 11.10 -69.82 EYE 14 IR 49.6 17.78 -146.97 COMBO HIM-8 21.9

[euro6208]

Comparing Norman to Jebi. Jebi much smaller so dvorak will have a hard time analyzing. Also looks to be stronger with a clearer eye yet still weaker operationally. Both gets a 6.5 dvorak yet it's still weaker but looks more impressive. That's dvorak to you...

Norman




Jebi

[mrbagyo]

well

25W JEBI 180830 1200 17.7N 146.8E WPAC 110 952

Catching up...

I guess we're waiting for JMA's advisory. I guess they would go with T6.0 (about 90-95kts, 935-940 hPa)

JMA keeps it at 85 knots

TY 1821 (Jebi)
Issued at 12:45 UTC, 30 August 2018
<Analysis at 12 UTC, 30 August>
Scale -
Intensity Very strong
Center position N17°50' (17.8°)
E146°55' (146.9°)
Direction and speed of movement W 20 km/h (11 kt)
Central pressure 950 hPa
Maximum wind speed near center 45 m/s (85 kt)
Maximum wind gust speed 60 m/s (120 kt)
≥ 50 kt wind area ALL 70 km (40 NM)
≥ 30 kt wind area N 330 km (180 NM)
S 280 km (150 NM)

[euro6208]

:uarrow:
Is there any human/ weather instruments there?

Is there any observation station in Pagan Island, they have an airstrip there but I can't find any METAR.

There are no direct obs in the Northern Marianas. Pagan, Alamagan, and Agrihan are all volcanic islands and are inhabited. METAR can only be found in the southern Marianas...

[mrbagyo]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.0

Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 30 AUG 2018
Time : 124000 UTC
Lat : 17:47:59 N
Lon : 146:40:47 E
CI# /Pressure/ Vmax
6.0 / 944.8mb/115.0kt

Final T# Adj T# Raw
T# 6.0 6.4 6.4
Estimated radius of max. wind based on IR : 13 km
Center Temp : +17.5C Cloud Region Temp : -70.9C
Scene Type : EYE


Massive jump on Eye temp

[euro6208]

Amazing how dvorak works. Jebi is much more organized hence why JTWC is underestimating this!

[NotoSans]

JTWC has an intensity estimate lower than Dvorak estimates, meaning that they are making reference to other methods, so from a logical perspective you should accuse either JTWC or other methods, but not Dvorak lol

[xtyphooncyclonex]

Amazing how dvorak works. Jebi is much more organized hence why JTWC is underestimating this!

Well, Dvorak's estimates have been higher than JTWC's

[euro6208]

Probrably will be the strongest typhoon to strike the Marianas since Soudelor 2015 which hit Saipan at a post analysis of 130 knots Cat 4...

[euro6208]

WPAC typhoons are known to be large. This is quite small...

[NotoSans]

JTWC in their latest prognostic reasoning expressly indicate that their intensity estimate is lower than subjective Dvorak estimates due to possible wind speed lag for a rapidly intensifying typhoon. Although I respectfully disagree with such reasoning, this is a typical example showing that the agencies can go against Dvorak, and not all so-called ‘underestimation’ are attributed to it.

[1900hurricane]

The SATCON estimate is likely distorted by the AMSU estimate. The AMSU estimate depends heavily on the estimated RMW due to resolution problem. The latest AMSU used an estimated RMW of 9 km, which is likely too small and leads to higher intensity estimates.

Maybe, but I'm not sure the AMSU RMW estimate is too far off. The ADT RMW estimates are fairly similar, oscillating from 9-13 km. Additionally, IR derived RMW estimates can sometimes be a little large. Haiyan '13 (via ground obs, radar, etc) and Meranti '16 (via radar imagery) would be decent examples, although the two systems aren't of the same scale as Jebi, and I assume it can go the other way sometimes too. For what it's worth, ATMS intensity estimates just prior to the latest AMSU intensity estimate came in just 4 kt weaker.

[euro6208]

WDPN31 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (JEBI) WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 25W (JEBI), LOCATED APPROXIMATELY 161 NM NORTH-NORTHEAST
OF SAIPAN, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX
HOURS. THE EIR SATELLITE IMAGE SHOWS DEEPENING CONVECTION AND
COLDER CLOUD TOPS ENCIRCLING THE EYE. THE INITIAL INTENSITY OF 110
KNOTS IS PLACED UNDER DVORAK CURRENT INTENSITY ESTIMATES OF T6.5
(127 KTS) FROM PGTW AND T6.0 (115 KTS) FROM KNES, AND IS BELOW A
300556Z SATCON ESTIMATE OF 118 KTS. WHILE THE STRUCTURE CONTINUES
TO IMPROVE, WINDS WILL LAG SLIGHTLY AS THE PRIMARY CIRCULATION
CATCHES UP TO THE SECONDARY CIRCULATION REPRESENTED BY CONVECTION.
THE ENVIRONMENT REMAINS FAVORABLE FOR CONTINUED INTENSIFICATION
WITH WARM SSTS (29-30 CELSIUS), LOW (10-15 KTS) VERTICAL WIND SHEAR
(VWS), AND RADIAL OUTFLOW AIDED BY A TUTT CELL TO THE NORTHEAST.
THE SYSTEM IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EAST-WEST
ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS WARNING.
B. THROUGH TAU 24, TY 25W WILL TRACK WESTWARD TO WEST-
NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR. AFTER TAU
24, A MIDLATITUDE TROUGH WILL CREATE A BREAK IN THE STR AND ALLOW
THE SYSTEM TO BEGIN A GRADUAL TURN POLEWARD. DUE TO FAVORABLE
ENVIRONMENTAL CONDITIONS, TY 25W IS EXPECTED TO CONTINUE
INTENSIFICATION THROUGH TAU 24 TO A PEAK OF 130 KNOTS, WHICH IT
WILL MAINTAIN THROUGH TAU 36. AFTER TAU 36, DIMINISHED OUTFLOW WILL
LEAD TO A GRADUAL WEAKENING TREND AS TY 25W LOSES ITS FAVORABLE
ORIENTATION WITH RESPECT TO THE TUTT CELL TO ITS EAST. NUMERICAL
GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A SPREAD OF 200
NM AT TAU 72. BASED ON THE LOW UNCERTAINTY IN THE TRACK GUIDANCE,
CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST IS HIGH.
C. AFTER TAU 72, TY 25W WILL CONTINUE ROUNDING THE STR AXIS. THE
INTENSITY WILL CONTINUE TO WEAKEN GRADUALLY AS SSTS COOL TO 28C AND
AS TY 25W BEGINS TO INTERACT WITH THE MIDLATITUDE WESTERLIES, WHICH
WILL BRING INCREASED VWS. HOWEVER, IMPROVING POLEWARD OUTFLOW INTO
A TROUGH MOVING INTO THE AREA AT TAU 96 SHOULD TEMPORARILY MITIGATE
THE WEAKENING TREND AT LATER TAUS. THE TRACK SPEED ACCELERATES TO
THE NORTHEAST AFTER TAU 96 AS TY 25W MOVES INTO THE INFLUENCE OF
THE MIDLATITUDE WESTERLIES, AND TY 25W IS NOW FORECAST TO MAKE
LANDFALL ON HONSHU SHORTLY BEFORE TAU 120, WHICH WILL WEAKEN IT
FURTHER DUE TO LAND INTERACTION. NAVGEM AND JGSM ARE WESTERN
OUTLIERS, TAKING LONGER TO RECURVE THE SYSTEM THAN OTHER MODELS,
WHILE ECMWF IS CLOSE TO THE MULTI-MODEL CONSENSUS, AND GFS, HWRF,
AND COAMPS-GFS SHOW A SHARPER TURN EAST OF THE MULTI-MODEL
CONSENSUS. BASED ON THE HIGH UNCERTAINTY (425 NM SPREAD IN
SOLUTIONS AT TAU 120, FROM NEAR TOKYO TO NEAR SHIKOKU), THERE IS
LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
NNNN

[1900hurricane]

Easy instantaneous DT of 7.0 right now.

[euro6208]

135 knots at best.

[euro6208]

DAMN

[euro6208]

000
WTPQ31 PGUM 301526
TCPPQ1

BULLETIN
TYPHOON JEBI (25W) Advisory Number 14
National Weather Service Tiyan GU WP252018
126 AM ChST Fri Aug 31 2018

...TYPHOON JEBI CLOSE TO PAGAN AND ALAMAGAN...

CHANGES WITH THIS ADVISORY
--------------------------
None.

WATCHES AND WARNINGS
--------------------
A Typhoon Warning remains in effect for Agrihan, Pagan and
Alamagan in the northern CNMI.

Destructive winds are occurring.

SUMMARY OF 100 AM CHST...1500 UTC...INFORMATION
----------------------------------------------
Location...17.8N 146.2E

About 20 miles east-northeast of Alamagan
About 35 miles southeast of Pagan
About 75 miles south-southeast of Agrihan
About 190 miles north of Saipan
About 195 miles north-northeast of Tinian
About 265 miles north-northeast of Rota
About 315 miles north-northeast of Guam

Maximum sustained winds...125 mph
Present movement...west...270 degrees at 14 mph

Discussion and outlook
----------------------
At 100 AM CHST...1500 UTC...the center of Typhoon Jebi was
located near Latitude 17.8 degrees North and Longitude
146.2 degrees East. Typhoon Jebi is moving toward the west at
14 mph. It is expected to make a slight turn toward the west-
northwest with little change in forward speed over the next
24 hours.

The typhoon is passing between Pagan and Alamagan this morning.

Maximum sustained winds have increased to 125 mph. Typhoon Jebi
is forecast to intensify through Saturday.

Typhoon force winds extend outward from the center up to
50 miles. Tropical storm force winds extend outward from the
center up to 185 miles.

NEXT ADVISORY
-------------
An intermediate advisory will be issued by the National Weather
Service at 500 AM ChST followed by the next scheduled advisory at
800 AM ChST.

$$

Ziobro

[euro6208]