WPAC: NEPARTAK - Post-Tropical

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Re: WPAC: NEPARTAK - Typhoon

#401 Postby 404UserNotFound » Thu Jul 07, 2016 11:37 pm

So what typically would happen next, when there is an extremely vigorous spin aloft, but much weaker spin at lower levels? (Come to think of it, this is probably the first time I've actually thought about this question, oddly enough.)
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Re: WPAC: NEPARTAK - Typhoon

#402 Postby CrazyC83 » Fri Jul 08, 2016 12:37 am

404UserNotFound wrote:So what typically would happen next, when there is an extremely vigorous spin aloft, but much weaker spin at lower levels? (Come to think of it, this is probably the first time I've actually thought about this question, oddly enough.)


Hard to say. It will likely have about 24 hours to reorganize, which may not be enough time given its disruption. A similar situation may have been Dennis in 2005 after hitting Cuba, it took about 12-18 hours to rebuild the core, then it took off.

It's probably a Cat 1 right now - guessing about 70 kt.
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Re: WPAC: NEPARTAK - Typhoon

#403 Postby beoumont » Fri Jul 08, 2016 1:13 am

vbhoutex wrote:From James Reynolds with Earth Uncut TV.


https://twitter.com/IrishEagle/status/751151715358011394


Aftermath footage, also shot by Mr. Reynolds, showed the winds got quite a bit stronger later on than during this video; as many cars got flipped. In this video it looks like a steady 80 mph with gusts to 90 or so to me (video was transmitted around 4:30 am, Taiwan time). The local station was reporting peak gusts of 40 m/s at this time.
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Re: WPAC: NEPARTAK - Typhoon

#404 Postby NotoSans » Fri Jul 08, 2016 2:43 am

Seems that it has entered the Taiwan Strait. Nearby surface observations suggest a central pressure of around 980 mb when it moves back over water.
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Re: WPAC: NEPARTAK - Typhoon

#405 Postby StormChaser75 » Fri Jul 08, 2016 3:33 am

Image
http://www.cwb.gov.tw/V7e/observe/radar/
Image11+ inches of rain in spots!
Image
Image
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Re: WPAC: NEPARTAK - Typhoon

#406 Postby wxman57 » Fri Jul 08, 2016 11:06 am

Looks like the storm decoupled overnight. I can clearly see a mid-level spin racing NW while the low-level center remained near the SW coast of Taiwan. It's unlikely that Nepartak is still a typhoon. Typhoons + mountains = not good.
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Re: WPAC: NEPARTAK - Typhoon

#407 Postby 1900hurricane » Fri Jul 08, 2016 11:27 am

The center still looks to be hanging right around here based on radar.

Image
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Re: WPAC: NEPARTAK - Typhoon

#408 Postby wxman57 » Fri Jul 08, 2016 12:27 pm

The mid-level center is nearing the coast of China south of Fuzhou, about 100 miles away from the LLC. Definitely not a typhoon now.
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Re: WPAC: NEPARTAK - Typhoon

#409 Postby gatorcane » Fri Jul 08, 2016 12:31 pm

Yeah Wxman I see what you mean looking for centers on this loop


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Re: WPAC: NEPARTAK - Typhoon

#410 Postby wxman57 » Fri Jul 08, 2016 12:40 pm

Here's a graphic demonstrating the decoupling. JTWC appeared to be following the mid-level center with their 15Z advisory. JMA sees the low-level center, but no way Nepartak has 70kt 10-min winds.

Image
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Re: WPAC: NEPARTAK - Typhoon

#411 Postby CrazyC83 » Fri Jul 08, 2016 1:25 pm

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K.

This is COMPLETELY unofficial, but here is what I would have as the best track (I know they don't do HURDAT2 in the WPAC but using it here). Taking a look through the satellite analyses, I believe it weakened even more in the last 16 hours before landfall.

WP022016, NEPARTAK, 30,
20160702, 1800, , TD, 8.2N, 145.5E, 30, 1007,
20160703, 0000, , TS, 8.8N, 145.0E, 35, 1005,
20160703, 0600, , TS, 9.5N, 144.7E, 40, 1003,
20160703, 1200, , TS, 10.1N, 144.1E, 45, 1001,
20160703, 1800, , TS, 10.8N, 143.1E, 50, 998,
20160704, 0000, , TS, 11.7N, 142.0E, 50, 997,
20160704, 0600, , TS, 12.7N, 140.9E, 50, 997,
20160704, 1200, , TS, 13.5N, 139.7E, 60, 992,
20160704, 1800, , TY, 14.6N, 138.2E, 70, 985,
20160705, 0000, , TY, 15.4N, 136.7E, 80, 977,
20160705, 0600, , TY, 16.3N, 135.1E, 105, 954,
20160705, 1200, , TY, 17.2N, 133.5E, 125, 938,
20160705, 1800, , ST, 18.0N, 131.8E, 135, 926,
20160706, 0000, , ST, 18.7N, 130.1E, 150, 912,
20160706, 0600, , ST, 19.5N, 128.4E, 160, 902,
20160706, 1200, , ST, 20.2N, 126.9E, 145, 914,
20160706, 1800, , ST, 20.7N, 125.6E, 130, 926,
20160707, 0000, , ST, 21.2N, 124.3E, 140, 916,
20160707, 0600, , ST, 21.6N, 123.4E, 150, 905,
20160707, 1200, , ST, 22.0N, 122.6E, 140, 914,
20160707, 1800, , TY, 22.4N, 121.8E, 125, 932,
20160707, 2245, L, TY, 22.6N, 121.0E, 105, 941,
20160708, 0000, , TY, 22.6N, 120.8E, 95, 954,
20160708, 0600, , TY, 23.0N, 120.0E, 70, 976,
20160708, 1200, , TY, 23.3N, 119.7E, 65, 980,
20160708, 1800, , TS, 23.3N, 119.5E, 55, 986,
20160709, 0000, , TS, 23.8N, 119.2E, 45, 994,
20160709, 0600, , TS, 24.2N, 118.7E, 35, 999,
20160709, 1000, L, TD, 24.6N, 118.4E, 30, 1002,
20160709, 1200, , LO, 24.9N, 118.2E, 25, 1005,

(revised October 27, 2016 for buoy data)
Last edited by CrazyC83 on Wed Oct 26, 2016 10:44 pm, edited 3 times in total.
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#412 Postby cycloneye » Fri Jul 08, 2016 2:00 pm

JMA downgrades from Typhoon.

STS 1601 (Nepartak)
Issued at 18:45 UTC, 8 July 2016


<Analysis at 18 UTC, 8 July>
Scale -
Intensity -
Center position N23°40' (23.7°)
E119°25' (119.4°)
Direction and speed of movement NW 10 km/h (6 kt)
Central pressure 980 hPa
Maximum wind speed near center 30 m/s (60 kt)
Maximum wind gust speed 45 m/s (85 kt)
≥ 50 kt wind area ALL 90 km (50 NM)
≥ 30 kt wind area NE 330 km (180 NM)
SW 280 km (150 NM)

<Forecast for 18 UTC, 9 July>
Intensity -
Center position of probability circle N25°30' (25.5°)
E117°20' (117.3°)
Direction and speed of movement NW 15 km/h (7 kt)
Central pressure 992 hPa
Maximum sustained wind speed 20 m/s (40 kt)
Maximum wind gust speed 30 m/s (60 kt)
Radius of probability circle 90 km (50 NM)

<Forecast for 18 UTC, 10 July>
Intensity -
TD
Center position of probability circle N28°10' (28.2°)
E117°30' (117.5°)
Direction and speed of movement N 15 km/h (7 kt)
Central pressure 996 hPa
Radius of probability circle 200 km (110 NM)
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#413 Postby wxman57 » Fri Jul 08, 2016 2:46 pm

That 60kts is for a 10-minute wind average. Converting to 1-minute, they're still saying it has 65-70kt winds, which I think is way too high.
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#414 Postby euro6208 » Fri Jul 08, 2016 5:57 pm

Image

WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (NEPARTAK)
WARNING NR 24//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 02W (NEPARTAK), LOCATED APPROXIMATELY 142 NM
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 01 KNOT
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICT A RAPIDLY DETERIORATING CONVECTIVE PATTERN ASSOCIATED
WITH THE CIRCULATION OF TS 02W, WITH THE CENTRAL CORE BECOMING
NEARLY DEVOID OF DEEP CONVECTION. THE CURRENT POSITION IS BASED ON
RECENT ANIMATED RADAR IMAGERY FROM TAIWAN, SUPPORTING THE CURRENT
BEST TRACK POSITION WITH FAIR CONFIDENCE. SUBJECTIVE DVORAK
ESTIMATES RANGE FROM T4.0-5.0 (65-90 KNOTS) FROM PGTW AND KNES, BUT
THESE MAY BE A BIT HIGH GIVEN DVORAK CONSTRAINTS AND THE
DISORGANIZATION OF TS 02W. THUS, THE CURRENT INTENSITY HAS BEEN
DECREASED TO 60 KNOTS. THE UPPER-LEVEL ENVIRONMENT CONTINUES TO BE
FAVORABLE, WITH GOOD POLEWARD AND WESTWARD OUTFLOW AND ONLY 5-10
KNOTS OF VERTICAL WIND SHEAR. HOWEVER, THE CIRCULATION OF TS 02W
CONTINUES TO BE DECOUPLED, WITH THE LOW-LEVEL CIRCULATION CENTER
(LLCC) LAGGING BEHIND THE MID-LEVEL CIRCULATION TO THE NORTHWEST OF
THE CURRENT BEST TRACK POSITION. GIVEN THESE FACTORS, CONTINUED
WEAKENING IS FORECAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. THE LLCC OF TS 02W HAS SLOWLY DRIFTED TO THE NORTH NEAR THE
PENGHU ISLANDS ACCORDING TO RADAR IMAGERY, WITH THE MID-LEVEL
CIRCULATION CONTINUING NORTHWESTWARD AS EVIDENT IN SATELLITE
IMAGERY. THE MESOSCALE STRUCTURE OF THE SYSTEM REMAINS DISORGANIZED,
WITH A REGION OF LOW-LEVEL CONFLUENCE SOUTH OF THE LLCC ENHANCING A
SEMI-STATIONARY OUTER RAINBAND. IN RECENT RADAR IMAGERY, CONVECTIVE
SHOWERS TO THE WEST OF THE PENGHU ISLANDS EXHIBIT SOME INCREASED
CURVATURE, WHICH SUGGEST THAT THE LLCC MAY REFORM TO THE NORTHWEST
WITH THE DYNAMIC SUPPORT OF THE MID-LEVEL CIRCULATION. UNTIL THE TS
02W VORTEX BECOMES MORE VERTICALLY COHERENT, THE LLCC IS EXPECTED TO
CONTINUE A NORTHWARD DRIFT. SYNOPTICALLY, THE SYSTEM SHOULD CONTINUE
ON A NORTHWESTWARD TRAJECTORY AROUND THE WESTERN PERIPHERY OF A DEEP
LAYERED SUBTROPICAL RIDGE WITH A WEAKNESS INDUCED BY A TROUGH AXIS
PASSING THROUGH THE KOREAN PENINSULA. THE NEAR-TERM FORECAST IS
NUDGED SLIGHTLY TO THE RIGHT OF THE PREVIOUS FORECAST TRACK IN
RESPONSE TO THE NORTHWARD JOG OF THE LLCC. THE FORECAST TRACK FROM
TAU 12-24 LIES TO THE RIGHT OF CONSENSUS BUT TO THE LEFT OF THE
OUTLYING NAVGEM, WHICH TRACKS THE LLCC MORE TOWARD THE NORTH. TS 02W
SHOULD CONTINUE A STEADY WEAKENING, WITH DISSIPATION BY TAU 48 AFTER
ITS LANDFALL ON MAINLAND CHINA IN APPROXIMATELY 18 HOURS. NUMERICAL
MODEL GUIDANCE IS IN GOOD AGREEMENT LENDING TO HIGH CONFIDENCE IN
THE JTWC FORECAST TRACK.//
NNNN
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#415 Postby euro6208 » Fri Jul 08, 2016 6:15 pm

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Re: WPAC: NEPARTAK - Severe Tropical Storm

#416 Postby euro6208 » Fri Jul 08, 2016 7:28 pm

Big blowup of convection in a country still reeling from devastating floods with hundreds killed... :(

Image
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#417 Postby 1900hurricane » Fri Jul 08, 2016 9:22 pm

I just thought of something. Does anyone know the sustained winds recorded by the buoy at the time of the 897 mb pressure reading? The NHC will take the surface winds measured by a recon dropsonde and subtract an additional millibar off the observed pressure for every 10 kt of winds observed to estimate the true central pressure. Could the same procedure be done here?
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#418 Postby euro6208 » Fri Jul 08, 2016 10:18 pm

Read somewhere that peak winds measured was 153 mph don't know if it's sustained or gust and it occurred close to 3 hours before the lowest pressure recorded by a buoy in world history.

Some say it could be as high as 180 knots... :lol:
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#419 Postby euro6208 » Fri Jul 08, 2016 10:54 pm

Image

WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (NEPARTAK)
WARNING NR 25//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 02W (NEPARTAK), LOCATED APPROXIMATELY 143 NM WEST-
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS FLARING CONVECTION IN THE CIRCULATION OF
TS 02W THAT IS STRUGGLING TO REMAIN INTACT. THE CURRENT POSITION IS
BASED ON RECENT RADAR IMAGERY FROM TAIWAN, SHOWING THE LOW-LEVEL
CIRCULATION CENTER (LLCC) ACCELERATING TO THE NORTHWEST AS
PREVIOUSLY FORECAST, AFTER DRIFTING FOR SEVERAL HOURS NEAR THE
PENGHU ISLANDS. THE POSITION IS CORROBORATED BY THE 082230Z SSMIS
91GHZ IMAGE. THE CURRENT BEST TRACK POSITION IS DETERMINED WITH FAIR
CONFIDENCE. SUBJECTIVE DVORAK ESTIMATES OF T2.5/3.5 FROM PGTW AT
090000Z AND T3.5/4.5 FROM KNES AT 082030Z SUPPORT A CURENT INTENSITY
OF 45 KNOTS. THE UPPER-LEVEL ENVIRONMENT CONTINUES TO PROVIDE GOOD
POLEWARD AND WESTWARD OUTFLOW AND LOW VERTICAL WIND SHEAR OF ONLY 5-
10 KNOTS. THE LLCC IS EXPECTED TO MAKE LANDFALL SOON, WHICH WILL
RESULT IN CONTINUED WEAKENING AND DISSIPATION.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 02W HAS RESUMED A NORTHWESTWARD TRAJECTORY, BEING STEERED
AROUND THE WESTERN PERIPHERY OF A DEEP LAYERED SUBTROPICAL RIDGE. A
TURN TO THE NORTH IN 24-36 HOURS IS EXPECTED AS A SHORTWAVE TROUGH
DIGS THROUGH EASTERN CHINA. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT LENDING TO HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
AFTER IMMINENT LANDFALL, DISSIPATION IS EXPECTED WITHIN 48 HOURS.//
NNNN
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Re: WPAC: NEPARTAK - Severe Tropical Storm

#420 Postby CrazyC83 » Fri Jul 08, 2016 11:52 pm

euro6208 wrote:Read somewhere that peak winds measured was 153 mph don't know if it's sustained or gust and it occurred close to 3 hours before the lowest pressure recorded by a buoy in world history.

Some say it could be as high as 180 knots... :lol:


I'm not sure either, but the Dvorak estimates only supported T7.0 at that time. It was likely at the end of an eyewall cycle and at a secondary peak, but I estimate at the time of that buoy report the intensity was 150 kt.
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