ATL: NATE - Post Tropical - Discussion

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Re: ATL: NATE - Hurricane - Discussion

#2622 Postby fwbbreeze » Sun Oct 08, 2017 5:16 am

Had rather squally weather in the Fort Walton Beach area. Quite a few power outages. Still blowing and raining pretty good.
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Re: ATL: NATE - Hurricane - Discussion

#2623 Postby kthmcc7319 » Sun Oct 08, 2017 6:16 am

fwbbreeze wrote:Had rather squally weather in the Fort Walton Beach area. Quite a few power outages. Still blowing and raining pretty good.


Same here in Choctaw Beach. The last 2 hours have been the heaviest. Still have power but we’ve had some surges. Looks like we may have a couple more hours of this. Under tornado watch as well. Stay safe
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Re: ATL: NATE - Hurricane - Discussion

#2624 Postby tolakram » Sun Oct 08, 2017 6:52 am

I would normally put this in the models thread but it gets very little traffic after a storm hits.

What's left of Nate combined with a cold front is going to produce significant wind gusts, looks similar to Ike. This is from the Euro.

Image
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Re: ATL: NATE - Hurricane - Discussion

#2625 Postby wxman57 » Sun Oct 08, 2017 7:09 am

NC George wrote:
I think I have some insight: We have a 50-55 mph tropical storm here with wind speeds augmented by a fast forward movement creating just strong enough winds at one point (due east of the center) to classify this as a hurricane. I'm guessing the winds on the west side are around 25 mph. I think the lack of a southern eyewall at all along with the weak radar presentation corroborates this analysis.


Hang on there, you don't add a storm's forward speed into the reported max sustained wind. The forward speed is already taken into account with the measured surface winds used to classify the storm. A 50 mph storm moving 25 mph produces 50 mph winds. Winds on the left side may be only 25 mph.

The explanation here for the lack of winds is that Nate was likely a 60-70 mph tropical storm when it made landfall. The NHC will never downgrade a hurricane as it's nearing land because their main job is to protect lives. People may have ignored the warnings and been injured. They believe it's better to over-warn to keep people safe, and I'm not saying that's a bad thing. A 60-70 mph tropical storm is dangerous.

Those stronger winds that recon was measuring at 10,000 ft were not transferring down to the surface very well. The standard wind reduction to the surface only applies for a well-organized eyewall, which was lacking with Nate. I was watching recon reports yesterday as the plane flew over coastal buoys south of Mobile. The plane found 60kt winds, but the buoys were reporting 25kts at the time. Nate may have been a hurricane considering only winds aloft, but I'm not finding any evidence that it was an 85 mph hurricane at landfall in the surface obs. While an 85 mph hurricane's peak winds could miss surface stations, the stations should at least report 60-70 mph winds. That wasn't the case, even offshore. Weakening storms at landfall do not transfer those winds aloft down to the surface well.

Buoy 42040, which was near, but not in, the eastern eyewall of Nate, reported sustained wind 38 kts.
10 07 7:20 pm SE 38.9 50.5 - - - - 29.49 - 77.7 82.4 76.3

Station PTBM6, offshore Pascagoula, reported peak sustained wind of 46 gusting 58 kts. It went through that heaviest squall east of the center.
10 08 12:24 am S 46.0 58.1 - - - - 29.39 - 77.0

All coastal stations remained operational through landfall and beyond. Pascagoula and Biloxi did report sustained tropical storm force winds. No gusts to hurricane strength reported. Biloxi got close with a peak gust of 61 kts (about 70 mph).

KPQL 080544Z AUTO 16034G54KT 4SM -RA BR OVC008 25/24 A2930 RMK AO2 PK WND 14056/0529
KBIX 080436Z AUTO 07046G61KT 1/2SM +RA FG SQ VV008 25/24 A2911 RMK AO2 PRESFR
KGPT 080444Z AUTO 03028G42KT 1 3/4SM +RA BR OVC011 25/25 A2914 RMK AO2 PK WND 02044/0400
KMSY 080150Z 34016G25KT 2SM -RA BR BKN011 OVC022 23/23
KNEW 080253Z 35025G32KT 4SM -RA BR OVC015 24/23 A2955 RMK AO2 PK WND 34034/0225

Peak surge appears to be just under 6 ft in Pascagoula, according to TWC.

Do any of you have reports of higher winds? I'll be preparing a post-storm report.
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Re: ATL: NATE - Tropical Storm - Discussion

#2626 Postby wxman57 » Sun Oct 08, 2017 7:26 am

Currently, I'm not finding any surface observations that indicate Nate is still a tropical storm. Peak winds I'm finding are about 25 kts (29 mph). I see a station just west of Montgomery reporting wind gusts to 38 kts. Perhaps the NHC will downgrade Nate to a TD on the noon intermediate.
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Re: ATL: NATE - Tropical Storm - Discussion

#2627 Postby funster » Sun Oct 08, 2017 7:39 am

There was a met tweeting about a buoy recording sustained winds of 71 mph and a gust to 88 mph. I think this was around the time of the first landfall.




https://twitter.com/MetDavidPaul/status/916847004512288773
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Re: ATL: NATE - Tropical Storm - Discussion

#2628 Postby stormreader » Sun Oct 08, 2017 8:04 am

Add Nate's name to the long list of north gulf coast landfalling hurricanes that lost much of its definition and structure in the hours before coming ashore. You could see this was happening early last evening. As usual, still carried a hurricane surge, but it was totally hollowed out, and probably a non-event for most people. At least from a scientific standpoint this is still pretty interesting IMO. People will give reasons (after the fact) for what happened, but if this weakening was truly well-understood, it could be anticipated ahead of time. But on Saturday, our best minds calculated that we would likely see a Cat 2 landfalling hurricane, when in reality we probably had a low to medium grade tropical storm.
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Re: ATL: NATE - Tropical Storm - Discussion

#2629 Postby wxman57 » Sun Oct 08, 2017 8:26 am

stormreader wrote:Add Nate's name to the long list of north gulf coast landfalling hurricanes that lost much of its definition and structure in the hours before coming ashore. You could see this was happening early last evening. As usual, still carried a hurricane surge, but it was totally hollowed out, and probably a non-event for most people. At least from a scientific standpoint this is still pretty interesting IMO. People will give reasons (after the fact) for what happened, but if this weakening was truly well-understood, it could be anticipated ahead of time. But on Saturday, our best minds calculated that we would likely see a Cat 2 landfalling hurricane, when in reality we probably had a low to medium grade tropical storm.


I would argue that Nate carried a tropical storm surge. If it had been a hurricane, then the surge would have been in the 8-10 foot range. Nate was not producing any significant area of hurricane force winds offshore long before it moved inland. Storm surge is not a function of the peak sustained wind in a storm. Surge depends more on the size of the wind field and the strength of that wind over a large area. Average winds over large areas were closer to 40-50 mph, which can easily produce a surge of 5-6 ft on the Mississippi coast.

The Mississippi coast is the most surge-prone area of the U.S. The shoaling factor multiplier is nearly 2.0 at Biloxi, while in Pensacola, that multiplier is closer to 0.6. A 30-40 mph onshore wind can produce tides 4-6 ft above normal in Mississippi.
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Re: ATL: NATE - Tropical Storm - Discussion

#2630 Postby wxman57 » Sun Oct 08, 2017 8:28 am

funster wrote:There was a met tweeting about a buoy recording sustained winds of 71 mph and a gust to 88 mph. I think this was around the time of the first landfall.


Thanks. Nate may have had a tiny area of 75-80 mph winds as it passed the mouth of the Mississippi. But those winds were not representative of the general winds around Nate.
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Re: ATL: NATE - Tropical Storm - Discussion

#2631 Postby panamatropicwatch » Sun Oct 08, 2017 8:32 am

A buoy just off shore of Panama City Beach recorded a wind gust to 50mph, sustained wind around 35mph. Lost power here in downtown Panama City for a short period of time so far.
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Re: ATL: NATE - Tropical Storm - Discussion

#2632 Postby PandaCitrus » Sun Oct 08, 2017 8:50 am

Looks like Pascagoula got 7 feet of storm surge.



https://twitter.com/weathergeek312/status/917019338779123712
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Re: ATL: NATE - Tropical Storm - Discussion

#2633 Postby PandaCitrus » Sun Oct 08, 2017 8:54 am

Parts of Mobile may have gotten up to 8 feet of surge.



https://twitter.com/JMichaelsNews/status/917020038930010112
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Re: ATL: NATE - Tropical Storm - Discussion

#2634 Postby Jelff » Sun Oct 08, 2017 8:56 am

Google + GIS map with rain forecast for the next 2 days. This data comes from NOAA’s nowCOAST GIS server. Each time you open the map it will show the forecast for the ‘next’ 2 days.

To see the map legend please click “Map Tips” in the upper left corner.

The map can also display 20+ other rain and flood related GIS overlay layers, including stream gages with links to the NOAA web page for each gage.

Map link: https://goo.gl/nKHHav
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Re: ATL: NATE - Models

#2635 Postby NDG » Sun Oct 08, 2017 8:58 am

I should had known better about the Euro being a little left biased lately on it’s short 24-48 hr forecast when a storm is turning. It did the same thing with Irma, it was showing it to go just west of Key West and West of Tampa instead it went up east of both locations. With Maria it was showing it to get a lot closer to the Outer Banks of NC before moving out to sea. You bet somebody in the NH center had that into account for sticking with the TVCN consensus model.
I scared a lot of friends and family members back in Nola by posting the Euro model run on FB.
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Re: ATL: NATE - Models

#2636 Postby stormreader » Sun Oct 08, 2017 9:55 am

NDG wrote:I should had known better about the Euro being a little left biased lately on it’s short 24-48 hr forecast when a storm is turning. It did the same thing with Irma, it was showing it to go just west of Key West and West of Tampa instead it went up east of both locations. With Maria it was showing it to get a lot closer to the Outer Banks of NC before moving out to sea. You bet somebody in the NH center had that into account for sticking with the TVCN consensus model.
I scared a lot of friends and family members back in Nola by posting the Euro model run on FB.



I did the same thing (giving lots of credence to Euro short term). Good example you give about the left bias that occured after Irma landfall. But still, overall it is the strongest model, don't know that we can beat ourselves up too much for relying on what the overall strongest model says. One thing nice to see was that the GFS long term solution did better with this storm. When all other models were saying Appalachicola area or just off Fl west coast, GFS said no, much further west (central La). It didn't go that far, of course, but I give it credit in the long range, for deciphering a generally more westward storm impact.
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Re: ATL: NATE - Tropical Storm - Discussion

#2637 Postby NDG » Sun Oct 08, 2017 9:58 am

wxman57 wrote:
funster wrote:There was a met tweeting about a buoy recording sustained winds of 71 mph and a gust to 88 mph. I think this was around the time of the first landfall.


Thanks. Nate may have had a tiny area of 75-80 mph winds as it passed the mouth of the Mississippi. But those winds were not representative of the general winds around Nate.


Those winds were not from a surface buoy, it was from an oil rig.

Oil Platform
29.296 N 88.842 W (29°17'46" N 88°50'31" W)

Anemometer height: 85 m above site elevation
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Re: ATL: NATE - Tropical Storm - Discussion

#2638 Postby CrazyC83 » Sun Oct 08, 2017 10:03 am

Without other data, I would go with 65 kt for the landfall intensity, based on the fact the SFMR was reading in the low 60s in shoaling and the radar velocities.
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Re: ATL: NATE - Tropical Storm - Discussion

#2639 Postby LarryWx » Sun Oct 08, 2017 10:05 am

PandaCitrus wrote:Looks like Pascagoula got 7 feet of storm surge.



https://twitter.com/weathergeek312/status/917019338779123712


Technically, that is really showing a 6 foot surge on top of a 2 foot high tide as opposed to the 7+ foot surge mentioned in the tweet. Still nothing to sneeze at by any means!
Last edited by LarryWx on Sun Oct 08, 2017 10:21 am, edited 1 time in total.
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Re: ATL: NATE - Tropical Storm - Discussion

#2640 Postby Blackwaterjoe22 » Sun Oct 08, 2017 10:10 am

Here on the far northeast corner of Blackwater Bay between the mouth of Blackwater River and Yellow River we had a 4-5 foot surge. This is a surge prone area. Several homes in my neiborhood took on water. We had approximately 10inches
Downstairs. Lost power for about 10 hours due to pine falling across power lines.. Water receded around 7-8AM this morning
Not looking forward to day of mopping and squeegee.

Joe
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