ATL: NATE - Post Tropical - Discussion

[Steve]

12Z CMC is one of the most interesting runs I've seen in forever. It repeats the same thing it did in the past 2-3 runs, but "Nate" is the weaker of the two systems. Both hit S LA, though Nate's intensity has to be off in that scenario. They'd both be semi-weak Tropical Storms if it was to verify. Fujiwara in the house for sure though. CMC is still running, but it brings the next SW Atlantic system south of Florida to repeat the pattern.

GFS re-loads the pattern with a surface high settling into the mid-Atlantic again. This would surely mean that another storm would be south or southeast of that high. It goes back to what Mark was saying on Tuesday that we have to get past this myth that cold fronts stop the hurricane season when often they are pattern indicators of genesis.

HWRF is a little closer to the coast in Nicaragua than the last run which had it farther inland. It's only out to 6 hours though. HMON is out to 18 hours and is farther north offshore of Nicaragua.

[Steve]

HWRF is coming in stronger (994mb vs. 1001) and is southwest of the prior run which had it at 18.8N 85W in 24 hours which on this run is at 17.2N 85.25W.

[Javlin]

Steve both models HWRF and HMON are ramping it pretty quick once N of Nic have to see if that is really the case both @24hrs.

HWRF: https://www.tropicaltidbits.com/analysi ... s=0&ypos=0

HMON: https://www.tropicaltidbits.com/analysi ... 0&ypos=228

[PSUHiker31]

Wxbell is having some serious issues with their model image output in case anyone was wondering

[Javlin]

Hwrf clips the Yucatan @82kts 984mbs.

https://www.tropicaltidbits.com/analysi ... =0&ypos=70

[LarryWx]

12Z GEFS members almost unanimous for LA hit Sat night with no members real strong. Thus it is implying TS hit most likely.

[crownweather]

Wxbell is having some serious issues with their model image output in case anyone was wondering

Give Dr. Maue's site a try - http://wx.graphics . All maps are free and after a lot of careful thought, I've gone and canceled my subscription to WxBell since same maps are available on Maue's page.

[Pearl River]

HWRF takes it in just south and moves just east of downtown New Orleans.

https://www.tropicaltidbits.com/analysis/models/?model=hwrf&region=16L&pkg=mslp_wind&runtime=2017100512&fh=54&xpos=0&ypos=0

Slightly east of the last run, looks to be a little quicker, about 3 hours quicker, and a little weaker by my guestimation

[bella_may]

HWRF is slightly east and stronger than the last run (I think)

[Steve]

LMAO at HMON with the small storm in the 930's coming in farther west still (Atchafalaya or Vermilion Bays).

https://www.tropicaltidbits.com/analysi ... 0&ypos=293

[SunnyThoughts]

HMON stronger as well

[PSUHiker31]

Wxbell is having some serious issues with their model image output in case anyone was wondering

Give Dr. Maue's site a try - http://wx.graphics . All maps are free and after a lot of careful thought, I've gone and canceled my subscription to WxBell since same maps are available on Maue's page.

I'm on a group subscription to wxbell for the year. I'll probably get out of it at the end since Maue has the high resolution Euro.

[chaser1]

All other factors aside......... Nate is over land. Nate is on the Western side of an upper anticyclone anchored just west of Jamaica. Another stout upper anticyclone is presently over Texas and the strong NNE upper-level winds that are presently being funneled down into the E. Gulf and N.W. Caribbean.

The hostile upper level conditions close to, and just north of Nate will be receding slowly westward HOWEVER Nate appears to be moving at a speed that will seemingly cause these upper level conditions to continue to impact its potential to significantly strengthen. There would be a huge difference if Nate were 125 miles East of Yucatan in 48 hours verses 125 miles Northwest of Yucatan. North Florida dodged a bullet thanks to Nate not remaining over very warm water and not remaining further east while continuing to build/extend an upper level anticyclone more vertically situated over itself. Regardless of any secondary weak low or mid level low pressure area also exists in the E. Gulf, Land interaction and upper level shear that Nate is moving over/into will be what primarily plagues it. The fact that Nate will likely en-train some of the continental dry air into itself prior to conditions over the Gulf had sufficient time to modify itself, AND any added degree of diminished low level convergence caused in part by the weak disturbance to its north.... will only add to the less than favorable conditions that Nate will encounter (and likely would not have encountered had it remained over water, drifted NNW or North, and remained in the W. Caribbean for an additional 24-48 hours. If the end result proves that a sheared T.S. or minimal hurricane make landfall between E. Louisiana and Pensacola, then the GFS will have accurately predicted a more abusive track causing Nate to encounter more hostile conditions than had Nate followed the earlier predicted EURO track keeping the storm in a more conducive W. Caribbean environment. Say what you want about "convective feedback" or other colorful denunciations regarding the GFS but it appears that the net end-result might well prove the GFS model correct given its forecast & timing of Nate's more northwestward initial track. It just goes to show though, that the difference that 24-48 hours, 200 miles, and perhaps only a 45 degree deviation in forward motion can make; The potential difference being a weaker hot mess of a storm striking around Biloxi/Mobile verses a potential Cat. 3 hurricane striking Apalachicola to Cedar Key a day or two later.

[canefan]

Nate looks to me like he is moving due north in the visible.

[N2FSU]

From Levi (Tropical Tidbits) yesterday, Levi discussed the differences in the GFS and Euro 12z runs. He stated we could know this AM which was more accurate. His comments were the GFS and it models run off the GFS showed a stronger signature to the feature in the straits compared to the Euro. Additionally the Euro would be somewhat verifiable by this AM if there was a northward moving area of heavier precipitation/signature in the northern end of the trof axis offshore the East coast of Florida. Both seem to have come to fruition. The feature south of Key West is still sheared and an OPEN wave ...it was modeled to be closed off. Additionally, the enhanced rain is off the east coast, he continued, this would help promote height drops which could eventually help weaken the ridge to some degree. That was the notable differences in the 2 runs. I know the Euro swung well west in its last run, but does anyone think since it appears it was on to something from its 12z yesterday that it may bring that baroclinic pressure falls idea back into play in future runs?

His discussion was very good, and it looks like a piece of energy has broken off and headed east of Florida like he said yesterday's Euro was showing. Interesting to see if this affects the ridge like he said.


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[tolakram]

Let's stay on the topic of Nate and the models please, thanks.

HWRF weaker and a bit east.

[otowntiger]

Baton Rouge met Steve Caparotta is really emphasizing this part of the 11am NHC Discussion on FB live feed.


The center of Nate is now inland over northeastern Nicaragua, and
little change in strength is expected until the center moves over
the northwestern Caribbean Sea. After that, a combination of warm
sea surface temperatures and light shear should allow for at least
steady strengthening. However, the guidance is producing mixed
signals despite a favorable-looking environment. The Rapid
Intensification Index of the SHIPS model is showing high chances of
rapid intensification, with better than a 50 percent chance of 25
kt of strengthening in the next 24 h and nearly a 50 percent chance
of 65 kt of strengthening in 72 h. On the other side, the GFS and
Canadian models show only modest development and keep the cyclone
as a tropical storm until it reaches the northern Gulf coast.
Given the environment, the intensity forecast leans towards the high
end of the guidance envelope and calls for Nate to become a
hurricane in about 48 h and reach the northern Gulf Coast as a
hurricane.


http://www.nhc.noaa.gov/text/refresh/MI ... 1447.shtml

Definintely worth noting and paying attention to. While the GFS keeps it relatively weak (although a little stronger in the last run) the position and angle of approach thru the Vermillion Bay on a nne heading would bring a good bit of rain and wind the Baton Rouge Metro area depending upon the storm's strength as it comes ashore. That's the shortest distance from water to the city and coming in on the 'dirty side'. Over the years the history of storms coming in there though are for them to rapidly diminish in strength just prior to landfall, keeping the worst weather offshore. There are several examples, I'm sure there are more: Carmen in '74, Isidore, Lily in '02.

[CrazyC83]

I don't think we'll have a good idea until tomorrow. It does seem that the ridge might be weaker than analyzed and that piece of energy may be reforming in the far western Atlantic. Maybe we will see a correction eastward?

Notice also there is a sharp difference in OHC between the eastern and western Gulf. The Loop Current is around 88W, while along and west of the forecast track it goes through a cool eddy with not much heat at all really.

[Aric Dunn]

CMC looks quite plossible through 48 hours and is more accurately showing the interaction.

one of the biggest short term to mid range factors is the noname system..

[bevgo]

I am afraid and am stuck here. House is on the gulf. I can't leave. My daughter won't let me get the boys out and I have no clue how if she changes her mind. I am down to one car AND hubby will be stuck in nola with it. I don't want to be here alone.