ATL: IRMA - Post-Tropical - Discussion

[SFLcane]

000
WTNT41 KNHC 011450
TCDAT1

Hurricane Irma Discussion Number 9
NWS National Hurricane Center Miami FL AL112017
1100 AM AST Fri Sep 01 2017

Irma is undergoing an eyewall replacement cycle. The small eye is
becoming less distinct, with both microwave and visible imagery
indicating the presence of a forming outer eyewall. Satellite
intensity estimates are lower, so the initial wind speed is reduced
to 95 kt. Some further weakening is possible over the next day or
so while Irma moves over marginally warm SSTs and continues the
eyewall replacement. After that time, the environment should be
generally conducive for some restrengthening, although forecasting
the timing of eyewall replacement cycles is next to impossible. The
biggest change from yesterday are the long-term wind shear
predictions from the global models, which shows a little more shear.
Still, the shear is not that strong, and the hurricane will be
moving over 29C SSTs. Thus, the NHC intensity forecast is reduced
somewhat from the previous one, but remains near or slightly above
the model consensus.

Irma has turned a little bit to the left, now estimated to be
moving 285/11. The general synoptic situation remains well
established due to a building mid-level high, which should cause
the hurricane to turn westward later today and then move
west-southwestward through the weekend. An upper-level low will be
dropping southward on the east side of that high, and should be a
key feature to how far south Irma goes before eventually turning
westward and west-northwestward early next week. There is a
noticeable clustering of guidance by day 5, with the ECMWF, HWRF and
corrected-consensus models to the south, and the UKMET, GFS, CTC and
HMON to the north. Since Irma is forecast to be a vertically deep
cyclone, it seems more likely to respond to the northerly flow from
the upper-level low, which leads me to believe the track will be on
the southern side of the guidance. Thus, the forecast will stay
similar to the previous one, very close to the southern cluster
mentioned above.


FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 18.5N 37.8W 95 KT 110 MPH
12H 02/0000Z 18.7N 39.5W 90 KT 105 MPH
24H 02/1200Z 18.5N 41.8W 90 KT 105 MPH
36H 03/0000Z 18.0N 44.2W 95 KT 110 MPH
48H 03/1200Z 17.3N 46.6W 100 KT 115 MPH
72H 04/1200Z 16.2N 51.0W 105 KT 120 MPH
96H 05/1200Z 16.7N 55.2W 110 KT 125 MPH
120H 06/1200Z 18.0N 59.5W 110 KT 125 MPH

$$
Forecaster Blake

[tolakram]

[jlauderdal]

nbc miami met

John Morales @JohnMoralesNBC6
1m
A FB Live regarding #Irma about to start on facebook.com/johnmoralesnbc6

[BensonTCwatcher]

Yep, It does get quiet when models don't show a CAT4 + bearing down on someone. But that's just our nature. I think that since models, visualizations, simulations, and satellites have gotten so much better, we tend to cling too much to model outputs and we're forecasting and pre-supposing much farther out these days. I can recall when a 3 day accurate landfall was not a sure thing. Back when you tracked on paper based on coordinates broadcast over a radio or TV. It was scarier back then for sure, and I am so glad we have gotten to pretty much spot on at 3 days out, and pretty darn close at 5 days. But 10 days out...still too many variables in the synoptic features to narrow it down more than about 1200 miles or so. And that's exactly where we are now.

I'll be gassing up cans, checking the generator, checking supplies and such this weekend because when we are at 5 days out, there won't be as much time. I'm reserving next weekend for final preps- extra measures son the boat, shutters, etc. if need be. Good thing is that the data we have now makes sure that is not waste of time. Harvey is also a start reminder to make a plan.

[tolakram]

SLIDER visible
http://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=full_disk&x=19393&y=7194&z=4&im=18&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&p%5B0%5D=1&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&s=rammb-slider

[Hurricane Andrew]

Can see the double eyewalls here. I measured the inner eyewall at about 11 miles across. The outer eyewall is about 27 miles across.

Also, note that it's the Hebert box, not the HeRbert box. It's named after former NHC forecaster Paul Hebert. I met Paul at a National Hurricane Conference a number of years ago. Turns out we grew up only a few miles apart in south Louisiana.

http://wxman57.com/images/Irma2.JPG

That's an awesome picture...one of the most clear examples of an EWRC on satellite I have seen.

It is really amazing to me how little we understand about these things. We know how to observe them, but we really don't understand the dynamics and causation all that well. Isn't science amazing?

[Blown Away]

5am disco had Irma reaching 16.5N before turning WNW...
11am disco has Irma reaching 16.2N before turning WNW...

Not much, but it is 18 miles farther S...

[robbielyn]

nbc miami met

John Morales @JohnMoralesNBC6
1m
A FB Live regarding #Irma about to start on facebook.com/johnmoralesnbc6

i am on his facebook page but cannot find it

[Blinhart]

Irma will probably hold a fairly steady state with gradual strengthening (due to ideal atmospheric conditions). SSTs are modestly warm enough to sustain her. The real warm SSTs that maintains cat 4/5 for duration is W of 45W so once she passes that point she will likely take off assuming atmospheric conditions remains ideal.

So might take the same path as Harvey, you can see the past track of Harvey in this pic.

[jlauderdal]

nbc miami met

John Morales @JohnMoralesNBC6
1m
A FB Live regarding #Irma about to start on facebook.com/johnmoralesnbc6

i am on his facebook page but cannot find it

i dont see it either, sorry

[Siker]

EWRC looks to be fairly complete. Larger eye warming quickly over the last hour with a new tower in the northern wall, could see this being a major again later today.

[PaulR]

I think I'll go get water and supplies this weekend!

Again I have to ask, why 'go and get water'? Why not have empty milk, juice or other jugs on hand and fill them from the tap a day or two ahead? And why not have other supplies like batteries and canned or dry goods on hand always? Fuel for generators and lamps should be on hand too, though it would have to be used since it can go bad.

I tend to lean that way (your way) myself, but, when it comes to many supplies, almost everything has a shelf life, so one has to cycle through the supplies, and have a permanent space to stash them. This can save money (pick up food & supplies on sale when practical), but requires some effort. And, many people don't like to eat much in the way of canned / dry goods (opting instead for always fresh from the organic produce store), so that makes rotating the stock more problematic, or expensive (throw out expired items). Many people are simply minimalist. (My wife gripes that we keep too many empty bottles around, I keep coming up short when I need 'em!) There's a cultural factor in this too, but I don't want to get too OT or get flamed! Let's just say those from cultures that have to survive long harsh periods when Nature isn't providing much are a little more likely to be "savers". There are many exceptions, of course.

[Aric Dunn]

I agree with the NHC southern track. I do not agree with his strength and the duration of the ERC.. the ERC is nearly complete and wont take a day or two. also the SSTS are still 27 c. plenty to maintain a major hurricane. maybe not a cat 4 or 5 but a cat 3 sure.

IR channel 9

very eveident this process is only a few hours away ..
https://weather.msfc.nasa.gov/goes/abi/ ... and14.html

[SouthDadeFish]

EWRC looks to be fairly complete. Larger eye warming quickly over the last hour with a new tower in the northern wall, could see this being a major again later today.

I agree with this. Looking more organized over the past couple of hours.

[Siker]

Make that a major in like an hour lol. TWC talking about how much the eye has popped out in just the past 45 minutes.

[mrbagyo]

EWRC is DONE. Irma is just venting out the remaining clouds from the collapsed inner eyewall.
Gorgeous eye once finally cleared.
Clearly shown in RBTOP loop

[wxman57]

Yep, ERC is about complete. Brand new eye is about 17 miles across. It'll take a few hours to gather up some steam.

[galaxy401]

Maybe it's still too early to say but the last few frames look as if Irma is now moving directly west.

[Kazmit]

So much for the 48hrs until it became a major again. Irma looks more impressive now than it did before the EWRC.

[txwatcher91]

So much for the 48hrs until it became a major again. Irma looks more impressive now than it did before the EWRC.

And also much bigger too...