ATL: IRMA - Post-Tropical - Discussion

[SouthFLTropics]

I'll just leave this here.

THERE HE IS!!! Us old timers from the beginning remember seeing that one!!!

[Kingarabian]

Irma appears much worse on satellite. Does anyone know why this is? Is there an EWRC going on, or is the cold water just getting to Irma and weakening her core? The convection is plenty cold but the eye appears nonexistant.

The dry/stable EPAC like air around it and the cool waters. Similar to the area where EPAC storms spin-down. However, once this gets into moist warm waters, it is off to the races.

Spot on. Also interested in to knowing why the NHC went with 105kts when the storms presentation had degraded. I know the satellite estimates supported it, but in the Epac, the NHC would override the estimates and go lower in similar cases.

[RL3AO]

Irma appears much worse on satellite. Does anyone know why this is? Is there an EWRC going on, or is the cold water just getting to Irma and weakening her core? The convection is plenty cold but the eye appears nonexistant.

The dry/stable EPAC like air around it and the cool waters. Similar to the area where EPAC storms spin-down. However, once this gets into moist warm waters, it is off to the races.

Spot on. Also interested in to knowing why the NHC went with 105kts when the storms presentation had degraded. I know the satellite estimates supported it, but in the Epac, the NHC would override the estimates and go lower in similar cases.

They might go 100 knots at the advisory. 105 knots made sense 3 hours ago at 0z.

[AxaltaRacing24]

Irma appears much worse on satellite. Does anyone know why this is? Is there an EWRC going on, or is the cold water just getting to Irma and weakening her core? The convection is plenty cold but the eye appears nonexistant.

The dry/stable EPAC like air around it and the cool waters. Similar to the area where EPAC storms spin-down. However, once this gets into moist warm waters, it is off to the races.

Spot on. Also interested in to knowing why the NHC went with 105kts when the storms presentation had degraded. I know the satellite estimates supported it, but in the Epac, the NHC would override the estimates and go lower in similar cases.

It looked like a cat 4 when they put that advisory out. Not now though.

[christchurchguy]

Since the water is cooler and the shear is light, could Irma be becoming annular,
The new eye looks quite a bit larger relative to the CDO.
Its moving west or WSW under a ridge.

Similar to Edouard 1996 or Luis 1995 in a similar area
https://en.wikipedia.org/wiki/Hurricane_Luis

[url]rammb.cira.colostate.edu/resources/docs/annular_Knaff.pdf[/url]

[drewschmaltz]

Since the water is cooler and the shear is light, could Irma be becoming annular,
The new eye looks quite a bit larger relative to the CDO.
Its moving west or WSW under a ridge.

Similar to Edouard 1996 or Luis 1995 in a similar area
https://en.wikipedia.org/wiki/Hurricane_Luis


[url]rammb.cira.colostate.edu/resources/docs/annular_Knaff.pdf[/url]

I was just about to pose this as a possibility. Didn't it seem to throw the feeder bands and decide to increase the cdo at the same time? If a larger eye appears I'd say that's a distinct possibility.

[Aric Dunn]

I step away for a few hours and this happens.. ? What did you all do ? Lol

[cycloneye]

...IRMA FLUCTUATING IN INTENSITY BUT STILL A POWERFUL HURRICANE...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.1N 40.5W
ABOUT 1405 MI...2260 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...967 MB...28.56 INCHES

----------------------------------------------------------------

Hurricane Irma Discussion Number 11
NWS National Hurricane Center Miami FL AL112017
1100 PM AST Fri Sep 01 2017

After developing a nearly clear eye during the afternoon hours,
Irma appears to have once again temporarily peaked. A WindSat pass
around 2100 UTC hinted at the beginning of another eyewall
replacement cycle, which would be consistent with the observed
cooling of the eye. However, the small size of the hurricane's
inner core relative to the resolution of the microwave instrument
makes it impossible for me to say for sure. The initial intensity
has been lowered slightly to 100 kt, but it should be stressed that
this is probably just another fluctuation, in what will likely
be a long string of small changes in intensity over the next
several days. Since we do not have the ability to predict
such changes, the NHC forecast shows very gradual intensification
throughout the forecast period, given the warm SSTs and increasing
moisture content along the forecast track. The NHC forecast is near
the intensity consensus, but slightly favors the higher dynamical
models.

The initial motion remains 275/12 kt. The hurricane has moved a
little farther north than previously expected, and the track has
been adjusted in that direction. Overall, the reasoning behind the
track forecast has not changed, and Irma is still expected to turn
west-southwestward on Saturday due to a building ridge over the
central Atlantic. After about 72 h, there remains a large
north-south spread in the guidance, with the GFS continuing to show
a weaker ridge (and a northern track), while the ECMWF shows a
stronger ridge/southern track. The ECMWF has performed better for
Irma thus far, so my forecast continues to favor that solution.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it approaches the
Lesser Antilles early next week, producing rough surf and rip
currents. Irma could also cause dangerous wind, storm surge, and
rainfall impacts on some islands, although it is too soon to specify
where and when those hazards could occur. Residents in the Lesser
Antilles should monitor the progress of Irma through the weekend and
listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will
have on the continental United States. Regardless, everyone in
hurricane-prone areas should ensure that they have their hurricane
plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 19.1N 40.5W 100 KT 115 MPH
12H 02/1200Z 19.0N 42.3W 100 KT 115 MPH
24H 03/0000Z 18.5N 44.6W 105 KT 120 MPH
36H 03/1200Z 17.9N 46.9W 110 KT 125 MPH
48H 04/0000Z 17.3N 49.0W 110 KT 125 MPH
72H 05/0000Z 16.8N 53.3W 110 KT 125 MPH
96H 06/0000Z 18.0N 57.5W 115 KT 130 MPH
120H 07/0000Z 20.5N 62.5W 115 KT 130 MPH

$$
Forecaster Zelinsky

[Blown Away]

NHC has uncertainty at 72 hrs, what kind of confidence at 220 hours... Very little IMO...

[angelwing]

910mb

[NJWxHurricane]

https://twitter.com/wxbrad/status/903812435768958976

[1900hurricane]

Eye is no longer apparent on BD IR. A center embedded in black yields an instantaneous DT of 5.0.

[AutoPenalti]

https://twitter.com/wxbrad/status/903812435768958976

Interesting, any implications for long term?

[TheStormExpert]

https://twitter.com/wxbrad/status/903812435768958976

Interesting, any implications for long term?

The 11pm discussion says the Euro is performing better?

[tarheelprogrammer]

https://twitter.com/wxbrad/status/903812435768958976

Possibly help keep it OTS or weaker. Who knows?

[otowntiger]

https://twitter.com/wxbrad/status/903812435768958976

Interesting, any implications for long term?

Yes- I would think so- the NHC said they adjusted their track north due to the current more northern position.

[Blown Away]

Irma has moved faster than predicted to the W if you look at the forecasts from earlier today, like 5am, Irma is a full degree farther W and @20 miles N...

[Pebbles]

I'll just leave this here.

Long time since I've posted, but I've always lurked. Couldn't resist cause dang does this one bring back memories of recon all nighters with senorpepr and the rest of the crew. Those were the days.

P.S. Shout out to Storm2k crew... I just happened to be in TX last week for a military graduation and was suppose to fly out of Houston Sunday night. It was because of my time here back in the days, what I learned, and the information available here last week (all easily accessed by cell phone/kindle because it was consolidated in on place on the forums) that I was able to plan accordingly and able to rearrange travel plans for myself and my daughter to fly safely back home ahead of the worst part of the storm. It was a crazy hectic mess to get out, but we did finally Sat afternoon from San Antonio. The early heads up was invaluable and that helped keep us safe. So Thank You!

[tarheelprogrammer]

Irma has moved faster than predicted to the W if you look at the forecasts from earlier today, like 5am, Irma is a full degree farther W and @20 miles N...

That should help it catch up to a trough I believe

[Frank2]

NHC discussion mentioned the northward motion mentioned earlier tonight, and they noted the GFS northward turn. Don`t be surprised if this continues. It is similar to Frances many years ago - everyone was flipping over a major hurricane so far east but it never made landfall. Interesting to note it was a 968 in the same place as Irma tonight and recurved soon after.