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General Discussion >> 2017 Forecast Lounge

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MikeCAdministrator
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Re: Irma Lounge [Re: ftlaudbob]
      #98075 - Sat Sep 02 2017 11:58 PM

0z GFS run just starting, but already a bit faster and further south around 90 hours out and slightly stronger, although it still misses the NE Carib islands to the north, it's much close to them (about half the distance) of the earlier run, not a good trend so far. Ridging also slightly stronger. Just northeast of the Turks and Caicos by Friday morning (a good deal south, now about 100nm from turks vs 200nm at 18Z) And approaching 160nm south of the old run a bit past that.

By Saturday it's slowing down, starting to feel the trough to the north, but not enough to get pulled in quickly, it may start to slow/drift just east of the northern Bahamas here.

By Sunday it's northeast of the Bahamas moving North-Northwest.

Landfall, Cat 5 near Wilmington, NC morning of Sep 11th rapidly moves inland, over Raleigh still at cat 3/4 strength, maintains hurricane strength into West Virginia.

0z CMC: Weaker hurricane, but passes through Central Bahamas on Friday, landfall near West Palm Beach Saturday Night/Sunday as a major.

0z UKmet is further southwest this run, misses Caribbean islands.

Overall trend, South and west.






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BloodstarModerator
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Re: Irma Lounge [Re: ftlaudbob]
      #98077 - Sun Sep 03 2017 02:46 AM

Quote:

Quote:

I am starting to suspect the US has run out of luck. If the models hold up, Irma will be pretty brutal if and when it makes landfall.




What are your thoughts on landfall?




I've been really hesitant to make much in the way of forecasts recently, I haven't really had the time and energy to follow the dynamics. And with the storm this far out. it's very possible for the models to miss something that will impact the final path of Irma. Given that. at 120 hours, there is a strong system over the great lakes, with a positive trough axis, unfortunately that system appears to lift out after that, and it looks like some weak steering currents in place, and a strong high pressure to the north and east of the system. I would imagine that would tend for a slowing system that is moving more north than west. but unable to move back east. I think that's why the models are showing landfall along the Florida through Carolina coast.

My current guess is that the trough that could pull Irma away from the US won't dig far enough south and will be lifting out leaving weak flow over the south east coast. I really don't want to pick a spot, there's just too much uncertainty. But right now I think the highest risk is between Jacksonville and the outer banks.

If there is any specific thing to watch, I think it's going to be the evolution of the trough over the eastern US. I think that'll let us know the ultimate fate of Irma.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2018.


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MikeCAdministrator
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Re: Irma Lounge [Re: MikeC]
      #98078 - Sun Sep 03 2017 07:07 AM

More overnight:

0z euro: Clips NE Caribbean islands (barely) with the weaker side of the storm on Wednesday (cat 3?), Over Turks and Caicos in the Bahamas Friday, through Central Bahamas into Saturday Northern Bahamas by Sunday and starts heading north Sunday, (Goes through nearly all the Bahamas as a cat 4) Landfall near Wilmington, NC Cat 4 or 5 Sep 12th, then rides north through Eastern Virginia with the Outer banks and Hampton roads on the dirty side (East) of the system as it weakens.

6z GFS run mirrors the 0z with a Cat 5 landfall near Wilmington midday September 11th, then heading into West Virginia It barely clears the Caribbean islands and Bahamas to the north and east.

Again worth watching along the entire east coast and Bahamas as this still could change particularly after 4-5 days since a lot depends on the trough and ridge situation at the time. We aren't at the phase of the NE Caribbean yet, much less Bahamas, any long range models or projections are guidence on odds for future impact, I'd have a plan ready along the Bahamas, east coast regardless from Florida all the way to Boston, and start implementing things as the odds go up, particularly when watches/warnings go up, which could come this coming Saturday or so for the US.


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MikeCAdministrator
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Re: Irma Lounge [Re: MikeC]
      #98080 - Sun Sep 03 2017 11:56 AM

12Z GFS starts by not quite going as far south, but a bit further west, stays north of the Caribbean islands (but still very close) by Thursday it's north of Puerto Rico, but slightly west of the earlier run, so Irma is forecast to move a bit faster.

By Midday thursday it's slightly southwest of the prior run, and midday thursday it's very close to the Central Bahamas as a cat 4/5. (40nm sw of the earlier run) Saturday morning it's over the northern part of Cat island in the Bahamas

Then over Great Abaco as a cat 4/5 on Sunday (Sep 10th) where it starts to head north.





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IsoFlame
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Re: Irma Lounge [Re: MikeC]
      #98081 - Sun Sep 03 2017 12:08 PM

I don't think Irma will continue to burrow WSW as deeply as last 12 hours for several reasons. First, historic tracks for the hurricanes of the similar strength in the same part of the Atlantic basin (though not many) did not continue south of due west. Second, the ridge north of Irma that has nudged her south of west appears to have a bit of weakness a few degrees either side of 50W, This very subtle weakness along the "belly" of the Bermuda high could allow her to track above 17N a bit longer during the next 24 hours. If this pans out, Irma may not bottom out at 16.4N as currently forecast in 36 hours.

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MichaelA
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Re: Irma Lounge [Re: MikeC]
      #98082 - Sun Sep 03 2017 12:40 PM

Definitely need to pay attention to Irma now even though still over a week out. I just checked the FSU model site and a couple of them are a bit disconcerting for those of us in The Bahamas and Florida. Everyone's "radar" should be on from the Florida keys through Nova Scotia.

--------------------
Michael
2017: 15/9/4
2017 Actual: 17/10/6


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BloodstarModerator
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Re: Irma Lounge [Re: IsoFlame]
      #98084 - Sun Sep 03 2017 12:49 PM

Quote:

I don't think Irma will continue to burrow WSW as deeply as last 12 hours for several reasons. First, historic tracks for the hurricanes of the similar strength in the same part of the Atlantic basin (though not many) did not continue south of due west. Second, the ridge north of Irma that has nudged her south of west appears to have a bit of weakness a few degrees either side of 50W, This very subtle weakness along the "belly" of the Bermuda high could allow her to track above 17N a bit longer during the next 24 hours. If this pans out, Irma may not bottom out at 16.4N as currently forecast in 36 hours.




Maybe, it's sometimes hard to tell if the upper air is exactly as analyzed, particularly without any real world soundings available. The big test will be when the Gulfstream does datasampling around Irma to get better data for the models to ingest. I think the first one will be taking off tomorrow afternoon.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2018.


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OrlandoDan
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Re: Irma Lounge [Re: MichaelA]
      #98086 - Sun Sep 03 2017 12:53 PM

Irma deserves monitoring. She is a long way out and it's too soon to tell how far the trough digs in to the east U.S. and how far the Bermuda high persists to the west.

--------------------
Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008), Mathew (2016), Irma (2017)


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cieldumortModerator
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Re: HUR IRMA Lounge [Re: cieldumort]
      #98087 - Sun Sep 03 2017 02:27 PM

Going to start out this reply by saying that I have been especially bullish on Irma's potential intensity for a couple of days now, and my confidence in this has only increased with each and every day. However, there are caveats. Subtle, but very possible changes in Irma's track, and/or degree of shear imparted by the upper low to her northwest, and/or potential for downstream effects from a (possible, but not yet NHC endorsed) development in the southern Gulf, etc. could have profound and as-of-yet unforeseen impacts on her future intensity, as well as track.

Given what is already known, plus considering the known unknowns, and unknown unknowns, my confidence for Irma's top wind speed during her lifetime breaks down along the following percentile basis (Please keep in mind, this is the "Lounge," and as such, I am taking wide liberty in sharing this, which is not, by any means, an official forecast. Please refer to the National Hurricane Center and its sister agencies for official information.

Opinion only. Top 1-min sustained wind speed attained by Irma at some point
High-end Cat 5 (175+ MPH) 35%
Cat 5 (160-170 MPH) 30%
Cat 4 (130-155 MPH) 25%
Cat 3 (Already attained) 10%

Put another way, it is my opinion (only) that Irma has almost a two-in-three chance of becoming a Cat 5 at some point before final landfall or dissipation at sea, and a 90% chance that Irma at least becomes a Cat 4.

I am rarely this bullish on a system. I was very bullish on Harvey, for example, but not nearly so much on any of the other TCs we had up until that point in the Atlantic basin this year.

Recon is finally getting in to Irma later today, which will help resolve some of the known unknowns, and maybe even some of the unknown unknowns. I will also be paying especially close attention to what happens with the Gulf trof, as well as (and they are of course all connected to greater or lesser degrees), the evolution of the Bermuda High. Again, recon flights will be very beneficial to my own opinions, as well as future model runs and official NHC forecasts.

Should Irma become both a large and very powerful hurricane (very plausible), locations prone to surge in her path may need to evacuate. Again, this is still highly speculative at this point, not an official forecast, and several days out.

- Ciel


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MissBecky
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Re: HUR IRMA Lounge [Re: cieldumort]
      #98088 - Sun Sep 03 2017 03:24 PM

I haven't seen any talk here of the UKMET, which seems to be doing a very good job so far this year. What is the general opinion on this model? As a SWFL resident I'm particularly uneasy about its latest runs.

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M.A.
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Re: HUR IRMA Lounge [Re: cieldumort]
      #98089 - Sun Sep 03 2017 03:26 PM

I agree with every point you made. Looking at the HMON it has a peak intensity at 142-149kts. Most of the other models are staying around 125-135kts. This is a monster in the making. The overall size of the storm is what I am concerned with. By the Navgem it looks the size of Alaska in the central Bahamas. At the peak wind speeds of 170+ is it out of the realm of possibility to have TS force winds and surge effects 200 miles from the center? I remember Gilbert, Mitch, Katrina, Rita Wilma. This storm looks to have the potential to be as strong and much larger overall size. I'm not trying to hype this storm, but it doesn't look good for any thing in its wide path.

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cieldumortModerator
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Re: HUR IRMA Lounge [Re: MissBecky]
      #98090 - Sun Sep 03 2017 04:25 PM

Quote:

I haven't seen any talk here of the UKMET, which seems to be doing a very good job so far this year. What is the general opinion on this model? As a SWFL resident I'm particularly uneasy about its latest runs.




UKMET is fairly reliable as a TC genesis tool. There are other models more fine-tuned to TC track and intensity. Also, its run goes out to 168, whereas other Globals being discussed here in the Lounge can be 240 +

As of the 0z 03 Sep run, the UKMET drives Irma towards South Florida, but that's where that particular model's run ends. To that point, its track is very similar to the other primary and consensus models.

Peak intensity up to the end of the Oz run is 139 knots at 925mb (roughly 2500'), which could correspond to about 140 MPH or so at the surface.


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JMII
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Re: HUR IRMA Lounge [Re: cieldumort]
      #98091 - Sun Sep 03 2017 05:18 PM

With each model run Irma gets further west and south.. not really happy with this trend. That cone is starting to get a little too close for comfort here in S FL. Every model has her going thru Herberts Box now. Right now she is pretty compact with hurricane force winds only 35 miles from the center.

--------------------
South FL Native... experienced:
David ('79) - Floyd ('87) - Andrew ('92) - Georges ('98) - Irene ('99) - Frances & Jeanne ('04) - Katrina & Wilma ('05) - Matthew ('16)


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WestFLJess
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Re: HUR IRMA Lounge [Re: JMII]
      #98092 - Sun Sep 03 2017 05:25 PM

yo.

JMII- I 2nd what you are saying about FL. 2 days ago it kept shifting north & east, now it's shifting south and west.

I guess we won't really know if it's going to hit FL until it goes over the islands (Leeward) & maybe Puerto Rico?

I haven't been on here in awhile but started coming on here back when Charley hit FL in 2003.

--------------------
Jess
Tampa Bay, FL

Elena '85....Charley, Frances, Jeanne....Emily '17


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MikeCAdministrator
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Re: HUR IRMA Lounge [Re: WestFLJess]
      #98093 - Sun Sep 03 2017 06:22 PM

Afternoon models
18Z GFS misses Caribbean islands to the north, (barely,they will still get affects), Friday morning over Turks and caicos cat 4, and moves through nearly all of the Bahamas through Sunday where it's over Great Abaco as a cat 5.then moves due north, staying east of Florida. Landfall near Wilmington, NC Overnight between Sep 11 and 12th as a cat 5 hurricane,

12Z Euro is further west over the Bahamas, but curves rapidly out to sea (Closest point to the us is sept 12).

Overall the entire East coast should be watching Irma, and hoping the out to sea scenario happens (like the Euro) Things are not looking good for the Bahamas, and the Northeast Caribbean may get some issues from the storm, but hopefully misses the core of Irma. Trying to specify where Irma will go at this point beyond 5 days is irresponsible, the western shifts are troubling for Florida, but odds still favor NC or out to sea. These aren't great odds though. So it really is too soon for any serious speculation on continental UI impacts.

GFS is likely overdoing the low pressures as well, it's very unusual to have cat 5 conditions last very long, so I'm hoping that is just overkill on the models part, odds are its way too strong (although Irma may very well be still very strong)


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Psyber
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Re: HUR IRMA Lounge [Re: WestFLJess]
      #98094 - Sun Sep 03 2017 06:43 PM

Ok,

First I have to say it's interesting that everybody is ignoring the cyclonic system to the north/north west of Irma. I get that it's not that likely to get too strong but there's a pretty clear eye and cyclonic activity there. The reason I bring this up is that system without a doubt is affecting Irma. I'm going to say that it's going to weaken anything looking to chew on Irma to the N/N/W. Simply this is going to help keep Irma South of doing a kissing run up Florida.

The N.Equitorial current isn't exactly pushing Irma North either.

Now for my Irma DEEP thoughts.

First, i'm going to point out the obvious.

If Irma stays south, it's going to nail the D-R and Cuba (we're going to ignore D-R and Cuba's Hurricane hits because it doesn't matter if it's a 1 or a 5, NOBODY ever needs (or gets) aid on the D-R or Cuba.--sarcasm because we all know it's true)

IF Irma hit's Cuba she's going to drop intensity and strength in the mountainous regions(as usual) if the eye gets anywhere near rolling over the island. It's at that point where I believe Irma goes north.

The cone is currently north of the D-R and Cuba however this S/S-W push(and that baby system to the North keeps weakening the Gulf Stream) is still ongoing so it very well could get there.

My personal opinion is that the S-S/W continues and it keeps pushing Irma West. Admittedly my own personal weakness is predicting how Western/North Western ridges(with the Gulf Stream) affect storms but Irma just looks more south than people are thinking IMO.

Edited by Psyber (Sun Sep 03 2017 06:49 PM)


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MikeCAdministrator
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Re: HUR IRMA Lounge [Re: Psyber]
      #98095 - Sun Sep 03 2017 07:07 PM

That upper level low is one of the things pushing Irma south of due west right now, but it should move off in time, that, and even other waves far away from Irma are making it a very complex system to track. I wouldn't doubt the NHC track though, but wouldn't be surprised to see it move a bit more south. I'm concerned that if the trend doesn't end soon the Caribbean Islands under watch right now may get a direct hit.

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Prospero
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Re: HUR IRMA Lounge [Re: MikeC]
      #98096 - Sun Sep 03 2017 07:31 PM

Quote:

MikeC on August 29th at 7:39 am:
"0Z Euro takes 93L into the Caribbean islands sep 6, then toward Puerto Rico Sep 7 and Turks & Caicos into the Bahamas on September 8th. As a hurricane."




Not a bad forecast for five days ago compared to what is a possibilty today.


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ftlaudbob
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Re: HUR IRMA Lounge [Re: Prospero]
      #98097 - Sun Sep 03 2017 09:00 PM

Given the projection of a cat 4 or 5,I am a little surprised that no one has brought up the polar effect.Could she be pulled north and hug the coast?

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

Survived:
Gloria,Bob,Katrina,Wilma and a bunch of tropical storms.


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Prospero
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Re: HUR IRMA Lounge [Re: ftlaudbob]
      #98098 - Sun Sep 03 2017 09:12 PM

Quote:

Given the projection of a cat 4 or 5,I am a little surprised that no one has brought up the polar effect. Could she be pulled north and hug the coast?



"...the polar effect"? OK, my initial Google search did not provide anything I can relate to a storm. So I'll bite.

What is the "polar effect"??


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