Isaac on Track to hit Hispaniola, then Florida

By: Levi32 , 5:16 PM GMT on August 23, 2012

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Tropical Storm Isaac is starting to become better organized this morning after struggling a lot last night with decoupled centers in the low and mid levels, and a more consolidated, vertically-stacked center appears to be forming south of Puerto Rico. Forward motion has slowed from 21mph yesterday to 13mph now, indicating that Isaac is approaching the western periphery of the subtropical ridge to the north, and this slowing should help the storm strengthen on approach to Hispaniola during the next 24-48 hours. Intensification into a moderate-strong tropical storm seems likely, but hurricane strength before Hispaniola seems a little bit too much to ask for. The intensity forecast remains a tad lower than the NHC in the short range, a theme which has verified very well so far. Interaction with the mountains of Haiti and eastern Cuba should weaken Isaac, but restrengthening should be quick to ensue north of Cuba due to improving upper-level conditions and very warm water in the storm's path. Isaac could quickly become a hurricane very close to Florida if it gets any significant time over water on either side of the peninsula.

Isaac is beginning to move WNW around the periphery of the subtropical ridge, which currently extends into the Bahamas. Isaac will be gradually curving more towards the NW with time, taking it over Hispaniola and eastern Cuba, and eventually towards Florida. The models are in close agreement, and Florida is very likely to be significantly impacted by Isaac. The only exception is the ECMWF, which is still a western outlier, taking Isaac into Alabama in 7 days. This is a slight shift eastward from previous runs though, and may be the start of a correction trend eastward for the ECMWF towards the other models. The upper pattern ahead of Isaac features a weakness in the ridge that will be directly north of the Bahamas in 3 days, something that a strengthening storm coming off of Cuba may be more likely to take advantage of than some of the models show. The forecast track is still east of the model consensus at Days 4 and 5, very close to the eastern coast of Florida, similar to the 00z CMC and 06z GFDL solutions. The wildcard in the track forecast remains the mountains of Hispaniola and Cuba, which are notorious for jerking storms around, and could easily cause an unexpected shift in track at any time. A NOAA G-IV recon mission into Isaac tonight will hopefully transmit new data in time to be put into tonight's 00z model cycle, which should result in more accurate track forecasts. If the model consensus remains on the west coast of Florida after they have received the G-IV data, my track may have to shift a bit to the west.

Overall, Florida is likely to get impacted directly by Isaac no matter what adjustments are made during the next few days. The average NHC forecast error for 5 days is 260 miles, and there is lots of room for adjustment while we are still 4-5 days away from a Florida landfall. Until Isaac clears the mountains of the greater Antilles, great inherent uncertainty with such a track will make nothing certain about the long-range forecast.

Elsewhere....Joyce has formed in the central Atlantic, and will be recurving near Bermuda in 5 days or so. This is no imminent threat to land, and can be mostly ignored until Isaac is out of our hair.

We shall see what happens!

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19. waterskiman
1:30 AM GMT on August 24, 2012
Thanks Levi,

I see you still have the storm shooting the gap, I am still leaning that way. With the trail of Isaac streaming north, north west as you will thats what I usually look for. Where the flow goes the storm usually follows. Thats just the way I look at them, not shear, not dry air just the place of least resistance. LOL thats about as techy as I get

Will be interested to see what you come up with with that G IV that you have been waiting for.
Member Since: June 6, 2010 Posts: 0 Comments: 4516
18. palmettobug53
1:21 AM GMT on August 24, 2012
Hey, Levi!

Good to see you but I don't like that track. It looks like it's heading right for me. ACK!

Hallelujah... I just noticed your links. Thank heavens. My old desktop died and I lost all my bookmarks. I've been emailing what I had at work to myself at home but I'm still missing some. Looks like you have them all, so I think I can quit asking Uncle Google!
Member Since: October 7, 2005 Posts: 247 Comments: 26433
17. Levi32
12:53 AM GMT on August 24, 2012
Quoting tramp96:
Hi Levi
Do they take the info. from the HH and plug it in to all of the models? What time will all the info be available. eg 6z gfs? 12z ecmwf. or just the NHC updates.


The 5pm NHC discussion stated the data would be available for the 00z model runs. I don't know if non-American models are able to integrate that data or not.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
16. tramp96
12:23 AM GMT on August 24, 2012
Hi Levi
Do they take the info. from the HH and plug it in to all of the models? What time will all the info be available. eg 6z gfs? 12z ecmwf. or just the NHC updates.

Member Since: August 15, 2009 Posts: 0 Comments: 1612
15. SunnyDaysFla
10:19 PM GMT on August 23, 2012
Thanks Levi!

I like the fact that NHC has moved the cone of doom west, but as the local TV met remarked, "Isaac does not listen to the NHC." Personally, I hope your more eastern forecast pans out. That would put Tampa on the "cleaner " side of the system. I truly appreciate all the time you spend explaining your reasoning to us.
Member Since: September 19, 2008 Posts: 0 Comments: 794
6:25 PM GMT on August 23, 2012

I don't have the training that you do, but you're confirming what my gut instinct is saying, east coast, hopefully north of Myrtle Beach, SC.

And of course the strengthening will depend on how long it spends over the Gulf Stream.

Looking forward to your next post.

Member Since: August 22, 2012 Posts: 0 Comments: 14
13. watercayman
6:23 PM GMT on August 23, 2012
Thanks Levi - always appreciate your excellent analysis.
Member Since: September 13, 2007 Posts: 0 Comments: 95
12. Greg01
6:08 PM GMT on August 23, 2012
Member Since: July 13, 2012 Posts: 0 Comments: 281
11. want2lrn
5:53 PM GMT on August 23, 2012
Another awesome job Levi, those who don't know really appreciate your concise and clear explanations. Thank you.
Member Since: July 28, 2010 Posts: 0 Comments: 285
10. TopWave
5:53 PM GMT on August 23, 2012
Thanks Levi! Im trying to figure out if I should go to Charleston for my vacation this Saturday. If your forecast verifies. Charleston may not be out of the woods quite yet. Especially if Issac makes it through the passage east of Cuba. If Issac does indeed make it through the passage, Issac could be a much stronger storm without much land interaction.
Member Since: August 31, 2008 Posts: 0 Comments: 21
9. canehater1
5:50 PM GMT on August 23, 2012
as usual..very professionally done...tks Levi!
Member Since: September 8, 2008 Posts: 1 Comments: 1214
8. HondosGirl
5:44 PM GMT on August 23, 2012
Thanks Levi -- Appreciate all you do, not just to forcast, but to help us understand the reasoning behind the forecast.
Member Since: August 20, 2011 Posts: 0 Comments: 112
7. Grothar
5:44 PM GMT on August 23, 2012
Good Blog, Levi. Nice reasoning on the two highs. Good explanation on the models hugging the Northern Coastline of Cuba. But did you have to be so condescending? :):)
Member Since: July 17, 2009 Posts: 74 Comments: 29891
6. Hoff511
5:41 PM GMT on August 23, 2012
Thanks Levi!
Member Since: September 2, 2009 Posts: 0 Comments: 266
5. Chicklit
5:37 PM GMT on August 23, 2012
Great video. Particularly appreciate your explanation of the background behind the anticipated tracks. Thank-you!
Member Since: July 11, 2006 Posts: 14 Comments: 11543
4. AtHomeInTX
5:37 PM GMT on August 23, 2012
Thanks Levi
Member Since: August 24, 2010 Posts: 0 Comments: 501
3. Alovell89
5:35 PM GMT on August 23, 2012
Thanks Levi! I always enjoy your updates. You are one of the best on here so thanks for the insight.
Member Since: September 2, 2011 Posts: 0 Comments: 1
2. aislinnpaps
5:33 PM GMT on August 23, 2012
Thanks, Levi. It will be an interesting week coming up.
Member Since: August 22, 2009 Posts: 0 Comments: 3196
1. rmbjoe1954
5:25 PM GMT on August 23, 2012
Thank you, Levi. That high sitting north of the Bahamas wnd that trough heading down into northern Florida are what I see will bring Isaac running up the east Florida coast.

Extremely cool todbit for today!
Member Since: June 16, 2005 Posts: 0 Comments: 1884

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