Isaac Could be a Double Hurricane Hit for Florida

By: Levi32 , 3:56 PM GMT on August 25, 2012

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Isaac is disorganized this morning, which is to be expected from interaction with the mountains of Haiti. The storm has taken a significant jog north of where it was "supposed" to be this morning, due to the frictional effects of the mountains which I warned about yesterday being a wildcard for the short-term track. It goes to show how the model cluster can be way off even at the 12-24 hour verification. The significance of this is that Isaac is now only moving over the eastern tip of Cuba instead of the entire eastern half of the island, and thus he will be spending more time over water before hitting the Florida keys or south Florida. With about 36 hours over the very warm Florida straights, Isaac should have enough time to regenerate a core and strengthen into a lower Cat 1 hurricane.

The models, although they have shifted east since yesterday, have not come over to the peninsula, and remain over the eastern Gulf of Mexico and into the Florida panhandle with Isaac's track. They have at least mostly dropped the improbable northwesterly track into the central gulf coast, and now show a more likely recurve northward into the coast farther east. With the models tightly clustered this close to the end of the forecast, my track has to shift westward to meet closer with the model consensus. There still, however, remains some uncertainty, and as we just saw last night, the models can be off even with a 24-hour forecast. With Isaac now coming west of Florida, further intensification is called for after he scrapes south Florida. However, intensification over the eastern gulf is expected to be slower than intensification over the Florida straights, due to a track close enough to the Florida peninsula that Isaac's main inflow channel, which is from the east, will be passing over land and bringing some drier air into the storm. Normally storms taking a track like this struggle to strengthen at all and often weaken. However, a very favorable upper pattern will be developing above the storm as a trough-split backs away to the southwest, ventilating the eastern gulf, and this should offset the normal trend and allow slow strengthening through a 2nd landfall in the panhandle. On the current track a low-end Cat 2 hurricane is expected near Apalachicola, Florida in about 3 days, though a track just a little farther west could result in a stronger storm, and a track closer to the Florida peninsula could result in a weaker storm.

We shall see what happens!



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24. mobal
6:34 PM GMT on August 25, 2012
Quoting zawxdsk:


Those are good reference points for a typical hurricane, but with a storm as large in size and scope as Isaac, you need to check on how tightly wound the storm is. With Irene last year or Ike a few years back, the pressures were low enough for the storms to be Cat 3 or 4, but wind speeds were more in the 1 to 2 range.

However, storm surges were more in line with the pressure categories - so I would expect that even if the winds don't make it to a higher category, the surge will.


It was only meant as a reference....
Member Since: August 3, 2005 Posts: 482 Comments: 5332
23. Levi32
6:30 PM GMT on August 25, 2012
The battle between the GFS and ECMWF has reversed. The GFS is now to the west of everyone else, and the ECMWF is now on top of my track:

12z ECMWF:



12z GFS ensembles:

Member Since: November 24, 2005 Posts: 635 Comments: 26647
22. zawxdsk
6:25 PM GMT on August 25, 2012
Quoting mobal:
I found this pressure to hurricane catagory chart. I find it helpful when looking at models.

Hurricane 1 > 980
Hurricane 2 965-980
Hurricane 3 945-965
Hurricane 4 920-945
Hurricane 5 < 920


Those are good reference points for a typical hurricane, but with a storm as large in size and scope as Isaac, you need to check on how tightly wound the storm is. With Irene last year or Ike a few years back, the pressures were low enough for the storms to be Cat 3 or 4, but wind speeds were more in the 1 to 2 range.

However, storm surges were more in line with the pressure categories - so I would expect that even if the winds don't make it to a higher category, the surge will.
Member Since: August 2, 2011 Posts: 0 Comments: 195
21. mobal
6:15 PM GMT on August 25, 2012
I found this pressure to hurricane catagory chart. I find it helpful when looking at models.

Hurricane 1 > 980
Hurricane 2 965-980
Hurricane 3 945-965
Hurricane 4 920-945
Hurricane 5 < 920
Member Since: August 3, 2005 Posts: 482 Comments: 5332
20. LoveThemCanes
5:13 PM GMT on August 25, 2012
Thanks Levi....helps us understand some of this craziness.
Member Since: September 28, 2010 Posts: 0 Comments: 48
19. Hoff511
4:52 PM GMT on August 25, 2012
Thanks Levi!
Member Since: September 2, 2009 Posts: 0 Comments: 265
18. zawxdsk
4:50 PM GMT on August 25, 2012
Quoting Levi32:


GFS still looks fishy to me. That kind of track hasn't happened in the last 170 years, which is as far back as records go. You can't really say never with the weather though.

Some say Charley in 2004 made his NE turn at the last minute due to frictional effects. Flattish terrain can still do it if the situation allows. There is still room for Isaac to do a little funny business. We've already seen it during the last 24 hours.


The ECMWF's last 2 runs had a similar effect to what the GFS was predicting as well, with a ridge developing in northern Florida and southern Georgia. Obviously we're still waiting for the new ECMWF, but if it has a similar jog to the GFS, will we need to start taking that track seriously? And where does that ridge develop out of?
Member Since: August 2, 2011 Posts: 0 Comments: 195
17. SouthTampa
4:47 PM GMT on August 25, 2012
Thanks Levi. Great and informative post. I think many people over look frictional pull/ drag when discussing these systems.
Member Since: June 18, 2012 Posts: 0 Comments: 133
16. ScarlettOHara
4:45 PM GMT on August 25, 2012
Thanks Levi! Getting ready here .. I'll check with you tomorrow about what we should expect - I live where Charley hit, between Sarasota and Fort Myers ..I don't live on the coast, so I am not concerned about surge, but I am concerned about downed trees because the ground is so saturated.
Member Since: October 25, 2006 Posts: 185 Comments: 5804
15. johnbluedog69
4:36 PM GMT on August 25, 2012
Thank you Levi,great analysis as always.
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14. prweatherwatcher
4:32 PM GMT on August 25, 2012
Levy what you think of the CV storm that GFS and EURO develop next week? And thanks for your post they are very educational for everyone.
Member Since: July 29, 2011 Posts: 0 Comments: 90
13. lavinia
4:30 PM GMT on August 25, 2012
Great update Levi. Thanks. :)
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12. Dakster
4:30 PM GMT on August 25, 2012
Thanks - I like your analysis.
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11. seflagamma
4:20 PM GMT on August 25, 2012
Levi, I am one of your biggest fans.
Great job! Thanks you!
Member Since: August 29, 2005 Posts: 298 Comments: 40903
10. AtHomeInTX
4:19 PM GMT on August 25, 2012
I'm with Ally. And I hope it is disrupted before it can strengthen too much. Thanks Levi.
Member Since: August 24, 2010 Posts: 0 Comments: 151
9. Levi32
4:17 PM GMT on August 25, 2012
Quoting Terradad:
Thanks Levi! I really respect your opinions. I have a question about frictional effects. Can Isaac be pulled closer to the Florida west coast due to friction effects, or is the land too flat? Also, I would love to hear what you think of the 12z GFS that just came out, as well as the new ECMWF when it comes out soon. It seems that the GFS is now going in the direction of the Euro?

Thanks again!


GFS still looks fishy to me. That kind of track hasn't happened in the last 170 years, which is as far back as records go. You can't really say never with the weather though.

Some say Charley in 2004 made his NE turn at the last minute due to frictional effects. Flattish terrain can still do it if the situation allows. There is still room for Isaac to do a little funny business. We've already seen it during the last 24 hours.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
8. TallyWeather15
4:16 PM GMT on August 25, 2012
do u still feel it will go this far east after the new model runs?
Member Since: June 26, 2012 Posts: 0 Comments: 39
7. Terradad
4:13 PM GMT on August 25, 2012
Thanks Levi! I really respect your opinions. I have a question about frictional effects. Can Isaac be pulled closer to the Florida west coast due to friction effects, or is the land too flat? Also, I would love to hear what you think of the 12z GFS that just came out, as well as the new ECMWF when it comes out soon. It seems that the GFS is now going in the direction of the Euro?

Thanks again!
Member Since: December 21, 2009 Posts: 0 Comments: 93
6. Carnoustie
4:11 PM GMT on August 25, 2012
good explanation,thanks.
Member Since: August 31, 2010 Posts: 0 Comments: 49
5. HarryMc
4:10 PM GMT on August 25, 2012
Good morning Levi. Good analysis again.
Member Since: March 30, 2010 Posts: 4 Comments: 339
4. AllyBama
4:07 PM GMT on August 25, 2012
Thanks Levi!...let's all pray that the trend eastward will continue and contain Isaac to a minimal storm at best...however, westward will a situation that none of us want to see.
Member Since: August 3, 2006 Posts: 132 Comments: 20635
3. floridaboy14
4:06 PM GMT on August 25, 2012
thanks levi. dare i say could this be the end of a streak where a major hasnt hit the US in 7 years? lets hope its not. im about to get battered by him.
Member Since: July 25, 2011 Posts: 0 Comments: 1102
2. Bluestorm5
4:02 PM GMT on August 25, 2012
Thanks, Levi.
Member Since: August 1, 2011 Posts: 28 Comments: 8009
1. Grothar
4:02 PM GMT on August 25, 2012
Not bad. :)
Member Since: July 17, 2009 Posts: 71 Comments: 26137

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Levi Cowan has been tracking tropical systems since 2002, and is currently working on his bachelor's degree in physics at UAF.

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