Isaac approaching hurricane strength

By: Angela Fritz , 9:14 PM GMT on August 27, 2012

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Isaac is walking the line of hurricane status this afternoon after a hurricane hunter mission investigated the storm and found winds of 80+ mph with the SFMR instrument, which looks down at the surface from the plane and estimates what wind speeds are. This instrument has a notoriously rough time in doing so when there's heavy rain, and since the strongest winds were recorded coinciding with the strongest rain, you can imagine that this region of high wind speed could be suspect. The hurricane hunter mission is still in the storm, so I imagine they will issue a special update if needed. Currently the best estimate of wind speed within the storm is 70 mph. Isaac's pressure has been dropping today as well and is now 981 mb. Isaac is moving northwest at 12 mph--no change since this morning. Satellite loops show that Isaac remains large, though asymmetric, with most of the strong thunderstorm activity on the west and southwest side. Isaac's southeast side continues to struggle with dry air and wind shear, which could help to moderate Isaac's intensity as it approaches the coast.

An oil platform in the northern Gulf of Mexico is reporting sustained winds from the north-northeast at 40 mph this afternoon. A buoy west of Tampa, Florida is recording sustained winds around 30 mph, and platforms south of Louisiana are recording winds from 35-40 mph. The widespread heavy rain of yesterday has lightened up in Florida, but a strong line of thunderstorms in one of Isaac's outer bands is training northward along and offshore of the east coast of Florida, affecting everyone from Miami to Jacksonville.

This afternoon the AP reported that Isaac's death toll in Haiti jumped to 19, which puts Isaac's total death count at 21. It appears most of the deaths in Haiti were due to collapsing structures.


Figure 1. Satellite imagery of Tropical Storm Isaac around 3pm EDT on Monday.

Track forecast:
Models seem to be coming into better agreement today on where Isaac will make landfall, closing in on Louisiana and New Orleans as most likely landfall point. The ECMWF, HWRF, and UKMET all suggest New Orleans as the landfall location. The GFS is only slightly west of that. The GFDL is the farthest west, predicting landfall near the Louisiana-Texas border. Landfall timing remains Tuesday night. Beyond landfall, Isaac is expected to move north toward the Midwest through the rest of this week, however, models are showing that the system will likely slow down around landfall time, prolonging impacts like surge and inland flooding.

Intensity forecast:
The closer Isaac gets to landfall without having formed an eye, the better it is for intensity at landfall. Isaac has strengthened only modestly in the past 24 hours, and is still struggling with a less-than-conducive atmospheric environment. The HWRF remains on the high end of the intensity spectrum, suggesting Isaac will be a weak category 2 upon landfall. Other models suggest it will be a strong category 1, but the difference is splitting hairs. The National Hurricane Center's official forecast is for Isaac to continue strengthening over the next day, reaching category 2 at landfall.


Figure 2. Tide gauge data from St. Petersburg, Florida. The green line shows the storm surge. As Isaac's counterclockwise winds blew offshore this morning, water levels feel two feet at St. Petersburg. The winds switched to onshore this afternoon as the center of Isaac moved more to the northwest, bringing a storm surge of two feet to the city.

Storm surge observations from Isaac
This morning, as Isaac's counter-clockwise winds brought offshore winds to the Tampa/St. Petersburg area, ocean waters fell two feet along the coast. This afternoon, winds have shifted to blow onshore, and a two foot storm surge has been observed at Naples, Fort Meyers, and St. Petersburg on the west coast of Florida. Water levels have also begun to rise along the coast of Louisiana, with a storm surge of 1.5 feet already occurring at Shell Beach on the east side of New Orleans in Lake Borgne.

Angela and Jeff

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Quoting MahFL:


So far I have .47 inch here in Orange Park, FL.


I'm in Central Jax, a bit east of Everbank Field.
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Is it me or does Isaac have some sort of eye/ eye in formation now?
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Quoting angelafritz:
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?

Check the comments from the last blog post.
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Isaac has been another challenging storm to predict, everyone in LA, MS, and others in the path of Isaac need to be ready for a cat1/2 hurricane.
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Eye.

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47. angelafritz (Admin)
Has anyone else noticed that I struggle most with simple figures of speech? First, it was the elbow of Florida. Now it's pulling hairs. :)
Quoting Articuno:
2nd to Fay, I think this is one of the most beautiful ts's


Fay
What was amazing about Fay is she strengthen over the Everglades and even formed an eye.
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Thank you Angela..Pretty cool seeing the Doc on TWC. I suspected this would occur, just not so soon..:)..Inland flooding will be a problem with Isaac..
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This has been quite a difficult storm to forecast (intensity-wise, as well as track-wise), but it seems like it has been getting its act together.

Thanks for the new blog, Angela and Jeff.
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Quoting Stoopid1:
Thanks for the update you two. Got 0.6" of rain so far in Jacksonville, nothing much. Hope all of those on the Gulf coast are prepared.


So far I have .47 inch here in Orange Park, FL.
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Thank You Ms. Fritz and hoping that we do not get much intensification. Not pleased with the track towards New Orleans........Last thing that recovering city needs is an encounter with eye wall winds......Residents there should take head.
Member Since: August 8, 2006 Posts: 0 Comments: 8278
Do any of you Treasure Coast folks know how bad the flooding is in the White City area? My daughter is waiting for me to pick her up at a friend's house on Sunrise just north of Midway, but I'm not sure whether I should attempt to get there or just let her spend the night.
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Quoting angelafritz:
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?


I've been working at home today and had TWC on as background. He's like an old friend now... but he's obviously never met me. Neat seeing the real person in the flesh.

I'm on several local boards and am on local TV a couple times a week... NEVER watch myself on replay though... it's amazing how different your on-camera persona is from what you think you are. He's probably the same?
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Thank you Angela and Jeff! I did see Dr. Masters on TWC today.
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2nd to Fay, I think this is one of the most beautiful ts's


Fay
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Thanks Angela and Jeff, Was Isaac forecasted to slow down now?
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34. bwi
.
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Hey Doc...Do you give any credence to the GFDL? Because how far west it goes into Louisiana greatly determines what kind of effects I feel. I am just to the North of Vermillion Bay
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Quoting angelafritz:
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?
Yes just saw him on a little while ago.... Great Stuff and even better to see him part of the Team as they Say on TWC.... :o)

Taco :o)
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Quoting angelafritz:
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?


Yesterday,

Storm surge is great as my house is only about 10-14 feet above sea level in not exactly sure
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Wow, sad to hear about Haiti. It's amazing how so much dry air cuts between the two huge areas of moisture in this storm. US Water Vapor
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Thanks to our weather "stars" Angela and Dr. M..
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Quoting acl8610:
Thank you for the new blog, anyways from the old blog...
Quoting CaicosRetiredSailor:



Dayton International Speedway

In preparation for Isaac DIS welcomed 5,000 workers and 2,500 trucks from as far as Wyoming, Texas and Pennsylvania before embarking on their individual assignments. This FPL Connect pre-positioning at DIS marks the largest to date.


Yes that's Daytona International Speedway... I was just there, it was crazy. I have never seen anything like that before, being from NE Ohio originally.


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Thanks for the update
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26. angelafritz (Admin)
Quoting CJ5:
"Splitting hairs" would be the correct term but watching this storm is like "pulling hairs". LOL


Hahaha - yes... pulling hairs is what Im doing right now. SPLITTING hairs is what Isaac is doing right now. Easy to get confused. ;)
Thanks for the update you two. Got 0.6" of rain so far in Jacksonville, nothing much. Hope all of those on the Gulf coast are prepared.
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Quoting angelafritz:
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?

He was on at 4:31 pm EDT.

Thanks for the blog entry.
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Thanks guys!
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Isaac still looks to have some dry air issues.
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Thanks, Angela.
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Thank you for the new blog, anyways from the old blog...
Quoting CaicosRetiredSailor:



Dayton International Speedway

In preparation for Isaac DIS welcomed 5,000 workers and 2,500 trucks from as far as Wyoming, Texas and Pennsylvania before embarking on their individual assignments. This FPL Connect pre-positioning at DIS marks the largest to date.


Yes that's Daytona International Speedway... I was just there, it was crazy. I have never seen anything like that before, being from NE Ohio originally.
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Quoting TreasureCoastFl:
Link
Ugh, dont know how to post photos correctly. Oh well... good luck to you all in this storms path!!
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15. CJ5
"Splitting hairs" would be the correct term but watching this storm is like "pulling hairs". LOL
Member Since: July 4, 2007 Posts: 0 Comments: 1755
14. angelafritz (Admin)
No prob, Dr. Masters might be dropping in to add some more info about storm surge. You can imagine he's very busy at TWC. Has anyone caught him on air yet today?
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Thanks for the update.
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Link
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Angela and Jeff? Awesome thanks.
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Thanks guys for the update.We had some intense weather today in St. Lucie. First time since Fay did my street flood.
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Member Since: August 1, 2007 Posts: 0 Comments: 163
Thanks, Angela... nice update.

Jo
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Thanks Doc and Angela... We've really been appreciating the two blogs per day.
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Thanks Dr. Masters!
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Keep us informed here in sela
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.