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 FelixTheKat:
look like upgrade should be 80-85 MPH at 11.


I agree. Storm needs to maintain structure though, any dry air punches like yesterday and every thing goes plbtt...which is what the people on the Gulf need to happen or we could be looking at a CAT 2 landfall.
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3152. LargoFl
Quoting Patrap:
12z Early Cycle NHC model tracks
Isaac

Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

pat you in a safe area..away from what could be massive storm surge?
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Everyone seems to be concentrating on the track storm surge & windspeed. All of these are great concerns. But as a former resident of the area, I am concerned with the amount of rainfall this will storm will generate. Do any of you have comments on this?
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Quoting Thing342:
AL, 09, 2012082812, , BEST, 0, 278N, 882W, 60, 976, TS, 50, NEQ, 80, 60, 50, 50, 1012, 300, 30, 0, 0, L, 0, , 0, 0, ISAAC, D,


Hasn't updated yet
Member Since: July 8, 2005 Posts: 259 Comments: 24580
3149. Patrap
12z Early Cycle NHC model tracks
Isaac

Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

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3148. divdog
Quoting ILwthrfan:


Radar shows that he is really cranking up. I don't think there is any question in my mind that he still achieve at least a 90 knot storm. Maybe a even a bit more. People should have been prepared though NHC has done a pretty darn good job with this system for 4-5 days outlooks.
Much better than some in here who have been bashing the Nhc you know who you are and it is a a shame. They will up it toa hurricane when it is one. Tired of the crap.
Member Since: August 22, 2008 Posts: 0 Comments: 755
3146. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting CybrTeddy:
Can't get to the ATCF on here, dang.

The latest:
AL, 09, 2012082812, , BEST, 0, 278N, 882W, 60, 976, TS, 50, NEQ, 80, 60, 50, 50, 1012, 300, 30, 0, 0, L, 0, , 0, 0, ISAAC, D,
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3143. LargoFl
outer bands just scraping the coast now
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Quoting RickWPB:
Lake Okeechobee is up to 13.12' today. One good thing from all the rain in the past two days.


They do no want it above 12 ft so they will probably start draining it again..
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3141. Max1023
This is what you get after hitting Hispanola and Cuba - a 976mb borderline TS/Cat 1 trying to develop a 50 mile wide eye. Land interaction flattens the cyclone out, combine this with the natural tendency to get larger at higher latitudes and you get a storm with a relatively low "intensity" spread over a very large area carrying a large rainfall and storm surge risk.
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Quoting CybrTeddy:
Can't get to the ATCF on here, dang.
AL, 09, 2012082812, , BEST, 0, 278N, 882W, 60, 976, TS, 50, NEQ, 80, 60, 50, 50, 1012, 300, 30, 0, 0, L, 0, , 0, 0, ISAAC, D,
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3139. Patrap
GOM Sea Height Anomaly



SST's




TCHP


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3138. Pastey
Quoting HimacaneBrees:


Had our 1st shower here in Denham Springs about 0730. It's actually nice out ATM, won't be later tonight and tomorrow though


I'm from Denham Springs as well. I just didn't post that because most people outside LA have no clue where that is. We'll be in for a ride but the storm is much weaker than it could have been. I'm at work right now and will likely be for the remainder of the day. Come hell or high water!
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Can't get to the ATCF on here, dang.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
3136. GetReal
I have a couple of last minute minor preps to make.... BBL
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Quoting lobdelse81:
NHC says still not a hurricane???????? COME ON!! and with the hurricane hunters finding flight level winds above 100mph and surface winds in the 80s along with pressures at around 968mb??? They will lose credibility if they don't upgrade this at 11am.

Actually, Ike had winds at the flight level well in excess of his surface strength. They just had not worked down to the surface yet. (if he had an extra 6 hours over water, he would have easily been a cat 3 hurricane on landfall)
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3133. Patrap
This Large CV Ballerina has finally pulled Her/His arm's in and well,..these LARGE System's don't fade, nor wind down easily.

A LOT of water is now being put into Motion N to Nw and that alone is GOING to create a substantial event for many, in 3 States easily.

The Time for ACTION will be first Light to Noon CDT and I urge all with preps outside to carefully,but prudently get those done.

The winds are beginning to pick up and they will only increase to Tropical Storm Strength and Greater in the Warned area's from the Coastal regions to well inland.

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finally breaking free from the ITCZ for real...


1000mb



990mb



970mb

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Quoting Thing342:
Not into the eye. Just outside.


Ment to say that, using the iPad is impossible.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
Thing about the gulf is the shallow waters are just as warm at the floor as the top, and I'm talking miles out, there is no cool water at the floor, that's how warm the near-shore waters are.
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Quoting Patrap:
/ CIMSS / CIMSS Satellite Blog /
Search for:
Day-Night Band Imagery of Isaac
August 28th, 2012
Glad to see you posting but sorry you have to deal with this mess again. Good luck to you and your neighbors.
Member Since: August 30, 2008 Posts: 0 Comments: 44
976mb
Extrap. Sfc. Press: 976.7 mb (~ 28.84 inHg)
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Quoting CybrTeddy:


Too add to that the NOAA hurricane hunters dropped a Dropsonde into the eye and showed 81mph winds on the surface. Everything supports an upgrade.
Not into the eye. Just outside.
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Looks like a Cat1 maybe at 11am EDT. It's attempting to further strengthen. If this storm lives up to it's reputation, something's about to go wrong soon to disrupt it's ambitions. I say that will be the expanding tongue of dry air to the north. I know it's trying to fight it now around the center itself, but he will be gagging on this later today. Don't shoot the messenger.
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GM all, FINALLY got some sleep after being obsessed with this storm since Friday and checking in to see the current status. Could everyone please knock off the personal attacks and "know it all" mentality? AGAIN let me reiterate, regardless what the storm is upon landfall there will be TONS of rain and flooding. Praying anyone and everyone in the storm's reach stays safe!
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Quoting NoloContendere:
Please take your political crap elsewhere. We're busy talking about weather. I have family in NOLA and I'm trying to follow debvelopments closely.




If you have DirecTV...you can follow news coverage on Isaac on channel 349.
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976 mb surface pressure.

Time: 13:35:00Z
Coordinates: 28.0333N 88.5167W
Acft. Static Air Press: 843.1 mb (~ 24.90 inHg)
Acft. Geopotential Hgt: 1,301 meters (~ 4,268 feet)
Extrap. Sfc. Press: 976.8 mb (~ 28.84 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 350° at 1 knots (From the N at ~ 1.1 mph)
Air Temp: 21.4°C (~ 70.5°F)
Dew Pt: 20.0°C (~ 68.0°F)
Peak (10s) Flt. Lvl. Wind: 2 knots (~ 2.3 mph)
SFMR Peak (10s) Sfc. Wind: 18 knots (~ 20.7 mph)
SFMR Rain Rate: 0 mm/hr (~ 0 in/hr)
(*) Denotes suspect data
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Quoting Pastey:
Baton Rouge checking in. I appreciate everyone continuing to post between updates. I've been following this storm for about a week now. I'm expecting weak Cat1 or strong TS winds here in Baton Rouge early tomorrow morning and into the mid-day. We're obviously still sunny here with a light breeze and some moderate cloud cover. I'll continue to post updates as the day and evening progresses. Thanks again for everyone's insight and updates.


Had our 1st shower here in Denham Springs about 0730. It's actually nice out ATM, won't be later tonight and tomorrow though
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Quoting lobdelse81:
NHC says still not a hurricane???????? COME ON!! and with the hurricane hunters finding flight level winds above 100mph and surface winds in the 80s along with pressures at around 968mb??? They will lose credibility if they don't upgrade this at 11am.


Too add to that the NOAA hurricane hunters dropped a Dropsonde into the eye and showed 81mph winds on the surface. Everything supports an upgrade.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
The thing is, it's a Category one with a pressure of a Category 2/Major Hurricane.. Like Alex in 2010. This means Isaac is a very dangerous and intense Hurricane despite the category and New Orleans should have evacuated, hopefully they did. Katrina aimed for New Orleans 7 years ago today.
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Isaac a hurricane???? IS THIS REAL LIFE???????
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3113. syn627
Quoting HCW:
SJ is live in South MS.... This has got to be the highest quality stream that I have seen this morning. Also if you have a coupe of extra bucks please help out PortLight . If you want more info I am sure that Press Lord will be around shortly
Link

Thanks for the link. You're right, the stream quality is excellent.
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Please take your political crap elsewhere. We're busy talking about weather. I have family in NOLA and I'm trying to follow debvelopments closely.


Quoting SrChiefFan1:


At least this POTUS has someone in charge of FEMA that knows something about disaster response instead of horse grooming....
Member Since: July 8, 2005 Posts: 0 Comments: 44
bbl
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NHC says still not a hurricane???????? COME ON!! and with the hurricane hunters finding flight level winds above 100mph and surface winds in the 80s along with pressures at around 968mb??? They will lose credibility if they don't upgrade this at 11am.
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Quoting CloudGatherer:


Sure. It's a dry spot, that just happens to be surrounded by hurricane strength wind maximi, to show a sharp temperature gradient, and to have the pressure of a Category 2 storm.

Whatever you're smoking, I wish you'd share some. Must be good stuff.


Looking at the time lapse history it looks like a slug of dry air that made all of the way to the core...a number of us appear in agreement on this so I think it is a legit argument & not smokin' anything. This has been happening for from time to time for days and that's why we're staring at TS...it has not been upgraded as of yet. Sure it will probably get upgraded but without all of the dry air entrainments it would have been a real bad storm...it managed to maintain even with these intrusions which was a pretty good feat.
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Quoting Patrap:
/ CIMSS / CIMSS Satellite Blog /
Search for:
Day-Night Band Imagery of Isaac
August 28th, 2012

Welcome home. Hope you had a good vacation. Not exactly the way you wanted to return I'm sure. Stay safe :)
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Dr Knabb just said ...not yet..waiting on more recon...
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CIMSS ADT confirms what we are looking at is indeed an eye.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
3105. kwgirl
Quoting Patrap:
New Orleans
NEXRAD Radar

Base Reflectivity 0.50° Elevation
Range 248 NMI

Hi Patrap. We have all been thinking of you. Hope you have your waders on and that you do not need them:)
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Isaac has a lot of winds on its south side most likely...
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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