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 Masquer08er:
I'll step in it and say C, but some will want F) none of the above
I always hated that in school, marking the wrong letter. B -80MPH, But I'll stand by my mistake
Member Since: August 16, 2007 Posts: 0 Comments: 397
Quoting Masquer08er:
I'll step in it and say C, but some will want F) none of the above


(B) tops
Member Since: May 31, 2007 Posts: 0 Comments: 1204
Quoting Matt1989:
It is not making landfall anywhere near Texas. Sure it might move that way in a few days after landfall as a reminent low...
I agree with this but for those who have been thru Hurricanes it is better to be safe and prepared. Looking back at the History of Hurricanes sometimes they do the unexpected. Best wishes for those in La. and Mississippi areas. If you are west of Isaac consider yourself fortunate, those in the path and east of Center I hope he speeds up some. The slow movement of this system is a huge concern and I hope he doesn't stall.
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Landfall according to the NHC track is Grand Isle La with the idea that Isaac will bend to the West. New Orleans Metro could take a long duration hit. This will be a water storm/event. The drought in Arky and points north should be helped.
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Quoting TheThinker:


Tell that to the President at 10:00. :-)

No it's meant for you - you are the one that brought it into this forum! Take yourself out with it!
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Quoting AtHomeInTX:


Don't fall for the trolls TXCWC. They got me yesterday. Had to leave before I got banned. Hopefully all TX gets is a nice northerly breeze. We'll see.


north breeze= more hot dry weather.. cant catch a break...
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After five days of reading post saying "Isaac will be a Hurricane in the morning" I would like to declare that everyone that said it last night are the winners!!! Congratulations you win a free parka and a flashlight! as you were...
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Quoting StormHype:


They've been calling for it to be a hurricane since it was in the Keys. It's 18 hours from landfall now and still a TS. This will finally be a Cat1 when it comes ashore.

The widely over-done hype is unfortunate because it will cause many to turn off the TV in 10 days when the next storm moves this way. I'm not against prep, just need to keep it sane and sensible. It's gonna be a cat1 like the NHC says.
Not overhyped. This is a TS (or C1) with close to the pressure of a major hurricane. The surge is going to be the problem, not the wind. It's also forecast to be a VERY slow mover, dumping lots of rain right upon that surge.
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2994. 10301
If you look at most of the imagery from this thing, the outflow on the south side certainly looks like an intensifying storm. The action around its core looks encouraging as its becoming more centric but at the same time there is dry air still in its system and on the northern flanks. 90-95 mph is its ceiling this late in the game
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2993. TXCWC
Quoting AtHomeInTX:


Don't fall for the trolls TXCWC. They got me yesterday. Had to leave before I got banned. Hopefully all TX gets is a nice northerly breeze. We'll see.


lol...thanks...I have worked all night and HAVE to get sleep anyway...so you can be sure I have said all I will on this...GFS AND EURO say what they say...NOT ME SAYING IT. :)
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About 18-24 hours to landfall Uh oh!!!!!
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Quoting matilda101:


I think that is why Isaac didn't get it togather quicker as all the energy yesterday over eastern Florida robbed the center of alot of energy. Our worst weather in Broward and Palm Beach occurred in during the morning early afternoon with tropical storm conditions including heavy heavy rains and winds 50-60 SE winds.


Yesterday it ingested a dry air slot that almost seemed to cause it to cut loose that east blob of convection and send it up the east coast of FL. That dry air kept the squalls in check along the west coast of FL as we didn't get much rain despite being closer to the NE side of the storm's center. In fact, the sun was out on Siesta Beach last night around 6-7pm.
Member Since: May 31, 2007 Posts: 0 Comments: 1204
Quoting lobdelse81:
Poll time:)
At 11am, Isaac will be declared a hurricane with____mph winds.

a) 75
b) 80
c) 85
d) 90
e) 90+
I'll step in it and say C, but some will want F) none of the above
Member Since: August 16, 2007 Posts: 0 Comments: 397
2988. hydrus
This is the most organized I have seen the system become so far. Those folks in LA know what to do, I hope there ready.
Member Since: September 27, 2007 Posts: 1 Comments: 21492
Quoting ncstorm:
not to take focus away from the GOM but we are getting heavy rains from Isaac..this storm is/will be affecting a lot of states



shows the massive size
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Mississippi River Cam New Orleans

Link
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Quoting CloudGatherer:
988mb (Surface) 195� (from the SSW) 70 knots (81 mph)

That's a NOAA dropsonde.

Ladies and gentlemen, I give you Hurricane Isaac.


It was inevitable.

With the central pressure so low and continuing to drop somewhat steadily, it was just a matter of time.

If the eyewall closes of and contracts a bit, the winds may still rocket up to near where they are supposed to be, which according to normal standards is 1/3rd inside the cat 2 intensity scale.

Adjusted intensity model projections and linear trend all suggest landfall at or below 970mb, so it may yet make the top end of category 2 if the trend continues.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
wow that was a jump.... at that rate. even high winds are possible
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Quoting StormHype:


They've been calling for it to be a hurricane since it was in the Keys. It's 18 hours from landfall now and still a TS. This will finally be a Cat1 when it comes ashore.

The widely over-done hype is unfortunate because it will cause many to turn off the TV in 10 days when the next storm moves this way. I'm not against prep, just need to keep it sane and sensible. It's gonna be a cat1 like the NHC says.


Oh? 12 feet storm surge from a TS is hype. Give me a break, if recon data says it has become a hurricane, it probably is one or are just going to ignore actual data?
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I'm here in nola. Cloud cover and winds are steadily increasing. Looks like the dry air is being flushed out and the storm is starting to "truly" intensify. Close to 35 mph wind gusts.
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Quoting CybrTeddy:
Dropsonde reported 81mph surface winds, that with 100mph flight level winds I think it is safe to say Isaac is a hurricane, finally.


So do you think there will be a special advisory coming soon then?
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Mars platform reporting 50 KT about 48 nm nne of the COC.
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Quoting Kristina40:


This is pertinent to weather how exactly? Why is it some cannot stop with the politics? WEATHER is the topic, not your tv viewing habits.
Exactly.
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Quoting lobdelse81:
Poll time:)
At 11am, Isaac will be declared a hurricane with____mph winds.

a) 75
b) 80
c) 85
d) 90
e) 90+


b
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I haven't been keeping up. Am i correct that plan for New Orleans "bowl " is not to evacuate? They're going to rely on 1 pumping station to pump out 20 plus inches of water...

Pumps can pump 1 in in 1st hour and 1/2 in per hour after that. So, if pumps are expected to run for 40 hours or more - no shutting off, clearing debris...

No room for problems at all.
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Decent chance we get a special advisory in about 10 minutes, now that there is no doubt it is a hurricane the NHC will need to get the word out and we're still an hour and a half from the next scheduled advisory.
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2974. ncstorm
not to take focus away from the GOM but we are getting heavy rains from Isaac..this storm is/will be affecting a lot of states

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Poll time:)
At 11am, Isaac will be declared a hurricane with____mph winds.

a) 75
b) 80
c) 85
d) 90
e) 90+
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Quoting TXCWC:


GFS AND EURO SAY DIFFERENT - no NOT LANDFALL IN TX - BUT both say a TRACK INTO TX definitely possible

0Z EURO


06z GFS


Don't fall for the trolls TXCWC. They got me yesterday. Had to leave before I got banned. Hopefully all TX gets is a nice northerly breeze. We'll see.
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Quoting weatherh98:


i may turn the tv off.
Please, no politics on this WEATHER blog.
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Quoting fredric1979:
My point was they are there In New Orleans for a reason. You see all these Katrina reminders. You see these flashbacks you hear all the time. It's the seventh Anniversary of Katrina. Katrina was a bad, bad, bad storm it was felt all the way over to here Alabama. I am not knocking this storm. They are pushing the issue though. They would be very foolish not to say this storm isn't a Katrina. They were hoping this was a Cat 2 or higher or they wouldn't have 4 reporters in N.O. I don't know it could be that there partnership with NBC has made it where they have to overhype about everything now.
Ive got a novel idea .If you dont like the weather channel dont watch.
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Quoting RickWPB:

Yep, if you happen to get under one of those "heavy moisture trains" you can get lots of rain. We got between 9 and 11 inches in two days here in Lake Worth. Out in Wellington FL they recv'd up to 15" of rain with some houses getting water in their houses.


I've heard that... He lives on the Golf Course but it has canals all around them.. a big house big lot..

They were creamed in 2004 with Francis and Jeanne..

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Quoting CybrTeddy:
Dropsonde reported 81mph surface winds, that with 100mph flight level winds I think it is safe to say Isaac is a hurricane, finally.


How strong you think he will get before moving ashore? Is he too close to land yet to intensify much more? His wind field is massive per recon.
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2967. TXCWC
Quoting Matt1989:
It is not making landfall anywhere near Texas. Sure it might move that way in a few days after landfall as a reminent low...


YA, that is what I just said..."NOT LANDFALL...BUT A TRACK INTO" - not as a remnant low but as a tropical storm
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Quoting justsouthofnola:




more proof.... i see the coc but show me actual recon data


You mean this? Here is the data.
Link
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So there is a definite eye, I think it is a hurricane now.

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2964. 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
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Quoting leftlink:
Important: water vapor loop shows complete wraparound of moisture around a DEFINED EYE. This happened only in the last 30 minute, and here is the image 4 minutes ago:



If you want to see the full 30 frame animation, here is a LINK.

Also, replace "1311" (9:11am) with a later time to see newer images.


I feel likeim watching someone slap somebody else in slow mo

thanks for that
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Quoting justsouthofnola:



i dont believe


For the skeptics, here's the full dropsonde report. I'd expect a bulletin any minute now, with the storm this close to shore. They won't wait for 11am on the upgrade:


Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 28th day of the month at 12:54Z
Aircraft: Lockheed WP-3D Orion (Reg. Num. N42RF)
Storm Number: 09
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 30
Observation Number: 20

Part A...

Date: Near the closest hour of 12Z on the 28th day of the month
Highest Mandatory Level For Which Wind Was Reported: 850mb
Coordinates: 27.4N 87.6W
Location: 211 miles (340 km) to the S (186°) from Pensacola, FL, USA.
Marsden Square: 081 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
988mb (29.18 inHg) Sea Level (Surface) 25.8°C (78.4°F) 25.3°C (77.5°F) 195° (from the SSW) 70 knots (81 mph)
1000mb -106m (-348 ft) This level does not exist in this area of the storm above the surface level.
925mb 581m (1,906 ft) 22.6°C (72.7°F) 22.1°C (71.8°F) 190° (from the S) 77 knots (89 mph)
850mb 1,318m (4,324 ft) 19.8°C (67.6°F) 18.4°C (65.1°F) 210° (from the SSW) 64 knots (74 mph)

Information About Radiosonde:
- Launch Time: 12:25Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.

Remarks Section...

Splash Location: 27.47N 87.57W
Splash Time: 12:29Z

Release Location: 27.41N 87.6W View map)
Release Time: 12:25:50Z

Splash Location: 27.47N 87.57W (
Splash Time: 12:29:05Z

Mean Boundary Level Wind (mean wind in the lowest 500 geopotential meters of the sounding):
- Wind Direction: 190° (from the S)
- Wind Speed: 77 knots (89 mph)

Deep Layer Mean Wind (average wind over the depth of the sounding):
- Wind Direction: 200° (from the SSW)
- Wind Speed: 66 knots (76 mph)
- Depth of Sounding: From 752mb to 988mb

Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 158 gpm - 8 gpm (518 geo. feet - 26 geo. feet)
- Wind Direction: 190° (from the S)
- Wind Speed: 72 knots (83 mph)

Sounding Software Version: AEV 30000

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point
988mb (Surface) 25.8°C (78.4°F) 25.3°C (77.5°F)
850mb 19.8°C (67.6°F) 18.4°C (65.1°F)
764mb 17.0°C (62.6°F) 16.0°C (60.8°F)
752mb 14.8°C (58.6°F) 14.8°C (58.6°F)

Significant Wind Levels...
Level Wind Direction Wind Speed
988mb (Surface) 195° (from the SSW) 70 knots (81 mph)
983mb 190° (from the S) 67 knots (77 mph)
970mb 185° (from the S) 77 knots (89 mph)
939mb 190° (from the S) 81 knots (93 mph)
909mb 195° (from the SSW) 74 knots (85 mph)
896mb 200° (from the SSW) 67 knots (77 mph)
850mb 210° (from the SSW) 64 knots (74 mph)
752mb 220° (from the SW) 54 knots (62 mph)
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06Z Nam thinks that Isaac will stay south of NOLA and skirt the coast too!

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Quoting Kristina40:


This is pertinent to weather how exactly? Why is it some cannot stop with the politics? WEATHER is the topic, not your tv viewing habits.
And it appears it is about to be a hurricane and it has already killed how many?
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Quoting justsouthofnola:




more proof.... i see the coc but show me actual recon data


Link
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Quoting Matt1989:
A lot of texas casters in here. Storm is not going toTexas..


I really haven't seen any 'texascasting' today....and the majority of the Texans would much prefer it not come here anyway.
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Dropsonde reported 81mph surface winds, that with 100mph flight level winds I think it is safe to say Isaac is a hurricane, finally.
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2956. Grothar
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Quoting TXCWC:


GFS AND EURO SAY DIFFERENT - no NOT LANDFALL IN TX - BUT both say a TRACK INTO TX definitely possible

0Z EURO


06z GFS
It is not making landfall anywhere near Texas. Sure it might move that way in a few days after landfall as a reminent low...
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Hello hurricane Issac
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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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