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 weatherh98:


Lets look shall we...



its growing
]

In the morning, I meant.
Member Since: June 16, 2006 Posts: 0 Comments: 1565
Quoting AussieStorm:
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?


u seen the track?

It looks equivelant to the path my sister took when she just started driving
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Time: 05:04:30Z
Coordinates: 25.9333N 88.4667W
Acft. Static Air Press: 843.5 mb (~ 24.91 inHg)
Acft. Geopotential Hgt: 1,479 meters (~ 4,852 feet)
Extrap. Sfc. Press: 1002.3 mb (~ 29.60 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 280° at 55 knots (From the W at ~ 63.2 mph)
Air Temp: 13.0°C* (~ 55.4°F*)
Dew Pt: 13.0°C* (~ 55.4°F*)
Peak (10s) Flt. Lvl. Wind: 57 knots (~ 65.5 mph)
SFMR Peak (10s) Sfc. Wind: 57 knots (~ 65.5 mph)
SFMR Rain Rate: 29 mm/hr (~ 1.14 in/hr)

Does this count,with all the rain and all?
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2051. sar2401
Quoting stormchaser19:




Is me or isaac is trying to standing up ?


Kind of looks like a chicken embryo now. :) I really think he's still sliding west and will make landfall somewhere around the LA/TX border. Isaac has been the most contrary storm I've seen in 50 years of tracking tropical systems.
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Quoting AussieStorm:
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?


The likelihood of that occuring would be very small. Also, considering the subsidence that Isaac is inducing over SE Texas right now it would not be very likely to strengthen significantly due to shear (already present) and a dry atmosphere.

Though, if it were, I can think of a handful of towers here I could get a FANTASTIC southeast view from.
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Isaac is a tired old dog.....someone put him out of his misery
Unfortunately Arkansas aint gettin any rain
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Quoting RitaEvac:


And I have cirrus over me and I'm over in Houston/Galveston area, that's a stretch from where you are and I am.


However, its cool in Charlotte. Is it a pleasant cool evening in Galveston?
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Quoting AussieStorm:
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?


The average course over the last 7 vortex reports is 312... almost bang on the projected course plus or minus (east or west) 10 miles.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Since yesterday I've thought the sweet spot for further intensification would be about 28n,88w. We'll see, be close.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting Orcasystems:


BS.
Going 315 that is right off GE with the Vortex reports plotted



Although i couldnt get it to save the text box that line heading is 292 degrees...take it or leave it!!
img src="Photobucket">
Member Since: May 31, 2011 Posts: 57 Comments: 572
Quoting nola70119:
He is going to look much better on visible, IMO....


Lets look shall we...



its growing
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Quoting AussieStorm:
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?

Now looking at both he has made a turn from NW to WNW and with Isaac anything is possible.
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Quoting AussieStorm:
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?


I dunno, zero?
Member Since: June 16, 2006 Posts: 0 Comments: 1565
He is going to look much better on visible, IMO....
Member Since: June 16, 2006 Posts: 0 Comments: 1565
Looking at the centre fixes from mission 28 and 29, what are the chances Isaac could be heading more west, maybe towards Galveston?
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isaac looks like a literal baby
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Quoting MississippiWx:
Could it be?


This storm has been really confusing and I thought I could control it or see into it since we have the same name but no.
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Is me or isaac is trying to standing up ?
Member Since: June 20, 2012 Posts: 0 Comments: 2169
Quoting dipchip:
Seems to me Isaac is going to slide along the South shore of La. and go into Cameron south of Lake Charles La.
Quoting midgulfmom:
Who was that guy either in 2004-5 or 2007-8 that had those rose colored glasses and his own blog, had some type of time with Coast Guard I think...and would quickly introduce himself to all new females?

Forget his name....Would normally post a list of definitions for all newbies, and give a morning update?



Sorry if someone answered...StormW I believe...


I was thinking that myself.
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Quoting MississippiWx:
Could it be?




What??????
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2032. EvilGN
Long time lurker here, have posted once or twice, was around for Ivan/Dennis in pcola, now live in new orleans, SE algiers area.
Unfortunately we left NOLA 9 days ago on vacation and are now stuck in the midwest. Its been a mind numbing couple of days wondering how/if/when/what we are coming home too, even a bad rain event will cause minor flooding in our house. (happened a couple weeks ago)
So far we have had some relief in seeing the lack of development, and I am wishcasting that to continue, please let that dry air disrupt things! All I can do now is sit and wait to see how things turn out in our part of town, and hope we can get home soon, and hope we have power and water when that happens. Hope everyone in the area is ready for the worst just in case though. Will be glued to the WC and this site for the next 48hrs obviously :P
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Quoting weatherh98:


what was the pressure, they didnt hit the vortex

Still 979mb was recorded from the dropsonde.
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Quoting MississippiWx:
Could it be?


Wheres taz when you need him
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Could it be?

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Quoting wxchaser97:
For the people saying its headed N or W, its heading 293 degrees per recon.


You cannot take a mean course off two plots, you need a minimum of 3.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting wxchaser97:
For the people saying its headed N or W, its heading 293 degrees per recon.


what was the pressure, they didnt hit the vortex
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The vector describes the average velocity of travel between the position 6hours earlier and the position at the posted time. ie It shows how the storm was travelling to get to the position,
and not the storm's direction&speed at the position's accompanying time.
All times in GMT. Derived from NHC_ATCF data for TropicalStormIsaac for 28August12am
26Aug.12pm , 23.5n80.0w
26Aug.06pm , 23.9n81.5w , 286.5*WNW@26.5km/h(16.5mph)14.3knots , 50knots , 992millibars , TS
27Aug.12am , 24.0n82.5w - 276.4*West@ 17.1km/h (10.6mph) 9.2knots , 55knots , 992millibars , TS
27Aug.06am , 24.9n83.7w , 309.6*NW @ 26.2km/h (16.3mph) 14.2knots , 50knots , 990millibars , TS
27Aug.12pm , 25.8n84.8w , 312.2*NW @ 24.8km/h (15.4mph) 13.4knots , 55knots , 987millibars , TS

17LA-Venice :: 5LA6-SouthwestPass,MississippiRiver :: EYW-KeyWest

The northwestern unconnected unlabeled dot covers FortJefferson,Florida
The southeastern unconnected unlabeled dot covers CaySal,Bahamas
The longest line is a straightline projection of TS.Isaac's 27Aug.6pm-to-12pm travel-direction to its closest approach (within 18miles or 29kilometres) to an inhabited coastline

27Aug.06am: TS.Isaac had been headed for passage just southwest of the SouthwestPass shipping entrance to the MississippiRiver (bottom,2TA5blob) on its way to GrandIsle,Louisiana
27Aug.12pm: TS.Isaac had been headed for passage over Venice,Louisiana

27Aug.06pm , 26.1n85.9w , 287.0*WNW@19.2km/h(11.9mph)10.4knots , 60knots , 984millibars , TS
28Aug.12am , 26.7n86.5w , 318.1*NWest@14.9km/h (9.3mph) 8.0knots , 60knots , 981millibars , TS
2TA5-PortO'Connor :: 17LA-Venice :: PST-Preston

The two kinked lines are (left-to-right) TS.Issac's path on its 6th and 5th days as a TropicalStorm
The southeasternmost dot on the longest straight line is TS.Isaac's most recent position

The longest line is a straightline projection through TS.Isaac's 2 most recent positions to its closest approach (within 18miles or 29kilometres) to an inhabited coastline
27Aug.6pm: TS.Isaac had been headed for passage over Seadrift,Texas (right,2TA5blob)
28Aug.12am: TS.Isaac was heading for a 29Aug.2:49amGMT passage 7.6miles(12.3kilometres)NEast of Venice,Louisiana in ~22hours from now (when this was posted)

Copy&paste eyw, 24.627n82.873w, 5la6-28.894n89.436w, 17la-29.268n89.322w, 2ta5-28.467n96.419w, pst, 20.8n75.3w- 21.7n76.7w- 22.8n78.2w- 23.5n80.0w- 23.9n81.5w, 23.9n81.5w- 24.0n82.5w- 24.9n83.7w- 25.8n84.8w- 26.1n85.9w, 26.1n85.9w-26.7n86.5w, 26.1n85.9w-29.347n89.263w, 17la-29.347n89.263w into the GreatCircleMapper for a larger map and other information
The previous mapping for comparison
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For the people saying its headed N or W, its heading 293 degrees per recon.
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Quoting xtremeweathertracker:
Last 3 fixes show isaac moving at a heading of 290 degrees or west-northwest!


BS.
Going 315 that is right off GE with the Vortex reports plotted
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting AllyBama:
Nite all! work day tomorrow is a possibly at this point - people gonna want to get their money out!..lol


Nite Ally!
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2022. will40
Quoting AllyBama:
Nite all! work day tomorrow is a possibly at this point - people gonna want to get their money out!..lol


nite ALLY
Member Since: September 19, 2005 Posts: 2 Comments: 4266
new hot tower
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Isaac has been a Mutant Hybrid all of his life. He has about 12 hours to either take a dump or get off the pot.

just my worthless 2 cents....
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Nite all! work day tomorrow is a possibly at this point - people gonna want to get their money out!..lol
Member Since: August 3, 2006 Posts: 133 Comments: 20639
Time: 04:56:30Z
Coordinates: 25.95N 88.5833W
Acft. Static Air Press: 842.5 mb (~ 24.88 inHg)
Acft. Geopotential Hgt: 1,494 meters (~ 4,902 feet)
Extrap. Sfc. Press: 1002.8 mb (~ 29.61 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 291 at 53 knots (From the WNW at ~ 60.9 mph)
Air Temp: 13.0C* (~ 55.4F*)
Dew Pt: 13.0C* (~ 55.4F*)
Peak (10s) Flt. Lvl. Wind: 54 knots (~ 62.1 mph)
SFMR Peak (10s) Sfc. Wind: 56 knots (~ 64.4 mph)
SFMR Rain Rate: 23 mm/hr (~ 0.91 in/hr)
(*) Denotes suspect data

Lotta rain it that reading though.
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Quoting weatherh98:


Im thinking it willbe a hurricane at 2

I got it a hurricane at 5 or 11am.
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Quoting wxchaser97:

Thanks, any reason as to why its delayed?



NOUS42 KWNO 280420
ADMNFD
SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD
0419Z TUE AUG 28 2012
THE 00Z GFS FORECAST IS RUNNING LONGER THAN USUAL AFTER 54
HOURS...EXPECT SOME DELAYS IN PRODUCTS AFTER 54 HOURS...AT THIS
POINT THE OUTPUT IS RUNNING APPROXIMATELY 25 MINUTES LATE...
OREILLY/SDM/NCO/NCEP


IOW: No reason given.
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Quoting nola70119:
Which GFS is this

Link?


That is the 00Z 500mb Vorticity output from NCEP.

GFS is running a little slow this evening.
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Isaac needs to turn northwest soon or hes gonna miss NOLA and come on down the coast farther west!
Member Since: May 31, 2011 Posts: 57 Comments: 572
whoopee!...sure would hate to lose my power and use of the computer! if so, I will be having to use my car charger quite frequently..thankgoodness for my smartphone!
Member Since: August 3, 2006 Posts: 133 Comments: 20639
Dry air swirl Isaac surrounded by Dry air

Good for NOLA.... Even Ileana with 45mph in the Pac, S of Mexico looks healthier....




Member Since: August 2, 2010 Posts: 21 Comments: 9882
Quoting KEEPEROFTHEGATE:


took a little nap to awaken to a much more southerly approach


Looks like his COC (such as it is) is heading almost due north now.
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Quoting nofailsafe:


GFS is delayed.

Thanks, any reason as to why its delayed?
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Which GFS is this

Link?
Member Since: June 16, 2006 Posts: 0 Comments: 1565
Quoting wxchaser97:

It should happen soon I think. Isaac shouldn't stay at 70mph forever.


Im thinking it willbe a hurricane at 2
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Quoting nofailsafe:


GFS is delayed.


Very strange....Hmmmmm!!!!



Member Since: June 20, 2012 Posts: 0 Comments: 2169
Quoting weatherh98:
I'm seriously waiting for the winds to catch up, it has to happen.

It should happen soon I think. Isaac shouldn't stay at 70mph forever.
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Quoting AllyBama:
MLC - BTW, are you wishcasting Isaac my way and away from you? LOL..


LOL, no way. I'm just looking at a weakening high pressure and a strengthening system. It could happen. And may!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting wxchaser97:
Still at 54 hours at Huffman's site, really wanted to know what the gfs had to say about future Kirk.


GFS is delayed.
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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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