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 LargoFl:
is this rain going into the drought area's of georgia?
The rain has passed over some drought area in central GA. But one band isn't nearly enough. :\ It's misting just north of Atlanta Metro and winds are dead calm. I'm wondering what the rest of the day will bring since it seems there's only the one band and then no more rain bands. Isaac throwing some weight off and will spin up a bit before land fall?
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One thing true about this storm,

Just as you think an eye has formed it collapses.....
and a new swirl forms near by.....just crazy
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Quoting acl8610:
TWC fail... President speaks, Norcross is about to make a valid and important point on what was said... cut to york peppermint patty commercial...


That REALLY made me angry. How unprofessional of TWC if I was Norcross, i'd be rather angry...
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Quoting reedzone:
Isaac is still forecast to make landfall tomorrow on August 29th, 2012, 7 years after Katrina
..... wow


its gonna half to stall now, its nearly on grand isle already
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3250. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Found a cam of downtown NO and they are just walking around, Looks like its raining though
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3248. Patrap
ENTERGY Louisiana just rang 300,000 Customers with the Following

Tropical Storm Force winds are expected for 30 hours and the yada, yada, yada, ..
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3247. hydrus
This is a clickable wind map. Click anywhere to find the windspeed. Highest I found was 58 mph..Link
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Quoting FelixTheKat:
isaac starting to look rather poor again.

dry air is once again destroying his little core lol. thank goodness he is such a pathetic little system.



A pathetic system that is generating more storm surge than some major hurricanes with a 976mb pressure. Really, keep on frame by frame forecasting like you are you're going to find that one frame will look like a RI hurricane, the other might look like its dissipating.
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Quoting catastropheadjuster:
I'm not wishcasting or nothing just trying to understand a little if some one could explain this to me.

what is stopping this tropical storm from turning and go into miss? or taking a NE turn. I see where there is 2 highs one over there by FL and one TX and LA. I'm not trying to cause controversy on the blog or a argument, just don't understand.

sheri


I honestly don't know what could cause that, but I'm sure happy it seems to be turning more to the west. I hope it doesn't intensify and all it brings is the necessary rain.
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3244. Patrap
ISAAC RGB Loop




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Quoting Wxouttacontrol:


I don't live there but here is a local news live feed

Link
. DirectTV has live coverage from New Orleans on 325
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Quoting GeorgiaStormz:


Well it didn't show up so we're good.

Quoting MAweatherboy1:
I'm a bit surprised no special advisory was issued, but we should see the upgrade come at the 11AM in 30-45 minutes.


I thought they would just wait until 11am so recon could collect more data. Isaac should be upgraded though.
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Dropsonde and flight level data support a hurricane, but SMFR estimates don't.
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3239. GetReal
Here is the recent data from a buoy in the north side of the eye wall:

Station KVOA
Federal Aviation Administration
Location: 29.229N 87.781W
Date: Tue, 28 Aug 2012 13:55:00 UTC
Winds: ESE (110°) at 56.9 kt gusting to 72.1 kt
Air Temperature: 80.6 F
Dew Point: 75.2 F
Visibility: 0.4 nmi
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3238. acl8610
TWC fail... President speaks, Norcross is about to make a valid and important point on what was said... cut to york peppermint patty commercial...
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3237. Patrap
Quoting reedzone:
Isaac is still forecast to make landfall tomorrow on August 29th, 2012, 7 years after Katrina
..... wow


See, Terrance McKenna was right, and well, you know.

I hope.

: )
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Quoting catastropheadjuster:
I'm not wishcasting or nothing just trying to understand a little if some one could explain this to me.

what is stopping this tropical storm from turning and go into miss? or taking a NE turn. I see where there is 2 highs one over there by FL and one TX and LA. I'm not trying to cause controversy on the blog or a argument, just don't understand.

sheri


I'm not sure what's stopping it but TWC said earlier they don't expect it to just hook N or NE all the sudden. Hope that helps.
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Quoting Charliesgirl:
Morning all! Pearl River, Louisiana on the Pearl River. getting our first rain band as we speak. He finally looks like a hurricane fo' sure and this new eye will probably hold. good thing he couldn't do it sooner.


Amen.
Prayers ensuing for all in harm's way. ♥
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Isaac is still forecast to make landfall tomorrow on August 29th, 2012, 7 years after Katrina
..... wow
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Quoting 7544:
anyone in la or ms have a link to the live coverage of issac thanks


I don't live there but here is a local news live feed

Link
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Best estimate, what time will landfall happen? Just heard president say he was told later today. I was thinking tomorrow morning.
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3229. LargoFl
flooding in wellington fl
Member Since: August 6, 2011 Posts: 4 Comments: 33344
I'm a bit surprised no special advisory was issued, but we should see the upgrade come at the 11AM in 30-45 minutes.

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3227. divdog
Quoting catastropheadjuster:
I'm not wishcasting or nothing just trying to understand a little if some one could explain this to me.

what is stopping this tropical storm from turning and go into miss? or taking a NE turn. I see where there is 2 highs one over there by FL and one TX and LA. I'm not trying to cause controversy on the blog or a argument, just don't understand.

sheri
Wondered the same ..I guess it has found the path of least resistance. I do remember opal pulling a fast one on us but much diff sceanario..
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3 Day Isaac Satellite Loop
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Say What?! Top of the hour I heard the NPR newscaster say that "Tropical Storm Isaac" now has winds of 75mph."
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Quoting ILwthrfan:
Just in the last hour storm has movied .16 degrees North and .29 degrees west.


Edit sorry. Officially he has moved .18 degrees North and .28 degree West in the last hour since Recon has investigated.
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3223. 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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I really don't like how much Isaac has slowed down...doesn't matter if the NHC declares him a hurricane or not...We're talking lots of rain + storms surge will cause a lot of coastal erosion along LA and MS and inland flooding.
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BUILDUP OF WATER IN NEW ORLEANS IS IMMINENT, SHOULD START AROUND 3PM eastern time! However winds will not be directly onshore in Alabama if storm continues to go west.

Here is an analysis with a prediction of the storm moving 40 miles in the next 5 hours:



Comments please. Will the high flight level winds just east of NO actually make their way down to the surface in 5 hours, or not?
Member Since: December 28, 2010 Posts: 0 Comments: 134
Quoting catastropheadjuster:
I'm not wishcasting or nothing just trying to understand a little if some one could explain this to me.

what is stopping this tropical storm from turning and go into miss? or taking a NE turn. I see where there is 2 highs one over there by FL and one TX and LA. I'm not trying to cause controversy on the blog or a argument, just don't understand.

sheri


Just to let you know now all major models are west of NO (don't know about Euro) never listed in the plots
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102mph flight level winds per vortex, pressure down to 977mb, NOAA dropsonde recorded 81mph winds, consistent hurricane force winds at flight level that would support hurricane at the surface. I'd be rather surprised if the NHC threw that out as they've been consistently saying for the past few advisories it is very close to hurricane status. With that added, the satellite presentation continues to improve even though there is dry air surrounding the circulation. Not enough to weaken or kill Isaac though as some make it out to be in the middle of the Saharan Air Layer, but enough to impede and prevent rapid intensification.
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3218. Patrap
Quoting SWLACajun:
Patrap, based on what you posted showing Isaac spinning, it looks to be just basically sitting there or moving just verrry slightly westward, but not toward Grand Isle area or northwestward. Is this what you see as well?


That is a good read and well, I concur.




NW at a Brisk walk 6-7 mph.

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Intense Hurricane here guys.. Pinhole eye, large storm. I really hope New Orleans is ready :/

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Morning all! Pearl River, Louisiana on the Pearl River. getting our first rain band as we speak. He finally looks like a hurricane fo' sure and this new eye will probably hold. good thing he couldn't do it sooner.
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Quoting TomballTXPride:

Tell me about it. I am at a complete loss for comprehending that. Of course not complaining by all means...but this has been a very bizarre system.


Makes you wonder if the planes aren't dropping stuff into the storm, lol
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3214. BlxMS
Latest surge numbers for Hancock County MS looking a little worse...Now Bay St, Louis / Waveland looking at 10-12 feet...This is still dangerous given the geography...but in perspective, we had 30+ feet in GPT / PC seven years ago...
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The 1200z models are out, link to the WUndergrand models,Link
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I'm not wishcasting or nothing just trying to understand a little if some one could explain this to me.

what is stopping this tropical storm from turning and go into miss? or taking a NE turn. I see where there is 2 highs one over there by FL and one TX and LA. I'm not trying to cause controversy on the blog or a argument, just don't understand.

sheri
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3211. Patrap
Tropical Storm 09L

UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 8.1.3
Tropical Cyclone Intensity Estimation Algorithm

Current Intensity Analysis



UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 28 AUG 2012 Time : 124500 UTC
Lat : 28:00:15 N Lon : 88:43:10 W


CI# /Pressure/ Vmax
3.6 / 987.1mb/ 57.0kt


Final T# Adj T# Raw T#
3.6 4.0 4.8

Estimated radius of max. wind based on IR : 17 km

Center Temp : -18.6C Cloud Region Temp : -55.8C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.5T/hour
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 160km
- Environmental MSLP : 1014mb

Satellite Viewing Angle : 36.0 degrees

************************************************* ***




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3210. Michfan
Quoting GeorgiaStormz:
Isaac has a MASSIVE sphere of influence, im about to get a big band up in GA.



Yeah its pretty steady here in Fort Gordon.
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Quoting cajunsurfer:
New to this site. Does anyone know if Dr. M. will update at 11:00 or when??


not sure... he's also helping out with/at TWC so we'll see.
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Westward extension of TS warning noted in NHC Advisory 29:

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

THE TROPICAL STORM WARNING IS EXTENDED WESTWARD ALONG THE NORTHERN
GULF COAST TO CAMERON LOUISIANA.
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Quoting WxNerdVA:


Now that's a big storm...

It will affect many states, mostly with rain inland.
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3204. 7544
anyone in la or ms have a link to the live coverage of issac thanks
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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.

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