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 LaPorteTX:

We can dream


No No No!
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Quoting JGreco:



wow and they just dropped the warnings for the extreme western panhandle from pcola-destin....wonder if this might be a slight mistake...


It'd have to really get intensity cranking to make that much of a bend. What's out still 250-300 miles? Plenty of time to change paths a bit, but the 1016mb area of high pressure has retreated to the north. Isaac will mostly move poleward at this point wnw, then nw, then eventually almost due north, imo. Remember, weaker means more west. Stronger will push harder against the high pressure, more northwards.


SFC MAP



The llc is intense but it'll take a lot of time to spin up a larger intensity into the very broad MLC that has been carrying the load for this system all along. Plus, it's not getting the advantage of loop eddy waters really now. So, given distance from shore, still warm water, better symmetric consolidation at the mid-levels so the tropical engine can get truly vertical, we'll see additional strengthening, but I doubt it'll be rapid. Doubt rapid dev despite low pressures found in the eye (near the llc levels). Isaac has the will to strengthen, just doesn't have quite enough lifting power at the llc in the present to really spin the mid-levels. Plus, still entraining a bit of dry air on the northeast side. Only way to strengthen really is to get that neast side closed off and churning.
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Quoting MississippiWx:


Still has at least 24 hours. Could still easily reach the forecast from the NHC.

I wouldn't say easily. Dry air is showing no signs of letting up Isaac's core is not well-defined.
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97L is still not out so don`t count him as dead.
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700. Caner
Well, i will say this for it... It is definitely moistening it's environment...

Link

It still has 24 hours, lets see whether or not it manages to moisten the dry air around it enough to center itself.. if so, we may see cat 2.

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Quoting angiest:


Tell the hurricane center:

http://www.nhc.noaa.gov/prelims/2001allison4.jpg



Allison 2001 flooded downtown Houston something terrible.
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000
ABNT20 KNHC 272351
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON AUG 27 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM ISAAC...LOCATED ABOUT 230 MILES SOUTHEAST OF THE MOUTH OF THE
MISSISSIPPI RIVER.

A BROAD AREA OF LOW PRESSURE LOCATED ABOUT 1100 MILES WEST-NORTHWEST
OF THE CAPE VERDE ISLANDS CONTINUES TO PRODUCING SHOWERS AND
THUNDERSTORMS TO THE NORTH OF THE CENTER. ALTHOUGH THIS SYSTEM HAS
BECOME A LITTLE ORGANIZED TODAY...ENVIRONMENTAL CONDITIONS ARE ONLY
MARGINALLY CONDUCIVE FOR FURTHER DEVELOPMENT. THIS SYSTEM HAS A
MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS AS THE LOW MOVES WEST-NORTHWESTWARD TO
NORTHWESTWARD AT 10 TO 15 MPH.

A TROPICAL WAVE LOCATED NEAR THE CAPE VERDE ISLANDS IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS. ENVIRONMENTAL CONDITIONS
APPEAR CONDUCIVE FOR GRADUAL DEVELOPMENT OF THIS WAVE DURING THE
NEXT FEW DAYS. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT... OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WESTWARD ABOUT 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BLAKE
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Quoting sunlinepr:
The last frame of this picture seems to show a shadow being cast by the eyewall clouds on the west side.Is that eye now totally closed?
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Quoting aislinnpaps:
Did Dr. Masters just say Issac is to take a Gustav track??

gulp, hopefully not as strong lolg
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Quoting aislinnpaps:
Did Dr. Masters just say Issac is to take a Gustav track??
Yeah he said a similar track with a similar storm surge. He also said, he doesn't think Isaac will become a hurricane tonight, probably tomorrow morning.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
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just took a big gulp of dry air
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12z GFS ENSEMBLE at 254HR

Member Since: May 23, 2012 Posts: 0 Comments: 4207
...ISAAC EXPECTED TO BE A HURRICANE SOON...SIGNIFICANT STORM SURGE AND FLOOD THREAT FROM RAINFALL EXPECTED ALONG THE NORTHERN GULF COAST... ...U.S. Warnings in Effect...
7:00 PM CDT Mon Aug 27
Location: 26.7°N 86.5°W
Moving: NW at 10 mph
Min pressure: 981 mb
Max sustained: 70 mph
Member Since: March 16, 2012 Posts: 123 Comments: 7885
BULLETIN
TROPICAL STORM ISAAC INTERMEDIATE ADVISORY NUMBER 27A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
700 PM CDT MON AUG 27 2012

...ISAAC EXPECTED TO BE A HURRICANE SOON...SIGNIFICANT STORM SURGE
AND FLOOD THREAT FROM RAINFALL EXPECTED ALONG THE NORTHERN GULF
COAST...


SUMMARY OF 700 PM CDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...26.7N 86.5W
ABOUT 230 MI...370 KM SE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 295 MI...470 KM SSE OF MOBILE ALABAMA
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...981 MB...28.97 INCHES
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Did Dr. Masters just say Issac is to take a Gustav track??
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slow.mover.tomorrow.morning.tampa.bad.rainbands
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Member Since: July 15, 2006 Posts: 163 Comments: 52197
Pinhole Eye?

Member Since: August 1, 2007 Posts: 0 Comments: 162
Quoting Pirate999:


You're probably right but sub or post, the effects were the same.

Source: http://en.wikipedia.org/wiki/Tropical_Storm_Alliso n

I have pictures of rapids in tunnels under the Penzoil building.


I remember exactly where I was when she came back and the heavy rain started. We were just leaving the Central Market on Westheimer when the sky opened up. And we didn't get that much rain on the west side of town, relatively speaking (except for Richmond Rd, where it was obvious cars had floated.)
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Quoting flwxboy:
Could this be Isaac Part 2?


Since its that far out I wouldn't put much stock in it yet.
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FYI the ECMWF sucks for not providing their model with the rest of the spagetti models. Anyone know what the issue is!!
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Quoting FL1980:
It's funny. Half say the storm is looking better and organizing, the other half says it looks ragged, does anyone know what they are talking about in here?


i do not, but i think it looks a little more organized. he seems to be getting moisture all around so may be able to "close off" an eye
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Quoting angiest:


Tell the hurricane center:

http://www.nhc.noaa.gov/prelims/2001allison4.jpg



Yes, that is Katrina, I lived in Hattiesburg at that time and the Eye came right over our heads.
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I'm 5 miles from the AL border, so one of the MS/AL outliers comes through, we'll be rocking and rolling and we've prepared like it will.

The tropical storm warnings are still up.
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Doc on TWC
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Quoting WxNerdVA:
I'm beginning to think that Isaac is just going to be a big rainmaker, and not much else.



Actually, the main threat is Storm surge.

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Jeff is on!! Watching TWC does pay off!!
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Quoting treehuggingsister:

What?! That's nuts.


yep...they did...
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Dr. Masters is back on TWC!
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Quoting FL1980:
It's funny. Half say the storm is looking better and organizing, the other half says it looks ragged, does anyone know what they are talking about in here?


A lot do...prob is, a bit of both is true with the storm right now LOL

I think there's a bit of....seeing glass half full - glass half empty between people too! Or wishcasters vs downcasters maybe :D
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Quoting truecajun:
does anyone know the best way to prep a wooden swingset for a storm? i'm so sick of having to fix the swingset after storms. we've repaired it twice. it always gets tumbled over and a beam breaks in the process. any suggestions?? my husband is a city boy, so he's not too handy


Anchor it about every three feet with spikes and tie-down straps if you can't lay it obits side. Then wrap the swings over the top and zip-tie them. Been there done that...ummm...and as for a trampoline...just duck and run. I have tried everything and the pool seems to have a trampoline magnet in the bottom of it. Gave it away yesterday...someone elses headache now! ;-)
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Quoting angiest:


Wiki says as a subtropical storm, which I believe is inaccurate. As far as I know, she was post-trop at the time.


You're probably right but sub or post, the effects were the same.

Source: http://en.wikipedia.org/wiki/Tropical_Storm_Alliso n

I have pictures of rapids in tunnels under the Penzoil building.
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My guess is it will have a closed eyewall by 11:00 pm E
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667. drj27
Ok I live in the panhandle fwb I work in destin every place has closed down I mean really it's not even hitting us am I missing something is the track suppose to change because I was on here since 12 untill I got to work and I was like its going west it's not hitting us no one in destin even did this when Katrina hit
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Quoting angiest:


Tell the hurricane center:

http://www.nhc.noaa.gov/prelims/2001allison4.jpg



i will..thanks
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well good night folks..tomorrows another day..stay safe out there
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Quoting JGreco:



wow and they just dropped the warnings for the extreme western panhandle from pcola-destin....wonder if this might be a slight mistake...

What?! That's nuts.
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Quoting uncwhurricane85:


yeah its hurricane katrina, and they do have this pic on allison on wiki, but its for sure not allison...she didnt even have an eye at landfall let alone 4 days after it was over land when it moved in the miss/al


Tell the hurricane center:

http://www.nhc.noaa.gov/prelims/2001allison4.jpg

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Who said RECON had gone home - I'm still seeing two - one is Air Force and the other is NOAA.
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I have never seen such a asymmetrical storm of this size!!!
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Quoting flcanes:

idk
anyways, here is isaac's current damage isaac affects
lesser antilles
3 inches of rain reported on martinque
1 indirect death in puerto-rico
minor costal flooding
road closure
widespread power outages in puerto rico
greater antilles
haiti
8 deaths( minimum)
7- year old electro-cuted
5,000 evacuees
3,000 homeless
360 flooded houses
spike in cholera
president cancels trip
14,000 left homes
13,500 in shelters
12 houses destroyed
269 houses damaged
DOMINICAN REPUBLIC
7,800 evacuees
10 rural towns cut off
santo domingo lost electricity
2 men swept away
2 deaths
cuba
elctricity outages
2 houses destroyed
230 in emergency shelters
guests moved out of rooms
intermmmitent rains
gusty winds


Here in Dominican Republic the evacuees risen up to 25,000
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Quoting truecajun:


is it better to stake or lay down? anyone have experience with both scenarios? it's too big to put in the attached storage room - slide, 3 swings, monkey bars and a little house thingy
I say tie down like you do a mobile home.
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Quoting GTcooliebai:
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
738 PM EDT MON AUG 27 2012

THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* TORNADO WARNING FOR...
NORTHERN HILLSBOROUGH COUNTY IN FLORIDA.
CENTRAL PASCO COUNTY IN FLORIDA.

* UNTIL 815 PM EDT

* AT 739 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
TORNADO NEAR THONOTOSASSA...OR 7 MILES EAST OF TEMPLE TERRACE...
MOVING NORTH AT 25 MPH.

* THE TORNADO WILL BE NEAR...
THONOTOSASSA.
HILLSBOROUGH RIVER STATE PARK.
WESLEY CHAPEL.
SAN ANTONIO.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF YOU ARE IN THE PATH OF THE TORNADO GO TO A SMALL INTERIOR ROOM IN
A STRONG AND WELL CONSTRUCTED BUILDING. CARS AND MOBILE HOMES ARE NOT
SAFE. IF NO SHELTER IS AVAILABLE...LIE FLAT IN A DITCH OR CULVERT AND
COVER YOUR HEAD WITH YOUR HANDS.

TO REPORT SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE PLEASE CALL
813-645-2323.
gee i thought it was over, guess not huh
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Due to this dry slot on the EAST side of the storm, SWFL is again spared any drama. Anyone think we will have another big band form but over the west side of FL? I see a small band starting to slide to the coast now.
Good luck Gulf coasters...
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Quoting Masquer08er:
Ragged, but getting organized?


Half the storm is organizing and the other half is ragged sort of like two face from batman.
Member Since: August 1, 2007 Posts: 0 Comments: 162
Could this be Isaac Part 2?
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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.