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 9030mike:
Am I wrong in saying that it doesn't look like Isaac has a ton of rain with it on radar? A lot of green, not much yellow or red. Is the rain factor overhyped?


It did not have a "ton of rain" in it over S Fla but if you were under one of those training bands with heavy rain for 2 days... 12.5" of rain is a lot of water.

and a few areas north of me got same amount.
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2903. HCW
Mesoscale Discussion 1826



< Previous MD




MD 1826 graphic





MESOSCALE DISCUSSION 1826
NWS STORM PREDICTION CENTER NORMAN OK
0701 AM CDT TUE AUG 28 2012

AREAS AFFECTED...PORTIONS FL PANHANDLE...SRN AL...EXTREME SERN
MS...COASTAL EXTREME SERN LA.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 281201Z - 281430Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TC-RELATED MINI-SUPERCELLS AND RELATED TORNADO POTENTIAL
MAY BEGIN TO AFFECT GULF COASTAL AREAS...MAINLY BETWEEN
AAF-GPT...THROUGH LATE MORNING LOCAL TIME. SUBSEQUENTLY...RISK MAY
SHIFT INLAND IN STEP WITH BOTH SHOREWARD TRANSLATION OF ISAAC AND
PACE OF INLAND DIABATIC DESTABILIZATION. INITIAL THREAT AREA MAY BE
TOO NARROW WITH MRGL TORNADO THREAT...LENDING SOME UNCERTAINTY AS TO
NEED FOR WW. HOWEVER...THREAT MAY INCREASE INLAND DURING DAYLIGHT
HOURS.

DISCUSSION...ISAAC CONTINUES TO MOVE NWWD TOWARD SERN LA
LANDFALL...PER NHC FCSTS. AS THIS OCCURS...FAVORABLE LOW-LEVEL WIND
FIELDS AND BOUNDARY-LAYER SHEAR FOR SUPERCELLS WILL OVERSPREAD
PROGRESSIVELY LARGER PORTION OF THIS AREA. MAIN LIMITING FACTORS
HAVE BEEN...AND WILL REMAIN...TWOFOLD--
1. EXTENT AND MAGNITUDE OF SUPPORTIVE INSTABILITY.
2. CONVECTIVE MODE AND COVERAGE...WITH SUSTAINED/DISCRETE ACTIVITY
BEING MOST FAVORABLE FOR CELL-SCALE ROTATION.

UNTIL SUBSTANTIAL DIURNAL HEATING OCCURS INLAND...PRIMARY CONCERN
FOR TORNADOES WILL BE WITHIN 15-20 NM OF COAST. SFC MESOANALYSIS
SHOWS RELATIVELY SHARP LAND/SEA THERMODYNAMIC GRADIENT...WITH INLAND
TEMPS/DEW POINTS AROUND 77/73 RESPECTIVELY COMPARED TO AROUND 82/76
IN PRECONVECTIVE/NEARSHORE MARINE ENVIRONMENT. AS CENTER OF ISAAC
PROCEEDS NWWD...GRADUAL VEERING OF FLOW WITH TIME ALONG COAST SHOULD
ADVECT MARINE LAYER SLIGHTLY INLAND. OVERALL WEAKENING IS EXPECTED
FOR ANY ECHOES CROSSING THAT BOUNDARY...HOWEVER CONVERGENCE ALONG
IT...AND BACKED FLOW JUST TO ITS N...WILL SUPPORT POTENTIAL FOR
BRIEF INTENSIFICATION OF ANY PRE-EXISTING MESOCYCLONES. FARTHER
INLAND...SUBTLE SFC TROUGH AND CONFLUENCE LINE -- ALSO CORRESPONDING
TO DEW POINT GRADIENT THAT MARKED SRN EXTENT OF SW-NE SWATH OF
LOW-LEVEL DRYING -- WAS DRAWN NEAR BHM-GPT LINE...AND WAS
QUASISTATIONARY. THIS BOUNDARY ALSO IS EVIDENT IN AUTOMATED
MESOANALYSES OF SFC VORTICITY...EFFECTIVE SRH AND ALONG NWRN EDGE OF
WEAK MLCAPE PLUME. BY ABOUT 14-16Z...HEATING OF INLAND AIR
MASS...UNDER RELATIVELY CLOUD-DEPRIVED SLOT EVIDENT IN IR
IMAGERY...WILL MAKE INTERIOR BOUNDARY MORE IMPORTANT BY BOOSTING
MLCAPE AND REDUCING CINH ALONG AND TO ITS S.

A FEW SMALL/SHALLOW ECHOES HAVE EXHIBITED WEAK CYCLONIC SHEAR
OFFSHORE AND INVOF AAF. HOWEVER...AMIDST APPARENT WEAK LOW-LEVEL
LIFT...CONVECTION HAS BEEN RATHER SPARSE...LACKING BOTH INTENSITY
AND TIME CONTINUITY. GIVE ABOVE FACTORS...CONVECTIVE TRENDS
PROBABLY WILL BE MAIN DETERMINANT IN ANY WW DECISION THIS MORNING.

..EDWARDS/THOMPSON.. 08/28/2012

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re: 2867
You have posted that photo twice and you made that childish remark about two meteorologists.
Enuff! POOF!!
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Landfall probably near area South Of Houma, La.

Slow forward speed is not good... Convective

activity is definitely increasing closer to the COC.
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Quoting lobdelse81:

Wouldn't this correspond to surface sustained winds at 85-90mph?



yep and it still has other 18 too 36hrs overe water
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
Quoting JasonRE:
In Lafayette awaiting this storm. I saw a couple of other posts from people in Lafayette asking if they should be worried. I'm worried but it seems like nobody here at work is at all. 1 to 2" of rain? Really? With a storm this size possibly making landfall slight West or directly on top of us? I just don't understand how we only get a small amount of that rain, especially with that slow forward movement. I know the West side is better than the East, but how do we not get anything when TWC has us in, possible power outage, wind variables for possible tropical storm winds/squalls, and rain-fall possibilities upwards to 6-12"?


Key words here or Possible just keep an eye on it
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why isnt twc putting someone on the northshore? its flooding.
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Am I wrong in saying that it doesn't look like Isaac has a ton of rain with it on radar? A lot of green, not much yellow or red. Is the rain factor overhyped?
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anyone got the latest models and when did they come out?
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Mobile, Alabama here...

Working at the courthouse downtown today because the "powers that be" decided that it wasn't necessary for us to be closed, even though the courthouse is in a mandatory evacuation zone. I hope this decision doesn't turn out bad for anyone.
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Good morning and now all eyes are on the northern Gulf areas as Isaac draws close.


My neighborhood ended up with 12.5" of rain and severe flooding.. pictures are in my blog.

but we never got water in the house so that is good.

We had to have police blocking every entrance to our neighborhood to keep people out who do not live here.
We were on all the local news channels and had a news helicopter flying over yesterday afternoon.
All the neighbors and kids, big and little, went out to play in the rain water after it finally stopped..
we were all stir crazy after being cooped up for 2 days...

Details are in my blog..


Thanks to all of you who send notes or stopped by my blog it was nice knowing we had so much support.

Now our prayers are for the next areas in Isaac's wake..
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When Isaac is all gone, I would love to discuss how and why he split over Florida if anyone is up for it. I found this particular action over Floria to be one of the strangest things I've ever seen a tropical cyclone do.
Member Since: September 9, 2005 Posts: 0 Comments: 562
Quoting mcluvincane:
88 flw is definitely a cane


Over a very wide area as well...Very wide.
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Mississippi River stages New Orleans and South

Link
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we should pay the nhc to give advisories every hour
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Quoting Dunkman:
Kermit just found an 88 knot FL wind...it's definitely a cane.

Wouldn't this correspond to surface sustained winds at 85-90mph?
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2886. TXCWC
Actually GFS looks JUST AS FAR WEST AS EURO IN 48 hrs - only further north. So BOTH GFS AND EURO show a westward movement - just a question of when- AND WHEN MAY MAKE A DIFFRENCE IN WHEATHER OR NOT ISSAC CAN GET TO CAT 1 OR EVEN 2 STRENGTH

GFS 48hrs


EURO 48hrs
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2884. Hhunter
Quoting weatherh98:


i dont think thats the case haha
definetly wrong. By pressure alone it has been a cane for 24 hours...
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Quoting mcluvincane:
88 flw is definitely a cane


Probably 80mph at the surface.

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Quoting Tazmanian:




i think this could really ramp up too a cat 2 or 3 storm this is looking more and more likey now


Taz, I sure hope not. We will see.
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2880. JasonRE
In Lafayette awaiting this storm. I saw a couple of other posts from people in Lafayette asking if they should be worried. I'm worried but it seems like nobody here at work is at all. 1 to 2" of rain? Really? With a storm this size possibly making landfall slight West or directly on top of us? I just don't understand how we only get a small amount of that rain, especially with that slow forward movement. I know the West side is better than the East, but how do we not get anything when TWC has us in, possible power outage, wind variables for possible tropical storm winds/squalls, and rain-fall possibilities upwards to 6-12"?
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2879. Hhunter
Quoting weatherh98:


Im expected to have 9-15 feet of water. problem is my house is roughly 14 feet up
Don't forget waves on top of that....
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88 flw is definitely a cane
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Quoting mbar62:
The only way this storm makes it to hurricane strength before landfall is for the NHC to make it so to cover its embarrassment for a blown forecast. This is nothing more than a strong tropical storm that, thankfully, keeps getting disrupted by dry air.



i dont think thats the case haha
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Wow--- not seeing that over here just north of Destin on the bay, it might be up a little, but no where 6 feet.
Quoting mfcmom:
If people don't think this storm surge issue is real think again. I live in Panama City beach, inland approx 8 miles on a waterway that dumps into St. Andrews Bay and the Gulf. Our boat came up over six feet last night, water is over the dock and it hasn't even rained here yet. Just saying. Can see the bottom of the pontoon boat which will probably be in my back yard before end of day, interesting the water is flat and smooth.
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Quoting iceman100:
The biggest impact of this storm won't be on New Orleans. It will be from the rain it brings to the parched U.S. heartland.


unfortunately, the parched soil isn't going to rapidly absorb a lot of that rain...there will be a lot of runoff if the rainfall rates are too high.
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2874. Hhunter
with an eye of course it's a hurricane. Man the hurricane center needs to think of a new way of classification. Combination of pressure, and wind. Just like Ike was really a 3 because of pressure and size. Wind alone is a bad judge. Hang on LA this is worse than you think.... Prayers.
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2873. Dunkman
Kermit just found an 88 knot FL wind...it's definitely a cane.

Peak (10s) Flt. Lvl. Wind: 88 knots (~ 101.2 mph)
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Quoting GetReal:
The the easterly fetch interacting with friction against the coastline of MS and SE LA is causing convection to form to the north of Isaac, is assisting him in strengthening. Watch for a feeder band to form just south of the MS coast, filling in the N side of Isaac today.




It's pulling in dry from the Midwest. I think we can thank the Midwest drought for issac not RI-ing.

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2871. mbar62
The only way this storm makes it to hurricane strength before landfall is for the NHC to make it so to cover its embarrassment for a blown forecast. This is nothing more than a strong tropical storm that, thankfully, keeps getting disrupted by dry air.

Quoting weatherh98:


pressure isnt dropping anymore, the winds are (finally)catching up
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holy we cows noaa recon this found 87kt and 88kt fight level winds
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
Quoting mfcmom:
If people don't think this storm surge issue is real think again. I live in Panama City beach, inland approx 8 miles on a waterway that dumps into St. Andrews Bay and the Gulf. Our boat came up over six feet last night, water is over the dock and it hasn't even rained here yet. Just saying. Can see the bottom of the pontoon boat which will probably be in my back yard before end of day, interesting the water is flat and smooth.


Im expected to have 9-15 feet of water. problem is my house is roughly 14 feet up
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2868. GetReal
The the easterly fetch interacting with friction against the coastline of MS and SE LA is causing convection to form to the north of Isaac, is assisting him in strengthening. Watch for a feeder band to form just south of the MS coast, filling in the N side of Isaac today.


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2866. mfcmom
If people don't think this storm surge issue is real think again. I live in Panama City beach, inland approx 8 miles on a waterway that dumps into St. Andrews Bay and the Gulf. Our boat came up over six feet last night, water is over the dock and it hasn't even rained here yet. Just saying. Can see the bottom of the pontoon boat which will probably be in my back yard before end of day, interesting the water is flat and smooth.
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Good morning everyone!

So for a storm that was WAY west of Florida yesterday, we here in the area of Ft Pierce/St Lucie, Florida got a pretty good bit of flooding. Isaac apparently had one very long rain band that went from south Florida to north Florida and just slowly walked up the state lol.

This is what my apartment parking lot looked like around 3pm last night.
Link
We had many road closures, and our studio had to shut down early.

Stay safe out there and never forget that flooding is often the overlooked and most devastating part of these storms.
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The biggest impact of this storm won't be on New Orleans. It will be from the rain it brings to the parched U.S. heartland.
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pressure is 1004.5 in mandeville
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Quoting Dunkman:


Intensity forecasting is pretty awful. The NHC can barely beat the SHIPS Decay model (3 year average is a 10% improvement), and in fact got owned by it to the tune of 20% after 36 hours in 2011. 4 days ago this could have been a TS at landfall and it could have been a category 4. 2-3 was the most likely. If you err on the high side then less people die than when you err on the low side. What would you have them do?


I know that the Intensity is the weakest part of the Technology for forecasting a Hurricane.. There's more to the story but if u want to know more.. Email me b/c obviously its going to offend a lot of ppl on here and this blog.. I really like this blog since 1995 when I first started lurking then.. And a few years after that I signed up under a different name then.. I have been in some close calls with these storms when Intensity was the difference..
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2860. CJ5
Quoting Tazmanian:



no we wont


this storm starting too rapid intensification recon and now noaa are finding a lot of 80 too 85kt fight level winds this storm is really starting too get it act togeter and will do so in tell it makes land fall


If I had a dollar for everything someone said it was about to RI, I would be rich. He has had every opportunity to intensify over the past 5 days and has petered out every single time. It is possible he could but history tells us he won't.
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Quoting Tazmanian:



no we wont


this storm starting too rapid intensification recon and now noaa are finding a lot of 80 too 85kt fight level winds this storm is really starting too get it act togeter and will do so in tell it makes land fall


pressure isnt dropping anymore, the winds are (finally)catching up
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Quoting weatherh98:


Its apparent that its dealing with dry air

surge may be higher because of the slow down


That and he has a MASSIVE area of winds in his eastern and southeastern side.
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Hello, Baton Rouge here. Just did a drive around town. Last night, I-10 was bumper to bumper, backed-up from Miss. bridge to Gonzales. This morning, hardly any traffic. Stay safe.
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Getting our 1st hard rain in Ocean Springs, MS winds still light
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Quoting AtHomeInTX:


Yeah I saw that and farther west. I haven't seen any other model like that though.


This may come in just east of Houston.

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Early 1200z runs - pay attention points west of NOLA. BAM models good short term early models for weak tropical systems.
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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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