ATL: ISAAC - Post-Tropical - Discussion

[PTrackerLA]

Entergy LA power outages up to 544,000 as of 10:05am. Looks like the center is slowly making some WNW progress. Conditions will deteriorate in Baton Rouge shortly but will probably not reach my area until 2pm or later as it looks now.

[ozonepete]

What it means is that Isaac is starting to weaken for sure now. The core is "sinking" means that the tops of the thunderstorms around the center are lowering (weakening storms) so the core is not as high as it was. The boundary layer inversion just means that air is warming just above the surface layer. this also aids in weakening.

So nothing to do with an anticyclone? I was thinking that the boundary layer inversion was an interaction with an upper anticyclone.

No. The boundary layer is the layer from the surface up to a few thousand feet. Here's a pretty good tutorial from U of Wisconsin: http://lidar.ssec.wisc.edu/papers/akp_thes/node6.htm

UL features such as the Upper Level anticyclone over a hurricane are WAY up higher at jet stream level (30,000 to 40,000 feet or even higher). GCANE was talking about two very different things.

[bonjourno]

A possible result of dry air to its West - Isaac may take on a right sided look as weather bulges that way
Lots moisture streamin up from Yucatan and Cuba now
Things reversed - as East Gulf got "wet" - W. Gulf got dry.
http://www.ssec.wisc.edu/data/geo/index ... thod=flash


This post is NOT official forecast and should not be used as such.

So, I'll kinda ask again, what are the chances that the remnants of this thing get pushed off further east than everyone seems to be expecting?

Here's what I mean (sorry if it's hard to see, it was hard to pick colors that showed up well on this backdrop). Black is (roughly) the official cone at the moment; orange dotted line is what I'd think it would do and why I'm wondering why the official forecasts predict what it does.



This post and graphic are NOT in any way an official forecast and should not be relied on as such - they are just my opinion and speculation as an amateur. Please refer to official NHC/NWS products for more information.

[KBBOCA]

Ok, one last comment from me for a few hours...
But I was really pleased to Stacy Stewart's props to the Hurricane Hunters in the 10 a.m. CDT disco:

A SPECIAL THANKS TO THE CREWS OF THE AIR FORCE RESERVE AND NOAA
HURRICANE HUNTERS WHO FLEW A TOTAL OF 34 HAZARDOUS MISSIONS INTO
ISAAC...WHICH RESULTED IN AN IMPRESSIVE TOTAL OF 95 CENTER FIXES.

Indeed!!!! Well done y'all.

[ozonepete]

So, I'll kinda ask again, what are the chances that the remnants of this thing get pushed off further east than everyone seems to be expecting?

Here's what I mean (sorry if it's hard to see, it was hard to pick colors that showed up well on this backdrop). Black is (roughly) the official cone at the moment; orange dotted line is what I'd think it would do and why I'm wondering why the official forecasts predict what it does.

http://i.imgur.com/rmMoF.gif

your question is really difficult to answer easily. There's a lot of complexity to steering and you used the wrong chart from CIMSS. YOu need the chart for a storm with pressure 972 mb. You used one for 1000-1010 which is way too high and thus shows different steering winds. The discussion from Stacy Stewart has a pretty good explanation:

THE INITIAL MOTION ESTIMATE IS 310/5. ISAAC IS EXPECTED TO MOVE SLOWLY NORTHWESTWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE FOR THE NEXT 24 HOURS...AND THEN TURN NORTH-NORTHWESTWARD AND NORTHWARD AROUND THE WESTERN PERIPHERY OF THE RIDGE BY 36 AND 48 HOURS...RESPECTIVELY. BY 72 HOURS...ISAAC IS FORECAST TO BECOME A POST-TROPICAL REMNANT LOW PRESSURE SYSTEM THAT SHOULD MOVE NORTHEASTWARD TO EAST-NORTHEASTWARD WHEN IT WILL BE CAUGHT UP IN WEAK MID-LATITUDE WESTERLIES. THERE ARE CURRENTLY NO INDICATIONS IN ANY OF THE MODEL GUIDANCE SUGGESTING THAT ISAAC WILL TAP INTO ANY BAROCLINIC ENERGY SOURCES THAT COULD RESULT IN EXTRATROPICAL STRENGTHENING OVER THE CENTRAL UNITED STATES. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND IS JUST EAST OF THE MODEL CONSENSUS.

[bonjourno]

Ah, I see. Makes sense. Sorry, didn't even realize there were different steering maps for different intensities. I see now.

[ozonepete]

Ah, I see. Makes sense. Sorry, didn't even realize there were different steering maps for different intensities. I see now.

And that's a really good thing to know for the coming storms.

I will add that this is a bad case to try and learn how steering works because it is very "fuzzy" at the moment. There are strong north winds on the northwestern side of Isaac which one might think would push it southwestward. But they are not close enough to have an effect, and their effect is reduced because they are blowing in the same direction as Isaac's circulation on its left side. In this case there is that "weakness", meaning area of light winds, to its north and northeast which it is now kind of drifting into; it's still going northwest partially just from prior momentum. Eventually it will get far enough north for the westerlies to pick it up and carry it eastward.

[JamesCaneTracker]

I posted a little Update on Isaac on my Blog:
http://www.theweatherwatch.org/hurrican ... louisiana/

[MGC]

Been raining so hard here in Pass Christian that my Direct TV has lost signal. Rain is pounding on the roof....tree debris littering the yard. Typical TS winds....big gusts then backs off a bit. Wish I could get down to the beach to see the surge.....Gonna be a long day.....MGC

[crimi481]

So, I'll kinda ask again, what are the chances that the remnants of this thing get pushed off further east than everyone seems to be expecting?

Here's what I mean (sorry if it's hard to see, it was hard to pick colors that showed up well on this backdrop). Black is (roughly) the official cone at the moment; orange dotted line is what I'd think it would do and why I'm wondering why the official forecasts predict what it does.

http://i.imgur.com/rmMoF.gif

your question is really difficult to answer easily. There's a lot of complexity to steering and you used the wrong chart from CIMSS. YOu need the chart for a storm with pressure 972 mb. You used one for 1000-1010 which is way too high and thus shows different steering winds. The discussion from Stacy Stewart has a pretty good explanation:

THE INITIAL MOTION ESTIMATE IS 310/5. ISAAC IS EXPECTED TO MOVE SLOWLY NORTHWESTWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE FOR THE NEXT 24 HOURS...AND THEN TURN NORTH-NORTHWESTWARD AND NORTHWARD AROUND THE WESTERN PERIPHERY OF THE RIDGE BY 36 AND 48 HOURS...RESPECTIVELY. BY 72 HOURS...ISAAC IS FORECAST TO BECOME A POST-TROPICAL REMNANT LOW PRESSURE SYSTEM THAT SHOULD MOVE NORTHEASTWARD TO EAST-NORTHEASTWARD WHEN IT WILL BE CAUGHT UP IN WEAK MID-LATITUDE WESTERLIES. THERE ARE CURRENTLY NO INDICATIONS IN ANY OF THE MODEL GUIDANCE SUGGESTING THAT ISAAC WILL TAP INTO ANY BAROCLINIC ENERGY SOURCES THAT COULD RESULT IN EXTRATROPICAL STRENGTHENING OVER THE CENTRAL UNITED STATES. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND IS JUST EAST OF THE MODEL CONSENSUS.

Any current data/chart that shows Ridge weakness - or where it will take place in Ridge?

[Elizabeth]

MAN!

Just sitting here bawling! Just saw the most heart wrenching interview with a woman that was just rescued off the roof of a house in Blaithwaite, Plaquemines parish. They had been up there since before dawn. She told the reporter what happened then gave the her name and the name of her son and daughter in law who were still out there waiting to be rescued.

[MGC]

Tornado Warning Bay St Louis Mississippi and Hancock County!

[crimi481]

Large Band starting to take shape in E. Gulf.
Should replace that "Arm" which broke off and now is off N.C. Coast

http://www.ssec.wisc.edu/data/geo/index ... thod=flash

[GCRain]

How are we looking in baton rouge guys?

My phone is tethered, power is out. Can someone explain why it looks like the storms all just die right before hitting us?

Be thankful they are.

[Extratropical1]

MAN!

Just sitting here bawling! Just saw the most heart wrenching interview with a woman that was just rescued off the roof of a house in Blaithwaite, Plaquemines parish. They had been up there since before dawn. She told the reporter what happened then gave the her name and the name of her son and daughter in law who were still out there waiting to be rescued.

Yes sad but if people just complied with the MANDATORY evacuations then they would not be in this grave situation. I do feel for them though and I am glad we have heroes to rescue them. I hope no lives will be lost. I know it sucks to evacuate since I live on the WEST coast of FL near Tampa and have had to do it many times in the last 35 years only for naught. We always seem to get bypassed fortunately but it has really made people extremely complacent. Godspeed!

[rtd2]

Tornado Warning Bay St Louis Mississippi and Hancock County!

Yes and concerned about its Speed of mvt


BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE NEW ORLEANS LA 1049 AM CDT WED AUG 29 2012

THE NATIONAL WEATHER SERVICE IN NEW ORLEANS HAS ISSUED A

* TORNADO WARNING FOR... HANCOCK COUNTY IN SOUTHERN MISSISSIPPI... THIS INCLUDES THE CITIES OF...WAVELAND...DIAMONDHEAD...BAY ST. LOUIS... SOUTHWESTERN HARRISON COUNTY IN SOUTHERN MISSISSIPPI... SOUTHWESTERN PEARL RIVER COUNTY IN SOUTHERN MISSISSIPPI...

* UNTIL 1115 AM CDT

* AT 1045 AM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR BAY ST. LOUIS...MOVING NORTHWEST AT 75 MPH.

[windnrain]

In Braithwaite...

Bad stuff.

[Frank P]

Typical tropical storm conditions at my beach house in Biloxi.. surge is 7- 8 feet at best... seawall is 10ft, and its a good two feet below that.. Gustav put an 11 foot storm surge several years back... no damage anywhere in the neighborhood, still have power.. Gustav taking his sweet time, looks to be moving between NW and NNW, my opinion only... still surprised we only got an 8 foot surge, expecting a little more, but happy no less.. friend reports from BSL and Slidell incidate they are getting much worse conditions and surge.. probably close to 11 feet or so at BSL, unofficial..

[CYCLONE MIKE]

MAN!

Just sitting here bawling! Just saw the most heart wrenching interview with a woman that was just rescued off the roof of a house in Blaithwaite, Plaquemines parish. They had been up there since before dawn. She told the reporter what happened then gave the her name and the name of her son and daughter in law who were still out there waiting to be rescued.

Yes sad but if people just complied with the MANDATORY evacuations then they would not be in this grave situation. I do feel for them though and I am glad we have heroes to rescue them. I hope no lives will be lost. I know it sucks to evacuate since I live on the WEST coast of FL near Tampa and have had to do it many times in the last 35 years only for naught. We always seem to get bypassed fortunately but it has really made people extremely complacent. Godspeed!

But also it puts the rescue teams that have to go out in this at risk for injury and death themselves to have try and save these people who refuse to listen and adhere to gov't officials. If they would have to start having to pay back for the rescue efforts or fined then maybe next time they will listen better.

[Extratropical1]

MAN!

Just sitting here bawling! Just saw the most heart wrenching interview with a woman that was just rescued off the roof of a house in Blaithwaite, Plaquemines parish. They had been up there since before dawn. She told the reporter what happened then gave the her name and the name of her son and daughter in law who were still out there waiting to be rescued.

Yes sad but if people just complied with the MANDATORY evacuations then they would not be in this grave situation. I do feel for them though and I am glad we have heroes to rescue them. I hope no lives will be lost. I know it sucks to evacuate since I live on the WEST coast of FL near Tampa and have had to do it many times in the last 35 years only for naught. We always seem to get bypassed fortunately but it has really made people extremely complacent. Godspeed!

But also it puts the rescue teams that have to go out in this at risk for injury and death themselves to have try and save these people who refuse to listen and adhere to gov't officials. If they would have to start having to pay back for the rescue efforts or fined then maybe next time they will listen better.

AGREED!!