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TS Isaac


BullCityWx

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Hey, Psalm, I guess the picture won't clear until it breaks into the gulf good. I feel like it won't go up the east coast at this point, but I guess it might flip and flop a few hundred miles along the gulf coast before it hones in on a beach it likes :) I'm glad the 12z has moved it off our road, as the old adage of not wanting to be in the bullseye a few days out with a snow storm, probably counts with hurricanes too, lol. As for Opal, that one took my shed roof and shoved it in the bathroom window. Big shed, small window. I can do without the wind, but with hurricanes if you wants the rain, you takes the winds, unfortunately, lol. Even if it is a big miss for us, I hope we get some rains eventually. And after, I wouldn't be suprised to see some stagnant air, and 90's. I won't feel safely free of summer, and 90's, until after the 15th, based on last year. T

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Unless the models are underestimating the strength of the trough or overestimating the speed of it, I don't see how it doesn't take the farther west path that the Euro has been showing for days. It seems the SE tropical storm shields are holding strong for yet another season.

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I will be interested to see if this was a hiccup on the 12z GFS or maybe the start of something new...

Something I noticed in the mid latitudes...6z run @ 81 hours (11 am Tuesday) has a s/w (1 contour) closed low just off the Oregon Coastline...slight negative tilt as well. That created a taller ridge in the Rockies/Plains and an Eastern trough axis following the contours which runs roughly from Memphis up into a closed low east of Hudson Bay. The trough was just sharp enough to pull Issac NNE.

The difference in the 12z run was that the Pacific s/w was a bit faster and had opened up. Meanwhile the Hudson Bay low was placed a tad farther north, the trough axis was the same but it just wasn't sharp enough

Anything coming out of the Pacific is void of real-time data so there's always a chance that could be either stronger or weaker which can wreak havoc in the entire flow...which could prove huge in the determining the ultimate destination of Issac.

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I will be interested to see if this was a hiccup on the 12z GFS or maybe the start of something new...

Something I noticed in the mid latitudes...6z run @ 81 hours (11 am Tuesday) has a s/w (1 contour) closed low just off the Oregon Coastline...slight negative tilt as well. That created a taller ridge in the Rockies/Plains and an Eastern trough axis following the contours which runs roughly from Memphis up into a closed low east of Hudson Bay. The trough was just sharp enough to pull Issac NNE.

The difference in the 12z run was that the Pacific s/w was a bit faster and had opened up. Meanwhile the Hudson Bay low was placed a tad farther north, the trough axis was the same but it just wasn't sharp enough

Anything coming out of the Pacific is void of real-time data so there's always a chance that could be either stronger or weaker which can wreak havoc in the entire flow...which could prove huge in the determining the ultimate destination of Issac.

Just after the 12Z GFS shows a sig. westward adj. the 12Z Euro adjusts 100 miles eastward on the FL panhandle. It then

moves slowly into far SW GA and then continues NE from there. Confusing!

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EURO goes EAST landfall near PCB....Weakness is DEF. stronger this run...AND this is a potent CANE

Dave Tolleris is probably in mourning :cry: after seeing the Euro finally cave in to what the GFS has been saying for a couple days...

I will be very interested to see Robert's update on his site, he's gonna post something after digesting the 12z suite...

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12Z Euro

Unless the models are underestimating the strength of the trough or overestimating the speed of it, I don't see how it doesn't take the farther west path that the Euro has been showing for days. It seems the SE tropical storm shields are holding strong for yet another season.

:arrowhead: Cold Rain :arrowhead:

:axe:

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One thing that has markedly changed with the guidance this morning is that the vertical wind shear expected over the gulf has been substantially reduced. Both the GFS and ECMWF now project a near perfect upper level pattern over Isaac in the 24-72 hour period with almost no restriction of outflow. While my forecast this morning of a hurricane before interaction with the Florida Keys might be on the high side, my second landfall intensity prospects look good and are probably on the low side given the expected upper level pattern. In fact, there is a possibility that 3 separate outflow channels may develop, which is normally only seen with the most intense tropical cyclones.

This possibility of RI is certainly increasing as long as Isaac is not too disrupted by its trek across Cuba.

200hPa2_8_25_12.gif

Great post Phil, and I have to agree that the RI potential is definitely worrying with the upper-level setup Isaac will have over the Gulf. I truly think all of this worrying about Isaac being too disrupted by Cuba is overblown.... obviously the major models disagree with it, and there is plenty of time for Isaac to recover.

Isaac has potential.

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^^

That map was a little out of date

Thanks.

Well, still thinking that same path. The new updated map has it moving differently once it hits the southern Apps I see. I like the northerly/easterly moving solutions better.

In other words, I am throwing out the current GFS.

I think we are in for a ride here in the South-East! Hopefully it busts the drought in Georgia.

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Thanks.

Well, still thinking that same path. The new updated map has it moving differently once it hits the southern Apps I see. I like the northerly/easterly moving solutions better.

In other words, I am throwing out the current GFS.

I think we are in for a ride here in the South-East! Hopefully it busts the drought in Georgia.

It would be nice if we could get a drought busting rain, but I get the feeling the heaviest rain in GA will be from Columbus to Macon to Augusta and points south and east. I think there will be a tight rainfall gradient with not too much rain in North and West GA. At least that's what it looks like from that HWRF map. Mostly south of I-85.

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Always great discussions over at Wunderground. Here is what Bamatracker posted.

NWS Mobile

SURFACE LEVEL HAND ANALYSIS DEPICTS THE HIGH

PRESSURE FEATURE ACROSS THE EAST COAST NOT AS PRONOUNCED AS THE GFS

INITIALIZATION. THIS MAY RESULT IN THE 26/0000Z GFS RUN SWINGING ITS

SOLUTION BACK TO THE EAST IF THE INITIALIZATION PACKAGE REFLECTS A

TRUER OBSERVATION.

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I wrote this in 2005:

I've found 14 tropical cyclones that have produced 5"+ rain in ATL since 1879:

-Seven of the 14 were in JUL, two in AUG, three in SEP, and two in OCT

- The most common single landfall area for the 14 was Ft. Walton Beach/Destin (FIVE of the 14). TWELVE of the 14 were Gulf coast hitters (range C LA to Panama City) while TWO were east coast hitters (including Jeanne from 9/2004.)

- Most (ELEVEN) were moving NNE, NE or ENE. One was moving N, one NNW and one WNW.

- Closest approach of center to ATL for the 14:

- FOUR very close to ATL

- ONE extreme NW GA

- ONE Chattanooga

- THREE NE AL

- ONE SW AL (Dennis of 7/2005 in a very unusual location)

- TWO Macon

- TWO S GA

Larry, was there any correlation with pressure/ strength at land fall? My guess is weaker storms..but then I'd probably bet against myself, for all the good my guessing does. I'm sure steering has a lot to do with how long it's overhead :) It just seems to me the strong ones blast through here.... the more wind, and tornados, the less the rain. To get over 5 means it's crawling, so it's weakened down south, and maybe wasn't so strong when it came in. Thanks, T

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true but Robert best around. All know that

whoa easy there! There's plenty better than me, I just wanted to show how I use a different approach to forecastinga lot of times. And I spelled out why I'm leaning toward a recurvature on this one, but honestly tropical forecasting is my weakest point. It could easily go to New Orleans for all I know. I think it's easier to forecast snow, much easier. Some of the reasons I pointed out :

1) A wet Alabama to Carolinas

2) All Summer long, except the heatwave, there’s been a graveyard of fronts around the Southeast and TN Valley to NC.

3) Weak upper low near Florida, helping to pull Isaac north initially today (more so than most models showed)

4) Climatological tendency for Florida Panhandle storms to hook north/northeast.

Plus the NHC has been pretty good with staying ahead of the changes on this, like the north jog today, whereas the ECMWF didn't like going north of Cuba for a long time, now looks like it will. The 18z NAM just in looks about right to me, maybe too fast though. The front should come into the TN Valley again (notice we've had a lot of these this Summer?), and be a weakness that TS like to take. When the outflow meets the front in southern VA stretching southwest to Alabama, then that whole area is game for a steady rain, and will become a baroclinic zone for the center of circulation to eventually ride along, maybe even splitting the circulation up. If the front is too fast though or the storm enters from too far west, then the whole thing changes and Isaac continues northwest, not recurving.. One other thing is how quickly all models deepen the center suddenly west of Tampa in the Gulf. Conditions could be just right for excellent outflow and nothing to stop it from growing by the minute right up until landfall, whereever that is...maybe even CAT 3...although I'm leaning Cat 2 or low 3...either way, very big deal. When TS hits land, plus a front nearby, the moisture spreads out from SW to NE in this case, so a Georgia drought buster is definitely coming as long as that track verifies, although Southeast GA may not get that much removed from the dynamics and constant training. Right now, Atlanta would be in a very bad spot and maybe Upstate to the southern mtns of NC thanks to how the storm initially pulls in moisture and upslopes , then it transitions to frontal rain induced, then transitions to being a path that the center of circulation takes and as you know being under the north quadrant of a TS wall is a good place to see extreme rain amounts and rainfall hourly rates..so somebody will get flooded. Also, tornadoes usually occur well inland even to NC from systems that hold their low level circulations for a long time, so I'm forecasting twisters (weak) in Al, GA and both Carolinas if this goes like my early call.

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