Wx: October 13-14

stuff that doesn't fit anywhere else.
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Wx: October 13-14

Post by KoD » Thu Oct 09, 2014 1:26 pm

I am hoping somebody else here likes meteorology, so i'll just delve into it...

Past several runs on the GFS (Global Forecast System) have been showing a deep trough dig through the SE CONUS... Given orientation of boundary, 500mb winds and surface pressure envelope the storm mode looks to be linear, but the fine details can be hammered out as the event nears. Hodographs on the 12z also show some nice curvature. It's advertising 500mb wind speeds over 70 knots Monday, opening up around the Ozark Mts-ArkLaTex. This strengthens and continues eastward; however the CAPE is not as high with this expansion.

The ECMWF is slower with regards to how fast this feature ejects NE, so timing is another big thing to be worked out. Finally I am wondering how warm the upper atmosphere will be for this event... The thermodynamics don't seem particularly impressive although the system has a lot of potential.
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Re: Wx: October 13-14

Post by Django » Thu Oct 09, 2014 3:31 pm

i saw the lunar eclipse that other day
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Re: Wx: October 13-14

Post by Ian7 » Thu Oct 09, 2014 7:31 pm

Can you put this into terms an layman can understand...
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Re: Wx: October 13-14

Post by Eviltechie » Thu Oct 09, 2014 11:52 pm

Ian7 wrote:Can you put this into terms an layman can understand...
No kidding. Weather is fun, but what you said is just too much for j2ers. You won't get any meaningful conversation.
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Re: Wx: October 13-14

Post by KatanaRama » Fri Oct 10, 2014 12:18 am

Is this supposed to be a statement or a question? Because something tells me you just threw in a bunch of meteorology terms to confuse people who would bother to read this.
However in doing so, you haven't made this into either a question or a statement. Both of which are essential to conversation.
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Re: Wx: October 13-14

Post by Django » Fri Oct 10, 2014 2:06 am

sooo hows the weather
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Re: Wx: October 13-14

Post by KoD » Fri Oct 10, 2014 11:43 am

This is meteorological layman speak, but I'll be glad to convert it to more sensible English. (EDIT: by meteorological layman, i mean a non-expert who knows a bit about weather forecasting)
KoD wrote:Past several runs on the GFS (Global Forecast System) have been showing a deep trough dig through the SE CONUS...
GFS is a weather model ensemble that runs four times a day. The "ensemble" means it predicts what is going to happen in the atmosphere over and over and over, then averages all of those runs together to produce a final product. A trough is, well... best explained by this drawing I found online just now:

Image

If you take one of the numerous jet streams overhead, they don't simply flow west to east in a straight line. They'll crunch and bend like boiling spaghetti or KatanaRama's pencil.
Here's another illustration
Image

The jet is still flowing west to east, but the "kink" in the line is jacking things up a bit. In that particular example, I'd expect the more extreme weather to be safely off in the Atlantic ocean while the center of the US is enjoying the ridge. So that's ridge vs trough.
SE CONUS = South Eastern Continental United States
KoD wrote:Given orientation of boundary, 500mb winds and surface pressure envelope the storm mode looks to be linear, but the fine details can be hammered out as the event nears.
By linear storm mode i am equating this to a squall line which is defined as "a narrow band of high winds and storms associated with a cold front." Here's an illustration:
Image
This storm wont look like this one however... It will be more north/south to NNE/SSW oriented and around East Texas, Arkansas, Louisiana ... translating eastward towards Mississippi, Kentucky, Tennessee, Alabama etc...

500mb = 500 millibars is a measurement and correlates to about 18,000 feet. As mb measurements go up (say to 850 [5k feet]) the distance goes down. 850mb is closer to the surface than 500mb. 1000 millibars is about surface level. 500mb is important to storms; it's where you assess for variables like vorticity advection, trough and ridge patterns (which was vaguely explained above) and shortwaves. Vorticity is a spin to the air parcels, which is also important... but complicated so we can go over that later if anyone is actually interested and still reading this.

The surface pressure envelope is basically contouring around altered regions of pressure (highs and lows). If you recall the above image of the troughing, you'll see a big red L above the kinked lines. You can think of these as a "dimpled" region of the atmosphere.
Here's an illustration:
Image
Over Illinois you can see a low pressure region and it's associated contours outlining the regions of the atmosphere that are being effected by it... that is, areas where our instruments or models have detected that the pressure has changed. If you have a new fancy smartphone, you may have a barometer in it to check surface pressure! Of course, you really want to know the surface pressure at 500 millibars (where half the mass of the atmosphere is above, and half is below) instead of at ~1013mb.
KoD wrote:Hodographs on the 12z also show some nice curvature. It's advertising 500mb wind speeds over 70 knots Monday, opening up around the Ozark Mts-ArkLaTex.
Ozark mts are in west Arkansas and East Oklahoma.. Arklatex is the Texas Arkansas Louisiana region (Texarkana, my hometown :D). 70 knots = 80 mph
Oh timescales... z is Zulu.
If you live in CDT:
00z = 7pm
18z = 1pm
Since we are still on our summer solstice timescale, we'll subtract "5" from whatever time Zulu is.. so 12z - 5 = 7am (CDT)

Hodographs are cool, but complicated. I wont explain them fully. Basically they show the change in direction of wind with height
Image
Important, especially if you want to know if there will be enough rotation to support tornadoes (among other uses).
KoD wrote:This strengthens and continues eastward; however the CAPE is not as high with this expansion.
CAPE is Convective Available Potential Energy and is a measurement of instability. This event looks to be low in instability, but very high in low level shear (change in wind direction and speed with height). If the CAPE was expected to be high, this would be looking very nasty...
KoD wrote:The ECMWF is slower with regards to how fast this feature ejects NE, so timing is another big thing to be worked out. Finally I am wondering how warm the upper atmosphere will be for this event...
ECMWF = European ensemble model forecast... they don't let us (non-Europeans) use their stuff though without charging $$$.
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KatanaRama wrote:Is this supposed to be a statement or a question? Because something tells me you just threw in a bunch of meteorology terms to confuse people who would bother to read this.
However in doing so, you haven't made this into either a question or a statement. Both of which are essential to conversation.
Just because you can't understand a foreign language doesn't mean what was said isn't a statement. Hows about we make this a conversation that you're not apart of?

As far as the current situation, the timing has not improved. NAM (North American Model) is flaunting this thing later than the GFS... although I haven't had much time to check run to run consistency yet.
I am more than glad to explain all of this. I was hoping somebody here may already be a bit versed in the field so that we could have nerdy discussions about what's going to happen in the future
Image

EDIT: OH! I almost forgot, here's the website I use for most of my model analysis: http://weather.cod.edu/forecast/
HRRR & RAP and short-term, rapid refresh models.. they only go out like 12-24 hours respectively (give or take)
NAM is medium-term, good resolution... the NAM 4K is short to moderate term and very high resolution, although from that site it seems to be down (at least for me) ... so I use the NWS page here: http://mag.ncep.noaa.gov/
GFS & ECMWF are long range models, although you'll get the most data from GFS since the Euro Guyszzz are data hogs and "funding the server costs money blahblahblah"

There's more models, data and stuff available at other websites, you just have to do some digging. That one as far as I know is the best.
You can view live satellite imagery from GOES here: http://weather.msfc.nasa.gov/GOES/

EDIT EDIT: Latest runs on the ECMWF pick up the low level jet (700mb + 850mb) up to 60+ knots! If that holds, it will definitely increase our risk for severe damaging wind gusts. Given some of the other latest parameters, shear vectors and such... I'd not be surprised if there were to be numerous embedded tornado warnings while this system moves through, especially in the aforementioned lower Mississippi valley.
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Re: Wx: October 13-14

Post by Django » Fri Oct 10, 2014 6:53 pm

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Re: Wx: October 13-14

Post by Malone » Fri Oct 10, 2014 7:26 pm

Even in layman's terms I didn't understand. Heh, that goes to show how much I pay attention in school 8O
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Re: Wx: October 13-14

Post by KoD » Sun Oct 12, 2014 11:34 am

Still looking to be a nasty setup. If you live in this region:
Image

Have a plan ready in case of dangerous weather

Threat still being analyzed further east, but it still looks like discrete cells are a possibility.... and if they do erupt, they can be tornadic and dangerous
Image
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Re: Wx: October 13-14

Post by Ikri » Sun Oct 12, 2014 4:32 pm

RANDOM QUESTION is it a bad idea to go to New Orleans in November? Or is that not hurricane/scaryshit season? I sure as fuck don't want to get stuck in what you southerners consider "not great weather." The other day I didn't have a jacket and it was like 62F outside WHICH WAS NOT COOL, I was not prepared.
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Re: Wx: October 13-14

Post by KoD » Mon Oct 13, 2014 3:36 pm

Hurricane season is over at the end of November, so probably not a bad idea. The weather wont be as hot... but it's also New Orleans.. so it'll be humid and cool probably. I'd guess... 60-70F highs, maybe 45-55/60 lows?
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Re: Wx: October 13-14

Post by scobywhru » Mon Oct 13, 2014 4:13 pm

Seems like that is happening farther East than normal.
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Re: Wx: October 13-14

Post by KoD » Mon Oct 13, 2014 4:27 pm

scobywhru wrote:Seems like that is happening farther East than normal.
You're right, the inline image used was not static so what was shown was the day 2 outlook even though the highest risk for severe weather is today. I edited the post to make it show the proper day 1 outlook. (That of course will only last for today)

EDIT: Threat over for Dixie alley, continues for Atlantic coast states through the day.
Thankfully not too much damage reported in the area. Several trees down, roofs blown off.. etc...
List of reports can be found here: http://www.spc.noaa.gov/exper/archive/e ... e=20141013
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Re: Wx: October 13-14

Post by Chaos Wake » Tue Oct 14, 2014 5:38 pm

I remember a few years ago I was in Indiana right when NOAA was basically reporting a near absolute certainty of multiple tornados in the region I was in (Bloomington, Indiana).

Amazingly we didn't get hit, but neighboring towns got clobbered.

It was kind of like waiting on getting hit by an artillery bombardment that never came.
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