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Central PA - February 2017


MAG5035

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Hey, just took a look at a bunch of runs/data, it is pretty up in the air, but I see enough to warrant keeping a close eye on things. Keep in mind in our neck of the woods the main threat is wind damage and heavy downpours as opposed to areas getting hammered tonight.



It's been bad out there; even bad in areas pretty far away from MDT risk area. Ottawa, Ill, 60 miles wsw of Chicago has been under a severe thunderstorm or tornado warning 7 different times. Tornado just formed in south east Kansas near front in area with temperatures in high 50's and dewpoint in the 40's.


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5 hours ago, 2001kx said:

How does tomorrow look up my way?

I hate severe storms (wind mainly) Im surrounded by huge pine trees.

I don't think our area will be as potentially favorable as the Sus Valley. We will probably have to watch the frontal passage for severe winds, maybe a line or two of storms that fires up ahead of that. 

The Sus Valley will have the benefit of the frontal passage coming through later in the day towards the evening and will also be the region that stands the best chance of clearing in the afternoon. If we end up with more cloud cover that will reduce CAPE, which will inhibit other severe parameters...specifically the tornado and discrete cell/supercell threat. The wind threat should be mostly region-wide, with the Sus Valley having the highest potential as there will still be some marginal CAPE to work with even if the clouds win. A line of storms that forms has the potential to tap down the deep unidirectional wind field aloft that is very robust wind-speed wise. 

I know the terms and jargon can get pretty confusing quickly with severe weather.. I'm still learning myself with applying and fully understanding them. I have mentioned helicity and EHI in my couple of severe posts.

Helicity is a measure of the rotation potential in right-moving supercells. SPC mesoanalysis definition below:

Quote

SRH (Storm Relative Helicity) is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and is calculated for the lowest 1-km and 3-km layers above ground level. There is no clear threshold value for SRH when forecasting supercells, since the formation of supercells appears to be related more strongly to the deeper layer vertical shear. Larger values of 0-3-km SRH (greater than 250 m**2/s**2) and 0-1-km SRH (greater than 100 m**2/s**2), however, do suggest an increased threat of tornadoes with supercells. For SRH, larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.

EHI applies an equation that involves both CAPE and helicity (SRH):

Quote

The basic premise behind the EHI (Energy-Helicity Index) is that storm rotation should be maximized when CAPE is large and SRH is large. 0-1-km EHI values greater than 1-2 have been associated with significant tornadoes in supercells.

Those two things get measured at 0-1km and 0-3km. In terms of tomorrow with our area...helicity is certainly good, but CAPE is marginal. Thus, the potential of discrete supercell formationis somewhat stunted. Although if we get some sun and daytime heating, we will have to watch anything discrete that forms because they will be in an environment conducive to rotating.

In other news, don't sleep on Thursday night either. That imaginary precipitation type might make an appearance. 

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Close-up of the 06z Day 1 SPC outlook for our region. 

Screen Shot 2017-03-01 at 7.10.38 AM.png

 

I'm willing to bet the ENH region gets shunted south towards the PA/MD border with the next update as near-term guidance is limiting any chance of good destabilization across at least the northern 2/3rds of PA. 

I woke up to thunder (first of the year) this morning which is pretty impressive for March 1st. It'll be an interesting day to track.

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Heard some thunder this morning.

The convection this morning may not allow for much destabilization later and will probably limit the instability, at least over central PA. However, we may still have a threat for strong winds as an MCS develops later today and mixes the high momentum air to the surface. There could still be some more discrete convection in SE PA as that area probably has a better chance of clearing out before the MCS arrives, and may be initiated by the gust front and/or the residual outflow boundaries from the morning/early-afternoon convection.

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I like to be in bullseyes but not these. Ugh. 

So....as I read Mags post which like usual is rather informative ( thanks)....what panels in shear do you focus on ?  Did I see 0 and 3k being thrown around?  

I will google CAPE unless someone wants to give me the cliff notes?

batten down the hatches gang. 

Nut

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9 minutes ago, pasnownut said:

I like to be in bullseyes but not these. Ugh. 

So....as I read Mags post which like usual is rather informative ( thanks)....what panels in shear do you focus on ?  Did I see 0 and 3k being thrown around?  

I will google CAPE unless someone wants to give me the cliff notes?

batten down the hatches gang. 

Nut

Check out UCAR a free info/training site for weather topics. It goes pretty indepth (well very indepth on some things). Also CAPE is Convective Available Potential Energy (CAPE) is measure of the amount of energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft; thus, higher values indicate greater potential for severe weather.

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48 minutes ago, Anduril said:

Check out UCAR a free info/training site for weather topics. It goes pretty indepth (well very indepth on some things). Also CAPE is Convective Available Potential Energy (CAPE) is measure of the amount of energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft; thus, higher values indicate greater potential for severe weather.

thanks man.  Will look around in there and try to connect a dot or 2.

 

Sauss......Wind = BOOO

 

Snow......whats this phenomenon you speak of??

 

Nut

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1 hour ago, Jmister said:

Close-up of the 06z Day 1 SPC outlook for our region. 

Screen Shot 2017-03-01 at 7.10.38 AM.png

 

I'm willing to bet the ENH region gets shunted south towards the PA/MD border with the next update as near-term guidance is limiting any chance of good destabilization across at least the northern 2/3rds of PA. 

I woke up to thunder (first of the year) this morning which is pretty impressive for March 1st. It'll be an interesting day to track.

Whats ENH?  

Nut

 

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1 minute ago, pasnownut said:

Whats ENH?  

Nut

 

 

Their abbreviation for enhanced. 

My assumption was wrong. There was no north/south movement of the enhanced area, just an eastward expansion. Crazy there's a 45% severe wind category up for the DC/Baltimore area now.

Screen Shot 2017-03-01 at 8.47.41 AM.png

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5 minutes ago, Wmsptwx said:

Bring honest, I like this to underachieve for pretty much all of us at this point. A good deck of clouds with rain for all southern areas as of 920am, we are trying to clear up here, but still overcast and we are further removed from best dynamics. We may get away without too much drama today.

For once, just this one time, I hope your pessimism is right. 

And if you are, I just might add it to my collection of your pessimistic thoughts in my 24 hours of Central PA weather thread. :) 

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2 hours ago, Jmister said:

 

Their abbreviation for enhanced. 

My assumption was wrong. There was no north/south movement of the enhanced area, just an eastward expansion. Crazy there's a 45% severe wind category up for the DC/Baltimore area now.

Screen Shot 2017-03-01 at 8.47.41 AM.png

I guessed right.... :)

 

thanks J.

 

See i can do this.

Nut

 

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14 minutes ago, Wmsptwx said:

Guys, fast approaching clouds and precip have me hopeful that worst of storms stay under the mason line. As usual, this is more of a quick obs, and mag or heavy remain welcome to body slam my thoughts if need be.

Rather sunny here in Etown as well.

Hurry up clouds.....

I think yo may be right though, as from what little I know about this side of stuff, less heating = less instability and dynamics, so I hopt thats the case.

many holes still remain in roofs round here.

Nut

 

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Looks like another swing and a miss for severe storms in Central PA. As expected, the clouds and showers never allowed for destabilization. We're still 57 degrees despite a forecast high of 67. 

Considering last year I think we had 2-3 "exciting" severe days to track, this year is already way ahead of schedule.

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