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Central PA - December 2017


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this may be what hes talking about, but as you cycle through both GFS and GEFS you cans see the potential for the trough to break down.....after the stemwinder moves out (which often happens).  need to dig more tonight to see where things are.  Regardless, its way too far out to worry attm, but nice to see the blues on the east coast.

Nut

 

 

gfs_z500a_us_47.png

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Just now, heavy_wx said:

Still snowing here with modestly reduced visibility. Mostly wet surfaces out there with decent-sized melting aggregates.

Eric Horst, meteorologist with Millersville University tweeted this morning that we were treated to some "Kelvin Helmholtz" clouds. Surely, you of all people can fill us in on what Kelvin Helmholtz clouds are. I know my cumulus, stratus, cirrus, etc., but this is new to my weather repertoire. 

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KH waves are beautiful! Here's a particularly dramatic example from Alabama a few years ago:

Helmholtz-top-550x410.jpg

Basically they form when there is a vertical gradient in wind shear and/or temperature. A small, random disturbance can then grow to produce the waves; these waves are visible to us if the temperature and/or shear gradients occur near the tops of clouds, as the cloud basically traces out the waves. They're actually fairly common on fair-weather days after a cold frontal passage if you look out for them.

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On 10/30/2017 at 11:47 AM, sauss06 said:

Its been a long time since i heard wind like that. Not sure i slept to much. I'd have to think maybe Hurricane Irene was the last time the wind had me a lil nervous. It was dark when i left so i don't know what or if anything was disrupted

A week late to this but just getting caught up -- I lost a tree and a couple medium to large branches from that wind during the overnight hours.  More tree damage than when Sandy hit but only lost power a couple times for only seconds whereas it was out for 8 hours after Sandy 5 years to the day I believe it was.  The AWOS instrumentation that Fort Indiantown Gap uses I have seen report bizarre 58-63 knot gusts at times both there and a few other sites with same equipment in PA before during strong but not that strong gusts so not convinced it was quite as high as ~70 mph but could easily been 50-60 mph as other nearby data supports if that difference even matters. 

...Cumberland County...
1 WSW Enola                  54 MPH    1141 PM 10/29   CWOP

...Dauphin County...
Manda Gap                    62 MPH    1218 AM 10/30   RAWS
Rockville                    57 MPH    1209 AM 10/30   CWOP
1 NNE Harrisburg             45 MPH    1146 PM 10/29   CWOP
Harrisburg Int`l Airport     44 MPH    0940 AM 10/30   ASOS

...Lebanon County...
Muir Airfield Ft. Indiantown 70 MPH    1154 PM 10/29   AWOS
2 WNW Fort Indiantown Gap    53 MPH    1213 AM 10/30   RAWS
Jonestown                    42 MPH    1200 AM 10/30   CWOP
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1 hour ago, heavy_wx said:

KH waves are beautiful! Here's a particularly dramatic example from Alabama a few years ago:

Helmholtz-top-550x410.jpg

Basically they form when there is a vertical gradient in wind shear and/or temperature. A small, random disturbance can then grow to produce the waves; these waves are visible to us if the temperature and/or shear gradients occur near the tops of clouds, as the cloud basically traces out the waves. They're actually fairly common on fair-weather days after a cold frontal passage if you look out for them.

 

Wasnt sure if I had seen those on the horizon or not, couldnt tell whether it was from factories or was actual clouds but did see Undulatus Asperatus clouds today quite vividly.

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35 minutes ago, djr5001 said:

A week late to this but just getting caught up -- I lost a tree and a couple medium to large branches from that wind during the overnight hours.  More tree damage than when Sandy hit but only lost power a couple times for only seconds whereas it was out for 8 hours after Sandy 5 years to the day I believe it was.  The AWOS instrumentation that Fort Indiantown Gap uses I have seen report bizarre 58-63 knot gusts at times both there and a few other sites with same equipment in PA before during strong but not that strong gusts so not convinced it was quite as high as ~70 mph but could easily been 50-60 mph as other nearby data supports if that difference even matters. 


...Cumberland County...
1 WSW Enola                  54 MPH    1141 PM 10/29   CWOP

...Dauphin County...
Manda Gap                    62 MPH    1218 AM 10/30   RAWS
Rockville                    57 MPH    1209 AM 10/30   CWOP
1 NNE Harrisburg             45 MPH    1146 PM 10/29   CWOP
Harrisburg Int`l Airport     44 MPH    0940 AM 10/30   ASOS

...Lebanon County...
Muir Airfield Ft. Indiantown 70 MPH    1154 PM 10/29   AWOS
2 WNW Fort Indiantown Gap    53 MPH    1213 AM 10/30   RAWS
Jonestown                    42 MPH    1200 AM 10/30   CWOP

damn, thanks for the info. 

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2 hours ago, heavy_wx said:

KH waves are beautiful! Here's a particularly dramatic example from Alabama a few years ago:

Helmholtz-top-550x410.jpg

Basically they form when there is a vertical gradient in wind shear and/or temperature. A small, random disturbance can then grow to produce the waves; these waves are visible to us if the temperature and/or shear gradients occur near the tops of clouds, as the cloud basically traces out the waves. They're actually fairly common on fair-weather days after a cold frontal passage if you look out for them.

That picture is amazing! Thanks for the explanation too. 

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Just got back from working up north above I-80 today and it was quite a nice drive home. First flakes and measurable snowfall in the books today in the backyard, about 0.7" on the colder surfaces. There was a mini dry slot that had moved into the Altoona area before I got home so may have been more like an inch a little bit ago. At the top of Wopsy Mountain above Altoona where it gets up around 2500' there's about 2.5" on the ground up there. 

Talk about a spur of the moment event for the central mountains. For as relentlessly warm as this fall has been this is literally the third time I've seen it snow since the November 1st Nor'easter in my travels around the general area here. I was working above Dubois last Wednesday and got to see that bit of snowfall. 

Here at home, I have a new vista this year (I moved haha) 

IMG_2341.thumb.JPG.a7d5a32c177612ff00162733a757c443.JPG

 

Top of Wopsy Mountain above Altoona (approx 2500' elevation). This is about 5 miles from my house. 

IMG_2339.thumb.JPG.940e589ca7bdb80615a7ef39d2ec8135.JPG

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Had about 1.5" on my Jeep when I got back to Hazleton from running two Tioga's today. Talk about a lot of miles. Anyway, it seemed as if the best accumulations were above 1,500 ft here along I-81. The snow level itself was about 1,000 ft as Hometown had a coating, but one mile down the hill in Tamaqua, at 800 ft, we had nothing.

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Sleet first started mixing in with the rain around 2:30pm here.  Temp was around 38 at the time.  By 4:00pm the temp had dropped to 35 and it was snowing with huge wet flakes and beginning to stick on the grass, my deck, and snowboard.  By 5:00pm temp bottomed out at 33.4 degrees and the snow varied in intensity from almost nothing to big fat flakes.  Precip-wise I picked up almost 0.40" of liquid.  The snowfall was pure slush, but I am going to record it as 0.1" officially.  It was actually more, but was melting while it was accumulating, making it almost impossible to measure.  What a sudden change from yesterday with a high of 64 degrees!  Also, this is fairly early for the first recorded measurement of the season.  All-in-all a pleasant "surprise".

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