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Mid to late October disco/banter thread.


CoastalWx

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A lot of it has to do with how snowfall is measured. In the old days, they almost always measured snow depth, sticking a ruler into the ground. This produces lower totals than the modern method of measuring each 6-hours.

Yeah I was thinking that... still amazing run though since 2000-2001 winter of large snowstorms.

It seems like every year there's some sort of HECS be it NNE, SNE, or Mid-Atlantic. Last year's just happened to be in October.

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16 mile EF-1 in Lancaster County PA last night.

Take a look at the radar from DIX. Debris Signature????

It's certainly possible. I think what you said in our earlier conversation is right, the timing is a little off radar versus survey report. If the tornado touched down in the Fern Glen neighborhood that was much closer to 0000z than 0010z. I know that at least at 0007z there could be a TDS (I for whatever reason couldn't get a 0002z volume scan like you have). You have the low CC and near 0 ZDR collocated with the velocity couplet at the time. Given the range from the radar though the beam was just around the freezing level (SPC mesoanalysis puts the freezing level about 8500 ft) so hail/graupel could be part of that signal too. I would doubt a pure hail signature there though, so 0 ZDR would be somewhat surprising. So it could certainly be some lofted organic debris. There have been quite a few examples of weaker tornadoes still have a well defined TDS, even at this range from the radar.

What a classic radar presentation otherwise though, with the broken S structure to the reflectivity. That storm was pretty much right on the triple point, with a large portion of the total CAPE located in the lower 3 km of the atmosphere.

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It's certainly possible. I think what you said in our earlier conversation is right, the timing is a little off radar versus survey report. If the tornado touched down in the Fern Glen neighborhood that was much closer to 0000z than 0010z. I know that at least at 0007z there could be a TDS (I for whatever reason couldn't get a 0002z volume scan like you have). You have the low CC and near 0 ZDR collocated with the velocity couplet at the time. Given the range from the radar though the beam was just around the freezing level (SPC mesoanalysis puts the freezing level about 8500 ft) so hail/graupel could be part of that signal too. I would doubt a pure hail signature there though, so 0 ZDR would be somewhat surprising. So it could certainly be some lofted organic debris. There have been quite a few examples of weaker tornadoes still have a well defined TDS, even at this range from the radar.

What a classic radar presentation otherwise though, with the broken S structure to the reflectivity. That storm was pretty much right on the triple point, with a large portion of the total CAPE located in the lower 3 km of the atmosphere.

Yeah it's a really neat case of a tornadic circulation embedded in a QLCS.

I was surprised that the TDS stuck around as long as it did... 23:58-00:26. Also was quite high... around 10kft.

You are right though I think it all is embedded within an area of some graupel or small hail. The beam was at the freezing level or so (per 00z LWX sounding) and the updraft was tickling -20c from time to time. There is a noticeable drop in CC from 23:54 when the supercell crossed the Susquehanna (lower CC in the updraft... 80-95% pre tornado) that drops dramatically in the next volume scan to 55-75% and becomes colocated with the TS (delta V at that point ~65 knots).

This was crossing a lot of farmland in Lancaster County and not heavily wooded area so I was a bit surprised the TDS would be so well defined for a period of time.

Really neat setup.

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A lot of it has to do with how snowfall is measured. In the old days, they almost always measured snow depth, sticking a ruler into the ground. This produces lower totals than the modern method of measuring each 6-hours.

Bingo! This is why you really can't compare todays storms with yesterdays. Modern doesn't mean better, it's just the current thinking of what is best.

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I wonder what I got in '78 using modern measurement...

Dec '92 would have been another good one. I think it was shortly after that the modern standard came out. I left the field in early '93 to pursue a Web programming venture and changes like that were coming through from the WMO & AMS.

The first time I heard about it was a storm (can't remember which one) when the Philadelphia airport had something like 30"+ from a storm when everyone around them had way less. I remember there being some discussion about it but the record stood because they were using an "official" measurement and everyone one else wasn't. I didn't know a single met at the time that thought it was right because of the comparison issues but I guess it's just accepted and done by most now.

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Dec '92 would have been another good one. I think it was shortly after that the modern standard came out. I left the field in early '93 to pursue a Web programming venture and changes like that were coming through from the WMO & AMS.

The first time I heard about it was a storm (can't remember which one) when the Philadelphia airport had something like 30"+ from a storm when everyone around them had way less. I remember there being some discussion about it but the record stood because they were using an "official" measurement and everyone one else wasn't. I didn't know a single met at the time that thought it was right because of the comparison issues but I guess it's just accepted and done by most now.

That was the January 1996 blizzard.

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It's certainly possible. I think what you said in our earlier conversation is right, the timing is a little off radar versus survey report. If the tornado touched down in the Fern Glen neighborhood that was much closer to 0000z than 0010z. I know that at least at 0007z there could be a TDS (I for whatever reason couldn't get a 0002z volume scan like you have). You have the low CC and near 0 ZDR collocated with the velocity couplet at the time. Given the range from the radar though the beam was just around the freezing level (SPC mesoanalysis puts the freezing level about 8500 ft) so hail/graupel could be part of that signal too. I would doubt a pure hail signature there though, so 0 ZDR would be somewhat surprising. So it could certainly be some lofted organic debris. There have been quite a few examples of weaker tornadoes still have a well defined TDS, even at this range from the radar.

What a classic radar presentation otherwise though, with the broken S structure to the reflectivity. That storm was pretty much right on the triple point, with a large portion of the total CAPE located in the lower 3 km of the atmosphere.

The lower tropospheric winds are very meh. Just pulled the 23z RAP sounding for KLNS and it's a pretty pitiful looking hodograph. Not sure where the horizontal vorticity came from to spin it up.

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The lower tropospheric winds are very meh. Just pulled the 23z RAP sounding for KLNS and it's a pretty pitiful looking hodograph. Not sure where the horizontal vorticity came from to spin it up.

Could be orographic enhancement...the tornado did occur across an area which tends to get llvl wind enhancement.

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