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Central PA & The Fringes - January 2014 Pt II


PennMan

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Man 10/20 miles may make a huge difference with this one. 18z NAM has a heck if a drop off NW. Getting nervous here in Shippensburg!

 

I wouldn't be surprised if there is a fairly sharp cut-off in precip rates north of the best banding. With frontogenetic circulations, there is rising motion on the warmer side of the boundary and sinking motion on the colder side (in order to restore thermal wind balance). The NAM has a fairly strong and deep frontogenetic circulation around 21z Tuesday which means there will likely be subsidence to the north. We'll have to wait and see exactly where the favored areas for banding will be as we get into the near-term forecast range.

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You have to think that if this is correct and the globals catch on or agree then corresponding qpf will increase in later runs.  We are in MECS range down here a tick up would be a minor hecs.

This is said a lot on this board, but 00z EURO will be important.  After the 00z runs tonight, you really want to switch into nowcasting mode.  Watch, satellite, radar, obs, traffic cams, etc.

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OK, so I just got home from being in the truck all day and haven't had time to really look at models until now. If I'm seeing things right, the 18z GFS is showing 6 inches of snow even up my way in Tamaqua. Could this possibly happen? Are things still ticking northward?

 

All I know is that Wednesday morning is going to be quite interesting if we have temps close to zero with 6 inches of snow being whipped around by the wind. Might be a good day to take a vacation day...

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OK, so I just got home from being in the truck all day and haven't had time to really look at models until now. If I'm seeing things right, the 18z GFS is showing 6 inches of snow even up my way in Tamaqua. Could this possibly happen? Are things still ticking northward?

 

All I know is that Wednesday morning is going to be quite interesting if we have temps close to zero with 6 inches of snow being whipped around by the wind. Might be a good day to take a vacation day...

You are right on the edge, but yes the trend is definitely colder and snowier even up your way.  South of I-81 looks to be the big winner.

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So I just did an analysis of the 15z SREF's 21z temperatures at various sites, specifically ORD, LAF, GRR, DTW, CMH, CLE, ERI, and IPT to get a sample on both sides of the "Arctic front". The idea was to see how the different members are handling the front. The members with the best temperature forecasts (average error below 3.0°F) are...

ARW3/ARN2

ARW4/ARP1

ARW5/ARP2

ARW6/ARN3

NMM3/NMN2

NMM4/NMP1

NMM6/NMP3

NMB1/MBCN

NMB4/MBP1

NMB7/MBP3

 

The members with the worst temperature forecasts (average error at or above 4.0°F) are...

ARW7/ARP3

NMM2/NMN1

NMM5/NMP2

NMB2/MBN1

NMB3/MBN2

NMB6/MBN3

 

The bold ones are doing exceptionally poorly, with average errors at or above 6.0°F.

 

post-300-0-69868700-1390256301_thumb.png

 

 

 

For fun, I also gave each member a weight based on how well they are doing and calculated a weighted mean precip and snow forecast for PSB (nearest to KUNV). That method gives a mean precip of 0.19", and a mean snowfall of 6.2".

 

What I found very odd/interesting is how extreme of snow ratios the SREFs are generally forecasting. Of the 17 members that forecast any snow at PSB, only three members have ratios of less than 25:1 (8, 16, and 20). Four have ratios of 40:1 or better (40, 40, 44, 45). The weighted-mean ratio turned out to be 32:1.

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