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Forecast Verification for the Christmas/Boxing Day storm


eyewall

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accum.20101225-26.all.gif

My final call:

nc-call6.jpg

In looking at my forecast the main point of error I had primarily had to do with underestimating the amount of snow that fell in the western piedmont and in the lee of the mountains on Christmas day/evening. This primarily had to do with a northern stream wave ahead of the main coastal storm. This is one thing the NAM hinted on in the short term but I admit in not giving it enough attention as my focus became primarily with the coastal low. It is something to learn from for the next time.

In looking at just the 26th my forecast thinking held up reasonably well overall in looking at the maps. This is more evidence that my thinking was based way too heavily on the coastal low only. I had the right idea but I did undercut amounts ENE of Raleigh and in the coastal plain even though I did specify locally higher amounts (they were a little more than locally higher there). I probably should have updated one more time once it was clear in real-time the storm was in fact deepening rapidly and the RUC was showing a clear deformation banding signature. Temps also crashed very quickly on the 26th all the way to the coast. It was a delayed start but once they did fall it happened more rapidly than I thought. I honestly think late on the evening of the 25th I let weenie panic trump what the science was telling me and I have to remember that in events down the road.

So in closing to sum things up I underestimated the initial wave and I was too cautious on coastal plain amounts with the coastal. My thinking on the coastal was sound with the exception of a few caveats. If I had to grade my forecast on this one it would be a C+. Not bad but I can certainly do better. Either way I think I want to do my own case study on this and learn what I can from it.

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Thanks to a huge disparity between the time that warning criteria was reached in the mountains (around 1 pm on Christmas) and our southeast Piedmont zones (around 5 AM on the 26th), we ended up with a respectable (but still sub-GPRA) average lead time of 13 hours. Not too bad I guess considering the trickiness of this system 24 hours out.

The POD was 1.0 and the FAR was 0.154.

We don't have a snowfall map completed yet, but I'll post one as soon as it's ready.

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I made this crappy map the night of Christmas Eve.

SEMAp.png

I didn't anticipate as much snow over the western foothills/leeside mountains as actually fell. In addition, I did not foresee the screwzone around Charlotte. I was also too high in the southern Piedmont which missed out on most of the moisture during the initial blow. However, these areas racked up good totals from the Coastal while the northern/western Piedmont and foothills failed to get much. I also was too low on the mountains, which got helped out a lot by the northwest flow event which followed the initial blow.

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I think u did a good job ewall. It was hard to anticipate what was going to happen for this storm.

Below was my call at 9am christmas morning. I think it was overall pretty good, just a little late for a final call. But this storm didn't appear likely until Christmas eve afternoon/evening.

map1_4.png

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Thanks to a huge disparity between the time that warning criteria was reached in the mountains (around 1 pm on Christmas) and our southeast Piedmont zones (around 5 AM on the 26th), we ended up with a respectable (but still sub-GPRA) average lead time of 13 hours. Not too bad I guess considering the trickiness of this system 24 hours out.

The POD was 1.0 and the FAR was 0.154.

We don't have a snowfall map completed yet, but I'll post one as soon as it's ready.

Yea you guys at GSP did a great job updating things as they were happening (with some really nice AFD's). It was really impossible given what the modeling was showing only 24 hours prior to the event to issue Winter Storm Watches for most of the CWA. Despite the lower lead time, the Probability of Detection and False Alarm Rate look pretty darn good. Looking forward to seeing the final snowfall map for the event!

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Here was my final forecast map as compared to the Raleigh snowfall map... Underestimated amounts in the NC mountains and some portion of the coastal plain in NC, but feel pretty good about my map otherwise.

accum.20101225-26.all.gif

2mheq2f.png

Nice job overall! You captured western areas and the first wave well! Thank you everyone for your comments so far.

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Nice job overall! You captured western areas and the first wave well! Thank you everyone for your comments so far.

Thanks... your map was also pretty nice for the area you were primarily forecasting for in the sandhills. Honestly, the last map I made was early on Christmas day when It was becoming obvious that the first batch of precip was going to nail the WNC mountains per the RUC and last runs of the NAM and GFS. So really I have to hand it to the short term models handling of the precipitation... as it was pretty spot on, which doesn't happen very often.

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Here was my final forecast map as compared to the Raleigh snowfall map... Underestimated amounts in the NC mountains and some portion of the coastal plain in NC, but feel pretty good about my map otherwise.

accum.20101225-26.all.gif

2mheq2f.png

pretty much spot on especially realizing the lack of accumulating snow here on the immediate coast

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Below was my call at 9am christmas morning. I think it was overall pretty good, just a little late for a final call. But this storm didn't appear likely until Christmas eve afternoon/evening.

map1_4.png

This was pretty much spot on for my area...(West Central GA)....Nice job on a difficult storm! :guitar: It had me sayin...It will...It won't...It will...It won't....right up to the last minute....Which was around 5:30 p.m. Christmas day.:thumbsup:

I'm right on your grey line...we got about an inch.

Here's to more potential storms in 2011!

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Thanks for posting..

Do you have a direct link for the 25-27 Heavy snow fall map?

Thanks

They should be up on our website later on...but I'm not exactly sure when. You can dl'd and feel free to pass around these images tho. Does it make a difference where the images are located? Just curious.

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