Honing Forecasting Skills in Events with OES Contributions

[40/70 Benchmark]

Leading up to this event, I was hedging isolated amounts of over 30" in the CJ weenie triad of the north shore, namely the small area bounded by Peabody, Salem, Danvers, Beverly. It is this region, owed to it's optimal positioning right at the concave section of the north shore, that almost always seems to benefit from extraordinary convergence born of oes/cf contributions. However this storm, likely do to the late cold/south trend that Leatherneck ( in the relentless manner that only he can) kept hedging toward, ended up jackpotting the south shore CJ G-spot....from Norwell up to Weymouth, down to Abington.

 

My question is, what exactly is that we should be looking at in these very cold events to to discern which area north, south or both, should be favored in the CJ Civil War.

Mesoscale wind analysis perhaps??

Thanks.

 

[CoastalWx]

Leading up to this event, I was hedging isolated amounts of over 30" in the CJ weenie triad of the north shore, namely the small area bounded by Peabody, Salem, Danvers, Beverly. It is this region, owed to it's optimal positioning right at the concave section of the north shore, that almost always seems to benefit from extraordinary convergence born of oes/cf contributions. However this storm, likely do to the late cold/south trend that Leatherneck ( in the relentless manner that only he can) kept hedging toward, ended up jackpotting the south shore CJ G-spot....from Norwell up to Weymouth, down to Abington.

 

My question is, what exactly is that we should be looking at in these very cold events to to discern which area north, south or both, should be favored in the CJ Civil War.

Mesoscale wind analysis perhaps??

Thanks.

 

 

A couple of things. I did notice the BTV WRF had two QPF jackpots. One in nrn PYM county into ern Norfolk County and then One by cstl Essex county. Two difference processes here at work I think. The coastal Essex county max was due more to strong convergence along the coastal front. It is that reason why they tend to do very well in KUs. East winds aloft advecting warmer and more "humid" maritime air over the coastal front squeezes out the snow. Take a look at the beginning of the 2005 blizzard to see this. In our classic KUs, the CF isn't going to go well inland and probably pinned near BOS helping this out. 

 

The second max is what I tend to experience at times. That is, strong onshore flow that is relatively cold enough to pick up moisture and deposit this as snow. Strong convergence over land and subtle elevation rise helping already unstable low level lapse rates squeeze moisture out. This tends to show up as small bands or cellular echoes. Once in a while, a wider band will form.

 

In this case, the models underestimated the cold air push which tends to happen. That high was in a perfect spot to push cold air right into SE MA. That was one of the reasons why I said I liked my spot the other day...I knew the GFS was out to lunch on the thermal profile. However, I thought maybe BOS was in the cross hairs..I didn't think areas south would be, although I thought that would do very well. High pressure is everything for coastal areas. When you have a high cresting over NNE and very cold air pushing south, money in the bank for heavy snow, OES or not.  That applies inland too. You want strong frontogenesis aloft to help out with the good mid level stuff as well. 

 

In any case, the mesoscale models usually do a pretty good job at hinting at the processes at play. But if we have a strong high cresting over NNE, perhaps take the max zone as modeled and push it south a bit. Otherwise CF behavior can also be governed by several things. Pressure falls, LLJ placement..etc. 

[40/70 Benchmark]

Thanks, man.

Forgot about this until now.

[powderfreak]

I would always assume in addition to the coastal front processes that low level east flow in general will cause land initiated speed convergence along the general coastal areas. You've got air flowing freely over the ocean surface then hitting friction when it encounters land...causing the pile-up speed convergence and low level lift along the shoreline towns.

[CoastalWx]

I would always assume in addition to the coastal front processes that low level east flow in general will cause land initiated speed convergence along the general coastal areas. You've got air flowing freely over the ocean surface then hitting friction when it encounters land...causing the pile-up speed convergence and low level lift along the shoreline towns.

 

Yeah that's why I mentioned the land covergence.  Definitely part of it.

[Clinch Leatherwood]

An interesting aspect to it all is that it almost always targets the area Scott is in straight back to Easton and Sharon. Today's OE was similar. ive always felt there's some type of funnel effect between the capes too. iE that area that gets hit has just enough of an open lane for it to work.