Replies

For Boston-area folks, as of 7:30 PM, here's what Todd Gross (the weatherman who recognized "the perfect storm") has to say (from http://www1.whdh.com/weather/ ):

"TECHNICAL DISCUSSION: For Weather Junkies Only :) Posted daily by Chief Meteorologist Todd Gross Monday through Friday around 6pm.

I can't keep this emotional roller coaster up. After the ocean enhancement verified and we received 8" of snow in Boston Thursday night, now we have another classic setting up with a twist. For days, the ECMF / GEM, and GFS were at odds with the NAM model , saying this would be a short wave running out into the water, rather than heading up inland. That short/medium wave that runs up along the full latitude trough is "key" to the track of the storm, but the track itself is ALSO influenced by the coastal front that sets up, it's initial position, climatology based on land-water interaction (coastline shape), and of course cold air damming from the retreating high,

Bottom line: Now that the models are converging on a short/medium wave that runs up coast and tears pretty much straight into us, and a surface system that stays just offshore, and intense vertical velocities to +30 (-30 omega) and intense warm advection, and 1000-850 thickness NOT going above critical until 11pm, we have on our hands a potential for an incredibly strong hit in a short period of time on Monday evening. Even if the NAM(ETA) is right, and the interior track takes place with the upper feature (the short/medium wave), the surface low will not be able to move inland due to the damming, and coastal front setup, meaning Boston will never really get into the warm air, the track would be up through the south shore. And even using that "warmer" scenario, BUFKIT still comes up with .7" of precip while it is snowing, and most of it falls in just a few hours. This is the basis for keeping Chikages 6-12" forecast.

Let's talk about something that may never happen, but is forecast by the GFS at the current time (and the GEM too, but especially the 18z GFS) 1" of precipitation in the period 7pm to 1am on Monday night. 1". No changeover, not even close downtown. Then another .5" of precipitation in the following 6 hours. Even if the ratio is only 10:1 (should be a bit more), then that means 15" of snow overnight Monday night inside Rt. 128. PLUS, being a farther east track, it is a smoother transition to additional backwash light snows tuesday into Wed.

7:30pm Sunday night: I just checked critical thicknesses again for the GFS, as of the 12z run, it is a bit close late in the game, with 1300 meters at 1000-850mb coming up to the south shore, possibly barely touching Boston briefly around 4am on Tuesday morning. Close, close close..

Looking at Kocin and Uccellini's original book Snowstorms Along the Northeastern Coast of the US 1955 to 1985 for the best analog storms (this IS classic) - i am finding some.. but like snowflakes, no two storms are exactly alike:

March 20th, 1956 (13-20" ) is one..
Dec 13th, 1960 is another, with 18" almost everywhere

Bear in mind that this book lists only the storms that actually DID end up producing big amounts, do don't run away with this. However, even with this funky short wave kicking up the east side, it is absolutely a textbook setup from the NW flow Jet streak initially over the Northeast prior to the storm (the NW flow that lifts out) to the digging short into the midwest that sets up the full latitude trough, and picks up our coastal storm, and the bombogenesis that follows. :)"