Snow Potential Dec 26-27

[eduggs]

11 hours ago, bluewave said:

 

I can see both of your points. Don is coming more from a letter of the law perspective and you from the spirit of the law. 

"Letter of the law" how so? All the data I've pored over supports the idea that the NAM performed best with QPF and ptype from about 3 days out until Friday afternoon. The ECM was probably second best with a late adjustment northeastward. The NAM was consistently 0.2 - 0.5" liquid across the NYC metro with a frozen ptype over its last few runs before the event. Despite "generous" final tallies for EWR and NYC, that's how it played out. It was best in the LHV, ENY, CT, and SNE. The ECM was too far southwest across the board. I'm not even sure how this is contentious. I feel like Don is/was biased against the NAM leading to a non-scientific and distorted assessment. 

[eduggs]

On 12/27/2025 at 8:21 AM, donsutherland1 said:

18z NAM vs. 18z HRRR: 

Here's how I fared against the two models:

Final Accumulations:

Bridgeport: 7.1"
Islip: 6.6"
New York City-Central Park: 4.3"
New York City-JFK Airport: 4.1"
New York City-LaGuardia Airport: 4.1"
Newark: 4.2"

The low end of the 4"-8" idea worked out. The loss of precipitation from the weak lift that developed in the spacing between the surface and mid-level low likely deprived the region of several inches of snow. It also allowed for some intrusion of sleet into the greater New York City area for a time until the lift improved.

Don, where did you get your numbers for the 18z HRRR and NAM output? They don't match pivotal, so I assume you derived them somehow. But using what method? I don't think you responded to this question from earlier. To my knowledge, bufkit does not output snow/ice accumulations. Your tables also reinforce the false belief that weather models generate forecasted snowfall as output.