Winter Banter 24-25

[donsutherland1]

On 1/18/2025 at 1:09 PM, donsutherland1 said:

Another Social Media post to be added to the verification pile (BAMWX's call for historic cold will be verified tomorrow):

The above post was made yesterday after the 1/18 0z HRRR came out and seemingly supported the 1/17 18z RGEM, which is posted below:

Before one prematurely claims verification, possibly based on confirmation bias, one should examine the pattern to see if the particular guidance makes sense. The pattern has some similarities with that of the January 22, 1987 snowstorm, that brought 8.1" to New York City and 8.8" to Philadelphia. This time around, the ridging off the East Coast will be less impressive than it was in 1987 and the storm won't be as moisture-laden. Thus, snowfall amounts will be lower than they were in 1987. At the same time, a mostly rain scenario in New York City is unlikely.

My thinking last evening, which incorporated my assessment of the pattern that I posted on this morning and considered all of the guidance:

Snow will likely accompany the arrival of the Arctic air to the region. A developing storm will likely bring a general 3"-6" snowfall from Philadelphia to New York City with a stripe of 4"-8" amounts to the north and west of this region. 1"-3" amounts are likely east of Islip.

The RGEM is a very good mesoscale model, but it appeared to be an outlier from a general consensus that existed among the guidance. Since then, it has corrected quite aggressively in its 1/18 6z and 12z runs moving into decent agreement with the model consensus.

 

The January 19, 2025 snowstorm underperformed in the I-95 Corridor. However, snowfall amounts were still much higher than those suggested by the 1/17 18z RGEM for which "victory" had prematurely been declared.

RGEM Amounts vs. Actual Amounts:

Bridgeport: 0.7" (Actual: 2.3")
Islip: 0.2" (Actual: 2.3")
New York City: 0.5" (Actual: Central Park: 1.6"; JFK Airport: 2.2"; LaGuardia Airport: 3.6")
Newark: 0.6" (Actual: 2.4")
Philadelphia: 0.5" (Actual: 2.0")