bluewave

33 and rain here in SW Suffolk. Yet another rainfall event approaching 1 inch.

Looks like a 2-3 day Arctic outbreak before the mild Pacific influence returns over the weekend. NEW YORK CITY-CENTRAL PARK KNYC GFSX MOS GUIDANCE 12/17/2019 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 TUE 17| WED 18| THU 19| FRI 20| SAT 21| SUN 22| MON 23| TUE 24 CLIMO X/N 40| 29 37| 17 26| 18 35| 27 38| 34 47| 37 49| 37 48 28 41 TMP 35| 31 29| 19 24| 20 34| 29 36| 36 44| 39 45| 39 45

Downed trees and wires in PA from the heavy icing.

37 with a light sleet and rain mix here in SW Suffolk.

That’s why ice storm warnings are often issued once the event is underway.

It would be nice if we could run the FRAM model on this to see how much freezing rain accumulates vs just runs off. PDF] The Freezing Rain Accumulation Model (FRAM) - NOAA VLab https://vlab.ncep.noaa.gov › documents › FRAM_VLAB_Presentation.pdf Wet-bulb helps account for evaporative cooling toward saturation. • The air-liquid interface along the edge of a raindrop is saturated. Microscale temperature ...

The record books are more about accurately recording what actually happens. Not getting much in a marginal situation isn’t that bad. But 1-26-15 is a whole different story with such a major underperformance and shift east.

I never saw the NAM go so heavy on freezing rain before. Even if just 25% of that freezes without running off, it will be a problem.

The MJO moving close to phase 5-6 around the holidays will amp the Pacific Jet up even more.

No surprise to see the models increase the overall precipitation amounts. That 200 KT jet streak to our northeast is near record levels for this time of year.

A few miles distance can make a big difference as to where the most significant icing sets up. A small change in temperature of a degree or two is all that it takes. Sometimes it just comes down to nowcast time. But areas that see icing will also have to cope with stronger winds on Wednesday with the sharp Arctic front. Then the very cold temperatures.

Remarkably consistent storm track pattern since last winter. Plenty of cutters through the Great Lakes and storms that hug the coast. Occasionally we see a weak disturbance in the Great Lakes acting to suppress a southern stream low. Rapidly deepening benchmark snowstorms have been missing. This is in stark contrast to our last excellent benchmark season in 2017-2018 which featured a 950mb benchmark blizzard. In some ways, the snowfall gradient is s throwback to earlier times. The heaviest snowfall amounts are higher inland and lower along the immediate South Shore Coast. This is a reversal from 2013 to 2018 where the heaviest snow falls occurred along the coastal plain. How long the is this type of unfavorable dominant Pacific Jet pattern lasts is anyone’s guess.

The 12z GFS just took a step in the direction of the other models. Now has a weak low in the GL and a separate southern stream low to the south. 12z 6z

The GFS is currently on its own. The Euro, UKMET, and CMC have a low in the Great Lakes and a separate southern stream low.

Need to lose that northern stream low over the GL so it doesn’t suppress the southern stream low.

It should be cold enough to maintain the monthly cold departures over the Northeast. Then we see what happens during the last week of December. While the rest of the country has been mild, a small area of cold departures remains over the Northeast.

This was a top 3 wettest first 2 weeks of December around the area. The recent warm up shrunk the cold departures to 0 to -1.3. Time Series Summary for JFK INTL AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Precipitation Dec 1 to Dec 14 Missing Count 1 2019-12-14 5.88 0 2 2014-12-14 5.30 0 3 1996-12-14 5.04 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Precipitation Dec 1 to Dec 14 Missing Count 1 1983-12-14 6.32 0 2 1996-12-14 5.70 0 3 2019-12-14 5.05 0 December temperature departures through the 14th. EWR...-0.9 NYC....-1.3 LGA.....-1.3 JFK.....-1.3 BDR....-0.6 ISP......-0.2

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Too bad our local NWS doesn’t keep track of daily pressure records like other offices do.

This is mostly a -AO though. The NAO is closer to neutral with a neutral to negative PNA. So the ridge axis on the current EPS is too far to the east. This favors late developers that deepen further offshore. Need to slow down that Pacific flow so the ridge can back up to the West Coast.

Yeah, that’s why a solid +PNA is so important.

Lose that weak low over the GL and it might be better. But that fast flow Pacific has me concerned about a fly in the ointment. Also notice that other low racing east just north of Montana.

The uninterrupted unfavorable Pacific began last winter. Before that, the favorable intervals within a season more than made up for the unfavorable ones. It usually takes the -AO falling to -4 to -5 and the NAO -1 to -2 on the CPC official site. But we generally need a robust MJO 8 or a start warming event to pull that off. That extreme a drop can usually get the ridge to retrograde back to the West Coast boosting the PNA.

The -AO and -NAO won’t matter if the fast Pacific flow doesn’t relax. Notice how the record Pacific Jet keeps knocking down the PNA.