bluewave

It does look like one of those days that struggles to get out of the low 20s during the afternoon. Looks like CAA maxes out from late morning into the early afternoon. Had the timing been 6-12 hrs earlier, NYC could have had a shot at around 10°.

Early snow signal for Central Park?

Friday should be the coldest day in over a year. The last time NYC had a high temperature of 25° or lower was 12-19-19. NYC hasn’t had a low of 15° or colder since 2-15-20. 2019-12-19 25 16 20.5 -15.8 KNYC GFS MOS GUIDANCE 1/28/2021 0000 UTC DT /JAN 28 /JAN 29 /JAN 30 / HR 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 18 00 X/N 34 15 25 14 29 TMP 30 27 26 28 32 31 27 22 19 17 16 19 22 23 22 19 17 16 15 26 28 DPT 17 14 12 10 6 2 0 -3 -5 -5 -5 -6 -6 -4 -3 -2 -2 -2 -1 -1 1 2020-02-15 31 14

This will be the 3rd winter in a row when a straight ENSO based seasonal forecast didn’t work out. Competing influences have been the way to go for 18-19,19-20, and 20-21. The previous 3 winters of 15-16, 16-17, and 17-18 were exaggerations or cartoon versions of ENSO climatology. 15-16 had the classic El Niño progression. Historic frontloaded +13.3 warmth followed by one of the best backloaded El Niño snowstorms in late January. 16-17 had the backloaded La Niña record warmth, but great snowstorms throughout. 17-18 had the expected front-loaded La Niña cold and snow through Jan 8th, then the historic backloaded La Niña 80° warmth in February with average temperatures near 40°.

A trough in the Pacific NW would be bad beyond February 2nd. But the trough in the Plains with phase 7 would be mixed. We would get the occasional cutter. But they could pull in colder air from the Plains behind the cold front. Maybe some gradient winter storm possibilities. As always, gradient storms only work if you end up in the right side of the gradient. Maybe better for interior sections? Then we have to see what happens with the mid and late February details which is beyond the range of the extended guidance.

Our system will make big headlines as it slowly comes ashore in California over the next several days.

Steady light snow here in SW Suffolk. Temperature is 35° so it’s melting on contact with the ground.

I think that the amplified MJO 7 is helping us with the PNA and EPO. Notice the west based block trying to link up with the Aleutian Ridge. The area of deeper blues are getting squeezed further SW off the West Coast than earlier runs. This can help us with the snow potential around Feb 1-2. The other thing to watch is if the MJO can make it over to Phase 8 before weakening in early February. The Euro has it currently stalling out in Phase 7 for a time. So we will probably need to watch later runs to see how they update. New run Old run

Some notable delayed cold records coming up later in the week. NYC should finally drop below 20° and HPN could get down to 12° or colder. This would be the 3rd latest to drop below 20° in NYC. It would be the 2nd latest for HPN to reach 12. The latest on record for HPN was set just last year. So this is the most recent version of how challenging it has been for winter cold since December 2015. KNYC GFSX MOS GUIDANCE 1/26/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 TUE 26| WED 27| THU 28| FRI 29| SAT 30| SUN 31| MON 01| TUE 02 CLIMO X/N 39| 34 42| 26 34| 15 26| 16 32| 23 32| 30 38| 30 37 24 39 Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Season Length 1931 02-15 (1931) 16 02-16 (1932) 18 365 2001 02-22 (2001) 17 02-05 (2002) 19 347 2012 01-22 (2012) 18 01-22 (2013) 13 365 1974 02-15 (1974) 18 01-15 (1975) 17 333 1981 03-18 (1981) 17 01-09 (1982) 17 296 KHPN GFSX MOS GUIDANCE 1/26/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 TUE 26| WED 27| THU 28| FRI 29| SAT 30| SUN 31| MON 01| TUE 02 CLIMO X/N 36| 30 38| 24 32| 12 21| 10 30| 15 29| 26 34| 24 34 21 38 Frost/Freeze Summary for WESTCHESTER CO AP, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Season Length 2019 03-08 (2019) 12 02-15 (2020) 9 343 2006 01-16 (2006) 11 01-25 (2007) 11 373 2012 01-16 (2012) 10 01-22 (2013) 11 371 1954 - - 01-21 (1955) 12 - 1974 02-10 (1974) 9 01-20 (1975) 9 343

It looks like the TPV drop into Eastern New England, which snuck up on the models, could give us a much needed assist here. We often get snows several days after an Arctic outbreak as the temperatures are moderating. The rising PNA and lingering -AO can also work in our favor.

The extreme south based blocking pattern with the +EPO has produced a real temperature oddity for NYC this month. Even with the current average temperature around 37°, this was the 4th lowest January monthly maximum temperature in NYC since 1980 at only 51°. The current forecast has this high holding for the rest of the month. Even when the coming Arctic air lowers this average temperature, it will still be way above the other years since 1980 with such a low monthly high temperature. So you can brag that we finally beat a cold record from Jan 94. New York City... Central Park, NY Ptcldy Snow Flrrys Ptcldy Sunny Sunny Mocldy /38 30/34 33/39 30/34 22/29 15/32 25/38 /00 20/80 70/40 20/20 00/00 00/00 20/30 Lowest January high temperatures in NYC since 1980 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Jan Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Avg Temperature 1 2009 47 27.9 2 1981 49 26.2 3 2003 50 27.5 4 2021 51 37.0 5 2011 53 29.7 - 1988 53 29.5 6 2001 54 33.6 7 1994 55 25.5 - 1991 55 34.9

This is a great example of why it’s such a struggle to get a significant snow near the coast in a -PNA -AO pattern. The -PNA pumped the SE Ridge a little more last minute. So the primary is rolling further north now. Had the -PNA been slightly weaker, then the -AO would have suppressed the storm more.This is why the analog composite that I posted over a week back for -PNA -AO had mostly small snow events if anything at all. Don also did a great job with his excellent -AO -PNA stats. There is no substitute for a good +PNA -AO -EPO during a Niña-like strong Pacific Jet pattern.

Even with the +5 January departure through the 23rd in NYC, the 50° high temperatures have been limited. The warmest temperature of the month so far in NYC has only been 51°. This is very low for such a warm departure pattern. All our other + 5 similar periods in January since 2000 have had more 50s and a warmer monthly max. This is a result of the very odd south based blocking pattern limiting the high temperatures. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Jan 1 to Jan 23 Max Temp and 50° days 1 2007-01-23 40.8 72°...11 2 2006-01-23 40.7 63°.....6 3 2020-01-23 39.0 69°.....5 4 2017-01-23 37.8 66°.....4 5 2008-01-23 37.7 64°.....6 6 2021-01-23 37.4 51°.....1

Maybe NYC can go for a December and February snowier than January which it hasn’t done in a while. I will pencil in a 0.2 for NYC so far with the undercount the other day. Year........Dec....Jan....Feb 20-21.....10.5.....0.2......? 09-10.....12.4.....2.5.....36.9 07-08......2.9........T......9.0 05-06......9.7....2.0.....26.9 02-03.....11.0...4.7......26.1 00-01....13.4....8.3......9.5 82-83.....3.0.....1.9.....21.5 79-80.....3.5......2.0.....2.7 68-69.....7.0......1.0.....16.6 66-67.....9.1......1.4.....23.6 61-62.....7.7.......0.1.....9.6 48-49.....25.3....6.4......10.7 45-46.....15.6.....4.2......7.9 33-34......14.9.....0.1....27.9 32-33......9.4.......T.......12.8

We could be in business if the MJO actually makes it all the way to Phase 8 during the 2nd week of February.

Yeah, northerly flow may be the best chance for NYC to drop to 15° or lower.

It does look like we could see our coldest temperatures of the winter next weekend. The models actually have the TPV diving south toward Eastern New England. So this could be a legit Arctic outbreak.

There is a limit on how far north this one can come. The ridge is too far to the east in the Plains. We also have a strong -AO and 50/50 low with and TPV pressing south from Hudson Bay. The due east motion off the coast would also tend to limit the deeper moisture from getting up here.

The GFS usually isn’t correct when it’s further north than the Euro, CMC, and UKMET 120 hrs out. The red flag is that the GFS usually has a suppression bias with our biggest coastal storms. So when it’s an amped outlier, it usually corrects to the other models as we get closer to the event.

The fast Pacific flow continues to make headlines.

Yeah, record south based blocking and warmth will do that. Pretty impressive how the blocking has gotten stuck east of New England and the Canadian Maritimes since the summer. Those record warm SSTs east of the Maritimes and New England have been pretty extreme.

NYC having a better snowfall departure than CAR and BOS through January 22nd highlights the challenges of seasonal forecasting with many competing influences. CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 433 PM EST FRI JAN 22 2021 ................................... ...THE CENTRAL PARK NY CLIMATE SUMMARY FOR JANUARY 22 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1981 TO 2010 CLIMATE RECORD PERIOD 1869 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... SNOWFALL (IN) TODAY 0.0 8.5 2005 0.2 -0.2 0.0 MONTH TO DATE T 4.8 -4.8 2.3 SINCE DEC 1 10.5 9.6 0.9 4.8 SINCE JUL 1 10.5 9.9 0.6 4.8 CLIMATE REPORT NATIONAL WEATHER SERVICE BOSTON/NORTON MA 431 PM EST FRI JAN 22 2021 ................................... ...THE BOSTON MA CLIMATE SUMMARY FOR JANUARY 22 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1981 TO 2010 CLIMATE RECORD PERIOD 1872 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... SNOWFALL (IN) TODAY 0.0 9.1 2005 0.4 -0.4 0.0 MONTH TO DATE 0.3 9.4 -9.1 3.1 SINCE DEC 1 13.3 18.4 -5.1 14.6 SINCE JUL 1 17.6 19.7 -2.1 14.6 CLIMATE REPORT NATIONAL WEATHER SERVICE CARIBOU ME 431 PM EST FRI JAN 22 2021 ................................... ...THE CARIBOU ME CLIMATE SUMMARY FOR JANUARY 22 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD: 1981 TO 2010 CLIMATE RECORD PERIOD: 1939 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... SNOWFALL (IN) TODAY 0.4 5.3 1981 0.9 -0.5 T MONTH TO DATE 7.8 17.9 -10.1 29.8 SINCE DEC 1 34.1 40.8 -6.7 47.7 SINCE JUL 1 42.2 53.0 -10.8 70.7

14 out of 17 winter months warmer than average is pretty extreme. We knew something was up when December 2015 went +13.3. It appears to have been a climate shift to warmer winters. NYC Dec 15....+13.3 Jan 16....+1.9 Feb 16....+2.4 Dec 16....+0.8 Jan 17....+5.4 Feb 17....+6.3 Dec 17....-2.5 Jan 18.....-0.8 Feb 18....+6.7 Dec 18....+2.6 Jan 19....-0.1 Feb 19....+0.9 Dec 19....+0.8 Jan 20....+6.5 Feb 20....+4.8 Dec 20.....+1.7 Jan 21.....+5.2....so far

Finally, temperatures are just slightly below normal. But nothing outrageously cold for this time of year.