GaWx

And then another wintry threat follows Barney on 12Z GFS

Barney cold follows this on 12Z GFS:

Going back to 1950, I couldn’t find a single La Niña Feb out of the 26 of them that had both a +PNA and a -AO! So, 2025 will end up quite unique in that regard.

RDU La Niña 4”+ snows Feb 15-28: 2/16/1996: 5.6” 2/23-4/1989: 4.2” 2/17-8/1989: 4.9” 2/25/1894: 5.0” GSO had 5.7” just after Feb (3/1-2/2009). Also, other areas like ATL and Athens had a big snow 3/1/2009. Athens, GA: 2/23/1989: 4.6” 2/24-5/1894 (this also hit ATL) So, 2009 (Mar 1-2), 1996, 1989, and 1894 had major SE snowstorms Feb 15th-Mar 2nd in La Niña in SE US. RDU had 2 big snows later in Mar in La Niña: 3/10/1934: 8.0” and 3/25-26/1971: 5.3”

Below is the latest GEFS +PNA prediction. If it were to verify closely, DJF of 2024-5 would end up at or very near the highest +PNA on record (back at least to 1949-50): If the above were to verify closely, I’d project Feb PNA of ~+1.60, which would mean DJF PNA of +1.45! Current highest on record are these: 1976-7: +1.43 2015-6: +1.43 2002-3: +1.20 1969-70: +1.14 1982-3: +1.08 1960-1: +1.07 1963-4: +1.06 1986-7: +1.01 Note that all of these were El Niño except the ENSO neutral 1960-1. The highest PNA on record currently for La Niña is only +0.86 (2000-01). So, that will be obliterated. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.pna.monthly.b5001.current.ascii.table

At NYC using Don’s projected 3.2 BN for Feb, it would rival the 2009-10 DJF average. But it doesn’t appear to me it would be quite as cold as 2014-5, 2013-4, and 2010-1 (using same base). @donsutherland1what do you think?

Barney says hi boys and girls on the 0Z UKMET 168 (7PM EST on Feb 18th: frigid N Rockies/Plains to upper Midwest with 2m anomalies -32 to -45) and it’s plunging south thanks to the extreme -AO/strong +PNA combo; temps <0F all day into NE/IA and dropping with lobe of TPV; near coldest of winter to date some of that area and it’s coming SE! https://www.pivotalweather.com/model.php?m=ukmo_global&p=sfct_anom-imp&rh=2025021200&fh=168&r=us_nc&dpdt=&mc= It is 12-48 hours after this that is the timeframe for the model consensus’ SE storm threat.

I think we’ll be tracking this for awhile am and currently thinking this has a good chance to be SE next significant threat. The progged extremely strong -AO just before along with solid +PNA gives me added confidence. 0Z EPS 10:1 snow:

0Z Euro: Similar position to GFS/CMC:

0Z GEFS mean (10:1) through Feb 21st

I since edited my wording about the 0Z CMC because it is actually about as far SE as the 0Z GFS. The reason the CMC’s wintry precip is centered further NW is that it’s Arctic high isn’t as strong/cold.

The latest Euro Weeklies got even colder for these two weeks (what would be coldest last half of Feb since 2010 for many) with a strong +PNA/-AO to start with +PNA continuing and suggests a crazy Feb with a mainly mild 1st half and mainly cold 2nd half, something not seen since 1999 in much of the SE: Feb 17-23 Feb 24-Mar 2:

0Z CMC fwiw: much less cold Arctic high than GFS

The GFS rang?

Hopefully Brick is in bed. If he sees this before bed, a good night’s sleep for him may be in jeopardy. But I’d still be in favor of a 2nd Brick storm thread. So, he needs to get plenty of rest beforehand.

It looks amazing for many in the SE and would be the biggest storm of the winter to date for most of NC/SC and far N GA. But always be wary about the favored NW trend, especially because this is still 8-9 days away. Any thoughts about that? Will the preceding potential -5 AO combined with a solid +PNA minimize any NW trend? Whereas Jan 10-11 had a typical NW trend, Jan 21-2 did not due to the massive Arctic high.

In addition to the snow on the 0Z GFS, check out the sleet and ZR:

Today’s high of 61 was the coolest high at KSAV since Jan 27, the last daily mean BN. Today’s mean was still slightly AN.

To their credit, the GEFS and EPS means never came that close to a 60N 10 mb wind reversal. The Euro Weeklies dropped several days in a row and got to as low as +15 on Feb 15th (Feb 2nd run) but that was it. Then it quickly headed back up. Several GFS ops had a major SSW and that in combo with the EPS falling to +15 and realizing that the GFS twice lead the way the prior 2 winters along with Joe D’Aleo’s study showing a high correlation of high solar/W QBO got me thinking there was a decent chance. Did Jim Hughes rule out a mid Feb major SSW two weeks ago? If so, kudos to him. But if not he’s just stating what’s obvious now.

Today’s GEFS based AO forecast is even more impressive for 2/15-18 as it suggests a dip to ~-5 is quite possible then! That would be lowest daily AO since 2/10-11/2021! Other Feb sub -5 AOs since 1950 were only these: -2/10-11/2021 (-5.285 on 2/10) (weak +PNA, MJO strong 7) -2/14/2010 (-5.132) (moderate +PNA, MJO moderate 8) -2/6-7/2010 (-5.205 on 2/6) (strong +PNA, MJO moderate 7) -2/5-6/1978 (-5.291 on 2/5, lowest Feb AO on record) (strong +PNA, MJO strong 7) -2/13-16/1969 (-5.282 on 2/13)(neutral PNA, MJO unknown) At the same time the PNA could be nearing +1: At same time, MJO could be in moderate phase 8:

12Z Euro for day 9: kuchera 24 hour snow (fwiw since day 9) ZR for day 9 (excludes the ZR in NW NC/VA):

12Z GFS: total ZR through day 10: -much of this is not til day 9-10 and thus still pretty far out and therefore very highly subject to major changes obviously -some of this over especially NW NC, far N NC, and in VA is from earlier storms….see 2nd image: This 2nd image is only for earlier storms. But that still means the first image’s heavy amounts in much of Triad to Charlotte area to upstate SC to NE GA are all from the day 9-10 storm.

I’ve seen in ATL bad icestorms where the temp was mainly 30-31. Not really bad on roads at those temps but bad on elevated surfaces. Especially if the ZR wasn’t pouring and winds were on lighter side. So many variables I guess. Tony @dsaurtold the forum many times about the terrible Jan 1973 icestorm in Buckhead portion of N ATL. He said the temp was mainly 31-32 in that one and the ZR was heavy at times. I think he said roads were bad, too. But there may have been some snow and sleet preceding the ZR contributing to road problems. So, you never know. How far temp aloft gets above 32 is important variable.