griteater

GFS happy hour is dropping the mother lode of cold into the lower 48 late in the run

CFS Weeklies for weeks 3-6 (Jan 23 - Feb 20)

EPS Day 10-15 Mean (850mb Temp Anomalies)

This GFS run from hr200 to hr324 gave me a flashback to the early Jan 2017 storm look where it tucks part of the upper wave in the NE Pac back west, but dives a piece of it southeast out of the Pac NW into the cold air over us

@Tom Niziol - Only 28.1% #snow cover across the US right now, have to go way back to 2012 to see less on this date at 12.9%

The PNA Index from now til Jan 14th

Based on what we’re seeing on the modeling and our current climate, nothing would surprise me on the warm side for January. Things like top 5 warmest January ever / warmest January day ever, etc.

Well this winter certainly isn't going as I expected. Kudos to @Isotherm as his winter outlook ideas have performed well to date. As CPC notes in the previous post, we need to see the tropical convection move away from the Indian Ocean and Maritime Continent and move into the Western & Central Pacific in order to give us a better shot at stirring up the Pacific side pattern. Climo-wise, February gives us our best shot at seeing a -EPO/+PNA pattern during +ENSO winters. Last winter (also +ENSO), we saw a -PNA pattern in February. As @raindancewx has noted on the main board ENSO page, one thing that has been different this winter compared to last is the SOI. The SOI was +9.3 in Dec 2018 and neutral to positive from Oct-Dec (atypical of +ENSO winters). The SOI was -5.5 just this past Dec, and also negative in Oct & Nov (more typical of +ENSO winters). That may be one indicator that we will see a more typical +ENSO response in February. 2 flies in the ointment would be: 1) Convection not moving out into the Pacific, and instead, hanging around in the Eastern Indian Ocean and Maritime Continent. That would likely lock in the warmth going foward; and 2) The continued +AO overwhelming any Pacific side shake up. We can see here the CFS model showing the tropical convection (-OLR) moving away from the Indian Ocean and Maritime continent (40E to 140E) and consolidating in the W Pac & C Pac (150E to 150W) in the second half of January. Accordingly, the CFS has been trending colder for February, with a deeper eastern trough in recent runs (trend on last 8 runs shown): That's just one model though - who knows if it is right, but it would fit well with +ENSO climo. Also of note is Paul Roundy's Experimental MJO Forecast Tool which shows the tropical convection kicking out into the W and C Pacific and a colder pattern in the eastern U.S. by early Feb. For reference, see: https://twitter.com/PaulRoundy1/status/1213065361727393798 http://www.atmos.albany.edu/facstaff/roundy/waves/rmmcyc/indexmjo.html

Here's the text from CPC to go along with those maps... Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks NWS Climate Prediction Center College Park MD 300PM EST Fri Jan 03 2020 Week 3-4 Forecast Discussion Valid Sat Jan 18 2020-Fri Jan 31 2020 The global tropical convective pattern remains weak, with ENSO-neutral conditions prevailing, an incoherent MJO signal, and a decaying Indian Ocean Dipole (IOD). Therefore, little contribution from the tropics to the downstream midlatitude pattern during the Week 3-4 period is evident in the statistical guidance. Dynamical models almost uniformly favor renewed MJO activity, however, with the enhanced phase crossing the Maritime Continent over the next two weeks at a high amplitude on the RMM-based MJO index. The weakening IOD signal effecting a change in the base state may partly explain the forecasted high amplitude signal, but should a robust MJO event develop and propagate to the Pacific, it could help promote a substantial late winter pattern change over North America. These impacts would occur largely after the Week 3-4 period.

^ Stronger +IOD look too, which makes sense (I think it will linger thru winter because of how strong it’s been )

You can get SST reanalysis maps back into the late 1800's here - https://www.esrl.noaa.gov/psd/cgi-bin/gcos_wgsp/printpage.pl

A boost to subsurface warmth may be on the way... From NOAA Weekly MJO Report (May 6) - "Some erosion of upper ocean heat content is apparent east of the Maritime Continent, but most noteworthy is a westerly wind burst appears underway near 150E. This is likely to trigger a downwelling oceanic Kelvin wave to help reinforce the warm water availability for the low frequency state in the Pacific."

Surefire signs that winter has gone bad: 1. Severe weather talk in the eastern U.S. 2. Snow in Seattle and Portland

I think we'll see radar break out nicely across E TN / NE GA / NC / northern half of SC overnight into early morning and spreading east thru the day. For you and I, soundings are sketchy for snow, but the timing is good (night and early morning) and it may be just cold enough. I'd keep expectations low on amounts....seeing flakes fly and maybe some light accumulations

It's overnight into early morning for Western Carolinas

A visual of the upper low dropping down thru Nebraska and Kansas - https://www.tropicaltidbits.com/sat/satlooper.php?region=atlpac-wide&product=wv-mid

It’s a closed contour upper low that’s dropping down into the trough behind our departing storm. It’s currently located over S Dakota/Nebraska and will drop into E Oklahoma, then swing thru the SE states. Euro has precip breaking out with it in E TN / N GA a little before midnight then swinging east thru the Carolinas overnight and into the morning. Shouldn’t be anything major, but could be some nice embedded snow showers in there

Some of us have started adding some model performance thoughts on the storm here, FYI: https://www.americanwx.com/bb/topic/49398-southeast-winter-storm-threats-model-performance/?do=findComment&comment=5065039

The NAM is the new Dr No

Yeah Euro bumped north with precip and temps

Upper level divergence on the GFS....this is what the big ones look like

RAP and HRRR are usually boiling with heat...so, it's good to see though the NAM has a great track record with these winter storms over recent years....I think we all just need to move to the high country and be done with it

University of Wyoming has a good site for the actual balloon launch soundings (launched twice a day at 12z and 00z) - http://weather.uwyo.edu/upperair/sounding.html