As we look at the current SST setup,(pic 1) we can see some similarities to last winter as well as some key changes in key places.(pic 3) While there are no overwhelming anomalies to point for certain one way or another, there are hints.
We have no overwhelming enso conditions that look to dominate the pattern. Therefore I like to look closer.
The North Pacific is key #1.
What is a prime puzzle piece to eastern U.S cold for the heart of Winter?(Mid Dec-Mid Feb)
We want cold anomalies at the dateline and just east at 30-40N. Thats piece 1. We currently have something that in a weakened state resembles that look. Last year those cold anomalies ran in the north Pacific from the dateline to Northwest coast of the U.S.
This was good for a cold winter in the Pacific Northwest with lots of snow. As the trough held tight in that area. The east was under a constant SE ridge for a duration of the winter. That held in place in part due to the well above warm sst anomalies in the Gulf and up the coast to the Mid Atlantic to New England. We also saw warm anomalies off the Sw Mexico coast. The cold anomalies in the Pacific north accompanied by warmth across the south and up the eastern seaboard helped keep the ridge strong and consistent warm pushes interluded with brief shots of cold.
February 2017 featured some amazing warmth. In looking back, it was similiar to the Feb of 1932 What was also similiar was the 1932 sst setup. (pic 4)Cold anomalies in the Pacific Nw, and overall the north Pacific was at or below normal and well above from sw Mexico coast, the Gulf and up the eastern seaboard. (I alluded to this often on facebook page last Feb) Feb 1932 saw many record highs that still stand over this past Feb.
As the seasonal jet changes and we flux the sst setup something also very similiar was noticed in the monthly reanalysis in the sst setup vs the 7 day changes last Feb. The setup was shifting in locations very similiar to each other and 1932 had a cold wintry stretch for 10-14 days in March. Given the likenesses and overall setup, it was alluded to, to watch what occurs. Models went strong to a almost dead on likeness at 500mb to 32′. Sure enough as March came a reoccurence happened.
As you see some reasons why patterns setup, you dig more and more into the setup and accompanying weather we experience.
Right now out SST setup has cold near the dateline, 30-40N and east. But this year instead of a overwhelming large cold anomaly on the Pacific coast, especially the Pacific NW coast. There is much more warmth(key 2) (pic 1) and over the past 7 days the sst trend has been gaining on that setup. NOT THERE YET.
The next key(Key 3). I’ll include this all in key 3. The gulf and eastern seaboard. These SST anomalies were all very warm last year. Helped the strong SE ridge hold and not break down.(much like 32′) This year up until 2 weeks ago we saw minimal cooling and a ebb n flow of warming cooling that left a slight decline vs last year. Then we just experienced Hurricane Harvey that upwelled and also dropped lots of precipitation cooling that area of the Gulf quite significantly. We also saw a unnamed storm ride up the Mid Atlantic coast cooling those waters(pic 2) and we await the affects of Irma which may significantly cool those eastern seaboard waters even more. With the possibility of more systems behind Irma.
This trifecta of hints in the ssts along with no strong enso may be a sign of a winter that will place more cold in the east. We are not there yet.
Continuing changes for east cold
1- the cold pool needs to grow in the area its currently located.
2- the warmth east of that need to enhance, become greater. Its not bad as is, but not great enough to lock a western ridge
3- gulf and eastern seaboard anomalies need to cool further and expand. Both of which are possible and I’d currently give a 60-70% likelihood this occurs more.
These are factors to watch. Not the only factors, but some hints and key changes vs the mild winter last year. The winter before was overwhelmed by the strong enso and warm east coast.
Allegheny Mountains Weather 