donsutherland1

The latest CFSv2 ENSO forecast is indicating that the ENSO Region 1+2 anomaly will be at or above +1.00°C throughout meteorological winter (December-February). It is also indicating this region's anomaly should have peaked, will fall, and then again increase. A secondary peak is actually not uncommon during strong or super El Niño events.The 1972-73, 1982-83, and 1997-98 events all had secondary peaks in this region. The 1997-98 event had a tertiary peak. Since 1950, only three meteorological winters saw 2 or more months have Region 1+2 anomalies of +1.00°C or above: 1972-73, 1982-83, and 1997-98. The latter two featured all three months with such anomalies. Given the modeling, it is very likely that August will have a Region 1+2 anomaly of at least +1.00°C. Since 1950, such anomalies have occurred in 1951, 1957, 1965, 1972, 1976, 1982, 1983, 1987, 1997, 1998, 2008, 2009, and 2014. However, only 3 of those 13 cases met the threshold being signaled on the CFSv2. By October, ENSO Region 1+2 anomalies of +1.5°C or above, filtered out almost all of those cases, leaving only 1972, 1982, 1987, and 1997. Hence, by October, we should have a strong signal as to whether this current CFSv2 forecast has a reasonable chance of verifying. In November, using the same anomaly threshold as October, only 1972, 1982, and 1997 remained. Such anomalies during meteorological winter would have implications for North American temperature anomalies and possibly snowfall along the East Coast. Should the strong PDO+ persist, the PNA+ could also predominate (1982-83 and 1997-98) leading to another warmer than normal winter in the Pacific Northwest. All of that is still far out, but the scenario currently shown on the CFSv2 would typically favor warmth across much of North America. In the more immediate future, one has typically seen El Niño events with Region 1+2 anomalies at or above +1.00°C produce cool anomalies in large parts of the East in August. Summer 2009 was an exception. Warmth has sometimes occurred in the Pacific Northwest and western half of the U.S. In the end, it's still too soon to be sure about the upcoming winter. But if the CFSv2 is right, a cool autumn could yield to a warmer to much warmer than normal December across a wide swath of the U.S. Given where things stand, one should be aware of this possible scenario, but not yet lock it in. Much can still change in Region 1+2. FOLLOW THE LATEST...

If one takes a look at the overnight 1/16 0z and 6z operational GFS runs, one finds both are very cold in the days 7-15 timeframe. Both also feature a strong EPO-. Both also contain a number of analog dates near moderate or larger snowstorms for some parts of the eastern half of North America. But if one looks more closely, there is actually a rather dramatic change between the 0z and 6z runs. The latter shows the development of meaningful Atlantic blocking to coincide with the strong EPO-. Indeed, if one goes to the 11-day objective analogs from each of these runs, one finds the following: 0z Run: Average AO: +0.125 AO > 0: 60% of analogs AO of -1 or below: 30% of analogs AO of +1 or above: 20% of analogs 6z Run: Average AO: -1.128 AO < 0: 80% of analogs AO of -1 or below: 70% of analogs AO of +1 or above 10% of analogs If one checks out the GFS ensemble forecast for the AO, one also finds that the many members are now favoring a negative AO in the extended range: If this forecast verifies and dual Atlantic and Pacific blocking develop, that would increase prospects for a cold February in the eastern third to half of the CONUS, along with southern Ontario and Quebec. The latter cold anomalies would depend on the magnitude of blocking. If the blocking becomes too strong, then the cold anomalies could be driven southward. Such dual blocking would also allow for potentially more opportunities for larger snowfalls. The Great Lakes region, northern Mid-Atlantic (e.g., Philadelphia) and southern New England areas remain on track for above normal seasonal snowfall, as the December outcomes were consistent with such seasons. The pattern ahead looks promising, particularly for the 1/25-2/15 period. If blocking develops, things could also become more favorable further south in the Mid-Atlantic region, including the Baltimore and Washington, DC areas. The takeaway is that the theme of a growing probability of a cold outcome in parts of the eastern CONUS has been sustained in the overnight guidance. In fact, even as it is still outside its skillful range, the CFSv2 has recently shifted from featuring widespread February warmth to an increasingly colder idea for the eastern third to half of North America.