Keith Huffman, filling in for Kevin Myatt thru Tues.
Low Humidity and high temps in the 70′s will anchor a spectacular weekend. Not much to write home about, just get out an enjoy these great late summer/early fall days.
Here are a few links you can eyeball for my winter discussion. Note the years 09/10, 02/03, 86/87 and 65/66– the number trends are close. We are NOT close to those years. We are in a 4 year run of La Nina into La Neutral, which is you examine those charts, is hard finding a decent match.
Last winter was interesting. There has been some research by Judah Cohen about the advent of Snow cover in Eurasia and how that relates to a colder and snowier winter of much of the USA(including our area). Winter showed some promise as the snowfall growth was great in October, but we didn’t have much cold air until March. So, I’m not sure that was just a “right for the wrong or different reasons, rather than backing up his research.
It’s a bit early to get into any type of winter outlooks. The biggest message I want to convey is that we have a higher level of uncertainty heading towards this cold season. The easiest type of winter to make an outlook for in the Roanoke and New River Valley is a moderate(west based) El Nino, add in a Positive PDO is as close to a slam dunk for a cold and snow winter. 09-10, 02-03, 86-87 and 65-66 are examples of this. (PDO ran up to near positive in 65-66, other two were very positive)
So, the further we move away from a Moderate, West Based El Nino, the harder it is to forecast winter here locally. To answer the question on WHY is Moderate El Nino’s create Thunderstorms(Convection) near the international Date line and that tropical forcing seems to be strong driver of global weather patterns when in place. (this goes back in the winters mentioned even back in the 60′s)
This year is somewhat uncharted with the 4 year running without an El Nino peaking in, Pacfic looks -PDO but has an odd looks and the QBO maybe sinking back towards 0 as the winter progresses.
What I need to make a decent outlook:
1. Any change in El Nino/La Nina. My guess is we don’t see any change that would matter.
2. Any switch in the PDO. It’s strongly negative (Positive favors good ridging in the west which makes cold and snow more likely in our area)
This falls in the possible and I’m watching it.
3. Eurasian snow cover in October. Even removing last years possible right for the wrong reason , it’s something that has shown to help.
4. October NAO and temps. This isn’t an exact science, but cooler than normal temps achieved without a -NAO could be a harbinger of a colder and snowier winter.
As of now, I’m thinking a moderate winter with temps close to normal and snowfall slightly below normal in the Roanoke and New River Valleys. Somewhat drier conditions, especially compared to this summer can be expected. I will fine tune this as we move in closer, but that’s a few general thoughts.