Monday, August 25, 2014

2014-2015 Winter Forecast Update: First Maps & Outlooks Released

This is the latest update to the 2013-2014 Winter Forecast, likely the last one before the release of our Official 2014-2015 Winter Forecast. In this update, we will publish our first maps, to give you a feel of what we've been saying in recent weeks, now in the form of graphics.
This update will be organized into two sections: the Temperature Outlook section and the Precipitation Outlook section, with regional breakdowns for each section.

I. Temperature Outlook: Cold Winter Now Expected

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The temperature outlook for this coming winter can be significantly determined by the global sea surface temperature anomalies we are currently seeing. The image above shows the latest weekly SST anomalies across the globe. We're going to focus in on two major items here.

I. Persistent Warm Pool in Northeast Pacific
We've discussed this a lot this summer, and the enormity of its influence is still a concern for this winter. The large pool of warmer than normal waters is still present in the Northeast Pacific and into the Gulf of Alaska. Last winter, this body of warm waters allowed a very strong ridge of high pressure to form along the West Coast of North America, which then enabled the infamous polar vortex to slide south into Canada, making the winter of 2013-2014 as cold as it ended up being. This winter, it looks like that same warm pool will be back again, which could set up yet another dicey situation for the risk of a cold winter.

II. Warm Waters Offshore Greenland, Canada
Something we didn't see last year, but is now present, is a swath of above normal water temperatures from the area west of Greenland to the waters in northeast Canada. Typically, the presence of these warm waters in this part of the world can enable strong high pressure to form over Greenland, forcing the jet stream in the United States to buckle south and bring cold air flooding into the Central and East US. While this wasn't present last year, it is certainly available this year, and is something we'll need to watch often for an increased risk of a cold winter.

Something else we're using to watch for this winter is the perfect-scoring analog winter of 1958-1959, which we discussed earlier last week.

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The analog of winter of 1958-1959 was quite a cold one, as the image above shows. Temperature anomalies were well below normal across the Northern Plains and Upper Midwest, as well as the Northeast. Below-normal anomalies still extended into the Plains and Mid-Atlantic. From there, warmer than normal conditions were observed across the Western United States, as well as a fraction of the Southeast, in Florida.
The analog year of 1958-1959 matched up with all five of my parameters set forth that help determine the synoptic atmospheric conditions for a long-range outlook. I had success utilizing this method last winter, and current indications are that it could be successful again this winter. Whether or not that happens remains to be seen, but for now, it supports the growing theory that the upcoming winter will be a cold one.

Because this is just an update and not the actual Official 2014-2015 Winter Forecast, we won't go in-depth into my explanations just yet, but some other articles pertaining to my temperature outlook include Sea Ice Records, and the concept of a Modoki El Nino set-up.

That said, here's my first outlook for the upcoming winter.

Subject to potentially drastic change
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My first outlook places the Pacific Northwest in slightly warmer than normal conditions due to the aforementioned warm pool in the Pacific Northeast and Gulf of Alaska, where a sustained ridge may form. The majority of the Rockies and the Southwest may observe around normal conditions, though a bump up to warmer than normal could be in the cards for the 2014-2015 Official Winter Forecast. I expect the majority of the Central and East US to see below normal temperatures for the upcoming winter at this time, with the Gulf Coast around neutral. New England may have to watch for bouts of warmth due to the proximity of warm waters near Greenland, which could spread ridging into the Northeast.

II. Precipitation Outlook Still Cloudy

We're going to start out this section by going back to our analog year of 1958-1959 and seeing what it says.

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During the winter of 1958-1959, the majority of the nation saw quite a dry season. The southern Midwest and Ohio Valley regions were hit by a strong drought-esque episode, which saw precipitation anomalies running more than 5 inches below normal. This episode was observed in the Gulf Coast, Plains, Mid-Atlantic and Northeast, in addition to the aforementioned two regions. Some dryness was observed in the Rockies and along the West Coast, but anomalies are too variable to determine a specific trend. Some above normal precipitation was seen in the northern Ohio Valley, as well as the deep Southeast, but the majority of the nation was dry.

Because some of the other variables are still too uncertain to definitively forecast on, I made this outlook based predominantly off of the analog year of 1958-1959, typical precipitation patterns with ridging in the northeast Pacific, as well as a couple other factors that are expected to play into this winter.

Subject to potentially drastic change.
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As of now, I'm expecting precipitation anomalies to be mainly below normal across the southern Midwest and Ohio Valley into the Mid-Atlantic and parts of the Southeast. Wetter than normal conditions should persist along the Gulf Coast, primarily in Florida, while slightly above normal conditions can be expected in the Southwest. Normal to slightly above normal precipitation anomalies may be observed in the Great Lakes and northern Ohio Valley, while average conditions are currently favored in the Rockies and New England.

These graphics are expected to change, potentially significantly, by the time the 2014-2015 Official Winter Forecast is released. However, this should give you an idea of where my thoughts are right now, even though they certainly are not set in stone.