Avg Oct temps worldwide highest recorded since 1880; in US, Oct 4th warmest in 120 yrs http://t.co/sYINFFQ9SL pic.twitter.com/YXnG6JLKAq

— NIDIS Drought.gov (@DroughtGov) November 20, 2014

Winter precipitation outlook issued November 16, 2014 via the Climate Prediction Center

Winter temperature outlook issued November 16, 2014 via the Climate Prediction Center

Season drought outlook issued November 16, 2014 via the Climate Prediction Center

From Climate.gov:

After a memorably cold winter in the central and eastern United States last year, and some very cold weather this month, folks are likely wondering if this cold weather is a harbinger of things to come. The simple answer is “not necessarily,” as the persistence of weather and climate from one winter to the next or even one month to the next is usually fairly low (Livezey and Barnston 1988; Barnston and Livezey 1989; Van den Dool 1994). While “persistence”—the prediction that recent conditions will continue—is a simple forecast to make, it rarely proves to be as accurate as forecasts made using dynamical models or more advanced statistical methods.

So does that mean this won’t be a cold winter in the central and eastern part of the nation? Again the answer is “not necessarily.” According to the NOAA Climate Prediction Center (CPC) mid-November outlook, odds favor below-normal temperatures in certain parts of the country, and many of those areas do turn out to be in the south-central and southeastern United States, as we will discuss shortly.

Furthermore, and perhaps more importantly, even in regions where above-normal temperatures are favored, a colder-than-normal winter is still a possibility. Remember, CPC’s outlooks describe probabilities, which means—as we’ve explained in earlier blog posts—that even when one outcome is more likely than another, there is still always a chance that a less favored outcome will occur.

The El Niño-Southern Oscillation (ENSO) provides strong clues as to what we can expect during winter across much of the United States. Of course, this only applies when El Niño or La Niña are present, and as we approach winter, we find ourselves still waiting and wondering if El Niño is going to begin or not. However, despite the reluctance of El Niño to show itself so far this year, CPC forecasters have considered potential impacts from El Niño and have slightly tilted the outlook (particularly the precipitation outlook) in that direction.

And if El Niño remains a no-show this year, what will this mean for the forecast? Actually, as you might expect, not much, because the forecasters understand the fact that El Niño has a 58% of developing, which also means that there’s a 42% chance that it won’t. To see how information about El Niño gets incorporated into the forecast, let’s take a look at the precipitation outlook. (El Niño often has a more robust influence on precipitation than on temperature.)

The winter precipitation outlook favors wetter-than-normal conditions across the southern tier of the nation extending northward along the East Coast, as well as in southern Alaska, and drier-than-normal conditions in central Alaska, parts of the Pacific Northwest and around the Great Lakes and Ohio Valley. This pattern is quite consistent with the average precipitation patterns seen during previous El Nino winters.

However, you’ll note that the largest probabilities on this outlook are all less than 50%. This means that while above-normal precipitation across the South is the most likely out of the 3 possibilities (below normal, near normal, or above normal), it’s more likely that we’ll see precipitation that is “not above-normal.” That is, the combined chance that the outcome will fall in one of the other two categories (near normal or below normal) is higher.

It’s like spinning a climate roulette wheel. While the “above” area is the biggest piece of the pie, the near-normal and even below-normal areas are not insignificant and could occur. These are very modest probabilities for an El Niño winter and reflect the reality that El Niño is not a sure bet for this winter. And even if it does develop, it’s likely to be a weak event, resulting in weak impacts.

For example, in contrast to this year’s ENSO situation, precipitation probabilities in Texas and Florida during the 2009-10 winter outlook exceeded 50% for above-normal rainfall, and they exceeded 70% during the peak of the 1997/98 event. In both cases, the most likely or favored result occurred, as wetter-than-average winters prevailed. This year our confidence level is not so high, but we still think the probability for above normal is higher than it would be purely due to chance, which would be 33.33%.

The temperature outlook favors a warmer-than-normal winter over Alaska, the Western United States, and northern New England, while below-normal temperatures are favored across much of the south-central (2) and southeastern parts of the nation. Probabilities of above-normal temperature exceed 50% along the West Coast, so this region has a significantly reduced chance (just 15%, according to the pie chart) of seeing a colder-than-normal winter.

Also note that both maps include areas where neither above- nor below-normal conditions is favored. Those areas are shown in white, which represents “equal chances,” and it means that the odds for above, near, or below-normal are all the same (33.33%). This doesn’t mean that temperature or precipitation is expected to be normal this winter in those regions (the probability for that is also 33.33%), but rather that there’s no tilt in the odds toward any of the three categories. Thinking back to the roulette wheel, the areas of each region would be the same, so the likelihood of any of the three categories occurring is also the same.

Making seasonal forecasts is a very challenging endeavor. Seasonal climate models are not as skillful as weather models, and phenomenon like El Niño or La Niña only provide some hints as to what might occur during an upcoming season. CPC issues probabilistic seasonal forecasts so users can take risk and opportunities into account when making climate-sensitive decisions.

However, keep in mind that these outlooks will primarily benefit those who play the long game. The maps show only the most likely outcome where there is greater confidence, but not the only possible outcome. For example, while the outlook favors above-normal temperatures in northern New England, it wouldn’t be shocking for temperatures this winter to be near-normal or even colder-than-normal. I just wouldn’t bet on it.

US Drought Monitor November 18, 2014

West Drought Monitor November 18, 2014

Colorado Drought Monitor November 18, 2014

Click here to go to the US Drought Monitor website. Here’s an excerpt:

Summary

Bitter cold along with some snow settled over the central U.S., affording little — if any — drought relief. Farther east, soaking rainfall eased drought conditions in the Southeast, while highly variable rainfall in the Mid-Atlantic and Northeast mostly prevented expansion of abnormal dryness. Out west, most of the region’s core drought areas remained dry, though locally heavy rain and mountain snow were observed in parts of the Northwest. A shallow to moderate snow cover encompassed more than 50 percent of the contiguous U.S. at the end of the period, establishing a new benchmark for the date…

Central Plains

Despite a mostly dry week, the drought depiction over the central Plains remained unchanged due to bitter cold. A historically cold air mass settled over the region, with temperatures averaging 20°F or more below normal. Long-term drought remained entrenched over the central High Plains, where precipitation dating back 36 months has tallied 60 to 75 percent of normal…

Southern Plains and Texas

Bitter cold — albeit dry — weather resulted in no change to the drought depiction except along the Texas Gulf Coast. Temperatures averaged 15 to 25°F below normal for the week, with some shallow snow noted over northern portions of the region at the end of the monitoring period. Despite the frigid, mostly dry conditions, some Abnormal Dryness (D0) was reduced along the southeastern coast of Texas where rainfall totaled locally more than 2 inches. Short-term drought remained most intense (Exceptional Drought – D4) along the Texas-Oklahoma border west of Wichita Falls, where 90-day precipitation has totaled less than 50 percent of normal. In contrast, many of the long-term drought areas (“L” designation) from Texas into Colorado have received above-normal precipitation over the past 90 days, but are still wrestling with the impacts of longer-term deficits (60-80 percent of normal over the past three years)…

Western U.S.

Variable conditions in the north contrasted with ongoing drought elsewhere. In addition, Santa Ana winds developed in California, exacerbating drought and enhancing the risk for wildfires. The current Water Year has been largely a disappointment in central and southern portions of the region, but has gotten off to a good start in the Northwest.

In northern portions of the region, a steady plume of Pacific moisture helped produce 1 to more than 4 inches (liquid equivalent) of precipitation in the Cascade Range, providing localized relief from Abnormal Dryness (D0) to Severe Drought (D2) in southwestern Oregon. Despite the beneficial moisture, the drought areas of southwestern Oregon are still contending with the impacts of last season’s poor end to the Water Year; 12-month precipitation averaged 60 to 85 percent of normal in the state’s remaining drought areas despite this week’s higher totals. In contrast to the localized Northwestern improvements, D0 was increased northward in Idaho and far northwestern Montana, where 60-day precipitation has tallied locally less than 60 percent of normal

Farther south, the 2014-15 Water Year has afforded little — if any — drought relief to California. Despite some light to moderate precipitation (0.2 to 1 inch, liquid equivalent) during the period across central and northern California, the totals still fell short of normal and did nothing to offset the impacts of the ongoing three-year drought. The current Water Year (which began October 1) has gotten off to an abysmal start; rainfall to-date (since October 1) has totaled 10 to 35 percent of normal in the Exceptional Drought (D4) areas around San Francisco, and locally less than 20 percent of normal in the D4 around Los Angeles. Likewise, the dry, mostly mild start to the winter has left snowpacks in the Sierra Nevada well short of normal. The dryness has been exacerbated by Santa Ana winds, which gusted over 40 m.p.h. in southern California.

In the Great Basin and Four Corners, there were no changes to this week’s drought depiction despite the very poor start to the current Water Year, particularly in western portions of the region. The season’s poor initial prospects are reflected by season-to-date (since October 1) precipitation, which has totaled locally less than 10 percent of normal in the Great Basin and western portions of the central and southern Rockies, with most areas reporting less than 30 percent of normal. Changes to the drought depiction across much of the west are typically slow to occur during the early part of winter, as the development of the Water Year will be crucial to the region’s drought relief (or development) prospects…

Looking Ahead

Milder weather will gradually develop over much of the nation, with precipitation chances greatest east of the Plains and in the Northwest. Following bitter cold early in the period, intensifying southerly flow will allow above-normal temperatures to develop across much of the nation. The moist, warm flow from the Gulf will set the stage for locally heavy rain from the southeastern plains and Mississippi Valley to the Appalachians. Meanwhile, an additional influx of Pacific moisture will produce locally heavy rain and mountain snow in the Northwest, with some moisture expected to spread into the northwestern quarter of California. However, the southern Rockies will remain mostly dry. The NWS 6-10 day outlook for November 25 – 29 calls for below-normal temperatures across much of the U.S., with warmer-than-normal weather confined to New England and west of the Rockies. Meanwhile, below-normal precipitation from California to the central and southern Plains and Delta will contrast with wetter-than-normal conditions along the East Coast and across the nation’s northern tier.

New GAO report shows we must act now to address the growing economic costs of climate change in Colorado: http://t.co/P6UnsS1zc3

— Michael Bennet (@SenatorBennet) November 20, 2014