Monday, July 21, 2014

First Full Winter Forecast from Long Range Climate Models Released

The first forecast encompassing the entirety of the 2014-2015 winter season has been released from the major long range climate models. Today, we will discuss the three-month averages of temperature and precipitation anomalies. Future posts will break down these averages into month-by-month increments.

The first graphic we will look at shows temperature anomaly forecasts averaged out over December-January-February. In this image, we do see a variety of solutions, with the majority of them supporting a warmer than average winter. The CFSv2 model, the long range forecast from the American weather services, inundates Canada and the United States with a well-above average winter. Only Mexico is safe from the extreme warmth here. The two Canadian weather service projections, labeled CMC1 and CMC2, show different projections. The CMC1 forecast keeps most of the nation warmer than normal through February, only sparing the Four Corners region in the United States, while the CMC2 projections has much of the Central and East US in below-normal temperatures for the winter. Alaska and western Canada look to experience warm weather. Rounding out the top row, the GFDL_FLOR, a version of another American model, has the Plains/Rockies in for a chilly winter, while keeping the North US warm.

Along the bottom row of forecasts, we begin with the GFDL model, a variant of the GFDL_FLOR model we just analyzed. This forecast keeps most of the nation warmer than normal during December, January and February, though a cool reprieve is given to those in the south-central Plains. The NCAR model, another American climate model system, turns on the oven for the Lower 48 while locking Alaska and northern Canada in the freezer. A variant of this NCAR model, the NCAR_CCSM, has nearly all of North America seeing warm readings on the thermometer this winter. Lastly, the NASA model, yet another American-based forecast, shows a cold Central & East US winter, with a warm West Coast, not unlike what we saw last winter.

As for precipitation, the picture is much less clear. The CFSv2 model has a dry Pacific Northwest and New England, but finally brings wetter conditions to the drought-stricken Southwest and South Plains. Additional wet weather continues into the Gulf Coast region. The CMC1 has a snowy winter for the Great Lakes while continuing the above-normal precipitation trend in the Plains, but the CMC2 model brings this moisture to the Ohio Valley, leaving the Pacific Northwest with the driest outlook. The GFDL_FLOR resembles the CFSv2 forecast, drying out the Pacific Northwest, moistening up the Southwest and South Plains, but this time extending this moisture into the East Coast.

Along the bottom row, the GFDL model has a nightmare forecast of wet conditions in Oregon and Washington state, resulting in yet another dry winter for California and the Southwest. Texas and the southern Plains see their winter forecast with added precipitation, but negative precipitation anomalies hold over the Ohio Valley and Northeast. For the NCAR forecast, the entire West Coast observes a very wet winter, also seen in the Eastern US. Only the Central US is kept out of this above-normal precipitation inundation. The NCAR_CCSM forecast brings above normal precipitation to nearly everyone in the Lower 48, except for the Pacific Northwest. Lastly, the NASA model has a very dry West Coast winter, reciprocated along the Midwest and Ohio Valley. Wetter than normal conditions are observed along the Gulf Coast.

Breaking it down, I want to first throw out the NCAR, NCAR_CCSM and NASA model forecasts, as they are known to exaggerate anything they forecast, and generally retain a very poor track record. I feel the general consensus of climate models is too warm, mainly because the primary factor that brought us a cold winter last year is still in place today. I realize that this factor can't control the entire atmosphere, but if anything's going to have a synoptic impact this winter season, it'll be the warm waters in the Northeast Pacific, bringing cold air down south from Canada into the US.
It is rather likely we will see a wetter than normal Southwest, South Plains and Gulf Coast, but beyond that, precipitation anomalies for other areas of the United States are in question. I'm not confident in the East Coast snowy anomalies, nor the both positive and negative anomalies seen across the Midwest and Great Lakes. We will need more time to figure that portion of the forecast out.