Winter Forecast 2015/16 Following El Nino Path

1. Below-normal precipitation, below-normal snowfall and milder-than-normal temperatures across the interior Northwest and northern Rockies. Warm PDO and split flow will lead to weaker fronts.

2. Significant wet and snowy periods expected in the Southwest; a very active, shifty storm track from start to finish this winter; heaviest precipitation can be in January and February with potential flooding.

3. Texas Panhandle can have above-normal snow, southern Plains above-normal precipitation, just past the much above criteria in southeastern Texas. There can be at least four or five big events in the Plains.

4. There is a good chance that several storms will make impacts in the central Plains, Midwest, mid- to upper Mississippi Valley late fall and early winter, then again late winter and early spring. This can lead to near-normal precipitation, near-normal snowfall, but still milder-than-normal temperatures overall.

5. Lack of arctic shots for much of the early and midwinter will lead to a low lake-effect season in the Great Lakes where snowfall and precipitation overall can be below normal.

6. We lean toward below-normal precipitation and snowfall in the Ohio and Tennessee valleys. It could be wet early in the season. Northern areas of this region look to be the driest.

7. Gulf Coast region into the Southeast can have frequent big rain events that over time can lead to higher flood risk. Also, there can be more frequent fog events in the mornings.

8. Northeast will be wet and mild through the middle of the season but could turn colder and snowier in February, not as brutal as last year. Snow events could linger into March. Confidence is lower and is addressed more in the discussion.

9. Higher chance for above-normal snowfall and ice storms in upstate New York, northern New England into Canada this winter where rain events along the coast early in the season can be snow events in the high elevations.

10. Severe weather, typical for strong El Nino, can impact Florida Peninsula, southern Georgia and South Carolina; warm PDO favors wet Southeast.

Temperature map falls in line with both the models and analogs for the winter season. However, the core of mild weather in the northern Rockies leans more toward the models at this point rather than the analogs. The analogs have the core centered over the northern Plains. December may be chillier than the analogs show. The Japanese model is the coldest in the middle of the nation than anything that I have seen.

Analog temperature and precipitation maps

We are very close on precipitation compared to both the analogs and models. We have two dry areas as you can see. We kept the below-normal area in the Northwest across the interior with fear that precipitation can right up the coast, especially early on in the season. The much above-normal areas just meet the criteria. We favor the Southeast more than the other two areas right now, although conditions may be more favorable, outside of rain amounts, for flooding in the other two areas.

Looking at the SST temperature anomaly map, there has been some change off the Northwest coast. Stormy weather in September has churned up the waters and they have cooled, weakening the PDO slightly. This will continue in October before leveling off later in the month. We now expect a moderate PDO through the winter, not a strong PDO. This could have impacts on the storm track, East Coast phasing and the intensity of dryness and mild temperatures in the Northwest. El Nino is strong.

There is a consensus among the models that El Nino will remain strong through the winter, start to weaken in the spring and potentially break down over the summer to neutral conditions. This trend has occurred upon most strong winter El Nino since the 1950s. El Nino will be a dominant signal through the winter and even the spring. The risk of the late winter season is whether our strong eastern Pacific El Nino will shift to a central Pacific El Nino before the winter is over. If this occurs, which has happened with many past El Ninos, then the stormy and colder weather can be more widespread across the country as the northern jet will be more involved, also leading to more phasing for the East. Timing is important as well.

Looking at the Pacific east of Hawaii, there is a warm area of water that could play a role in the positioning of the jet and storm track for the West Coast. This could also enhance rainfall on the West Coast if it stays warmer than normal, which we feel it will. This is positive for rainfall in California. Our feeling is the central California coast to the central mountains may be in line for heavier rain and snow in the middle of the season, much more than the past couple of years. Whether or not rainfall matches 1997/98 totals, the amount of burnt land and patterns left can lead to devastating flooding and mudslides for home owners in the region, but the positive note will be the snow that piles up in the mountains to help very low reservoir levels for the future.

We have changed to percentage of normal snowfall on our maps. This can be challenging in the South where seasonal snowfall averages are very low and it takes only one storm to exceed normal, but I can add from the map above that the frequency of snow events and ice can be near to slightly above normal for northern New England and upstate New York. What should be different this year compared to last winter in central and southern England to the northern mid-Atlantic is the number of snow events to rain events. Changeover and rain events will be up compared to last year which cuts into the snowfall amounts by half or even more in some spots, but some more research, done by my co-worker Brian Wimer, found that a couple of the current analog years did have high snowfall totals for the season in the East's big cities. However, much of the seasonal total came with a couple of storms with big breaks in between. This could be what we see this season for the big East Coast cities.

The frequency of storms producing snow in California will triple at least this coming winter season. Even the coastal ranges should wind up above normal on snowfall. Another area we are high on is the Four Corners. Climatology says that this area gets hit early then late but eases in between. This may not be the case this season, where the storm track will be busy for much of the time. The Midwest and central Plains may have frequent chances for snow or mixed events early on in the season, then quits before returning again in the very late winter or early spring time period. The Cascades will run just below normal but will have some systems. Interior Northwest and northern Rockies will be way down on snow events. Across the Great Lakes, with the lack of arctic air in the early to midwinter season, the lake-effect events will be down this season, which is the reason why we kept below-normal snowfall in the east-facing normal lake-effect regions.

Two potential storm tracks that bring risk to snowfall map

But there are always risks in the winter forecast. Putting out forecasts in the summer and again in September can be tough because the mean upper jet has not yet been decided on its exact placement which affects the storm track. So we have two potential storm tracks for later in the winter season which can lead to two major differences in snowfall for the Northeast and how far north precipitation will reach on the West coast. This may be determined by the strengthen of the PDO and how much influence it will have on the upper pattern in the northeast Pacific and western Canada. Also, there is a lack of sea ice. This, combined with the warm, northwest Atlantic water, can produce more ridging and perhaps blocking later in the season. Scenario 1 would give much more snow and ice to the Northeast, higher than what we have right now, and lead to colder late season temperatures with a stronger PDO and late-season blocking. Scenario two leans more toward our predictions, but we may be too low on temperatures in the Northeast for late in the season. Temperatures could be 2-4 degrees higher if El Nino completely takes over in scenario 2.

Report a Typo