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- Temperatures can be warmer than average in the western and northern states.
- The South could be wet but the Canadian border could be dry.
- El Niño could play a role in this winter's weather conditions.
The winter of 2018-19 may lead to above-average temperatures in the north and west of the United States, and it is likely that some areas of the south and east will experience wetter than average weather conditions, according to the forecasts published Thursday by the NOAA.
A weak El Niño event is expected to develop this winter, which could have an impact on large-scale weather conditions. Last week, NOAA announced a 70% to 75% probability of El Niño forming later this fall and during the winter of 2018-2019 (December to February).
"Although a weak El Niño is expected, it can nevertheless influence the winter season by bringing wetter conditions to the southern United States and warmer, drier conditions in some parts of the north" said Mike Halpert, deputy director of NOAA's Climate Prediction Center, a press release.
(PLUS: winter storm central)
La Niña, El Niño, or the absence of one or the other, called the neutral phase, is only a large scale forcing on the atmosphere. This is not the only factor in determining whether a season is wet, dry, cold or hot. Other factors are at play such as the Arctic Oscillation and the Madden-Julian Oscillation., and their influence can not be predicted in the months to come.
Temperature outlook
Forecasts for this winter – December, January and February – predict the highest temperature probabilities above the average of the western United States north of the plains, Great Lakes and New England.
El Niño winters generally lead to milder temperatures than average temperatures. in much of these areas, including the northwestern Pacific, northern plains, upper Midwest and northern Great Lakes. This does not mean that there will be no freezing cold in northern climates; overall temperatures for the three month period should be above average.
Global temperature forecasts from December to February. (NOAA)
According to NOAA, much of the Ohio, Southeast and Central Atlantic Coastal Valley has an equal chance of seeing higher, lower, or near average temperatures this winter because of the uncertainty surrounding long-term forecasts and short-term weather influences. which develop in the middle of winter.
The aforementioned Arctic Oscillation (AO), which plays a role in determining the number of arctic air dives that extend into the depths of the south, is a factor in this uncertainty. If the AO enters its favorable phase to allow the arctic air masses to slide south, this could lead to prolonged periods of below-average temperatures in the east, NOAA says.
Precipitation Outlook
A band from the southern Rockies to the Gulf Coast states and the central Atlantic is the most important sign of above-average precipitation this winter.
El Niño winters are generally characterized by wetter than average conditions across the southern level of the United States
If cold air has a better chance of precipitation in these areas, it could result in snow, melted snow or freezing rain.
Forecast of global rainfall from December to February. (NOAA)
Meanwhile, some northern areas of the Rockies, High Plains and Great Lakes may experience a drier than average winter.
On the west coast, the Madden-Julian Oscillation (MJO) could play a role in heavy snow and snow rains this winter, especially as El Niño is expected to be weak, according to the NOAA. But the influence of the MJO can not be predicted long in advance.
Do not forget that these outlooks represent overall trends over a three-month period from December to February.
An individual cold front or an upper peak of high pressure may result in a colder or warmer period of time, respectively, which goes against the general trend of the three months. The same front or area of high pressure may result in a brief period of increased precipitation or drought that may or may not indicate a forecast of the overall trend.
What is El Niño?
El Niño, the periodic warming of the eastern and central Equatorial Pacific Ocean, can change the weather conditions in the space of several months, thus offering the possibility of a longer time, hot, cold, wet or dry in some parts of the world.
The sea surface temperature in the equatorial Pacific Ocean has recently exceeded the mean, which is why NOAA anticipates the potential for low El Niño conditions to develop later this fall or winter.
The black box highlights the warming of the water in the equatorial Pacific Ocean from early August to early October. (NOAA)
The maximum atmospheric response to equatorial Pacific anomalies tends to occur during the winter months of the northern hemisphere. This is why the possible development of El Niño or its counterpart La Niña is the subject of great attention before the winter.
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