La Nina to continue into the winter months
MANKATO, Minn. (KEYC) - A La Nina Advisory will continue as we close out fall and transition into winter. La Nina conditions are present across the central and east-central Pacific Ocean. The atmosphere along the tropical Pacific is also consistent with La Nina conditions. The likely hood of La Nina continuing into our winter months(DJF) is at 90 percent while a 50 percent chance it will protist into our spring (MAM).
The latest weekly sea surface temperature departures show a negative difference of -0.7 to -1.1 along the Nino index regions of the tropical Pacific Ocean. Forecast models indicate that these negative sea surface temperatures will continue into our winter and spring months. With sea surface temperatures forecasted around -1 to -1.5 below normal through the winter that means this will be a moderate La Nina event.
La Nina can impact the weather pattern over North America, especially during the winter months. Just like all weather events, not all La Nina events are the same but they do have similar tendencies. The most consistent pattern is that of the polar jet stream hanging out further to the south.
This southerly trajectory of the polar jet enhances the chances at below-normal temperatures across the western portions of the Midwest. As for precipitation, areas across the Ohio River Valley tend to see some wetter conditions during late winter.
For Mankato, past moderate La Nina events showed both above and below normal conditions during the winter months(DJF). Last winter was a moderate La Nina event and Mankato had an average temperature of 19.6º F which was 1.5º F above normal. Snowfall was just slightly below average from 19″ to 23.5″. Normally Mankato picks up around 23.7″ of snow during the winter season.
The coldest moderate La Nina year was back in 1955-1956 when the average temperature was almost 5º F below normal coming in at 13.2º F. The snowiest moderate La Nina even during the winter of 1970-1971 when some 34.7″ of snow accumulated.
Using both past climatological data and long range forecast models, the Climate Prediction Centers winter outlook is a good outline on what to expect this upcoming La Nina winter. That is expected an equal chance at being above or below normal. As for the first week of this winter season, models are showing signs to a near normal to slightly above average start temperature wise with near normal precipitation chances.
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