During the past month, sea-surface temperatures have further warmed, especially across parts of the eastern Pacific. Much of the Equatorial Pacific Ocean now has sea-surface temperatures that are at least slightly warmer than average. This indicates that the ENSO phase is continuing to transition from a neutral phase to at least a weak El Nino phase.
Long-range climate models predict that this El Nino phase will continue to develop and persist through the winter and possibly into at least the first half of the upcoming spring. Based on this weak El Nino being in place, slightly above normal temperatures are expected across the Pacific Northwest, northern Rockies, Midwest, and western Great Lakes during the month of January. Total monthly heating degree days are projected to be lower by between 20 and 60 across these parts of the United States. Energy costs with respect to heating will also likely be lower than average throughout these regions.
Much of the southern and eastern United States is forecast to see temperatures average closer to normal in January. It should be noted that if the NAO (North Atlantic Oscillation) has more periods of being negative in December, as has been the case over the past couple of months, that colder than average temperatures will be possible across parts of the eastern third of the United States in January. This trend will have to be closely monitored.