Tropical Pacific water temperatures are shockingly hot. Last week equatorial Pacific water temperatures averaged 3 degrees Celsius above normal for the first time ever in the key Niño 3.4 region. The previous weekly high Niño 3.4 value of 2.8 degrees was tied last week with Nov. 28, 1997. The Niño 3.4 region, used to measure the strength of an El Niño ranges from 170W to 120W from 5 degrees north to 5 degrees south of the equator. If temperatures continue to rise, or plateau for a few more weeks, this will be the strongest El Niño in history.
When warm water stored below the surface of the western Pacific ocean moves east along the equator it moves the earth’s tropical atmospheric convection cells with it. Responding to the eastward shift in the tropical convection, the jet stream moves south on normal on the west coast bringing heavy winter rains to California in strong El Niño years. With this year’s El Niño at record or near record strength NOAA’s CFS climate model predicts a strong southward drop of the storm track off the west coast. A very stormy winter can be expected from California, across the gulf states and up the east coast. This year’s intense jet stream pattern will bring much warmer than normal temperatures to the northeastern United States and eastern Canada.
This winter, California can expect heavy rains, floods and mudslides, but snow levels (elevation of rain snow line, not amounts) will be high because moisture flows from the tropics in an El Niño winter are warm and wet. California’s water situation will improve but ground water levels are unlikely to rebound to levels seen before the drought began. One year’s rains will not alleviate the long-term water problems caused by the record California drought but reservoir levels will rebound.
Heavy rains are forecast for California and the southeast from January through March 2016 by NOAA’s CFS model.
The extraordinary surge of heat in the equatorial Pacific continues to push from the dateline towards the Americas. Temperatures anomalies are predicted to peak over the next month by a number of climate models, but the effects of the excess oceanic heat will continue to grow in the atmosphere into the winter months. 2015 is already crushing records as the warmest year on record but 2016 may be even warmer because the peak in atmospheric temperatures is months later than the peak in sea surface temperatures.