The Pacific is now officially in a state of La Niña, but with a subtle/important difference from a normal La Niña as the coldest SST anomalies are located further east than is typical in most -ENSO events.
Articles by Ryan Truchelut
WeatherTiger’s weekly U.S. winter forecasts are back for winter 2017-18, and will be out each Tuesday afternoon through March. This week, we look ahead…
Winter 2017-18 is unlikely to be a historically cold winter on average, but there are signals that it is likely to be a somewhat active one nonetheless from a snow/ice perspective, particularly the further north and west you go.
The equatorial Pacific remains on the borderline between neutral-negative conditions and a weak La Niña. WeatherTiger’s November modeling again trended modestly cooler this month, with chances of at least weak La Niña in place by year’s end now well over 75%.
WeatherTiger’s October modeling has trended modestly cooler this month, with chances of at least a weak La Niña developing by December rising to well over 50%. La Niña is now likely to be strong enough to influence growing season precipitation distribution in South America, and potentially the U.S. winter pattern as well.
Our first look ahead to winter shows temperatures are likely to skew warmer than average in the U.S. Midwest, with snow/ice expectations ranging from below normal accumulations south to near normal in the northern tier.
WeatherTiger’s August modeling shows a solidly neutral ENSO state through year’s end. Major changes to this overall outlook are not expected in the next 3-6 months, as there are seldom large shifts in the Pacific in the latter half of the year.
A final update to WeatherTiger’s 2017 hurricane season update for August shows that an above normal year in terms of total activity and U.S. landfall risk is the most likely outcome. Key considerations including sea surface temperature anomalies, wind patterns, and steering currents are in relatively good agreement for this projection.
After calling for at least moderate El Niño to develop by the summer throughout the spring, dynamical models are still backpedaling in favor of projecting a continuation of warm-neutral conditions. WeatherTiger’s June modeling is cooler again showing solid neutral conditions through year’s end.
A favored pattern for the summer based on historical analogs and our proprietary modeling is an increasing tendency for ridging over U.S. Southwest and Southern Plains. All else equal, this means a warmer and drier summer than average in the Plains and Midwest.