JEFF JOHNSON S 2017-2018 Winter Weather Outlook
TABLE OF CONTENTS ABOUT THE AUTHOR Components of the seasonal outlook... 2 ENSO state/ocean temperatures... 3 Sub-seasonal outlooks... 4 Forecast models... 5 Main seasonal drivers this winter... 6 DTN s 2017-2018 winter weather outlook... 7 U.S. winter outlook highlights... 8 La Niña s impact on winter precipitation... 9 La Niña s impact on winter temperatures... 10 North central outlook... 11 Northwest outlook... 12 Southwest outlook... 13 Northeast outlook... 14 Southeast outlook... 15 Jeff Johnson is the chief science officer for DTN, focusing on long-range and seasonal weather. He has over 35 years of experience in weather forecasting for various industries. Johnson holds a Bachelor of Science in Meteorology from the University of Wisconsin- Madison. In 1993, he became an American Meteorological Society Certified Consulting Meteorologist, a highly-regarded expert accreditation. 1 South central outlook... 16 About DTN Weather... 17
COMPONENTS OF THE SEASONAL OUTLOOK 2
ENSO STATE/OCEAN TEMPERATURES El Niño/Southern Oscillation (ENSO) is the cycle between the atmosphere and the Pacific Ocean near the equator. It determines the location of the west to east jet stream. ENSO factors in SEA-SURFACE TEMPERATURES CONVECTIVE RAINFALL SURFACE AIR PRESSURE ATMOSPHERIC CIRCULATION In its opposite extremes, it can produce El Niño and La Niña cycles, which can persist for months at a time. Analogs from past events can provide clues for upcoming seasons. LA NIÑA EL NIÑO 3
SUB-SEASONAL OUTLOOKS Sub-seasonal outlooks can help determine the intensity and shape of Polar Vortices in winter, but only a week or two in advance. Strong Polar Vortices are more circular, which keep the coldest air at higher latitudes; weak ones are broken, creating dipping pockets of extremely cold air. Polar Vortices: DETERMINE NORTH/SOUTH JET STREAM FLOW Different Jet Streams and (lower atmosphere) Polar Vortex PRODUCE HIGHLY ABNORMAL TEMPERATURE & PRECIPITATION PATTERNS November 14-16, 2013 January 5, 2014 STRONG WAVY CAN CREATE BLOCKING PATTERNS BY DISRUPTING THE JET STREAM 4
FORECAST MODELS Seasonal forecast models project the future state of the atmosphere based on initial conditions of OCEANS AIR ICE These more generalized forecasts extend out several months even seasons. However, individual storm events are best predicted by shorter-range global models and ensembles, which anticipate conditions from a few days to up to two weeks in advance. 5
MAIN SEASONAL DRIVERS THIS WINTER This season, our climatologists expect A WEAK TO MODERATE LA NIÑA A NEGATIVE PHASE (COOLER) PACIFIC DECADAL OSCILLATION* A PERSISTENTLY WARM ATLANTIC OCEAN A WEAK POLAR VORTEX WITH GREATER, PERIODIC RISK OF ARTIC COLD * Pacific Decadal Oscillation is a pattern similar to ENSO, but varies over a much longer time scale. 6
DTN S 2017-2018 WINTER WEATHER OUTLOOK 7
U.S. WINTER OUTLOOK HIGHLIGHTS WEAK TO MODERATE LA NIÑA, WHICH HAS ALREADY STARTED WARMTH FOR THE SOUTHERN STATES; MORE FREQUENT COLD IN THE NORTH INCREASED DRYNESS & REDUCED RAINFALL ACROSS THE SOUTH ENHANCED RAIN & SNOWFALL TOTALS OVER THE NORTHWEST, MIDWEST, OHIO VALLEY, & GREAT LAKES 8
LA NIÑA S IMPACT ON WINTER PRECIPITATION This winter we expect Reduced snow in the Southern Rockies & Mid-Atlantic Increased snow in the Northwest, especially the mountains Increased snow for the Upper Midwest 9 Increased snow for New York, New England, & the Ohio Valley
LA NIÑA S IMPACT ON WINTER TEMPERATURES This winter we expect Greater cold than last year in the northern United States Overall milder conditions likely in the south central & Southeast More Canadian arctic air will dip south at times Cold & snow will be slow to end, lingering into March 10
NORTH CENTRAL OUTLOOK TEMPERATURES Brief, sharp cold periods Notably colder than last winter Extended winter chill into March PRECIPITATION Limited drought relief for Northern Plains Snowfall higher east, seasonable west Snow cover will linger more than last winter 11
NORTHWEST OUTLOOK TEMPERATURES Variable temperatures Short cold periods Influxes of milder Pacific air PRECIPITATION Significantly enhanced rain/snow amounts Stormier in the Pacific Northwest Abundant mountain snowfall in most ranges 12
SOUTHWEST OUTLOOK TEMPERATURES Warmer across the south Cool periods will be short-lived More seasonable north PRECIPITATION More dryness across the south Adequate rain/snow in northern areas Drought will worsen in southern California, Arizona, & New Mexico 13
NORTHEAST OUTLOOK TEMPERATURES Colder than last year Brief arctic air intrusions Coastal areas near normal PRECIPITATION Enhanced precipitation for interior areas Heavier snowfall in western & far northern areas Slightly drier Mid-Atlantic 14
SOUTHEAST OUTLOOK TEMPERATURES Warm winter expected Limited, brief cold events A good year for Gulf Coast vacation PRECIPITATION More limited rainfall, especially Gulf Coast & Florida Elevated rainfall in the Tennessee Valley region Developing dryness near the coast 15
SOUTH CENTRAL OUTLOOK TEMPERATURES Warmer temperatures will be common Only a few, brief cold periods Not as warm as last year PRECIPITATION Mainly a dryer than normal pattern Developing dryness/drought areas, especially south Near average amounts across the north 16
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