Introduction: There’s a lot of interest in the summer 2018 climate forecast EARLY this year due to the wide area of dry soils affecting the U.S. now and indicated in yesterday’s Climate Impact Co. U.S. Soil Moisture Outlook. Large areas of dry soils generally foreshadow a hot summer ahead. NOAA issues a new long-lead climate forecast today. Here’s what is expected from model-based forecasts averaging dynamic/statistical scenarios.
Discussion: Dry soils to drought conditions are affecting much of the U.S. now except most of the northern states. This dry condition is expected to continue for the Southwest, Central and Mid-Atlantic States through spring possibly easing in the Southeast and across parts of the North. Therefore the table is set from a soil moisture point of view for intensifying drought due to hot weather once summer arrives.
La Nina is present now. Forecast models vary with some hanging onto La Nina through summertime while analogs favor dissipation and an uncertain trend toward either weak El Nino later this year or back toward weak La Nina. Analogs are not certain about the last third of 2018 but agree on a La Nina to neutral ENSO scenario for summer 2018. The analog years from the current climate pattern are 2001, 2016 and 2012.
The Atlantic multi-decadal oscillation influence will weigh heavily on the summer forecast. A robust warm phase continues. The Pacific decadal oscillation is uncertain but leaning toward the weak cool phase is the most likely scenario as global models forecast SSTA to be warm across the Pacific but near normal in the northeast Pacific. Therefore the +AMO and possibly the -PDO are a good combination to estimate drought risk for summer 2018.
The AMO and PDO analogs are 2004 and 2006. +AMO is present both years while PDO is weak.
Fig. 1: Projecting ENSO scenarios for 2018.
Fig. 2: The PDO/AMO scenarios for drought risk. In 2018 we’re certain +AMO is present but less certain on the PDO regime. A -PDO is favored slightly.
Forecast: A simple analog combining the ENSO years (2001, 2006 and 2012) plus the AMO/PDO analogs (2004 and 2006) to produce a preliminary summer temperature and precipitation outlook is provided. Expected is that NOAA (and other providers) will generally follows the indicated scenarios.
The summer temperature outlook is hot! But the heat is in the West and Central U.S. and to a lesser extent New England while the Southeast U.S. is temperate. It’s early but this projection is reasonably confident. The precipitation outlook is wet on the Gulf Coast and East Seaboard while dryness centered in Iowa and Kansas will grab agriculture attention.
Much more to come on the summer outlook but expect markets to see something close to the scenario projected (below) issued today. And coming weeks/months.
Fig. 3: An estimate of summertime temperature anomalies across the U.S.
Fig. 4: An estimate of summertime precipitation anomalies across the U.S.