Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu Mar 19 2020 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS ENSO-neutral conditions remain in place across the Pacific Ocean and ENSO-neutral conditions are favored to continue through summer 2020. Thereafter, there is considerable uncertainty for the phase of ENSO entering autumn into early winter 2020. The April-May-June (AMJ) temperature outlook favors seasonal mean temperatures to be above-normal for nearly all of the United States with the greatest odds forecast for northwest Alaska, California and the Southwest, along the Gulf Coast and for the eastern one-third of the country. Lower probabilities for above-normal temperatures are forecast for areas of the central lower 48 and the Alaska Panhandle. A similar pattern is forecast through the summer and autumn months moving forward. For precipitation, there are elevated odds for above-normal seasonal total precipitation amounts for northwest Alaska and for most of the central and eastern U.S. with the highest chances located across the Ohio Valley. Below-normal precipitation is most likely for the South coast of Alaska southward and eastward to include the Pacific Northwest and northern California, the central Rockies, New Mexico and western and southern Texas. Progressing into and through summer 2020, the aforementioned regions of above- and below-normal precipitation are maintained, but at decreased coverage and confidence. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS ENSO-neutral conditions are in place across the Pacific Ocean at the current time. Sea surface temperature (SST) anomalies vary across the equatorial Pacific Ocean and range from greater than +1.0 degrees C west to just east of the Date Line while only small SST anomalies (positive and negative) are evident in the east-central Pacific portion of the basin. The Nino3.4 regional SST anomaly has oscillated between +0.2 to +0.6 degrees C for the last several months. At depth, there is a substantial area of positive ocean temperature anomalies from 160E to 120W primarily over a layer of 50 - 150 meters depth. Negative ocean temperature anomalies are present in the western Pacific and also in the far eastern Pacific Ocean close to the surface to a depth of 100 meters. Atmospheric conditions do show enhanced convection along the equator near the Date line associated with the positive SST anomalies located in this region. This convective anomaly has linked with the subtropical and mid-latitude circulation in the northeast Pacific in recent weeks. Monthly mean wind departures from normal currently indicate a small region of westerly wind anomalies along and just south of the equator west of the Date Line. Anomalously high soil moisture content is present from the northern Plains to the western Great Lakes southward to include most of the Great Plains, Mississippi Valley, Ohio Valley, Tennessee Valley and Southeast. Severe and extreme drought conditions are now present across south Texas and deteriorating drought conditions continue across much of California, Oregon and the Florida Peninsula. An additional factor this spring is the substantially below-normal snow cover and/or snow depth in many areas across the country due to the anomalously warm winter for most of the country. This is especially true for the Northeast, mid-Atlantic, parts of the Great Lakes, Ohio Valley and much of the upper Mississippi Valley and north central Plains. Coastal SST anomalies are small in magnitude this year for waters in proximity to the Alaska south and west coasts and sea ice coverage in the Bering Sea and Bering Strait are for the first time in a while generally near the long term average - although ice is primarily first year ice, is thin and likely to melt out relatively quickly. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC Nino3.4 SST anomaly statistical forecasts indicate a continuation of ENSO-neutral with the CCA and Markov models on the positive side of the zero Nino3.4 SST anomaly line while the CA forecast trends to slightly negative anomalies during the summer and autumn seasons. There are greater differences between these statistical forecasts and dynamical model forecasts as part of the NMME. All NMME model contributions forecast a decrease in the Nino3.4 SST anomaly from current values to either ENSO-neutral or weak La Nina ocean conditions. One of the most aggressive models is the CFS which forecasts crossing into La Nina territory by August 2020 along with a couple others. One ECCC and the 2 GFDL models decrease more gradually and remain in the ENSO-neutral category through October. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS The temperature and precipitation outlooks for AMJ 2020 were based on a few factors, primarily bias-corrected and calibrated dynamical model guidance, statistical forecast tools utilizing various methodologies (including "bridging techniques") and recent trends. Objective, historically skill based combinations of the above information was weighted quite heavily in the current set of outlooks. ENSO-neutral conditions have been assumed in these outlooks given current conditions and the high uncertainty moving forward through the summer and autumn months. This point in the seasonal cycle is historically the lowest forecast skill period for ENSO prediction. Recent climate trends are considered for all leads but were relied on more heavily for the middle and later forecast leads. Simultaneous and lagged relationships between soil moisture anomalies and subsequent temperature and precipitation anomalies, along with snow cover / depth information was considered for the AMJ and MJJ outlooks. PROGNOSTIC DISCUSSION OF OUTLOOKS - AMJ 2020 TO AMJ 2021 TEMPERATURE The AMJ 2020 temperature outlook favors seasonal mean temperatures to be above-normal for nearly all of the United States. A small region in the northern High Plains is designated as "Equal Chances" (EC) where forecast probabilities for either above-, near- or below-normal temperatures are no different than the 33.3% climatological odds for a 3-class system. The greatest odds for above-normal temperatures is for northwest Alaska, California and the Southwest, along the Gulf Coast and for the eastern one-third of the country. Overwhelming agreement between numerous seasonal forecast dynamical models across a number of operational forecast centers and general consistency from previous months model forecasts strongly support this outlook. Also, nearly all statistical guidance is consistent with the dynamical model guidance. Strong long term positive trends (especially in the eastern CONUS, parts of the West and Alaska) and the lack of snow cover / depth in many areas also contributed to the elevated odds of above-normal temperatures. Lower probabilities for above-normal temperatures are forecast for areas of the central lower 48 due to some consideration of high soil moisture content in some of this region. This is also where the model spread and forecast uncertainty is the highest, where the confidence was the lowest and so probabilities here are only modest tilts to the warm side. The greatest odds for above-normal temperatures are across south Texas where severe and extreme drought are currently in place and odds for above-normal temperatures are slightly increased further across California and Oregon as a result of current below-normal soil moisture content. A similar outlook pattern as shown in the AMJ 2020 outlook continues through the ASO 2020 season and is based on an objective, historical forecast skill weighted consolidation of dynamical model guidance and statistical forecast tools which indicates a quite robust signal. Outlooks from SON 2020 through DJF 2020-2021 are based on similar, compelling forecast guidance and indicate a decrease in odds for above-normal temperatures appearing and increasing in coverage from the north central CONUS to the Southeast and then the eastern CONUS by the DJF 2020-2021 season. Greater uncertainty, more coverage of EC and a more zonally oriented outlook is depicted with favored above-normal temperatures forecast for the southern CONUS from JFM 2021 into the spring 2021. Statistical guidance, primarily from long term trends supports a small region of favored below-normal temperatures for areas of the far northern High Plains during FMA - MAM 2021. PRECIPITATION The AMJ precipitation outlook depicts elevated odds for above-normal seasonal total precipitation amounts for northwest Alaska and for most of the central and eastern CONUS. The primary driver for the outlook across the central and eastern U.S. is consistent signals from the majority of dynamical model guidance, but also significantly due to positive long term trends in much of this region. The highest odds are located across the Ohio Valley where there was a convergence of a wet signal among the dynamical model and statistical forecast guidance. Below-normal precipitation is most likely for the South coast of Alaska southward and eastward to include the Pacific Northwest and northern California, the central Rockies, New Mexico and western and southern Texas. Similar information as noted above is utilized as the basis for the outlook in these regions. Below-normal soil moisture content to a small degree increased the odds for below-normal precipitation for parts of California, Oregon and southern Texas due to potential less local recycling of boundary layer moisture. Progressing into and through JAS 2020, the aforementioned regions of above- and below-normal precipitation are maintained, but at decreased coverage and confidence (i.e., smaller regions with lower probabilities). Given the absence of a confident forecast for the phase of ENSO, the remainder of the precipitation outlooks through AMJ 2021 are largely based on precipitation long term trends which are primarily positive. The coverage based on these trends is minimized during the ASO 2020 through DJF 2020-2021 seasons and maximized at the longer leads of JFM - AMJ 2021 seasons. FORECASTER: Jon Gottschalck The Climatic normals are based on conditions between 1981 and 2010, following the World Meterological Organization convention of using the most recent 3 complete decades as the climatic reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals. For a description of of the standard forecast tools - their skill- and the forecast format please see our web page at http://www.cpc.ncep.noaa.gov/products/predictions/long_range/tools.html (Use Lower Case Letters) Information on the formation of skill of the CAS forecasts may be found at: http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Outlook/outlook.shtm l (use lowercase letters) Notes - These climate outlooks are intended for use prior to the start of their valid period. Within any given valid period observations and short and medium range forecasts should be consulted. This set of outlooks will be superseded by the issuance of the new set next month on Apr 16 2020 1981-2010 base period means were implemented effective with the May 19, 2011 forecast release. $$