Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 830 AM EDT Thu Oct 15 2020 30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2020 The November 2020 monthly temperature and precipitation outlooks are based primarily on dynamical model forecast guidance in the context of ongoing and likely strengthening La Nina conditions as we progress through the autumn months. In addition, some areas of the forecast domain consider current land surface states and nearby ocean surface temperatures. The MJO was considered but played a lesser role in the outlook, as the MJO signal over the Maritime Continent is not expected to lead to significant subtropical impacts. Due to expected interaction of any eastward propagating MJO convective signal with suppressed convection over the west-central equatorial Pacific, related to La Nina, it is unclear if a coherent MJO enhanced convective phase over the Pacific will alter tropical-subtropical interactions. Also, statistically significant impacts on higher latitudes from the MJO are small during November, compared to winter months. The November 2020 temperature outlook favors above-normal monthly mean temperatures for nearly all of the forecast domain except for areas in southeast mainland Alaska, the Alaska Panhandle, and from the Pacific Northwest to the Northern Plains, where Equal Chances (EC) is forecast. Dynamical model forecast guidance and typical temperatures observed during November under La Nina conditions support this outlook. Decadal temperature trends along with dry surface conditions enhance probabilities for above-normal temperatures for parts of the southwestern CONUS into the Southern Plains states. Strong negative decadal trends in sea ice coverage and thickness and warmer than normal ocean surface temperatures near the coasts of Alaska also increase chances for above-normal temperatures for parts of western and northern Alaska. La Nina conditions tend to favor near to below-normal temperatures in parts of the Pacific Northwest, southeast Alaska and the Alaska Panhandle, but with positive decadal trends in some of these areas counteracting this generally weaker La Nina signal in autumn, EC is forecast for these areas. Decadal positive temperature trends, dynamical model forecast guidance, and to a lesser extent warm coastal ocean surface temperatures and dry land surface conditions support increased chances for above-normal temperatures for the Northeast. For precipitation, consistent dynamical model forecast guidance and typical La Nina impacts in autumn favor below-normal precipitation stretching from Southern California across the Southwest region and south-central Rockies eastward to include the Central and Southern Plains, the Lower Mississippi Valley, and the remainder of the Southeast region, excluding the southern Florida Peninsula. The consensus of dynamical model forecast guidance favors above-normal monthly total precipitation amounts for parts of the southern Alaska Panhandle and a small area of the Pacific Northwest centered around northeastern Washington. La Nina conditions increase the chances of below-normal precipitation along the south coast of mainland Alaska and the northern Alaska Panhandle later in autumn and in winter, where EC is forecast for November. La Nina conditions and warm ocean waters near the coast support above-normal precipitation for the west coast of Alaska, as does the consensus of dynamical model guidance. FORECASTER: Dan Collins The climatic normals are based on conditions between 1981 and 2010, following the World Meteorological Organization convention of using the most recent 3 complete decades as the climate 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. An updated monthly outlook... for Nov will be issued on Sat October 31 2020 These outlooks are based on departures from the 1981-2010 base period. $$