Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 830 AM EDT Thu Sep 15 2022 30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2022 A review of background climate conditions continues to show established La Nina conditions which are forecast to remain in place at least into the upcoming winter months. Both the Nino4 and Nino3.4 latest sea surface temperature (SST) values remain near -1.0 degrees C and tropical atmospheric conditions (i.e., convection/rainfall, low-level and upper-level winds) continue to be consistent with La Nina. Although this is a monthly outlook and impacts from La Nina to the mid-latitudes are generally weak at this time of the year, the La Nina base state was considered in the October monthly outlook to some degree. The MJO signal is not particularly coherent especially in certain indices such as the RMM index which is being heavily influenced by interference from ongoing La Nina conditions. Some predictions of other variables such as 200-hPa velocity potential show some potential for more MJO organization as we enter the month of October with the enhanced convective phase located in Phases 1-2-3. This may promote enhanced convection to develop in the Central America and Caribbean region at a time of the year when primary tropical cyclone development begins to shift from the eastern and central Atlantic westward to these areas. In addition to the considerations noted above, dynamical model guidance from the North American Multi-Model Ensemble (NMME), Copernicus model suite (C3S) and extended (30-day) ensemble model systems from the CFS, ECMWF and GEFS that target the Week 3-4 period were utilized in preparing the outlook. The October 2022 temperature outlook depicts favored above-normal monthly mean temperatures for the majority of the CONUS with the only exception being the far Pacific Northwest. The greatest odds are forecast for an area from the central Rockies to the central Plains where the anomalously warm signal was most consistent amongst all the forecast tools and potential La Nina influence. The Week 3-4 dynamical model guidance and multiple linear regression forecast tool (ENSO, MJO, trend as predictors) supported a warmer than average start to October across the CONUS associated with forecast ridging and northward shifted westerlies. For Alaska, the signals overall were quite weak and conflicting. Slight tilts toward above-normal (below-normal) temperatures are depicted for coastal northwest Alaska (south-central Alaska) driven primarily by long-term trends (model guidance). For the October 2022 precipitation outlook, elevated odds for below-normal monthly total precipitation amounts is depicted from north-central California eastward across the central Rockies to the central and southern Plains and parts of the central Mississippi and Ohio Valley's. The La Nina base state, dynamical model guidance and long term trends contributed to this outlook. A slight tilt toward above-normal precipitation is shown for parts of Washington and the Alaska panhandle associated with model guidance and potential La Nina impacts. Probabilities in all locations are modest due to the low predictability common during this time of the year. Considerations of tropical moisture from the Gulf of Mexico or Caribbean Sea region related to any potential intraseasonal influence noted above resulted in an Equal Chances (EC) forecast for parts of the Gulf coast and Southeast despite considerable forecast guidance favoring drier-than-normal precipitation. There were weak and conflicting signals for mainland Alaska so EC is currently forecast in this area. FORECASTER: Jon Gottschalck The climatic normals are based on conditions between 1991 and 2020, 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 Oct will be issued on Fri September 30 2022 These outlooks are based on departures from the 1991-2020 base period. $$