NOAA Updates their September 2022 Outlook on August 31, 2022

NOAA Discussion (I have shown certain important points in bold type)

30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2022

The current state of the El Niño Southern Oscillation (ENSO) remains in the negative phase with the latest weekly observed Niño 3.4 Index value standing at -0.9 degrees Celsius. Meanwhile, the magnitude of the Real-time Multivariate (RMM) based Madden Julian Oscillation (MJO) index has increased during the past week over the Indian Ocean, but is forecast to gradually weaken as it propagates eastward across the Indian Ocean and the Maritime Continent during the next two weeks. Composites from this combined ENSO/MJO state for the month of September depict anomalous 500-hPa mean troughing over the southeastern Contiguous United States (CONUS) and over the Gulf of Alaska. Near to above normal 500-hPa heights are depicted across much of the western and northern CONUS as well as over the Alaeutians. However, as we close out the month of August, short term dynamical model guidance is increasingly relied upon with the official short and medium range outlooks from the Weather Prediction Center (WPC), 8-14 Day Outlooks from the Climate Prediction Center (CPC), and Weeks 3-4 Outlooks from CPC forming the backbone of the updated September 2022 outlooks. Dynamical model guidance from the Climate Forecast System Version 2 (CFSv2), the Global Forecast System (GFS), the European Centre for Medium Range Weather Forecasts (ECMWF), and Environment and Climate Change Canada (ECCC) were utilized to supplement the official outlooks. These inputs predict strong anomalous ridging over the western CONUS and Northern Plains during the beginning of the month. Cyclonic flow is depicted across much of Alaska and troughing or a weakness in subtropical ridging is forecast across much of the eastern and south-central CONUS. By mid-month, above normal heights are forecast to overspread most of the northern CONUS and a slight tilt toward below normal heights is expected across most of the Southern Tier. Cyclonic flow forecast across Alaska early in the month and is generally predicted to weaken and retrograde across western parts of the state as time progresses. The latest CPC Week 3-4 Outlook indicated the potential for increased troughing for the northwestern CONUS toward the middle or latter parts of September with near to above normal heights favored across most of the remainder of the forecast domain.

The updated September temperature outlook indicates increased probabilities of above normal temperatures across much of the western and northern CONUS as well as along the Eastern Seaboard. The greatest confidence for above normal temperatures is across the northern Intermountain West and High Plains, where probabilities exceed 60 percent. This represents a northward shift in the most favored area of above normal temperatures relative to the mid-month outlook, due to the likelihood for strong, anomalous ridging over the western CONUS to start the month. Conversely, increased probabilities of below normal temperatures are indicated across the south-central CONUS, as a weakness in subtropical ridging and enhanced moisture are likely for this region during much of the month. A weak tilt toward above normal temperatures is indicated for southeastern Alaska, as troughing is forecast to weaken and retrograde across the state, promoting advection of milder air ahead of this weakening trough. Above normal sea surface temperatures (SSTs) also contributed to enhancing probabilities of above normal temperatures across the Alaska Panhandle.

The updated September 2022 precipitation outlook favors above normal precipitation across most of the Southern Tier of the CONUS due to predicted weaknesses in subtropical ridging, near to below normal heights, and potential influxes of tropical moisture. Conversely, below normal precipitation is likely across much of the northern CONUS as above normal heights are forecast to overspread the Northern Tier as the month progresses. Additionally, predicted strong anomalous ridging early in the month contributed to the tilt toward below normal precipitation across much of the Northern Rockies, Northern Plains, and Upper Mississippi Valley. Increased probabilities of above normal precipitation are indicated for the Alaska Panhandle, ahead of weakening cyclonic flow predicted upstream.