And the maps that were released last month.

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

The coupled oceanic and atmospheric observations reflect La Niña conditions. During August 2022, La Niña continued with below average sea surface temperatures (SSTs) persisting in the central and east-central equatorial Pacific Ocean. In the last week, all of the Niño index values ranged from -1.1°C to -0.7°C. Negative subsurface temperature anomalies (averaged from 180-100°W) were mostly unchanged during the month, reflecting the dominance of below-average temperatures across the eastern Pacific Ocean. Low-level easterly wind anomalies and upper-level westerly wind anomalies continued across most of the equatorial Pacific. Convection and rainfall remained suppressed over the western and central tropical Pacific and enhanced over Indonesia. Overall, the coupled ocean-atmosphere system continued to reflect La Niña.

The Real-time Multivariate Madden Julian Oscillation (RMM) index and upper-level velocity potential anomaly analyses indicate a weakened and incoherent Madden Julian Oscillation (MJO) during the past week. Although weak, continued eastward propagation of the intraseasonal signal is evident in both the observation and forecast fields, where dynamical models  depict a potential strengthening of the MJO over the western Hemisphere, Africa and Indian Ocean.

PROGNOSTIC DISCUSSION OF SST FORECASTS

The most recent International Research Institute (IRI) for Climate and Society plume forecast of the Niño-3.4 SST index indicates La Niña will persist into the Northern Hemisphere winter 2022-23. There is an interesting split in the dynamical versus statistical model forecasts, with the latter set suggesting La Niña will persist longer, through JFM 2023. At this time, the forecaster consensus sides with the statistical models, although there is still large uncertainty over how long La Niña will last and when it will transition to ENSO-neutral (56 percent chance of a transition to ENSO-neutral during February-April 2023). In summary, La Niña is favored to continue through Northern Hemisphere winter 2022-23, with a 89 percent chance in OND, decreasing to a 54 percent chance in JFM 2023.

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.

Temperature

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).

Precipitation

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.

Tropical

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.

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS (Focus on October through December)

La Niña conditions are present, as represented in current oceanic and atmospheric observations. A continuation of La Niña is likely through the Northern Hemisphere Winter 2022-23, with an 89 percent chance during October-November-December (OND) decreasing to a 54 percent chance for January-February-March (JFM). Conversely, the chances of El Niño are exceedingly small, with probabilities less than 3 percent through the upcoming winter.

Temperature

The OND 2022 temperature outlook favors above normal temperatures for the southern two-thirds of the Contiguous United States (CONUS), the eastern third of the CONUS, and northwestern Alaska. The largest probabilities (greater than 50 percent) of above normal temperatures are forecast across the Four Corners Region, much of the Southwest, the Rio Grande Valley, much of the Southern Plains, the Florida Peninsula, and eastern New England. Conversely, a weak tilt toward below normal temperatures is indicated for southeastern Alaska.

Precipitation

The OND 2022 precipitation outlook depicts enhanced probabilities of below normal precipitation amounts across the Southern Tier of the CONUS extending northward to include much of the Central Plains and Central Rockies. Above normal precipitation is more likely for the northwestern CONUS and parts of southwestern Mainland Alaska. Equal chances (EC) are forecast for areas where probabilities for each category of seasonal mean temperatures and seasonal accumulated precipitation amounts are expected to be similar to climatological probabilities.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

Dynamical model forecasts from the North American Multi-Model Ensemble (NMME), the Coupled Forecast System Model Version 2 (CFSv2) , the Copernicus (C3S) multi-model ensemble system were used extensively for the first six leads when they are available, as was the objective, historical skill weighted consolidation and Calibration, Bridging, and Merging (CBaM) guidance, that combines both dynamical and statistical forecast information.

Additionally, the official ENSO forecast depicts probabilities of La Niña that are significantly higher than climatological probabilities through the upcoming winter. This anticipated La Niña signal played a role in the construction of these outlooks. At later leads, decadal trends  in temperature and precipitation were increasingly relied upon in creating the seasonal outlooks.

PROGNOSTIC DISCUSSION OF OUTLOOKS – OND 2022 TO OND 2023

TEMPERATURE

Above normal temperatures are favored throughout a majority of the southern and eastern CONUS and northwestern Alaska during OND. Conversely, below normal temperatures are more likely for southeastern Alaska. EC of below, near, or above normal temperatures are forecast for the northwestern and north-central CONUS. This EC area is due to weak or conflicting signals  among temperature tools. Probabilities of above normal temperatures are reduced relative to last month across the northern CONUS due to a trend toward a colder solution in the temperature consolidation coupled with a cold La Niña signal across parts of the Northern Plains and Northwest. Above normal temperatures remain likely (greater than 50 percent) from the Four Corners Region to the Southern Plains as well as for the Florida Peninsula and eastern New England, due to good agreement among both dynamical and statistical guidance. Guidance has trended colder across much of Alaska relative to last month. Thus, increased probabilities of below normal temperatures were introduced to southeastern parts of the state, which is also consistent with natural analogs  from the current ENSO state.

From November-December-January (NDJ) through March-April-May (MAM), impacts from the ongoing La Niña continue as above normal temperatures are favored across the Southern CONUS and the Eastern Seaboard while enhanced below normal temperature probabilities persist across southeastern Alaska and expand southward to the northwestern and north-central CONUS by December-January-February (DJF). After MAM, the forecast pattern increasingly begins to reflect trends with above normal temperatures generally favored across most of the southern, western, and eastern CONUS next spring and expanding to most of the remainder of the CONUS next summer and into the fall. Probabilities of above normal temperatures peak across the interior Northwest next summer and across the Northeast next summer into early fall consistent with trends . Across Alaska, above normal temperatures are most likely for western parts of the state during the Spring, shifting to the South Coast during the summer months, and eventually expanding northward to northern parts of the state by next fall.

PRECIPITATION

Model guidance remains consistent from previous months depicting elevated probabilities of below normal precipitation for much of the southern CONUS, and increased chances of above normal precipitation for the Pacific Northwest during OND. Models have trended toward an expansion of the dry signal eastward across the Southeast relative to last month, with influences from potential tropical disturbances decreasing and La Niña influences increasing as we progress deeper into the fall and early winter. Conversely, precipitation guidance has trended wetter across the northwestern CONUS, resulting in an increase in above normal precipitation probabilities relative to last month. A slight tilt toward above normal precipitation is indicated for parts of southwestern Alaska, based primarily on dynamical model guidance from the CFSv2 and a wet signal derived from natural analogs  to the current ENSO state. EC is indicated for most of the rest of the forecast domain as signals  for the various dynamical and statistical tools are too weak or conflicting to issue a forecast with a sufficient degree of confidence.

As we progress further into late fall and through the winter, dynamical and statistical guidance persist with a dry signal across the southern CONUS, consistent with a La Niña signature. An eastward progression of enhanced above normal precipitation probabilities is noted across the northwestern CONUS, peaking in coverage during the late fall and through the winter months. A wet signal is also favored to expand southward from the Great Lakes across much of the east-central CONUS during the winter and early spring, consistent with La Niña composites. During next spring through next fall, trends  become the dominant factor with increased chances of above normal precipitation generally indicated across parts of the east-central CONUS and Gulf Coast Region for much of the period. Conversely, trends  favor a dry pattern for much of the Southwest during early spring shifting northward to the Northern Rockies by late Spring, with increased chances of dryness for parts of the Northern Plains next summer as well. As dryness potentially expands into the northern Plains next summer, a corresponding weak tilt toward above normal precipitation makes a brief appearance for parts of the Southwest Monsoon Region during May-June-July (MJJ) and June-July-August (JJA), consistent with recent trends . Thereafter, an area of slightly enhanced probabilities of above normal precipitation is indicated across the Pacific Northwest in August-September-October (ASO) and September-October-November (SON), based primarily on statistical guidance from trends and ENSO. There exists high uncertainty across much of Alaska with large areas of EC indicated. However, dynamical guidance supports increased odds of above normal precipitation across parts of the western Mainland through the February-March-April (FMA) season. Conversely, statistical guidance from trends and ENSO support a slight tilt toward below normal precipitation for parts of the southwestern and central Mainland Alaska late in the spring into the early summer. Thereafter, trends  support slightly increased chances for above normal precipitation for parts of the northwestern Mainland next summer and slightly increased chances of below normal precipitation for parts of the Panhandle next fall.

Review of the ENSO Assumptions utilized by NOAA (CPC) in Preparing this Four-Season Outlook

It is useful to review the ENSO forecasts used by NOAA to produce this Four-Season Outlook.  We reported on that last week and you can read that article by clicking here

The key information used by NOAA follows.