IRI Weather Regime Subseasonal Forecast Product Added to CW3E S2S Webpage

February 23, 2022

The International Research Institute for Climate and Society (IRI) has recently collaborated with CW3E, the NASA Jet Propulsion Laboratory, and the University of Arizona on a project funded by the California Department of Water Resources to investigate sources of subseasonal-to-seasonal (S2S) predictability of precipitation over the western United States.

A main focus of this effort is to produce experimental S2S forecast products that are regularly updated throughout the water year. IRI’s subseasonal weather regime outlook, which shows the likelihood of particular large-scale circulation patterns influencing the western U.S. region out to 5-weeks lead time, has now been added to the suite of CW3E subseasonal forecast products on the CW3E S2S Webpage. The latest such forecast is shown below, along with a description of the forecast product.

The graphic shows forecasts of large scale meteorological patterns, issued every day during winter (along x-axis) by the NCEP CFSv2 model. The four large scale “weather regimes” are the West Coast Ridge (red), Pacific Ridge (blue), Pacific Trough (green), and Greenland High (yellow), each of which leads to distinct precipitation and temperature conditions over the West. Darker colors indicate more confident forecasts, which run diagonally up the chart from 0 to 45 days ahead. This product was developed with support from NOAA’s Next Generation Global Prediction System (NGGPS) program and the California Department of Water Resources. Please see for the precipitation and temperature signatures of the regimes or Robertson, Vigaud, Yuan & Tippett (2020) for additional details.

CW3E’s collaboration with IRI on this DWR-funded effort has also involved the co-organization of the 2022 IRI S2S Water Workshop, which will take place virtually on March 15-17, 2022. NASA JPL and the University of Arizona have also served as co-organizing institutions for this event.