EXPERIMENTAL Zonal/Meridional Wind Anomaly Forecast EXPERIMENTAL Relative Humidity Anomaly Forecast Valid: March and April 2023 Executive summary: For major wind and solar regions maily across the Southwest and South U.S., forecast highlights for March and April 2023 include stronger than normal southerly wind across Western Texas in March (although below normal wind speeds in eastern Texas). In April, below normal wind speeds and above normal cloudiness (wuth rain) plague Texas and vicinity. Cloudiness limits solar across Southern California in March while much of the North/East U.S. receive above normal sunlight for early meteorological spring. Beneath high pressure, most of the West Coast receeives above normal sunlight in April. Methodology discussion: The March/April 2023 zonal/meridional wind and solar forecast is based on a constructed analog (CA). The wind speed/relative humidity anomaly forecast to generate estimated wind/solar potential is experimental. Zonal (west-east) and meridional (north-south) anomalies are forecast for wind generation use. The relative humidity at 850 MB (5,000 feet) is used to project low cloud potential interference with sunlight and similarly at 300 MB (30,000 feet) to project sunlight potential interference from high (cirrus) clouds.    Climate discussion: The Climate Impact Company constructed analog (CIC-CA) forecast is based on regional SSTA and the U.S. soil moisture pattern. Regional SSTA include an expected fading La Nina, very warm SSTA north and northeast of Hawaii in the Northeast Pacific associated with marine heatwave NEP22A and NEP23A, and the warm North Atlantic basin particularly the western basin including the Gulf of Mexiico. The U.S. soil moisture pattern, a signal of longterm climate, indicates Central and Southwest U.S. drought. March/April 2023 wind forecast: Based on the CIC-CA climate forecast, the prevailing upper air pattern for March features an upper-level low-pressure trough just west of the California Coast and an amplified upper ridge across Northeast Mexico extending to the Mid-south U.S. A weaker upper trough is located southeast of New England. The sensible climate pattern is temperate across much of the U.S. except colder than normal across the Interior West. The central Great Plains are wetter than normal. Dryness dominates the Pacific Northwest. The zonal wind anomalies projected for March across the U.S. feature below normal results for much of the West States (Fig. 1). Only the New England States have stronger than normal west-to-east wind anomalis in March. However, the meridional wind anomalies are stronger than normal in coastal California and much of the Southwest U.S. into Western Texas (Fig. 2). Above normal strength northerly wind is forecast for the Coastal California areas while stronger than normal southerlies are likely into Western Texas. Eastern Texas wind speeds are lighter than normal. Meridional wind speeds are lighter than normal along the East Coast in March. Fig. 1-2: The experimental Climate Impact Company constructed analog forecast of zonal and meridional wind anomalies for the U.S. during March 2023. During April, a polar vortex pattern is forecast to generate over North-central Canada with upper-level high-pressure ridge areas across the Coastal Northwest and Southeast Canada. The sensible weather pattern includes a mild April across the Northeast with very warm risk for the West Coast States especially California. The Upper Midwest and Texas are cool. Texas is a midspring focus for above normal rainfall. Above normal zonal wind (westerlies) persists across Montana to Kansas and eastward to the Western Ohio Valley (Fig. 3). However, meridonal wind is either absent or weaker than normal for much of this region (Fig. 4). Due to the clouds and rain across Texas, below normal wind speeds are expected for ERCOT in April. In the San Juaquin Valley to the coast, meridonal wind speeds are stronger than normal. Wind speeds are lighter than normal on the Northwest Coast. Wind speeds are generally near normal on the East Coast. Fig. 3-4: Experimental Climate Impact Company constructed analog forecast of zonal and meridional wind anomalies for the U.S. during April 2023. March/April 2023 solar forecast: Low clouds are below normal in March across a large portion of the North and East U.S. due to subsidence associated with high-pressure ridging in the Central U.S. and backside of an upper low mostly just offshore the Northeast States (Fig. 5). Due to an upper-level low just-off the California Coast, above normal cloudiness is forecast in the lower atmosphere for the southern half of California and into the Great Basin. A streak of high cloudiness associated with the subtropical jet stream extends across Northern Mexico to Texas (Fig. 6). In April, due to high pressure on the West Coast, low clouds are generally absent (Fig. 7). Low cloudiness is below normal for a good portion of the U.S. during April except rainy Texas. Above normal sunlight is expected across the Southeast States in April (Fig. 8). Fig. 5-6: Experimental Climate Impact Company constructed analog forecast of 850 MB (low cloud) and 300 MB (high cloud) relative humidity anomalies for the U.S. during March 2023. Fig. 7-8: Experimental Climate Impact Company constructed analog forecast of 850 MB (low cloud) and 300 MB (high cloud) relative humidity anomalies for the U.S. during April 2023.

Discussion: January 2023 was the 18th wettest in the 1895-2023 U.S. climatology. Consequently, mid-winter was remarkably cloudy much of the time across the U.S. At 850 MB (5,000 feet), above normal cloudiness was most anomalous across California where the 13th wettest January on record was observed (Fig. 1). Low and high clouds (Fig. 2) occurred together to strongly limit solar influence across most of the Great Plains, Midwest and Northeast U.S. Two areas enjoyed above normal sunlight during January: Southern Texas and the Florida Peninsula. The Climate Impact Company Experimental Forecast for January did an excellent job of projecting well above normal low cloud cover in California (Fig. 3). The outlook also performed well with the above normal low clouds centered on the Missouri Valley and vicinity. However, high cloudiness was well under-forecast (Fig. 4). The southern Texas/Florida Panhandle below normal cloud cover forecast verified. Fig. 1-2: January 2023 observed 850 MB and 300 MB relative humidity anomalies. Fig. 3-4: January 2023 forecast of 850 MB and 300 MB relative humidity anomalies. During January 2023, wind speeds were generally below normal across the northern tier of the U.S. while both zonal and meridional wind speeds were above normal across the Southwest U.S. including Southern California and much of the Southeast States (Fig. 5-6). The Climate Impact Company Experimental Forecast for January produced excellent results forecasting below normal wind speeds for the Northeast States and above normal wind speeds in Florida. However, the stronger than normal windspeeds observed in the Southwest U.S. were under-forecast (Fig. 7-8). Fig. 5-6: January 2023 observed zonal and meridional wind anomalies. Fig. 7-8: January 2023 forecast of zonal and meridional wind anomalies.