09/26/2023, 5:27 am EDT

U.S. Month 1-3 Ahead Climate Outlook: Q4/2023 is warm-biased East, wet Midwest to Southeast.

Executive Summary: The Climate Impact Company constructed analog (CIC-CA) month 1-3 ahead climate outlook for Q4/2023 is updated. Forecast highlights include insistence on a cooler pattern change for the West-central U.S. into the Great Plains late in October, a wet mid-autumn Midwest to Southeast U.S., and followed by warmer changes for November, and ending with a very warm East U.S. in December while the West turns colder. The El Nino storm track relaxes in November but returns during early meteorological winter. High impact climate includes weakening of the Midwest and Mid-south U.S. drought, a raising of below “low water” river levels on the Mississippi River, and sharply below normal heating demand in the East to start the winter season. The overall forecast is warm although (except for November) trending cooler from previous outlooks. Fig. 1-2: CIC-CA temperature/precipitation anomaly forecast for Q4/2023. Climate summary: The CIC-CA month 1-3 ahead climate forecast is based on the influence of regional sea surface temperature anomalies (SSTA) and their historical upper air patterns projected forward using the NMME global SSTA forecast valid for December 2023. Currently, El Nino is moderate in strength and intensifying while mid-latitude SSTA are exceptionally warm. The ocean is ice free north of all continents. Due to seasonality, the polar vortex strengthens during OCT/NOV and creates cold wind across the northern open oceans which causes snow to generate in the northern continents spreading south toward wintertime and allowing cold air masses to generate. El Nino Pacific westerlies are likely to prevent the colder air masses from shifting south into the U.S. through early winter. Instead, an energetic southern latitude storm track, typical of an El Nino climate is generated and if sufficiently intense can generate locally cold (polar) air in the U.S. The cold risk is highest in the West or Central U.S. on the front end of the cool season. The record warm North Atlantic SSTA will bias the East/Southeast U.S. climate warmer than normal through December. October 2023 outlook: Despite very warm forecasts indicated by operational models into the middle third of October, the CIC-CA forecast continues to insist that a colder regime is likely to develop later in the month in the Great Plains. Given the expected colder pattern change early season freeze/frost (after a warm start to autumn) in the West-central/Central U.S. is expected. The East U.S. trend is warmer, and the West Coast has increased risk of a warmer climate including Santa Ana episodes. The Gulf States also trend warmer. Unchanged is the wet forecast for the Midwest to Mid-south U.S. and eastward which eases drought intensity in the Midwest and South-central U.S. Heaviest rainfall is projected across the location with the worst drought (Louisiana). Fig. 3-4: The Climate Impact Company October 2023 temperature and precipitation anomaly outlook.  November 2023 outlook: Interestingly, the late autumn forecast has a sustained warmer trend. Initial outlooks issued 2-3 months ago were marginally cold. However, subsequent forecasts have trend milder, and the new November outlook sustains that change. Pacific westerlies, thematic of El Nino climate are well-established and lead to a warmer than normal regime across the Central and East U.S. The upper flow is “zonal” therefore less capable of anchoring storms. Consequently, the U.S. forecast is mostly drier than normal in November especially in the East-central U.S. and much of the Northwest States. The exception is Florida to the Carolinas where the southern latitude storm track is well-established. The updated forecast completely removes cold risk from the November outlook previously indicated for the East-central States. The outlook also implies below normal snow cover heading into winter for the northern U.S. Fig. 5-6: The Climate Impact Company November 2023 temperature and precipitation anomaly outlook.  December 2023 outlook: Meteorological winter begins with a high contrast in the prevailing climate pattern. The CIC-CA forecast indicates cold air developing in Western Canada, not typical of El Nino, and surging into the northwest quadrant of the U.S. during early winter and with ferocity (on occasion) in Montana to the northwest Great Plains. This type of climate is more typical of a La Nina December climate. The explanation is likely related to the strong support for anomalous warmth in the East due to above normal 500 MB heights related to the very warm North Atlantic SSTA regime which leads to the upstream compensating upper trough over Northwest/West North America. A strong El Nino climate signature is indicated: Stormy in the Southeast/Mid-Atlantic region and after a dry November, turning wet again in the Midwest States. Later in December, the Midwest precipitation begins to favor snow. Fig. 7-8: The Climate Impact Company December 2023 temperature and precipitation anomaly outlook.   
08/13/2023, 3:47 pm EDT

U.S. Month Ahead Wind Forecast; July Review

Highlight: In September, stronger than normal southerlies is forecast across the Central U.S. Executive Summary: The latest Climate Impact Company month ahead zonal/meridional wind speed forecast valid for September 2023 is issued. Sprawling high pressure across the eastern half of the U.S. will lead to stronger than normal southerly return-flow around the back side of the Bermuda High affecting the Great Plains at times. Fig. 1-2: The observed July 2023 zonal and meridional wind anomaly verification. July 2023 verification: Mid-summer 2023 featured a semi-permanent upper trough across Western Ontario/Upper Midwest and a high-pressure heat dome across the Southwest U.S. The Upper Midwest was temperate while Southwest U.S. and Great Basin observed their hottest summer on record. The West, South, and East U.S. were all in the top-10 warmest given the 129-year history. Given the upper air pattern, zonal wind speeds were slightly stronger than normal across much of the Great Plains eastward to the Ohio Valley (Fig. 1). Meridional wind speeds for the same area were below normal wind speed (Fig. 2). In fact, the only zone with consistent above normal wind speeds in July was Tennessee and the eastern Ohio Valley. Above normal meridional (southerlies) wind speed were observed in Western Texas, and across Louisiana plus Florida during July. Above normal meridional wind speeds in California were offset by below normal zonal wind speeds. Remainder of August 2023 forecast: Brief periods of moderate southwest wind flow appear in the 5-day, 6-10-day, and 11-15-day forecast periods (Fig. 3-5). On average, each 5-day period produces 30-45% of wind power potential across the central and southwest Great Plains classified as below normal. The pattern is transitional for much of the 15-day period and unable to generate a consistent “windy” scenario. Fig. 3-5: The ECM ENS 15-day wind power potential forecast for the Central/East-central U.S. September 2023 forecast: An interesting late warm season forecast is forecast during September. The upper air pattern features a sprawling high-pressure area centered on the Great Lakes region. The result of this upper air pattern features below normal zonal wind speeds across the Great Plains, Ohio Valley, and into the Mid-Atlantic region (Fig. 6). However, when the wind is blowing from the south, above normal wind speeds are likely for the entire Great Plains to Upper Midwest (Fig. 7). As compared to last September, this year features considerably higher meridional wind (southerlies) across the Great Plains and Great Basin to California (Fig. 8-9). Fig. 6-7: The CIC-CA zonal and meridional wind speed anomaly forecast for September 2023. Fig. 8-9: The September 2022 zonal and meridional wind speed anomaly verification.