Above-average temperatures continued across most of the western and eastern parts of the United States during July, although the middle of the nation did get a respite from the intense heat. Rainfall during the month was generally above average in parts of the central part of the nation (consistent with the below-average temperatures) and also along the Gulf Coast and much of the Southeast. However, conditions were quite dry in the interior Mid-Atlantic and much of the West, which resulted in drought conditions worsening. As we head into the last month of meteorological summer, will we see temperatures moderate during August, or will temperatures remain above-average? Where will the hit-and-miss nature of summertime rainfall result in a wetter-than-average month? This is what NOAA’s Climate Prediction Center (CPC) predicts will happen during August.
The U.S. temperature outlook for August 2024, showing where the average temperature is favored to be much warmer than average (orange and red) or much cooler than average (blues). Darker colors mean higher chances, not more extreme temperatures. White areas mean that there are equal chances for a warm, cool, or near-average August.Much warmerormuch cooler than averagemeans "in the upper or lower third" of average August temperatures from 1991-2020. Text-onlyforecast for Hawaiiavailable from NOAA Climate Prediction Center.
On July 31, CPC released its updated monthly climate outlooks for temperature, precipitation, and drought across the United States for August 2024. The temperature outlook again favors well above average temperatures across almost the entire nation, with no tilt in odds toward any category over parts of the northern Midwest, along much of the West Coast, and in South Texas. The precipitation outlook favors well above average precipitation along the Gulf Coast, the entire Atlantic Seaboard, and the northern Midwest. Well below average precipitation is favored in a region extending from the Pacific Northwest southeastward to the Southern Plains.
The precipitation outlook for August 2024, showing where the average precipitation (rain and snow) is favored to be much higher than average (greens) or much lower than average (browns). Darker colors mean higher chances, not more extreme precipitation departures. White areas mean that there are equal chances for a wet, dry, or near-average August.Much higherormuch lower than averagemeans "in the upper or lower third" of total August precipitation amounts from 1991-2020. Text-onlyforecast for Hawaiiavailable from NOAA Climate Prediction Center.
In addition to providing the basis as well as more specifics about the outlooks, I’ll also discuss the current state of drought and changes in drought observed during July. And of course, here’s my monthly reminder that the colors on the temperature and precipitation outlook maps only provide information about the most likely outcome, but that other outcomes are always possible, just less likely. More details about interpreting the outlooks can be found here.
The updated outlooks were produced considering the Week 1 forecast from the Weather Prediction Center (WPC), and CPC’s own Week 2 and Week 3-4 outlooks. Other tools that forecasters examined this month were longer-range forecast models such as the Global Ensemble Forecast System (GEFS), the Climate Forecast System (CFSv2), the European Ensemble Forecast System (ECMWF) as well as products derived from these models. With ENSO-neutral conditions persisting across the tropical Pacific, El Niño did not play a role in the August outlooks. Observed soil moisture was again considered for these outlooks, as extremes in soil moisture (both wet and dry) can influence temperatures and precipitation during the summer. Finally, coastal sea surface temperatures (SSTs) were considered this month, as they can modulate temperatures right along coastal regions.
Temperature outlook favors the heat to persist
The August temperature outlook favors well above average temperatures across almost the entire contiguous United States. (Well above average means “in the warmest third of all Augusts in the recent climate record.”) The exceptions are in parts of the northern Midwest from western Michigan extending westward to eastern North and South Dakota, along the West Coast and in extreme south Texas, where equal chance odds are found (1/3 chance each of below-, near-, and above-average). Similar to July, a large part of the nation has very high odds for the heat to continue, with probabilities exceeding 60% in significant parts of the western and eastern parts of the country, and with odds exceeding 70% in the Great Basin and parts of the Intermountain West.
August looks to begin the month with much of the nation experiencing above-normal temperatures (WPC Week-1 forecasts). Week-2 outlooks do favor below-average temperatures across much of the northern part of the nation, but CPC’s longer-term (Weeks 3-4 outlook) implies this break will be short-lived. Monthly forecasts from the GEFS and ECMWF generally favor ridging (jet stream shifted north of normal) over the entire nation, with the shift largest over the West and over the East. This leaves the potential for at least weak troughing at times (jet stream shifted south of normal) over the middle of the country. This provides enough doubt to produce an equal chance (EC, no tilt in the odds) forecast in the Upper Midwest/Northern Plains region. An EC forecast is also found right along the West Coast, as normal to below-normal SSTs currently extend along the entire coast which could help to modulate temperatures there.
Precipitation outlook slightly tilts wet in the East, dry in parts of the West
Also similar to July, the precipitation outlook for August has a fairly large amount of the country with a non-“equal chances” forecast, but the probabilities (and therefore confidence) are quite modest, with all odds under 50%. Probabilities favor above-average rainfall in the Upper Mississippi Valley, the southern borders of New Mexico and Arizona, and along the Gulf Coast, Florida, and the entire Eastern Seaboard. The tilt toward above-normal precipitation along the Gulf and Atlantic Coasts is a nod toward potential tropical activity and longer-term trends, while the potential for weak troughing in the upper Mississippi Valley slightly tilts the odds in that region and over the Great Lakes states.
Below-average precipitation is favored in the Pacific Northwest and Northern Rockies, as ridging over the West that is favored throughout most of the month is expected to limit precipitation at the same time it’s bringing the heat. Below-average rainfall is also indicated for parts of the Southern and Central Plains, where current soil moisture anomalies are below-normal with much of the region currently in some classification of drought.
U. S. Drought area increases during July
The amount of drought increased across the continuous United States during July, from about 16% at the end of June to almost 20%. And with almost 30% of the country remaining in the D0 category (abnormally dry) as we begin August, it’s quite likely that drought will further increase during the month. On a more positive note, the percent of the country in the two most intense categories (D3-D4, representing extreme and exceptional drought) although increasing during the month, remained low overall, at just more than 1%.
Drought conditions across the contiguous United States as of July 30, 2024. In the West, small pockets of extreme (red) and exceptional (dark red) drought were present in Montana, Arizona, New Mexico, and Texas. In the East those categories of drought appear only in South Carolina and in the border area of West Virginia, Virginia, and Maryland. A fairly large area of the West was at least abnormally dry (yellow), as were the Mid-Atlantic and the Southern Appalachians. Map by NOAA Climate.gov, based on data provided by theU.S. Drought Monitor project.
Regionally, the change in drought was quite variable, with some improvement, but also degradation observed in both the central and eastern parts of the nation. Out West, drought did worsen on the order of 1-2 classes. The middle of the country saw improvement in parts of the southern and central Plains and in the Midwest, but also degradation over parts of Kansas, Oklahoma, and Texas, generally 1-2 classes. Drought changes in the East were even more mixed, with 1-2 class improvements common in the coastal regions, but 1-2 and occasionally 3-class degradation farther inland.
Drought outlook mainly predicts persistence and development out West, improvement in the East
U.S. map of predicted drought changes or persistence in August 2024. Several new areas of drought are likely to develop (yellow) in the Pacific Northwest, Montana, and the Southern Plains. Existing drought in those areas and in the Southwest, Tennessee, and central Kentucky are likely to continue or worsen (brown). Existing drought in the Central and Southern Appalachians is expected to improve by at least 1 category (tan) or end (green). NOAA Climate.gov map, based on data from the Climate Prediction Center (CPC). See CPC version for Alaska and Hawaii.
Given the outlook for above-average temperatures during August over much of the nation, and with significant parts already abnormally dry, it’s not too surprising that drought persistence and development is likely over parts of the western and central part of the county. This forecast generally coincides with the regions also favored to see below-average rainfall. What might be surprising, though, is the forecast for improvement and even removal of drought over large parts of the Mid-Atlantic and Southeast. After rapid-onset drought occurring from June to mid-July, some of these regions experienced very heavy rainfall during the latter part of July. And with a tilt (albeit slight) toward above-average precipitation during August, drought improvement is predicted, despite the likelihood of above-average temperatures.
To read the entire discussion of the monthly climate outlooks from the Climate Prediction Center, check out theirwebsite.
