With the strong El Niño event underway and expected to continue through the forecast period, the NWS Outlook is based primarily on conditions typically observed during these events, with some consideration for longer-term trends and model output, all of which is reflected in the October -November-December 3-Month Outlooks.
Impacts on the drought include likely persistence for the small areas in the Northeast and the broad area of drought in the northwest and much of California, with some development expected in concert with the favored dryness in the northern Rockies.
Along the central and southern California coast, and in a broad swath from the Southwest to the Southeast, abundant precipitation, especially later in the period, is expected to bring widespread improvement. As this is a relatively dry time of year, drought is most likely to persist where it exists in Puerto Rico and Hawaii while additional slow relief is expected in Alaska.
Since the previous, seasonal outlook release on August 20, conditions deteriorated substantially from central and northeastern Texas eastward through the lower Mississippi Valley. Record and near-record late summer dryness was observed at a few locations, and accumulated deficits over the last 75 days exceeded 4 inches across much of the region.
A few spots in northern Louisiana and east-central Texas had drought intensities go from D0 (abnormally dry) to D3 (extreme drought) during the past month. Heavy rain (6 to 10 inches in the last 30 days) was confined to the Texas and Louisiana Gulf Coast region, where dryness generally eased.
The southwestern monsoon resulted in scattered areas of above-normal rainfall during the past 30 days, while seasonal dryness prevailed elsewhere across the remainder of the interior West. Drought maintained its intensity across most of the region, with abnormally hot weather contributing to some deterioration in the northern Intermountain West, while locally heavy rain prompted improvement in parts of western Washington, southeastern Arizona, and southwestern New Mexico.
Scattered heavy rain and flash flooding affected a few spots in the West in mid-September. Los Angeles, CA recorded over an inch of rain on September 15, which almost equaled their normal for the 6-month May – October period.
A few inches of rain fell quickly in northern and southern Utah, causing excessive runoff and deadly flash. However, these isolated extreme events did not affect the longer-term dryness and drought that covers the region. Away from Los Angeles, wildfires spread quickly and consumed homes in a few locations, most notable the mountains outside San Francisco, CA.
A broken pattern of abnormal dryness was observed in the central Plains, the Upper Peninsula of Michigan, the Ohio Valley, the mid-Atlantic, and the Northeast, reflected by areas of new D0 conditions during the last couple of weeks. There was also a slight expansion of the moderate drought in and around the New York City area.
Meanwhile, dryness and drought improved in the upper Midwest, parts of the Southeast, and southern Florida.
Heavy rain has soaked the Florida Panhandle and the adjacent south Atlantic and northeastern Gulf Coasts. 30-day totals of 6 to 10 inches were common, with isolated sites receiving almost 15 inches, prompting the improvement in south Florida.
Unseasonably heavy rain continued to pelt much of Hawaii, where widespread improvement has been observed. From mid-August to mid-September, both Honolulu and Lihue received over 10 inches of rain, compared to normal of just 0.5 inch and 1.08 inches, respectively.
Both Alaska and Puerto Rico experienced regional relief from moderate rainfall, with a significant decrease in drought coverage across central and southeastern Alaska.
Forecaster: Rich Tinker