July 25, 2023 National Drought Summary

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilizedinclude the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast webpage used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

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The U.S. Virgin Islands continued to experience both long- and short-term drought, with adverse impacts on surface and groundwater reserves, as well as agriculture. The drought-monitoring period, ending the morning of July 25, featured hot weather and minimal rainfall, resulting in no changes to the drought depiction. Based on supporting evidence from Standardized Precipitation Index (SPI) values at time scales ranging from 1 to 9 months, St. John remained in severe drought (D2), while St. Thomas and St. Croix remained in extreme drought (D3). From July 18-24, rainfall at the first-order observation sites totaled 0.13 inch at King Airport on St. Thomas and 0.34 inch at Rohlsen Airport on St. Croix. During the drought-monitoring period, volunteer (CoCoRaHS) observers measured rainfall ranging from 0.00 to 0.12 inch. The U.S. Geological Survey’s Adventure 28 Well on St. Croix had a depth to water approaching 33 feet by July 25, a sharp increase from near 25 feet in November 2022. Similarly, depth to water at the Grade School 3 Well on St. Thomas topped 16 feet on July 25, an increase from less than 1.5 feet in early-November 2022.

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The Joint Typhoon Warning Center’s Invest 98W (later Typhoon Doksuri) moved away from western Micronesia and the Republic of Palau early in the drought-monitoring period, but was trailed by Invest 91W, taking a similar path. The new system (91W) also helped to enhance a Micronesian monsoon surge, maintaining generally wet conditions—with widespread weekly rainfall totals of 4 to 10 inches—extending across the Federated States of Micronesia and into the Republic of Palau.

Meanwhile, mostly dry weather returned across American Samoa, following the previous week’s significant rainfall. Through July 25, month-to-date rainfall at Pago Pago International Airport totaled 4.44 inches, with most of that precipitation (3.68 inches) falling from July 12-18. Much higher totals, ranging from 6 to 9 inches, had been observed during the mid-July wet spell at American Samoa’s National Park Service sites (Toa Ridge and Siufaga Ridge).

In the Marianas, automated observing equipment on Saipan has recorded less than an inch of rain during 7 of the last 8 weeks, with month-to-date precipitation through July 25 totaling 3.11 inches (55 percent of normal). Other observation sites on Saipan have also received little rain in recent weeks, resulting in the introduction of abnormal, short-term dryness (D0-S). Elsewhere, abnormal dryness (D0-S) persisted in northern sections of the Republic of the Marshall Islands, across Wotje and Kwajalein, despite a slight increase in shower activity. Wotje’s weekly (July 19-25) total of 2.03 inches followed 4 weeks in a row with rainfall ranging from 0.00 to 1.72 inches, while Kwajalein’s sum of 1.61 inches followed 4 consecutive weeks with rainfall totaling less than 0.60 inch.

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