April 20, 2021 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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Dry and very warm conditions continued to affect the USVI this week. St. Croix had no rain at the Henry E. Rohlsen airport and the Christainset 4.1 ESE CoCoRaHs station this week, while only 0.11 inch of rain was reported at the Christiansted 4.11.6 E station. The dry conditions were accompanied by very warm temperatures, with daily maximum temperatures of 87 deg F or higher. On April 14, the maximum temperature of 89 deg F at the airport tied the daily record last set in 1993. Groundwater levels at the Adventure 28 well in St. Croix dropped to 22.63 feet below land surface as of April 17. This was the greatest depth since November 2016. Meanwhile, the month-to-date rainfall total at the airport of 0.56 inch was only 50% of normal precipitation. Similarly, the airport’s year-to-date rainfall total was 3.85 inches, which is only 59.4% of normal. SPI values at the 1 (-0.53) and 3 (-0.53) months are consistent with abnormally dry conditions, while the 6 (-1.28) and 12 (-1.08) month periods are indicative of moderate drought. Due to the little rain and groundwater impacts, the drought classification was changed to severe drought.

St. Thomas and St. John also continued in severe drought this week as they received no rain. The month-to-date rainfall total at St. Thomas airport was 1.52 inches or 105.6% of normal rainfall. However, the year-to-date rainfall of 4.01 inches was 60.1% of normal. SPI values for the 1 (0.03) and 6-month (-0.37) period was indicative of drought free conditions. On the other hand, SPI values for 3 (-0.69) and 12 month (-0.79) periods were indicative of abnormally dry conditions. The Grade School 3 Well had groundwater at 13.51 feet below land surface (as of April 17), which is also the greatest depth since August 2017. St. John’s month-to-date rainfall total at the Cruz Bay 1.6 E CoCoRaHs station was 0.57 inch and 1.18 inches at the Windswept Beach. SPI values for the 3 (-0.68), 6 (-0.55), and 12 (-0.62) months were indicative of abnormally dry conditions. Groundwater at the Susannaberg DPW 3 Well was 15.79 feet below surface.

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Palau had over 12 inches of rain in just one week, surpassing the monthly threshold of 8 inches to meet most water needs. This resulted in continued drought free conditions for Palau.

Dry conditions were present across the Marianas this week, with Guam, Rota, and Saipan reporting less than half an inch of rain. Monthly precipitations for the last few months were also below the threshold of 4 inches to meet most water needs for all three locations. According to the NWS Tiyan, Guam forecast, the KBDI (an index used to determine forest fire potential) was 718. The maximum value for KBDI is 800, which represents very dry conditions. Due to the dry weather, the NWS doesn’t recommend outdoor burning since spot fires will ignite easily. Given this, Guam’s drought classification was degraded by one category this week. Rota’s (D0-S) and Saipan’s (D1-S) drought remained unchanged.

Across the Federated States of Micronesia, Yap, Kosrae, and Lukunor had the highest rainfall totals this week, with rainfall totals above 5 inches. Pohnpei, Pingelap, Nukuoro, Ulithi, and Woleai also had a wet week with rainfall totals surpassing the weekly threshold of 2 inches of rain. Fananu had a little less than 2 inches of rain this week. However, all of these locations continued to be drought free. Chuuk was the only location with little rain this week, receiving only 0.32 inch of rain. However, drought free conditions were unchanged this week since last month rainfall totals were over 18 inches. Kapingamarangi also had over 5 inches of rain this week, resulting in a month-to-date rainfall of 15.05 inches. According to the drought information statement produced by the NWS Tiyan, Guam, catchments are full and vegetation is starting to recover across the region. For this reason, Kapingamarangi's drought classification was improved by one category (from D2-L to D1-L).

This was a wet week for most of the Marshall Islands, with most locations receiving over 2 inches of rain. Ailinglaplap had the most rainfall at 5.61 inches. Meanwhile, Wotje had the least rainfall at 0.90 inch of rain. Wotje’s drought classification of extreme drought continued since the last few months have been very dry. Even though Kwajalein had a very wet week (3.90 inches), its drought classification of severe drought was unchanged due to local reports on yellowing vegetation and water shortages. There were no drought concerns in the other locations.

Drought free conditions persisted in Tutuila since rainfall totals across the three locations were close to or over 2 inches of rain.

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