In Puerto Rico, abundant showers across interior locations led to the removal of two small patches of dryness (D0), but the drought depiction was unchanged in coastal areas.

Alternating weather conditions occurred across the U.S. Virgin Islands (USVI) during this USDM week (07/21/21-07/27/21). A low-level trough/tropical wave brought showers early in the week, with another tropical wave and a Tropical Upper Tropospheric Trough (TUTT) causing more rain later in the week. Drier and more stable airmasses preceded and followed these systems, along with a Saharan Air Layer, which inhibited showers.

Radar-based estimates of rainfall (QPE) for the 7 days ending at 12z on Tuesday showed widely-varying precipitation amounts, ranging from less than half an inch (over eastern St. Croix) to locally 2 inches or more on all three islands. Satellite-based (IMERG) estimates of 7-day precipitation revealed a large area of 2+ inches of rain that extended from St. John and St. Thomas northward for several hundred miles, with St. Croix having from half an inch to 2 inches in places.

Seven-day rain gauge totals ranged from 1.15 inches to 2.54 inches on St. John, 0.98 to 1.63 inches on St. Thomas, and 0.33 inch to 1.73 inches on St. Croix. The rain improved Standardized Precipitation Index (SPI) values on St. Croix and St. John, but groundwater levels still remain historically low. The groundwater level at the USGS Grade School 3 well on St. Thomas rose in the last few days but was still well below where it was back in December 2020. Groundwater levels on St. John and St. Croix continued to decline, although the rate of decline has slowed in recent days. There was no change in the USDM status this week, with St. Croix continuing at D2-SL, St. John continuing at D1-L, and St. Thomas continuing at D0-L.

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