Aside from a few pockets in western and northern Puerto Rico, rainfall across the island was mostly below normal this week. Drought conditions remained the same, with short- and long-term moderate and severe drought occurring in parts of central and eastern Puerto Rico.
Patches of moisture embedded in the trade wind flow, and a tropical wave, alternated with a dry air mass over the U.S. Virgin Islands (USVI) during this USDM week (July 27-August 2). A Saharan dust layer made its way into the region late in the week, limiting the potential for rainfall activity. The shower activity resulting from the tropical wave and trade wind flow produced the greatest rainfall amounts in the south (St. Croix) with lesser amounts in the north (St. John and St. Thomas). Satellite observations of vegetative health (VHI) showed some improvement in recent weeks on St. Croix, and groundwater levels on the island fluctuated up and down during the last couple weeks. The VHI showed significant to severe impacts to vegetation continuing on St. John and St. Thomas, and groundwater levels continued their steady decline since February on these islands. The groundwater levels were at or near record low levels, based on the 2016-2022 record, at the gauges on all 3 islands.
Weekly rainfall totals on St. Croix ranged from 0.28 inch to 1.72 inches, with reports of half an inch or more common. Rohlsen AP received 1.26 inches for the week and 4.15 inches for the month of July, which was 157% of normal. Previous months were dry, with March 1-August 1, 2022 ranking as the 4th driest such period in 63 years of data. The year-to-date precipitation total was 89% of normal. But with improving vegetation (VHI) and Standardized Precipitation Index (SPI) values, and the decline in groundwater levels temporarily stopped, the status on St. Croix was improved to D2-SL.
On St. Thomas, weekly rainfall totals ranged from 0.11 inch to 0.80 inch, with the King AP recording a mere 0.13 inch. The July 2022 total at King AP was 1.99 inches, which is 68% of normal, and the year-to-date total was only 77% of normal. Recent months were dry, with May 1-August 1, 2022 ranking 3rd driest for the period in 58 years of data, and April 1-August 1 ranking 4th driest. The groundwater level set a new record low value (in the 2016-2022 record) on July 31. SPI values held steady or got slightly worse, so D2-SL continued for St. Thomas.
St. John was dry this week, with rainfall totals ranging from 0.17 inch to 0.28 inch. Three (3.02) inches of rain fell at the weather station at Windswept Beach during July, but the year-to-date total was only 72% of the long-term average. The VHI showed severely dry vegetation that was not improving in recent weeks and the groundwater level at the USGS Susannaberg DPW 3 Well was at the lowest level since November 2016. SPI values mostly held steady or got slightly worse, so D3-SL continued for St. John.
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