At the beginning of the U.S. Drought Monitor (USDM) week, an upper-level trough present over the region along with sufficient moisture led to the production of showers in the northern U.S. Virgin Islands (USVI), especially on Wednesday and Thursday. About 0.50 to 1.25 inches of rain fell over St. Thomas and St. John according to Doppler radar estimates. Through the end of the week and into the weekend, precipitable water decreased to below-normal levels causing a reduction in shower activity. A tropical wave passed south of the area Monday resulting in some passing showers. By Tuesday, a strengthening ridge to the north of the USVI and below-normal precipitable water combined to strengthen the trade wind cap inversion and produce primarily fair weather.
On St. Croix, only trace amounts of precipitation were recorded at Rohlsen Airport this week, while 0.05 inch was recorded at Christiansted Fort on June 10. (The rest of the week’s data is missing.) At Rohlsen Airport, SPI values at the 1- and 3-month time scales (0.31 and 0.09, respectively) indicate no drought or dryness, but the 9- and 12-month SPIs (-1.27 and -1.37, respectively) indicate D1 and D2, respectively. Although this week was dry on St. Croix, May precipitation ranged from 106% to 151% of normal at Rohlsen Airport, Christiansted Fort, East Hill and Montpellier. Therefore, abnormally dry conditions with lasting impacts from drier conditions in the previous 6 plus months remain on St. Croix (D0-L).
King Airport on St. Thomas recorded 0.24 inch of precipitation this week from showers on the morning of June 5. Trace amounts of precipitation were also recorded June 6 and June 10. The 1-month SPI value for the King Airport is 0.12, indicating no drought or dryness. SPI values at the 3-, 6-, 9- and 12-month time scales all indicate moderate drought (D1) with values of -0.89, -1.17, -1.11, and -1.04, respectively. The island remains abnormally dry this week with lingering impacts from more intense drought earlier this year (D0-L).
Moderate to heavy rain was observed on St. John on the morning of June 6 due to a nearly stationary cell. The rain was heavy enough to warrant the issuance of a flood advisory by the NWS in San Juan. According to doppler radar estimates, approximately 0.50 to 1.25 inches of rain fell around the island. At East End, 1- and 12-month SPI values (0.13 and -0.43, respectively) calculated using data through the end of May indicate drought-free conditions, while the 3-month SPI (-0.61) indicates abnormal dryness (D0), and the 6- and 9- month SPI values (-0.77 and -0.86, respectively) indicate moderate drought (D1) conditions. With the shower activity earlier this USDM week, and after consideration of the SPI values, St. John remains abnormally dry with lingering impacts from drier conditions on a longer-term scale (D0-L).
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