May 21, 2024 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/.

Weather Summary: Placeholder

Northeast: Placeholder

Southeast: Placeholder

South: Placeholder

Midwest: Placeholder

High Plains: Placeholder

West: Placeholder

Caribbean: Placeholder

A dry, stable air mass, associated with a high-pressure ridge, dominated the U.S. Virgin Islands (USVI) during this U.S. Drought Monitor (USDM) week (May 15-21), interrupting a recent string of wet weeks. A couple CoCoRaHS stations recorded a tenth to a fourth of an inch of rain this week, but most locations received no measurable rain or less than a tenth of an inch. For St. Thomas and St. John, USGS data showed groundwater levels rapidly declining this week, but they were still in the upper third of the recent historical record. Satellite data (VHI) showed no vegetative drought stress in the USVI. Precipitation for the last several months resulted in wet Standardized Precipitation Index (SPI) values at the 1- to 12-month time scales. As a result, on the USDM map, St. John and St. Croix continued free of drought and abnormal dryness. An analysis could not be made for St. Thomas this week due to the lack of sufficient precipitation data.

Pacific: Placeholder

Placeholder

Several tropical weather features brought rain to parts of the U.S.-Affiliated Pacific Islands (USAPI) during this U.S. Drought Monitor (USDM) week (May 15-21). These features included a near-equatorial trough, weak circulations, surface troughs moving in the Inter-Tropical Convergence Zone, and convergence created by surging trade winds. These features generated weekly rainfall totals of 2 to 5 inches across southern and eastern parts of the Federated States of Micronesia (FSM), the Republic of Palau, and the Marshall Islands, with as much as 7.55 inches recorded at Kosrae. Meanwhile, a dry trade-wind pattern dominated the Marianas Islands and western parts of the FSM (Yap State), where weekly rainfall totals were less than an inch in the Marianas and less than 2 inches in Yap State. A high-pressure ridge helped inhibit showers over American Samoa, where weekly rainfall totals were just over an inch. A weekly total of one inch of rain is needed to meet most water needs in the Marianas and American Samoa, with 2 inches needed for the rest of the USAPI.

The abundant rain this week added to monthly totals at Pohnpei, Kosrae, Lukunor, Kapingamarangi, and Nukuoro. With a wet week and monthly totals exceeding the 8-inch monthly minimum needed to meet most water needs, no drought or abnormal dryness was present at these locations. A wet week and/or month also kept drought and dryness away from Chuuk, Ailinglaplap, Jaluit, and American Samoa.

It was a wet week at Airai in Palau, but the May monthly total was still dry (below minimum), so abnormal dryness (D0-S) continued. Rain this week and month improved the status at Kwajalein from D1-S (moderate drought) to D0-L (long-term abnormal dryness) and at Wotje from D3-SL (extreme drought) to D2-SL (short- and long-term severe drought). Even though monthly totals at Wotje were below the monthly minimum for the last 7 months, the totals showed improved percentiles based on the historical record. The status at Majuro was changed from D0-S to D0-L to reflect dryness that lingered at the 5-month time scale.

Short- and long-term exceptional drought (D4-SL) continued at Ulithi and Yap. Based on data through this week, if no more rain falls for the rest of this month, Ulithi will have the driest May and April-May, second driest March-May, and third driest January-May in their 41-year historical record. Likewise for Yap, if no more rain falls for the rest of this month, Yap will have the third driest March-May and fourth driest January-May in their 73-year record. With dry conditions continuing, the status at Woleai was worsened from D1-S (short-term moderate drought) to D2-SL (short- and long-term severe drought), mainly reflecting the fourth driest May in a 41-year record (assuming no more rain falls this month).

In the Marianas, satellite observations (VHI) showed areas of stressed vegetation on Guam. Persistent dry conditions prompted the continuation of severe drought (D2-S) on Guam and extreme drought (D3-S) on Saipan and Rota.

Placeholder

]]>