The weather pattern during this USDM week (6/5/19-6/11/19) consisted of several features which comprised the Inter-Tropical Convergence Zone (ITCZ). A surface trough across Palau and Yap State, at times extending into central parts of the Federated States of Micronesia (FSM), and a weak circulation in western Yap State near the end of the week, combined with upper-level divergence associated with an upper-level trough over western Micronesia to generate rounds of showers and thunderstorms over Palau and western FSM. Surface troughs, converging trade winds, and trade-wind disturbances generated showers and thunderstorms over parts of the Marshall Islands (RMI) and eastern FSM, although dry trade winds mostly dominated the northern RMI. Descending air and dry trade winds kept precipitation sparse over the Marianas. A broad area of high pressure lingered over the Samoan Islands at the beginning of the week, with mid-level moisture and instability convergence moving into the region near the end of the week.
Satellite-based estimates of 7-day precipitation (QPE) showed a broad band of ITCZ precipitation which stretched across the western Pacific between the equator and about 10 degrees N latitude. Precipitation within this band was estimated to amount to 1-4 inches, with locally more than 4 inches, over Palau and western FSM and parts of the southern RMI, but mostly less than an inch across eastern FSM and adjacent RMI. The QPE showed a band of precipitation from western Micronesia stretching south of the equator southeastward toward the Samoan Islands. In the vicinity of the Samoan Islands, most of the 1-3 inches of rain was indicated just south and west of American Samoa.
Rainfall was below the 1-inch weekly minimum needed to meet most water needs on all three islands analyzed in the Mariana Islands. Saipan saw 0.38 inch of rain and Rota saw 0.17 inch leaving extreme drought for both (D3). Guam only received 0.13 inch of precipitation this week and remains in severe drought with dryness having lasted less than 6 months (D2-S).
Palau received 5.67 inches of rain this week following the 2.93 inches of rain that fell last week. Both totals are well above the 2-inch weekly minimum needed to meet most water needs, and the June total (7.96 inches) is already close to the 8-inch monthly minimum. Because of this, severe drought (D2-S) was changed to moderate drought (D1-S) with dryness having lasted less than 6 months.
In the Federated States of Micronesia, Yap met the 2-inch weekly minimum this week (2.38 inches; 1 day missing) but remains in short-term severe drought (D2-S) due to dryness the previous 4 months. Woleai saw 4.41 inches of precipitation this week and has recorded 10.05 inches of precipitation so far in June but remains in moderate drought (D1-S) after improvement from severe drought (D2-S) last week. Fananu (2.24 inches; 1 day missing) and Chuuk Lagoon (1.95 inches; 1 day missing) saw precipitation totals near the 2-inch weekly minimum but remain in severe drought (D2-S) since previous weeks and months were dry. Kapingamarangi (0.67 inch; 1 day missing), Pingelap (1.10 inches; 1 day missing), and Kosrae (1.59 inches; 1 day missing) were all somewhat dry this week but remain free of drought and abnormal dryness since they have all exceeded the monthly minimum in the recent past. Pohnpei was wet this week with 3.54 inches (1 day missing) and so remains free of drought and dryness.
The northern and central Marshall Islands remained relatively dry this week. Utirik saw yet another dry week with only 0.72 inch of rain while Wotje has seen no rain this week (1 day missing). Kwajalein and Ailinglapalap saw relatively wet conditions in May (10.71 inches and 10.28 inches, respectively) but only received 1.33 inches and 0.80 inch, respectively, this week. Kwajalein remains in moderate drought (D1-S) while Ailinglapalap remains abnormally dry (D0-S). Jaluit saw only 0.39 inch this week and remains abnormally dry (D0-S). In contrast, wet conditions continued for the second week in a row for Majuro (2.21 inches; 2 days missing) and Mili (5.48 inches). Majuro remains abnormally dry (D0-S) since it was just improved from moderate drought (D1-S) last week and was especially dry in April. Mili remains free of drought and dryness.
Pago Pago recorded 3.08 inches of precipitation this week, which is above the 2-inch weekly minimum. Along with the wet conditions in previous months, there is no concern of dryness or drought at this time.