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Moisture From the Remnants of Bud Is Spreading Needed-Rainfall Into the Southwest
Published: June 16, 2018
Rain and gusty winds from the remnants of Bud are bringing a surge of moisture into the Desert Southwest through Saturday.
Tucson, Arizona, reported its first measurable rainfall since February 28 on Friday with 0.17 inches. Phoenix has reported a trace of rainfall so far and has not seen measurable rain (at least 0.01 inches) in more than three months, but this streak may be broken Saturday.
Bud will not affect the United States directly as a tropical storm, but a strong southward plunge of the jet stream by mid-June standards across the western states has pulled its moisture and energy northward into the Desert Southwest.
This moisture surge has triggered the development of showers and thunderstorms in the Desert Southwest that will persist through Saturday.
Current Radar, Watches and Warnings
As of early Saturday, 1.07 inches of rainfall was reported near Duncan, Arizona and 0.99 inches was measured in Nogales Wash.
Through this weekend, some parts of eastern and southeastern Arizona and western New Mexico may pick up a total of an inch of rainfall, which may trigger some localized flooding of normally dry washes, arroyos and urban areas.
A few spots, especially in eastern Arizona, may see up to 3 inches of rainfall.
Flash flood watches have been posted for portions of New Mexico and southwestern Colorado where heavy rainfall over recent burn areas could result in flash flooding through Saturday.
Rainfall Outlook Through Sunday
This rainfall will generally be beneficial as this region continues to experience drought conditions. Just under 75 percent of Arizona is in severe drought, with just over 15 percent in exceptional drought, the highest drought category, according to the U.S. Drought Monitor.
The rain will also be welcome for those battling the wildfires in southwestern Colorado near Durango, though any modest rainfall occurring on newly-charred land could lead to debris flows.
Another impact from this potential moisture surge would be an increase in cloud cover, which will bring a welcome break from the intense heat and keep temperatures well below average for mid-June this weekend.
Early Start to the Southwest Summer Monsoon
The wet phase of the summer monsoon in the Desert Southwest is defined as the period from June 15 to Sept. 30 and is when the region picks up the majority of its annual rainfall.
However, the actual monsoon start date is when the first 0.01 inches of rain is measured at a particular city after June 15, according to the National Weather Service in Phoenix.
Phoenix has not picked up measurable rain since March 11, but Tucson, who's monsoon season started June 15 with 0.17 inches of rain had not seen measurable rain since February 28, 106 days prior. This is only the eighth time on record that Tucson has gone at least 100 days between measurable rainfalls.
The dry streak is finally coming to an end due to the moisture surge from the remnants of Bud.
This could end up being the earliest start to the summer monsoon in Phoenix in records dating to 1948. The earliest start on record currently stands at June 17, 2000, according to NWS-Phoenix.
If Phoenix receives 0.01 inches of rain Saturday (June 16), a new record would be set for the earliest start to the summer monsoon in that city.
The average monsoon start date is July 5 in Phoenix, although it has begun as late as July 25 in 1987.
(CATEGORY 6 BLOG: Big Moisture Heading for Southwest U.S., Thanks to Bud and a Caribbean Surge)
In addition, the track of Bud for June was very rare. According to Kristen Corbosiero, associate professor of atmospheric science at the University at Albany, from 1958 to 2003 there has never been a tropical cyclone that tracked as far north as Bud has and brought moisture to the U.S. Southwest in June.
However, in 2015 Hurricane Blanca did track as far north as Bud and did bring rainfall to California and parts of the Southwest in June. The track of Bud and Blanca is more common later in the year.
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