Thanks, Hurricane Rosa: Storm provided some drought relief to Arizona

The remnants of Hurricane Rosa provided a wet start to October in Arizona and it’s already showing up as drought relief, at least on the surface.

The latest map released by the U.S. Drought Monitor on Thursday shows significant reductions in two of the five categories of surface drought on the map.

Short-term drought vs. long term

The Drought Monitor map shows surface, or short-term, drought conditions. Those conditions can be affected by as little as a few days of rain or snow.

Arizona has been in a long-term drought, the type that causes depleted water levels in lakes and reservoirs, for about two decades. It would take years of above-average precipitation, particularly in the form of snow in the high country, to ease long-term drought.

So, we’ll have to take what we can get in the meantime.

Rain from Rosa eases drought

Much of Arizona got significant rain from the remnants of Hurricane Rosa. Phoenix received 2.75 inches as what was left of the storm moved through the area. The city also got rain from another disturbance over the weekend, bringing the month’s total to 3.09 inches through Oct. 9.

That’s reflected in the latest drought map.

Drought Monitor categories roughly represent how frequently various levels of drought occur and they attempt to put current conditions into historical context. Before 2018, Arizona hadn’t seen extreme levels of drought since 2015.

What the numbers show

Comparing the Oct. 2 map with the Oct. 9 version shows a 23.1 percent decrease in severe drought as 53.9 percent of the state now falls under that category. There was a 10.5 percent decrease in extreme drought as 23.6 percent of the state is covered by that category.

There were smaller drops in the levels of exceptional drought and moderate drought. The percentage of exceptional drought dropped from 8.6 percent to 6.9, while the level of moderate drought fell from 98.8 percent to 96.3.

The pockets of exceptional drought (the driest category on the map) are in northeast Arizona, parts of the state that received the least rain during the 2018 Arizona monsoon season.

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