Tuesday, August 3, 2021

Extreme July Rainfall

Following up on last week's post, recent rainfall has been prodigious in western and northwestern Alaska, leading to the wettest calendar month of record in Kotzebue (5.32" versus 5.26" in August 1998) and easily the wettest July on record (old record 4.16" in 1931).  Nome surpassed the very wet July of 2012, with the wettest July since 1920 (6.41" vs 8.43").

Note, however, that the 30-day rainfall record in Kotzebue is 6.54", which occurred mostly in August 1946.  Remarkably, Nome has twice seen over 10" of rain in 30 days: in 1922 and 1954.

The rainfall since late June has been most excessive in the far western Brooks Range; check out this accumulated precipitation chart from the Red Dog CRN site, at about 1000' elevation and 80 miles north of Kotzebue.  The site has seen over 12" of rain since late June, and the June-July total was an astonishing 14.5".

The nearby Kelly Station SNOTEL instrument (~20 miles SE of the CRN site) has measured over 10" since late June:

Much farther to the south, the Rocky Point SNOTEL on the southern coast of the Seward Peninsula (not far from White Mountain) has seen 9" in the same period:

For the record, and following on from the last post, here are the NWS rainfall estimates from the past week:

Looking more broadly afield, the west-east contrast in July rainfall across Alaska was very striking; here is Rick Thoman's summary graphic, via Twitter:

The monthly-mean circulation pattern involved an unusually strong trough of low pressure from the Chukchi Sea down to the western Bering Sea, but a ridge over southern Alaska kept jet stream disturbances away from the eastern and southeastern parts of the state.

Not surprisingly, temperatures were quite cool in the west, but were generally warmer than normal in the Arctic, eastern interior, southeast, and Alaska Peninsula.

1 comment:

  1. With that rain I wonder about the effect on ocean temps and salinity? All that water ends up there eventually.