Thursday, October 29, 2015

A Week of Rain Reduces Drought

A week of rain associated with an upper level trough moving across the U.S. interacting with moisture remaining from Hurricane Patricia brought significant reduction in drought conditions across the southern Plains eastward into the southeastern U.S.

The Drought Monitor (l) and weekly change (r) as of October 27.

Parts of the Midwest and Ohio Valley shown in drought received one to four inches of rain after the Drought Monitor was finalized and will likely show some improvement in next week's map.

In the Caribbean, another upper level trough brought heavy rain to Puerto Rico, though the southern coastal region, where drought is in the Extreme category, missed out on much of the rain.  

Location of Navarro County
The week started with heavy rain in Texas on October 22 and October 23 as an upper level trough dropped south though the Rockies. Rain became more widespread and heavier as this trough began to tap in to the moisture from Patricia as is streamed northeast from Mexico. Eastern and southern Texas endured several days of rain which caused widespread flash flooding. The highest amounts were found  in east-central Texas where two CoCoRaHS stations reported almost two feet of rain in Navarro County between October 22 and October 26.

The highest rainfall totals for the period October 22-October 29, 2015 in Texas.

The upper trough and associated surface low slowly crawled east during the week, producing heavy rain over Louisiana, Arkansas and the Ohio Valley, and eventually into the eastern seaboard. A well defined low formed along the Texas Gulf cost on Sunday, October 25.

Surface map for 10:00 a.m. CDT October 25, 2015

 On Monday, October 26 the surface low was still well-defined on satellite over southern Louisiana.

Visible satellite image for 1:15 p.m. CDT on October 26, 2015.

Rainfall over eastern Texas, Louisiana, and Mississippi ranged from 5 to 10 inches on October 26. Two to five inches of rain fell from Mississippi east through Florida on October 27. As the upper trough over the middle of the country deepened rain shifted into the Ohio Valley and east through North Carolina with 3 to 6 inch amounts. In response to the deepening upper level trough a strong surface low developed over the Great Lakes. Heavy rain yesterday and last night was reported from the Great Lakes to New England, with 3 to 4 inches from New Jersey to Vermont. Enough cold air was pulled in behind this system to bring 1.5 to 2.0 inches of snow to parts of Minnesota and Wisconsin.

Sequence of CoCoRaHS precipitation maps for October 22 through October 29.

A large trough aloft is forecast to develop along the west coast this weekend, and that's setting the stage for more rain in the same areas that were drenched this week. This system will also bring rain to the Pacific Northwest and scattered rainfall to California.

Quantitative Precipitation Forecast for the 7-day period ending at 6:00 p.m. CDT November 5, 2015

1 comment:

  1. That is so neat to see the animated map of all the CoCoRaHS stations!