Thursday, October 31, 2013

Soggy Weather from Texas to the Great Lakes

A potent storm system traveling through the nation's midsection produced some of the heaviest rain in two months over a large swath of the central U.S. Much of this area has been dry the last two months so the rain is needed. In parts of Texas, however, it was too much of a good thing.

This storm came ashore in the Pacific Northwest on Sunday and intensified over Nevada High winds associated with this low pressure system buffeted California, Utah, Nevada, and Arizona early in the week. The winds were responsible for tipping over six tractor trailers on Interstate 580. The winds, sometimes gusting to 60 mph or higher, also damaged some buildings and caused areas of blowing dust. Blowing dust along Interstate 10 in Arizona resulted in a 19-vehicle crash that caused three deaths and a dozen injuries.

Surface weather map for Monday, October 28, 2013 at 5:00 a.m. PDT.
By Wednesday this system was moving out of the Rockies and into the Central Plains, with waves of
Surface weather map for Wednesday, October 30, 2013 at 7:00 a.m. CDT
low pressure moving along the frontal boundary. Strong southerly winds ahead of this system drew warm, moist air into the Plains and Midwest, leading to widespread showers and thunderstorms. Overnight Wednesday training thunderstorms dropped a foot of rain on parts of south-central Texas. A number of CoCoRaHS observers in Hays County, TX, just southwest of Austin, went out this morning to find out that their rain gauges had overflowed during the night. There were quite a few reports of rain around 11 inches, but some of these measurements are low because the rain gauge overflowed.  The highest amount reported was 12.45 inches in Wimberly, TX. The rain caused widespread flash flooding, as you might expect. The NWS office in Austin/San Antonio has compiled a description of this event including radar images and photos.

CoCoRaHS 24 hour rainfall amounts for Hays County, TX for the period ending the morning of October 31, 2013
Further north, two to three inches of rain fell from southeastern Kansas into northern Illinois as of Thursday morning, with three to four inch amounts in Chicago and the southern suburbs. Additional areas of showers and thunderstorms brought more rain to areas from central Illinois through Indiana during the day.

24-hour precipitation ending at 7:00 a.m. CDT Ocotber 31, 2013
Tornado watches were issued for southern Illinois, southeastern Missouri, southern Indiana, western Kentucky, and northern Tennessee Thursday night.  Two unconfirmed tornadoes were reported in southern Illinois this evening. Earlier today two tornadoes were confirmed in southwestern Louisiana.

Rain will fall in the eastern third of the U.S. the next 48 hours as the main low pressure system heads northeast into Canada and the trailing cold front sweeps to the the east coast.

48-hour Quantitative Precipitation Forecast for the period from 7:00 p.m. CDT Thursday to 7:00 p.m. CDT Saturday.

Friday, October 18, 2013

What Goes Around, Comes Around

Here in the continental U.S. we usually look to the west to see "where our weather is coming from". On the west coast, they look out into the Pacific.  In Alaska, they look even further out into the Pacific Ocean.

Alaska is in the midst of a stormy period right now.  A large storm battering the Bering Sea and the Aleutian Islands yesterday and today is the extratropical alter ego of Typhoon Wipha, a huge storm which slammed into Japan earlier this week. Typhoon Wipha dumped 33 inches of rain in 24 hours on Izu Oshima island, 75 miles south of Tokyo. The rain triggered massive mudslides destroying 280 homes on the island. The storm caused 17 fatalities, 16 of them on Izu Oshima.

This animation of the Total Precipitable Water (TPW) product revealed the large amount of tropical moisture that was transported northward toward Japan as Typhoon Wipha began its poleward recurvature. At the end of the animation Wipha began its extratropical transition as it merged with a cold front that was exiting Asia and beginning to move southeastward across the North Pacific Ocean. Image and caption: Cooperative Institute for Meteorological Satellite Studies blog.

The storm will continue to affect much of western Alaska through the weekend, although by Sunday it should be weakening.

Surface weather for Friday, October 18.

Some of the energy associated with the upper level trough with this sytem will ride over the ridge in the western Pacific and help deepen the trough over the central U.S. early next week.

500 millibar map for Monday, October 21, at 4:00 p.m. CDT

The strong northwest flow aloft will mean a colder than normal week from the Rockies to the east coast and an end to the growing season in many areas.

Maximum temperatures and departure from normal for Tuesday, October 22 (left), and Friday October 25 (right).

Thursday, October 3, 2013

An Octoberfest of Weather

October is one of my favorite months of the year. Sandwiched between the leftovers of summer in September and the often dreary damp days of November, October can feature mild to crisp days, cool nights, brilliant tree colors, in some cases, a variety of contrasting weather across the country.

That's the case this first week of October 2013. So far this week the weather has been mild to much warmer than normal over the eastern two-thirds of the country. However, today's weather map is offering up a buffet of interesting weather. CoCoRaHS observers will be getting a workout from the Rockies to the Gulf Coast and east.

Surface map for 4:00 p.m. CDT October 3, 2013
In the west, a strong storm system is gathering strength in the central Rockies and will bring the first significant snow of the season to parts of the Northern and High Plains.  The Rockies will be getting plenty of snow as well, although it won't be the first time this year.

It's likely that snow could accumulate up to two feet in northern Wyoming and to a foot in western South Dakota. The snow will be whipped around by winds expected to reach sustained speeds of 45 to 50 mph in South Dakota.  Blizzard warnings are in effect for several counties in western South Dakota beginning the morning of October 4 and continuing through until Saturday morning October 5. Rain is falling in the area now and is expected to change to snow Friday morning.

Probability of at least 12 inches of snow between 6:00 p.m. MDT October 3 to 6:00 p.m. MDT October 4.

Watches, warnings and advisories in effect for eastern Wyoming and western South Dakota.
NWS Rapid City, SD

Zooming down to the Gulf of Mexico, Tropical Storm Karen poses the first serious threat to the U.S. mainland since Andrea in June. As of 7:00 p.m. CDT a Hurricane Watch is in effect from Grand Isle, Louisiana to west of Destin, Florida. Karen is expected to strengthen some on Friday, possibly reaching minimal hurricane strength before expected landfall on Saturday afternoon.

Six to eight inches of rain with locally higher amounts may accumulate from southern Mississippi to southern Alabama.

Back in the central U.S., the cold front associated with the storm system now in the Rockies will bring much needed showers and thunderstorms to dry areas of the Midwest. Storms could be severe on Friday from western Oklahoma northeastward to western Wisconsin. The outlook from the Storm Prediction Center for Friday outlines an area of Moderate Risk for severe weather over northern Iowa and southern Minnesota. Be sure to check the latest update to this outlook on Friday morning.

Convective outlook for Friday, October 4 issued at 11:30 a.m. CDT October 3.
NWS Storm Prediction Center

On Sunday the Rockies storm will be affecting the Great Lakes with strong winds and cooler weather, while the remnants of Karen slog their way through the southeastern U.S.