What the heck is a 'derecho'? Hold onto your hat
I promised several Cd'A Press subscribers, including Ken Royal of Athol, Dennis Williams of Hayden and Betty Larsen of Post Falls, that I would attempt in this article to give an accurate description of the meteorological phenomenon known as a 'derecho' (deh-REY-cho).
According to the National Oceanic and Atmospheric Administration (NOAA), a derecho is a widespread violent windstorm that is usually associated with a strong band of thunderstorms accompanied by torrential downpours, large-sized hail and, at times, even deadly tornadoes.
The term "straight-line wind damage" is given to the disastrous consequences of a derecho like the one at the very end of June that left millions without power from Ohio eastward through the Mid-Atlantic states - in some cases, for more than 10 days.
Unlike a hurricane, which can be tracked for days or even weeks prior to its impact, the recent derecho gave no warnings of its arrival. It came 'like a thief in the night.'
Randy Mann's sister, Susan Ayers, who lives in Annapolis, Md., was affected by the extremely damaging derecho that moved into the Mid-Atlantic region at the very end of June.
Susan told Randy what happened at that time: "We were 5 days without power, which means, in addition to no electricity, and no air conditioning in 97 degree-plus heat, that those of us with wells and septic tanks had no water. Therefore, no showers! Smelly!
"The power generated by our portable generator was used for keeping the refrigerator and freezer going, and plugging in and out small appliances, such as a microwave, a coffee pot and a couple of hairdryers.
"After 5 full days, I gave up and went to our marina for a shower. Then we went boating, and Mark (my husband) washed in the bay, with a bar of soap!"
By definition, if the wind-damage swath extends for more than 240 miles and includes gusts of at least 58 miles per hour or more, then the event may be classified as a derecho.
Following the recent derecho, power crews from as far away as Florida and Oklahoma assisted local power crews helping to get the power back on after massive outages like the one in Maryland.
Derechos in the U.S. are most common in the late spring and summer seasons from May through August. In the Midwest Corn and Soybean Belt - hit this summer by the worst crop damage since at least 1988 due to extreme heat and drought - a damaging derecho usually strikes at least once or twice a year.
Elsewhere, east of the Rockies, a derecho hits other areas approximately every three or four years, including the East Coast. West of the Continental Divide, derechos are very rare, occurring less than once a decade.
The term 'derecho' was coined in 1888 by Dr. Gustavus Hinrichs, a physics professor at the University of Iowa. Dr. Hinrichs decided to use the word derecho to define various non-tornadic events. In Spanish, derecho means 'direct or straight ahead.' The definition was published later in 1888 in the American Meteorological Journal, so it's been around for nearly 125 years. Despite this fact, most people had never heard the term 'derecho' until this past destructive event. Thank you, Dr. Hinrich. (Better late, than never.)
North Idaho weather outlook
In our continued cycle of WIDE WEATHER 'EXTREMES,' we've gone from chilly record rains in June to our predicted near-record heat in the mid 90s in early to mid July. Some stations to the south of us have seen readings above the century mark.
Long-term, as Randy Mann and I promised months ago, we should see an additional 25 days or so this summer by late September of readings at or above 90 degrees. This would give us an above normal 30-32 'Sholeh Days' for the 2012 summer season. The normal is 23 such torrid days. Last summer, in 2011, we had 22 'Sholeh Days,' a bit below normal. But, the month of September had a record string of eight days in-a-row of 90 degree plus temperatures from Sept. 5-12. A ninth afternoon at 90 degrees occurred on Sept. 24.
We still don't see more than three inches of total precipitation during the 60-day period between now and mid September. That amount of rain would be more than an inch below normal. Most of this precipitation will probably arrive in the form of brief thunderstorms mainly over the mountains east of Kellogg.
There is a chance of some thundershowers spreading back into Kootenai County this next 'new moon' week. But, most of the rainfall should be light, except in the heart of the thunderstorm cells, where there will be a few isolated areas of heavy downpours, gusty winds and pea-size hail.
I still see good weather, not as hot as it was in late August of 2011, for the 2012 edition of the North Idaho Fair and Rodeo. It may not be totally dry, however, this year due to the slight chances of scattered thunderstorm activity in the region, again mainly in the mountains to the east of us.
The upcoming fall and winter seasons are likely to be somewhat drier and milder than last year, especially if we do see the continuation of the slowly-developing 'El Nino' event in the waters of the Pacific Ocean. We will have some new sea-surface temperature and solar charts in the Aug. 6 edition of this 'Gems' column. Stay tuned.
Special note
We observed a brief detour from the hot, dry weather this past weekend, and in fact saw record-shattering precipitation in Coeur d'Alene on Sunday.
The 1.07 inches of rain (as of 4 p.m. Sunday) easily smashed the previous record precipitation for July 15, which was 0.45 inches in 1975. Flash flooding did occur Sunday in some low-lying areas.
Sunday's downpour was more rain than the monthly average precipitation for July, which since 1895 is 0.92 inches. Thus far in 2012, our whopping 28.65 inches of rain (again, as of 4 p.m. Sunday) is nearly 5 inches more than the previous record of 23.70 inches of rain recorded as of July 15, 1996. That year still holds the annual precipitation record of 38.77 inches.
I still expect hotter and drier conditions to prevail later this week.
Cliff Harris is a climatologist who writes a weekly column for The Press. His opinions are his own. Email sfharris@roadrunner.com
Weekly Weather Almanac
n Week's warmest temperature: 97 degrees on July 12
n Week's coldest temperature: 59 degrees on July 15
n Weekly precipitation: 1.32 inches
n Precipitation month to date: 2.17 inches
n Normal precipitation month to date: 0.45 inches
n Precipitation month to date last year: 0.64 inches
n Precipitation year to date: 28.65 inches
n Normal precipitation year to date: 14.43 inches
n Precipitation last year to date: 22.51 inches
n Normal annual precipitation: 26.77 inches
n Total precipitation last year: 31.62 inches
n Precipitation predicted this year: 35.93 inches
n Precipitation predicted in 2013: 28.40 inches
n Record annual precipitation: 38.77 inches in 1996
n All-time least annual precipitation: 15.18 inches in 1929
Readings taken week ending Sunday, 4 p.m., July 15
Harris
Weather Gems