Desert Research Institute, Reno, NV
For the six months ending April 1, June Lake (near Mt St Helens) recorded 146.7" of precipitation, or 123 percent of average, and through the middle of summer had 165" of precipitation, about 108 percent of average (Figure 5).
The month of April brought above normal precipitation to most of the West.
Temperatures were much above normal across the north, and much cooler than normal across the south. Portland OR recorded its earliest 90 degree day on the last day. Meanwhile Flagstaff AZ recorded its third coldest April.
New Mexico reported its driest April-June period on record.
Sogginess prevailed west of a rough line from San Diego to Great Falls. In Oregon, particularly the east side, there were 64 locations that set May records, many of them 50 percent higher than the previous records. A number of sites measured from 400-650 percent of average. The past seven Mays have been well above average in precipitation in the northern Great Basin. Figure 6 shows May precipitation for a representative climate division in eastern Oregon for the past 104 years. This wet area extended into southern Idaho, northern Nevada, and nearly all of California, where 400-800 percent of normal amounts were common.
By mid-May, Bakersfield CA had already recorded its wettest year on record, exceeding the 11.17" measured in 1938.In keeping with the wet, cloudy conditions in the far west, temperatures were very cool, near record levels, which delayed agricultural schedules. Temperature departures were greatest in California, as much as 10 degrees F below average. Bakersfield, during its coldest May, only reached 84, and Fresno, 85. The only other years on record in which those cities have not reached 90 in May were 1917 and 1961. Because of both the cool temperatures and heavy precipitation, snowpack in the Sierra Nevada was late in melting, and actually increased in many places. Austin, Nevada recorded 10" of snow on the 26th-27th.
In Hawaii, Hilo finally had a wet month, with 15.65" of rain, (158% of average), but other locations remained dry, such as Honolulu, with 2.99" in 7 months (17% of average).
Arizona remained very dry (usual) and New Mexico also saw almost no rain in June (unusual).
Precipitation began to fall over many of the dry areas that had developed in Montana. Glasgow caught 4.11" (195% of average), Billings, 3.63" (182%), and Missoula in the west saw 4.23" (238%). Many remote elevated sites in western Montana captured 5-7", and some were greater: Flattop Mtn Snotel near Glacier Park recorded 8.9" (compared with an average of 5.9"), Shower Falls near Bozeman had 10.8" (5.3" average) and Crystal Lake had 11.8" (4.9" average). In late June a heavy shower dumped more than 9" in 36 hours on a campground north of the Bearpaw Mountains south of Great Falls. Billings began the month with 19 wet days out of 20. The May-June period represents a kind of "second chance" to pick up missed winter precipitation in the northern Rockies, and this year that occurred in abundance. However, many farmers had already given up and plowed fields under or adopted other strategies.
Earlier in the year, dry spring conditions following on the heels of a dry and mild winter had led some Montana farmers to give in and plow crops under, or switch to other alternatives. May and June rains were generous in some places, even excessive; but dry pockets still existed. Lack of adequate (spatially dense) observations needed for documentation held up relief. Seeded winter wheat acreage was the smallest in the state since 1941.
Much of Idaho, Wyoming, Utah, Nevada, and again California were also significantly wet. At 3.84", Salt Lake City exceeded its June precipitation record by 31 percent, and exceeded the record for any summer month (June-August). On the strength of a late-season 1.88" downpour on June 6-7, Fresno set a new June mark of 1.93" (monthly average 0.08"). Reno had at least a trace the first 13 days, and 11 days of measureable rain (former record 9 in 62 years, average is 3), with a total of 1.39" (302%).
Figure 7 shows the Standardized Precipitation Index for April-May-June of 1998. Areas above +2 or below -2 occur only about 5 percent of the record. Figure 8 shows the percent of average precipitation for April-June.
Once again, a very cool month was experienced from Montana to California. Billings, for example, had its coldest June. Frost visited the northern Great Plains in early June, with Williston reaching 26, its fourth coldest June reading. Salt Lake City noted its second coldest June, with its latest 90-degree reading on the 30th. Snow, some quite heavy, was recorded at relatively low elevations in the region, and again Sierra snowmelt was only a trickle. Reno did not reach 90 until July 5, a week short of the latest ever.
Figure 9 shows the departure of temperatures from average for the three months April-June for the United States.
The twelve months that ended June 30 in California yielded some very impressive statistics. Downtown San Francisco, with a 149-year record from 1849, measured 47.22" of precipitation, falling just shy of the venerable 49.27" total of 1861-62, when an enormous flood put one quarter of California's assessed value under water. Sacramento's 103 days with measureable rain, and UCLA's 63 both exceeded July through June records set in 1982-83. San Francisco likewise notched a record 119 days with measureable rain, far surpassing the 1889-90 record of 107.
Some season-ending precipitation totals for winter 1997-1998 in California.
Location 7/1/97-6/30/98 average % of average Bakersfield 14.66" 5.72" 256% Eureka 58.62" 37.53" 156% Fresno 20.36" 10.60" 192% Oakland 46.72" 21.79" 214% Redding 65.61" 33.30" 197% Sacramento 32.25" 18.61" 173% San Francisco Airport 40.06" 19.70" 203% San Francisco downtown 47.22" 20.52" 230% San Jose 28.89" 14.42" 200% Santa Rose 53.90" 30.30" 178% Los Angeles 31.01" 14.77" 210% San Diego 17.78" 9.90" 180% Northern California Eight-Station Index for the Sacramento River Basin 80.8" 48.3" 167%
Even Death Valley reported nearly 6 inches of rain over the past 12 months, compared with an average of just over 2" (Figure 10). A spectacular and profuse display of flowers erupted during the spring in this location and in many other desert locations in southern California and Nevada and in Arizona, to the delight of many visitors.
Cotton was especially impacted in California, but for just the opposite reason as in Texas. The extended wet season, which proceeded into the first week of June, caused a number of problems with disease and insects, and with growth conditions. Cotton was generally three to four weeks behind. Mold, mildew, fungus, and rot affected waterlogged fields. Stonefruits had less than optimal conditions also, and many vegetable crops fell two to three weeks behind in the Sacramento Valley. During this quarter, lettuce prices rose prohibitively, four to five fold, but later returned.
Having just finished dealing with El Nino, climate observers watched during June as La Nina put in a dramatically sudden appearance early in the month, and appeared destined to dominate the next winter's headlines.
July was generally near to above normal in precipitation throughout the western states, except for seasonally dry California and southwest Oregon. However, on the west side of the Cascades, an extended dry period began in July. Far to the west, all of the Hawaiian Islands received below average precipitation.
A developing dry pocket in southeast Colorado was washed away in extremely heavy rainfall. Lamar noted 11.34", nearly three-quarters of its 14.62" annual average, much above its monthly average of 2.24", and the highest by more than 2" since at least 1918. This wet area extended northward to western Montana, and the interior Columbia Basin received 400 percent of average and more.
In the far West, after a very cool June and first half of July, the western summer abruptly shifted into a very warm mode. This transition is easily visible in daily temperature records from Bakersfield (Figure 11), and Yosemite Valley (Figure 12).
The warming brought a reading of 129 F to Death Valley on July 17, the hottest temperature at a North American station in 38 years, and tying the highest for at least the past 50 years. Death Valley reach 120 on 25 days, double the average of 12, but well short of the record 40 set in 1996; this number of 120-degree days occurs about once in 10 years. Figure 13 shows "Death Valley Days" for calendar 1998 through December 13, along with long-term averages and extremes from the current site for each day.
The warmup in July finally raised the freezing level to begin melting the enormous Sierra snowpack, which had hung on much later into the summer than usual. Figure 14 shows a visible satellite image of the Sierra Nevada taken on July 25, 1998. The white dendritic pattern shows very deep snow lingering on ridgetops. An NRCS Snotel sensor at a medium altitude of 9400 feet at Leavitt Lake just north of Yosemite (Figure 15) shows that the snowpack not only failed to begin melting near the normal early April maximum, but even continued to accumulate long afterward, peaking at 91 inches (nearly 8 feet) of water in the snowpack on the first of June, a time when the average water content is typically 35 inches. The melt began in earnest, and levels had dropped to 60 inches by July 1, and to zero by August 1. Whitewater rafting enthusiasts were treated to an extra element of fun and danger, in very swift, cold and powerful water. A dozen rafters, some quite experienced, drowned in the Sierra, tying the worst year on record.
August was very dry west of the longitude of the Nevada-Utah border, which is seasonal and not especially unusual. Hawaiian precipitation was generally below average, although Lihue on Kauai was wet.
Nome AK recorded its wettest month ever with 8.58", surpassing the 7.82" total of July 1951. Their total of over 25" through mid December surpasses the previous annual record of 22.38" set in 1990.
New Mexico had a dry September, and seasonal dryness prevailed along nearly the entire Pacific Coast. A lesser dry spot developed in western Wyoming and Montana. Eugene, Oregon ended an 83-day spell of no measureable rain on September 17, the longest since record-keeping began in 1890.
In Hawaii, Honolulu noted just 0.05" of rain in September, 0.73" less than average. For the calendar year through October 10, Honolulu received only 2.66", 17 percent of the historic average for that period. Similarly Kahului, with 3.66", has accumulated a mere 23 percent of average since January 1.
September was very wet for the lower Colorado River, and most of Arizona, the entire Great Basin, most of Utah and Idaho, and much of Wyoming. Numerous locations had more than 400 percent of the September average, some among the wettest on record, partly on the strength decaying of tropical storms. Remnants of Isis brought rains to the desert on September 4, including 2.26" in 24 hours at Yuma, more than seven times its September mean, and a significant fraction of its 3.17" annual average.
Going into the new winter, reservoir storage was above average in all the western states except Washington, which was not significantly below average.
Large parts of New Mexico experienced especially dry conditions from April through June of 1998. Drought damages may exceed $60 million, with almost 6,000 farms and ranches affected, including 1,100 with losses exceeding 80%.
Low soil moisture levels significantly reduced the harvested acres of crops, although many crop yields were higher, which partly ameliorated the losses. Some of the losses included:
Sorghum: Harvested acres down 66% from last year (yields up but total bushels down 54%) Upland cotton: Harvested acres down 11% from last year (yields up and total bushels up 3%) Summer potato: Harvested acres down 9% from last year (yields down and total bushels down 13%) Peanuts: Harvested acres up 16% from last year (yields down 7% and total bushels up 7%)
Septmber 30 marks the end of the Water Year, used by many western water interests to track hydrological elements of the climate system. This year ended up especially notable in the Sierra Nevada. This was the fourth consecutive substantially wetter than average winter season, something not observed before in the long records from the central Sierra near Lake Tahoe. The past two decades have brought an astonishing range of precipitation behavior to this area. At Tahoe City, the outlet of Lake Tahoe, this memorable period includes the driest winter (12-month season) on record (1976-77), the wettest winter (1982-83), an extended major drought (1986/87 to 1993/94 with 1992/93 excepted), the driest four-year period on record (1975/76-1978/79), and the wettest four-year period on record (1994/95-1997-98).
Wet weather continued in New Mexico, with eastern portions receiving upwards of 400 percent of average. Also, eastern Montana and Wyoming received over 400 percent of average. Glasgow MT, for example, reported 3.05", much above the October record of 1.80" in 1994. A broad swath from the eastern plains of Montana southward to Arizona and New Mexico received generally 200 percent of average or more.
Wet conditions affected southern Alaska, with Juneau at 12.33" (157 percent), partly because of its greatest 2-day total on record, 6.28" on the 19th-20th. Kodiak noted 13.96", with its annual total up to 93.12" (169%).
Honolulu continued to resist liquid moisture, receiving only 0.13" (6%), for an annual total of 2.28" (15 percent of average). Meanwhile, its rainy counterpart to the south, Hilo, measured 16.01" (167 percent).
Temperatures were cool over most of the western states. Bakersfield averaged 62.7 F, (departure -5.1), the coolest October since 1984, and the ninth of the past ten months to be cooler than normal there (Figure 16). Alaska was near average, with the notable exception of the North Slope, where Barrow ended the month 12 degrees F above average.
La Nina helped kick the precipitation season into high gear in the Pacific Northwest. Astoria's 19.60" (195%) exceeded the former November record set in 1995, and Seattle's 11.62" (199%) exceeded its 1990 November record, and was the wettest month at that airport since 1979. Medford ended the month with 7.67", second highest in the 87 year record to the 8.62" recorded in 1942. Brookings OR, on the far south coast of Oregon, reported 25.03" (218%), its third highest November total behind the 26.01" that fell in 1973 (also a La Nina year). Other Oregon totals from the coastal mountains included 35.35" at Laurel Mountain (average is 17.97"), 27.19" at Elk River Hatchery (average 18.75"), and 28.17 at Nehalem 9 NNE (average 17.77"). A little further down the coast, Eureka had 14.09" (219%).
Again, Hilo picked up copious precipitation, with 15.57" (107%), and once again Honolulu mustered just 0.85" for an 11-month total of merely 3.37", or 18 percent of average. Figure 17 shows accumulated precipitation for the last year in Honolulu, compared with the long term average.
Figure 18 shows the precipitation for October-November combined, in terms of the relative rank since 1895. Similarly, Figure 19 shows the same statistic for the first 11 months of 1998. For the year to date, parts of the West are in their wettest few percent in the past 104 years.
Crater Lake ramped up its snowfall season with 137" of white material, compared with a November average of 69.1". The 148" so far compares with an average to date of 95.3', but still well short of the winter-long average of 495 inches. Snowfall for 1998-99 is off to a good start in the Pacific Northwest and northern Rockies. Figure 20 shows the snow water content at Mount Rainier Paradise last year and so far this year. Figure 21 shows the deficient season last winter near Glacier Park MT and the relatively good start for winter 1998-99.
For a second consecutive month, extreme North Slope temperatures occurred, with monthly averages of 16 F above normal in Barrow, while the remainder of the state was near average. In fact, the record for the entire year at this site is most remarkable (Figure 22), with extended periods far above normal temperatures during much of 1998.
Strong winds occurred on November 23. Salem OR reported gusts to 68 mph, and gusts reached 70-80 mph at many places along the Oregon coast. Highest gusts topped 100 mph along the north coast. This very powerful storm remained far enough offshore to avoid destructively high speeds on land. Ocean waves with this storm were reported to have reached heights of 45 feet.
On the same day prolonged high winds affected Reno NV. The Western Regional Climate Center's rooftop sensor recorded 28 separate 10-minute periods with gusts exceeding 70 mph, 7 periods exceeding 80 mph, and a peak gust of 89.6 mph. The recurrence interval for such winds is approximately 5-10 years.
Through December 12, 80,000 wildland fires had been reported, burning 2.3 million acres. The year 1998 is generally regarded as an unusually lackluster fire year.
The winter is off to a fast start for snowpack accumulation in the Pacific Northwest and northern Rockies, and a relatively slow start for Arizona.