Oregon Climate Service, June 2003

Overview

June was dry and rather warm. There were several heat waves. Summer arrived in Oregon.

Table 1 is a summary of monthly averages and totals at selected stations throughout the state. Table 2 lists daily temperatures and precipitation for most of the locations listed in Table 1. In Table 3, monthly and seasonal precipitation totals throughout the state are listed. Figure 1 shows the percentage of seasonal precipitation statewide.

Basin Summary

Here is a summary of precipitation, water supply, and snow pack as of the end of the month, by river basin:

Precipitation

Stream Flow

 SWSI
BASIN

(1)

(2)

(3)

 (4)

(5)

(6)
OWYHEE 11 87 84 27 25 -2.0
MALHEUR 41 88 95 13 12 -1.6
GRAND RONDE, POWDER, BURNT 42 109 90 97 94 -1.1
UMATILLA, WALLA WALLA, WILLOW 1 97 86 46 98 -0.6
UPPER JOHN DAY 12 94 83 63 71 0.0
UPPER DESCHUTES, CROOKED 6 82 80 37 59 -0.5
LOWER DESCHUTES, HOOD RIVER 16 97 82 66 75 -0.8
WILLAMETTE 15 97 83 78 87 +1.7
ROGUE, UMPQUA 1 104 81 83 93 +0.2
KLAMATH 1 91 90 69 72 -1.7
LAKE COUNTY, GOOSE LAKE 5 90 85 73 70 -0.2
HARNEY 8 86 91 75 72 -0.9
NORTH COAST 26 92 n.a. 54 92 +0.1
SOUTH COAST 9 96 n.a. 26 106 +1.0

n.a. Not available

(1) Percent of normal March precipitation, from NOAA Cooperative sites
(2) Percent of normal seasonal precipitation (since Oct. 1), from NOAA Cooperative sites
(3) Percent of normal seasonal precipitation, from Natural Resources Conservation Service (NRCS) SNOTEL sites
(4) Percent of normal snow water equivalent, from NRCS SNOTEL sites
(5) Percent of normal March stream flow, from U.S. Geological Survey (USGS)
(6) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(7) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)


EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION
Issued by CLIMATE PREDICTION CENTER/NCEP
July 10, 2003

Current atmospheric and oceanic conditions do not support the development of La Niña in the next few months. Negative sea-surface temperature anomalies weakened across the central and eastern equatorial Pacific during June, resulting in an upward trend in SST anomalies in all of the Niño regions. By early-July equatorial SSTs were near or below normal between 150degW and the South American coast, and above normal west of 150degW. Also, since late May positive equatorial upper-ocean temperature departures have increased in magnitude in the western Pacific and spread eastward into the central and eastern Pacific. This evolving subsurface pattern is associated with an eastward propagating oceanic Kelvin wave, resulting from a period of weaker-than-average easterlies in the central equatorial Pacific that occurred during late May and early June. These recent trends in surface and subsurface ocean temperature departures do not support the development of La Niña conditions during the next few months. In addition, some atmospheric indices, such as the Tahiti-Darwin SOI (-1.1 in June) and low-level (850-hPa) zonal wind in the central and eastern Pacific (negative in June), also do not support the development of La Niña in the near future.

The latest statistical and coupled model forecasts indicate considerable uncertainty for the next several months. However, the majority of the forecasts indicate near neutral conditions (Nino 3.4 SST anomalies between -0.5 and +0.5 degC) during the last half of 2003. This is consistent with current conditions and recent observed trends.

 

The 100th Anniversary of Oregon's deadliest weather event

Heppner, 1903

Many farmers in Oregon east of the Cascades were worried about water conditions during the late spring of 1903. Very low precipitation totals in April and May had left the soil dry and began to threaten crops. The agricultural report for May 25 stated "ranges drying up, and more rain needed in eastern and southern Oregon. Wheat backward and becoming weedy ... corn, sugar beets, field onions and gardens making very slow growth." Dry and warm weather continued, although local showers brought some relief. The June 8 report included a single sentence about water conditions: "Spring wheat and forage plants deteriorating on account of the drought." Little wonder, then, that gathering clouds on the afternoon of June 14th were welcomed by the residents, many of them dry-land farmers whose economic survival depended on summer rains.

Heppner is the county seat of Morrow County, and had a population in 1903 of about 1,400. Willow Creek, which originates in the Blue Mountains only a few miles southeast of Heppner and flows northwestward toward the Columbia, had created an alluvial valley 500 to 1,500 feet wide, a fertile strip of cropland on which Heppner was built.

As storm clouds gathered over the Columbia Plateau on the afternoon of June 14, they seemed to congregate near the slopes of the Blue Mountains just south of Heppner. They grew darker and darker. Thunder was heard. Abruptly, a massive (and deadly) hailstorm began. John T. Whistler, a U.S. Geological Survey agent, later reported:

Some of the hail stones are said to have measured 1 1/4 inches in diameter ... A grim evidence of the amount of hail that fell is that, while most of the bodies being recovered on the fifth day were already badly decomposed, one was occasionally found almost perfectly preserved in a large drift of hail. Nearly all the hail was of clear ice and, unlike the usual hail stones, which are of a more opaque ice, being built up from a nucleus in successive layers.

As bad as the hailstorm was, things quickly grew worse. Heavy rain, appropriately called "cloudbursts" by residents, inundated the slopes of the Blues and the upper parts of the valley. Most of the rain fell in areas beyond any measurement gauges, but later reports estimated that an average of 1.5 inches fell over an area of 20-square-miles, most of it in a short period of time.

Unfortunately for Heppner, most of this 20 square mile area funneled into Willow Creek and its tributaries. A wall of water surged downstream; in many places, the first surge of water coincided with the peak depth. Eyewitness reports of the height of the "wave" at the head of the floodwaters ranged from 15 to 50 feet high, but many of these appear to have been exaggerated. Nonetheless, the water was very deep, and arrived so suddenly that residents were taken almost completely by surprise. The first notice that the people in the business district had of the flood was when T.W. Ayers' large two-story residence left its foundation, floated across the street, and crashed into some wooden buildings. Poplar trees over 2 feet in diameter were "snapped off like cornstalks." Julian Keithley, age 70, stayed in his home until everything was gone but the roof. He rode the current atop the roof for almost 2 miles, saving the life of another resident by pulling him onto the roof as he floated by.

About one-third of Heppner was completely destroyed, and more than 200 people died (about one-fourth of the total population). About 150 residences were destroyed. Whistler speculated that the destructiveness of the flood "is due more to the rugged character of the topography and the almost utter absence of vegetation than to the unusual rainfall." If this statement is true, it suggests that the biggest reason for the disaster was the location of Heppner in a very exposed and potentially dangerous location.

In the days following the flood, many remarkable stories were told as residents began to clean up, bury the dead, and rebuild their town. The heroic story of a Paul Revere-like ride by two horsemen became a legend. Leslie Matlock and Bruce Kelley, expert horsemen, secured horses from a livery stable and, armed with pruning shears, set out to warn ranchers and residents of Lexington (9 miles away) and Ione (18 miles away), both on lower Willow Creek. Below Heppner, Willow Creek meanders considerably, so the two riders cut across country, cutting fences as they went. Said Matlock in recalling the ride later, "We (Kelley and I) didn't talk much, except to call warnings at homes along the way. The flood waters had already beat us to Lexington, but we felt we could make it to Ione before the water hit." In Lexington the floodwaters had swept through the community at about 7:00 p.m., destroying several buildings and forcing residents to evacuate to the hills nearby. Matlock and Kelly secured fresh horses and continued on to Ione, beating the crest of the flood.

From "The Oregon Weather Book" by George H. Taylor and Raymond Hatton, OSU Press, 1999

 

African Dust Brings Drought, Rain across Atlantic

Krishna Ramanujan, NASA Goddard Space Flight Center

BOULDER--Dust from the Sahara Desert in Africa may modify clouds and rainfall both in Africa and across the tropical North Atlantic as far away as Barbados, according to a study that uses data from NASA satellites, ground measurements, and computer models. Natalie Mahowald, a scientist at the National Center for Atmospheric Research (NCAR) and University of California, Santa Barbara, and Lisa Kiehl, a graduate student at UCSB, published their findings in a recent issue of Geophysical Research Letters.

The dust particles act as surfaces, or kernels, for water vapor to attach to in low clouds, and for ice crystals to form around in higher clouds.

"The interaction between clouds and aerosols is critical for understanding climate change," says NCAR's Mahowald. Clouds play a pivotal role in reflecting and absorbing the Sun's rays, as well as radiation emitted from Earth's surface. The dust and cloud interplay also helps explain rainfall patterns over the Sahara Desert and areas to the south.

This is the first long-term regional study to confirm observations that mineral aerosols (dust particles in the air) can act as kernels for precipitation to form around. It is also the first to suggest that African dust interacts with clouds over a large region. NASA funded the study in cooperation with the National Science Foundation, NCAR's primary sponsor.

In low clouds, such as cumulus and stratocumulus, near the Sahara Desert, water attaches to dust particles. Higher dust concentrations can suppress rainfall and enhance drought conditions by dispersing water among many dust particles. This prevents the droplets from becoming heavy enough to fall, resulting in more thin, low clouds and less rain.

In high clouds, such as cirrus, cirrostratus, and deep convective clouds, there is some evidence that dust particles over wetter regions south of the desert provide surfaces for ice crystals to form around. The crystals grow rapidly, drawing moisture from surrounding cloud droplets. They become heavier and eventually fall, generating more rain and reducing the total amount of high clouds.

Dust from North Africa, where the desert lies, has blown increasingly into the atmosphere since the 1960s. Though the reasons for this are not clearly understood, some scientists believe the increase may be linked to human activity.

The researchers used 16 years of monthly mean observations from satellites, ground stations, and computer models to look at the relationship between cloud properties and mineral aerosols. They found a positive correlation between low-altitude cloud amounts and dust at the coast of North Africa, which supports the theory that dust particles act as sites for water droplets to form around in thin, low clouds.

The researchers also found a negative correlation between high clouds and dust along the equator across North Africa and the Atlantic Ocean. That is, more dust creates heavy ice particles in high clouds that rain down and ultimately reduce high cloud amounts. Still, since there are no long-term ground measurements for dust and high clouds in these areas, and because it has been hard to measure these high clouds with satellites, it is difficult to make firm conclusions regarding high clouds, rainfall, and ice forming around dust kernels.

Data on the number and thickness of the clouds, and cloud top pressure and temperature, came from NASA's International Satellite Cloud Climatology Project (ISCCP). ISCCP data covered 1984 to 1999 and combined Advanced Very High Resolution Radiometer (AVHRR) data from three satellites created and launched by NASA, including GOES-8, GOES-10, and GOES-12.

The study also used data from the Total Ozone Mapping Spectrometer (TOMS) instrument to determine the amount of radiation being absorbed by aerosols between 1984 and 1990. Data from the ground in Barbados was collected by scientists at the University of Miami.

NASA's Earth Science Enterprise is committed to studying the primary causes of the Earth system variability, including both natural and human-induced causes. Geophysical Research Letters is a publication of the American Geophysical Union.

On the Web: This press release and accompanying image can be found at www.ucar.edu/communications/newsreleases/2003/dust.

See also www.gsfc.nasa.gov/topstory/2003/0618dust.html.

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under primary sponsorship by the National Science Foundation. Opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.


Oregon Climate Service

George H. Taylor, Oregon State Climatologist

Wayne P. Gibson, Programmer/GIS mngr.

Mandy Matzke, Research Assistant/Manager of Data Services

Melanie Mitchell, Undergraduate Assistant

Derek Gilbert, Undergraduate Assistant

Wolf Read, Undergraduate Assistant

Emily Gibson, Student Assistant



Oregon Climate Service, Strand 316,                                 Phone: (541) 737-5705  
Oregon State University                                                      Fax: (541) 737-5710   
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