Overview

Wet and cool spring conditions continued for another month. Nearly every station in Oregon had below-normal monthly temperatures, and about three-quarters of the reporting stations were wetter than normal. While some farmers were disappointed about “too much rain,” water supply folks were ecstatic: what appeared to be a REALLY bad year in March now is looking pretty good after all.

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.

Basin Summary

Here is a summary of water indicators at the end of the month, by river basin:

n.a. Not available
(1) Percent of normal June 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 June stream flow, from U.S. Geological Survey (USGS)
(5) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(6) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecasts

The Climate Prediction Center’s (CPC) forecasts for July-September appear below. Temperatures for western Oregon are likely to be above normal. Precipitation probabilities suggest an equal chance of below-, near-, and above-normal rainfall.
Look below to see what we think is going to happen this summer.

El Niño update

The Australian Bureau of Meteorology (BOM) suggests that the chances of an El Niño event this year continue to decrease. Their July 6 update states:

Summary: El Niño risk gets lower.

History shows that the risk of an El Niño developing after June is reasonably low. Although most of the equatorial Pacific Ocean remains about half a degree warmer than average, there are currently no obvious triggers to enhance this warming to an El Niño state.

The current patterns of Pacific cloud, wind and subsurface temperatures remain neutral. Furthermore, the SOI has risen strongly during the past month reaching a value of +3 for June following a reading of -15 in May. This is a good sign against El Niño formation, as El Niños are associated with sustained negative SOI values.

Most international models, including the POAMA climate model run at the Bureau of Meteorology, clearly favour neutral conditions in the equatorial Pacific Ocean during the southern winter and spring.

NOAA’s Climate Prediction Center reported on July 7:

Synopsis: ENSO-neutral conditions are expected during the next 3-6 months.

Sea surface temperature (SST) anomalies increased throughout the eastern equatorial Pacific during June (Fig. 1, bottom). By the end of the month, positive equatorial SST anomalies were observed in most areas between Indonesia and 90°W, while negative anomalies persisted along the South
American coast (Fig. 1, top). The increase in SST anomalies in the eastern equatorial Pacific during June was reflected in an increase in the SST departures in the Niño 3 and Niño 3.4 regions (Fig. 2). However, the overall pattern of tropical convection was near average. During June there was very little week-to-week variation in circulation features, as the MJO became inactive.

A majority of the statistical and coupled model forecasts (Fig. 3) indicate that SST anomalies will likely remain positive during the next 3-6 months, but still within the ENSO-neutral range.

Looking Ahead to Summer

Here’s what I wrote in my Weather Matters column, June 26, 2005:

As our wet spring nears its end, it appears to be leaving some memorable events in its wake – just in case we hadn’t noticed already. Last weekend I was in Eugene watching the Wood Bat Tournament; my son Tim plays for the Richey’s Market American Legion team. Both Saturday and Sunday saw tremendous thunderstorms, at least by western Oregon standards. The sky east of Eugene was very, very dark. Lightning crackled every few minutes, followed by loud thunder. Just after Richey’s won the Sunday afternoon game, the skies opened up and dumped rain, and some hail, forcing cancellation of the evening game. Richey’s won the tournament.

One of the opposing teams was from Bend, and the players and families left to return home. It must have been an exciting trip. I found out later that the Cascades were getting the brunt of the storm, with golf ball sized hail, strong winds, and intense rain. The next day a friend told me his son, who lives in Bend, had hail 4-5 inches deep on his deck that evening.

As the storm moved northward, it headed for the Portland area. Lightning, hail, winds, thunder – all the trappings of a big, severe thunderstorm – were present. I heard a report that Tigard recorded an inch of rain in less than an hour.

So what about summer? Is it ever going to come? Does the wet spring give us indications of what summer will be like? Will it be warm and dry, please?

Yes. But maybe not right away.

Looking back on Oregon spring-summer periods, there’s a pretty definite pattern. I would summarize it like this:

1. We nearly always get several months of warm, dry weather every year. The only truly wet summer in recent decades was 1983. 1993 was wet all spring and clear through July, but dry afterward.
2. Most of the time, when summer arrives late, it extends well into fall. For example, 1993’s wet March-July was followed by a very dry late summer and early fall.
3. On the other hand, when warm, dry weather arrives early, it often leaves early. Case in point: last year, when spring came early and warm, but wet weather arrived in August, followed by a wet September and October.
4. Years with warm, dry springs are more likely to have hot summers.
5. There is a strong tendency for alternating early-late years. In the early-to-mid-1990s, the odd years had wet springs and mild summers, while the even years had early, dry springs and hot summers. This alternating tendency broke down in the late 90s and early 00s, but seems to have returned in the last 4 years.

Putting all that together, here’s what I come up with for a summer forecast:

1. Mild conditions will continue for several more weeks, with some occasional rain.
2. By mid-July, drier conditions will set in, and temperatures will warm up.
3. Summer will be warm and dry but not excessively hot – more like an “average” summer than a hot one. In my humble opinion, an average Oregon summer is about as close to perfect as one can get, so I’ll be happy if this pans out.
4. Early fall will be dry (September-October).
5. In late October-early November we’ll have a very cold period, but it won’t be particularly wet.

In August, I’ll release my annual fall-winter forecast. In the meantime, enjoy the summer! When it arrives…
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As I write this in the second week in July, that forecast is looking pretty good! Then on July 10, I wrote the following:

Many of you already know the difference between a “weather forecaster” and a “climate forecaster.” You’re more familiar with the first one, probably. Tune in to local news or the Weather Channel, or access the National Weather Service Web site or radio broadcast and you’ll get a weather forecast: expected conditions for the next several hours, or several days.

But what I do is issue climate forecasts. If “weather” is day-to-day conditions, “climate” is longer-term (months, seasons, years, decades). Climate forecasts are much less specific, but over longer time periods.

One of the tools used in climate forecasting is the use of “analog” years. This means finding past years with similar conditions to those currently being experienced, and then assuming that what will happen in the next several months will be similar to what followed the analog periods.
For example, in February of this year I predicted that we were going to have a wet spring…yep, got THAT one right! I used the analog approach for that forecast, identifying past years with similar conditions – wet fall, dry winter, and similar ocean conditions – and looking to see what happened the following spring. Most of the analog years had wet springs, so I broke ranks with the federal Climate Prediction Center (CPC) and predicted a wet spring.

CPC had predicted a dry, warm spring. Drought conditions were well-established and predicted to worsen. Fire danger was high and expected to get worse. A scientist friend of mine told me, “the West is toast!” But based on what we’ve seen in the past (rather than on climate models), I figured I had a 3 in 4 chance of being right, so I went with the odds and got it right.

But last summer I figured there was a 2 in 3 chance of a wet winter, so I predicted that – and got burned. Sometimes you lose, even when the odds are in your favor.

By now you may have figured out that being a climate forecaster is a lot like being a Las Vegas oddsmaker, issuing odds for a Super Bowl game or a horse race. And there’s truth in that – except for the amounts of money that changes hands.

Now that summer is here, I’ll tell you about an analog year that several scientists have noticed: 1995. Here in the Northwest, spring was similar to this year – wet and mild. Those conditions continued through June and into early July, just like this year. In mid-July we had a heat wave (5 days in a row above 90, starting on the 17th, with a high of 99). Things cooled off after that, and the rest of the summer was pretty close to average. Kinda dull, actually, in the Northwest, but NOT in the Atlantic!

After a 20-year period with very few hurricanes, and the quietest 4-year period ever recorded in 1991-94, the Atlantic warmed up -- and woke up! 1995 had nineteen named storms, the second-highest ever (there were 21 in 1933). Eleven reached hurricane status, again the second-highest ever.

And this year? We’re up to four named storms already, with Dennis, the first hurricane of the season, heading toward the Gulf Coast. This is the earliest 4th storm ever.

Now then, is there anything to suggest what will happen next fall and winter? Yes! I noticed many years ago that there was a strong correlation between Atlantic hurricane activity and our weather the following winter. Busy hurricane years were usually followed by wet winters, while quiet
Atlantic conditions foreshadowed dry winters.

Looking back at the fall-winter of 1995-96, things look ominous. In November there were two very large rain storms, producing floods in Washington and extreme northern Oregon. There were ice storms in December and early February. And then we had the big flood from February 6-10, the largest in 30 years.

Mind you, I’m not quite ready to predict a repeat of the 1995-96 winter, but the odds of a wild and crazy winter are looking better and better.

Oregon Climate Service

George H. Taylor, Oregon State Climatologist

Wayne P. Gibson, Programmer/GIS mngr.

Eileen Kaspar, Research Assistant/Manager of Data Services

Melanie Mitchell, Undergraduate Assistant

Wolf Read, Undergraduate Assistant

Emily Gibson, Student Assistant

Cadee Hale, Publications Assistant

Sara Joos, Student Assistant

Sean Daly, Student Assistant

Kirk Borgerding, Undergraduate Assistant

Kelsey Kuykendall, Undergraduate Assistant

Oregon Climate Service, Strand 326,                             	     Phone: (541) 737-5705  
Oregon State University                                                      Fax: (541) 737-5710   
Corvallis, Oregon  97331                                                     E-mail: oregon@coas.orst.edu   
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