Overview
October saw some very significant transitions, with cooler temperatures beginning to be observed in many locations in Oregon. On the other hand, there were several very warm periods as well, including a brief heat wave late in the month that saw record-setting temperatures. Generally speaking, the month was drier than an average October.
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:
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| OWYHEE | 2 | 14 | 53 | -2.8 |
| MALHEUR | 15 | 33 | 11 | -2.4 |
| GRAND RONDE, POWDER, BURNT | 48 | 43 | 71 | -2.0 |
| UMATILLA, WALLA WALLA, WILLOW | 56 | 92 | 87 | +0.4 |
| UPPER JOHN DAY | 62 | 92 | 61 | -0.9 |
| UPPER DESCHUTES, CROOKED | 51 | 62 | 35 | -0.9 |
| LOWER DESCHUTES, HOOD RIVER | 93 | 83 | 90 | -1.4 |
| WILLAMETTE | 82 | 71 | 58 | -1.8 |
| ROGUE, UMPQUA | 24 | 19 | 73 | -1.0 |
| KLAMATH | 7 | 19 | 79 | -2.6 |
| LAKE COUNTY, GOOSE LAKE | 31 | 5 | 62 | -1.0 |
| HARNEY | 39 | 29 | 72 | -1.5 |
| NORTH COAST | 105 | 122 | 85 | -1.1 |
| SOUTH COAST | 43 | n.a. | 16 | +2.0 |
(1) Percent of normal October precipitation, from NOAA Cooperative
sites
(2) Percent of normal seasonal precipitation, from Natural Resources
Conservation Service (NRCS) SNOTEL sites
(3) Percent of normal October stream flow, from U.S. Geological
Survey (USGS)
(4) Surface Water Supply Index, from NRCS (-4 = very dry, 0 =
normal, +4 = very wet)
Forecasts
The Climate Prediction Center's (CPC) forecasts for November-January appear below. Temperatures for Oregon (and all of the West) are likely to be above normal, while there are equal chances of above- and below-normal precipitation. The 3-day prediction for November is nearly the same as the 90-day forecast.
Oregon Climate Service predicts above-normal temperatures and normal precipitation for the rest of the calendar year, and normal temperatures and above-normal precipitation for January-March. Since last summer we have been suggesting that we will experience one or more severe weather events this winter, most likely either a major wind storm or intense rainfall event. Washington has already experienced the latter: in October, record-setting precipitation was recorded in Washington and British Columbia. In Oregon, we have seen a number of extremes, including both record high and record low temperatures. More is expected in the next several months!
ENSO Update (from CPC)
Oceanic conditions in the tropical Pacific were slightly warmer-than-average (but still ENSO-neutral) during September 2003. Equatorial SST anomalies greater than +0.5°C (~1°F) persisted in the region west of the date line during September, and developed over most of the region between the date line and 120°W during the last half of the month. Observed SST anomalies in the Niño 3, 3.4 and 4 regions have been positive since July 2003. Positive equatorial upper-ocean temperature departures persisted in the central and east-central equatorial Pacific. Overall the basin-wide upper ocean heat content was warmer-than-average during the month.
Generally, atmospheric conditions in the tropical Pacific have been near average in recent months, with no significant trends that would support large-scale anomalous warming or cooling of SSTs in that region. Thus, slightly warmer-than-average conditions are likely to persist through the next several months.
A majority of the statistical and coupled model forecasts indicate near-average (ENSO-neutral) conditions in the tropical Pacific (Niño 3.4 SST anomalies between -0.5°C and +0.5°C) through the NH winter 2003-2004. However, over the past few months there has been a trend in the suite of forecasts towards somewhat warmer conditions, consistent with observations. Thus, it is likely that slightly warmer-than-average conditions will persist through the Northern Hemisphere winter of 2003-04.
Review of Old Farmer's Almanac 2002-03 California Weather Forecasts
Jan Null, CCM
Golden Gate Weather Services
Original article at http://ggweather.com/2003/almanac.htm
INTRODUCTION
Once again its time for the Old Farmer's Almanac to hit the streets
and tout how good their weather forecasts have been for the past
two-hundred or more years of relying on their "secret formula".
In their latest press release they claim 80 percent accuracy.
But how often does anyone go back to scrutinize an old forecast
to see if it "verified". I have found that people often
don't even remember last week's forecast let alone one that was
printed a year ago.
But, here's what I found by looking back at the regional weather forecasts from last November's Western Edition of the Old Farmer's Almanac (Yankee Publishing, Dublin NH, 2002). The weather forecast section of the Almanac is divided into 16 regions; with Region 16 encompassing the southern three-fourths of California. Each month has a summary of the forecast average temperature and rainfall for the month and how much above or below normal the forecast is. The actual forecasts from the 2002 Old Farmer's Almanac (OFA) for Region 16 (Fig 1.)
DATA
To evaluate the veracity of the forecasts each monthly
forecast was compared to the actual temperature and rainfall by
month for the United States Climate Divisions generated by the
NOAA-CIRES Climate Diagnostics Center US Climate Divisions Plotting
Page. Data for climate divisions was chosen because of the large
number of sites that are used in determining the division average,
thus eliminating the bias of a single station.
U.S. Climate Division precipitation were used for the period
November 2002 - April 2003. [Note: on Jan's Web page he has links
to diagrams showing monthly precipitation and temperature]
ANALYSIS
The analyses in Table 1 and 2 (below) compare the monthly
forecasts for Region 16 from the 2002 Old Farmer's Almanac with
the actual observed monthly climate division anomalies for temperature
and precipitation. Because of the negligible rainfall in the California
in the summer months, precipitation for the months May through
September was not examined. Furthermore, if either the forecasts
or the observed data were geographically split then separate analyses
were done for each geographic area.
SUMMARY
For California, Region 16, the precipitation forecast
(Table 1) was only correct for one month (February 2003) and that
was only in Southern California. Consequently of the 6 months
of rainfall data that was evaluated the Old Farmer's Almanac was
correct just 8 percent of the time and had the right sign but
incorrect quantity another 8 percent, meaning that it was wrong
about 84 percent of the time.
The temperatures forecasts for region 16 (Table 2) were correct for 5 of the 12 months or about 42% of the cases. If climatology had been used it would have been correct 58% of the time. The OFA was wrong 58% of the time, with the wrong sign in half the those cases and the right sign but wrong amount in the other half.
Table 1. Precipitation Anaysis Region 16 - California
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Table 2. Temperature Analysis Region 16 - California
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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
Wolf Read, Undergraduate Assistant
Emily Gibson, Student Assistant
Cadee Hale, Publications Assistant
Kelsey Kuykendall, Undergraduate Assistant
Oregon Climate Service, Strand 316,Phone: (541) 737-5705 Oregon State University Fax: (541) 737-5710 Corvallis, Oregon 97331 E-mail: oregon@oce.orst.edu Web: http://www.ocs.oregonstate.edu