Is winter on hiatus?
This excellent winter for gardeners (not so for skiers) had me thinking about the weather. So far we’ve had typical El Nino conditions. Weak storms, dirty ridges, fog and inversions and mild temperatures. California has had an improved rainy season. Its all playing out as forecast. And the forecast for the next month is for temperatures above normal and precipitation below normal. So, we shall see, its more than possible that winter is pretty much over.
What happened to all the fish?
El Nino or ENSO (El Nino Southern Oscillation) is a powerful weather phenomenon that occurs typically 3 out of 10 years. Essentially, it is caused by a reversal in wind flow along the equator in the Pacific Ocean. Typically the flow is from east to west. The wind near South America (Ecuador, Peru) blows off shore. This blows the warmer surface waters to the west and results in upwelling of rich, oxygen dense cold water from below. This is a boon to living creatures and this is a fantastic place to fish. Fisherman noticed almost immediately that every few years though that fishing was AWFUL. The ocean became warm (thus less oxygen) and sea life was scarce. It could be so catastrophic to kill even native animals. This phenomenon was noted as occurring beginning in December- Hence, the fisherman named it El Nino- after the Christ child. Now we know that this 6-9 month long reversal of winds is part of a large pattern and it has specific effects on the weather all around the globe.
El Nino and the Pacific Northwest
The global effects of El Nino are extensive. In the Pacific it can energize the subtropical jet and merge with the polar jet stream- thus wet storms are more prone to move into California- the whole southern United States is wetter. El Nino even quashes the formation of Hurricanes in the Atlantic- good news. In the northern tier of the US, including us- there is a different set of effects. The weakened polar jet is often obstructed by a ridge of high pressure. (We are currently as of 1.27.15 under this regime). This prevents storms from moving inland. Less rain. Instead dry conditions appear and often with a strong inversion. An inversion is just that- cold air trapped at the surface (and often foggy and stagnant) and warm air above- it forms a virtual lid on the atmosphere. The atmosphere is inverted. On 1.25.15 this was in full evidence- would you believe that while we were in the upper 50’s in the Willamette Valley up at the 3,000-4,000′ elevation temperatures were basking in the 70’s? Not good news for skiers. This lid can trap pollutants at the surface and often fog forms as the lowest elevations cool and the saturation point is reached.
El Nino typically lasts 6-9 months and its effects can linger a bit longer than that. By the way La Nina is the opposite of El Nino- the wind blows very strong the other direction at the equator and ocean temperatures plummet. Its effects on us are just as you would guess. Wetter and colder weather. Cold wet springs and summers that are slow to warm. These conditions results in what gardeners know as bad ‘tomato years’. As far as we can tell La Nina is about 1/2 as likely to occur as El Nino. And there is growing evidence that global warming could spawn more frequent ENSO. Only in the future by judging the past will we know for sure.
My house, my numbers!
People often confuse facts with opinion and the weather is one such casualty. Everyone’s perception is different. Hot for one person is comfortable for another and so on. It occurred to me that it might be good to describe exactly how weather statistics are measured- and what the home gardener can do to REALLY get to know their garden and its micro-climates.
Temperature: Place your thermometer 5′ off of the ground on the north side of a structure. It should always be in the shade. Yes, the official temperature is the shade temperature. Just several minutes in the sun will wreck your readings. This is especially important if you are tracking the highs and lows. So no cheating- it must be in the shade. Also, you are taking the air temperature where we live at 5′ above the ground- not at the ground and not 20′ above the ground. 5′ above the ground is where the official temperature occurs. Personally, I like my Taylor Min/Max mercury thermometer- though there are better more reliable digital units out there. Just be wary of dying batteries- this can skew your results. It goes without saying that the remote sensor for digitally broadcast thermometers be placed in the shade, 5′ off the ground.
Note: The coldest temperature of the day often occurs briefly AFTER the sun has risen so be patient. On the other hand our hottest temperatures (in summer) occurs between 5:00pm and 7:00pm. Wait to reset your thermometer for the truest readings.
Rain: Rain gauges are pretty self explanatory. They must be in the full OPEN air with NO overhead obstructions. Empty them out at the same time every day for the most complete picture. Remember that Portland has HUGE differences in average precipitation with in its boundaries. The Airport at 90′ above sea level records 37.10″ of rain on average. In the West Hills above 500′ to 1000′ the average is more like 60″ to 65″. Elevation has a huge impact on precipitation. Because we are in Oregon algae can grow in the bottom of your receptacle- If you can’t scrub it out a few drops of bleach will kill it.
Snow measurement: Take a ruler and then find 3 even surfaces covered with snow. Do NOT immediately go over to a drift of snow and measure it. Take the depth of each place, record it and then divide by three. That average is your official snow depth. Typically, .05″ of precipitation yields 1″ of snow.
Wind: Wind is typically measured 10’+ above the ground. A gust of wind is the average speed over 3 second intervals. A hand held anemometer will record slightly lower speeds than a professionally placed device. Generally, though you can make estimate the wind speed using the Beaufort scale of observation. For instance: Smoke rising perfectly vertical is obviously calm. Whistling noises
through power lines is a gale (33 mph +) Entire large trees in motion and losing small branches is likely to be 58 mph+- storm force winds. Above that all hell breaks loose and you should be in your house anyway.
Its fun to take the time to record weather in your own garden. If you compare it to your closest reporting station for the NOAA. (There’s a map on the website). You’ll be amazed at the difference.
SHOPPING SEASON IS HERE:
Our shop is open from 10 to 5pm Fridays and Saturdays. We will open with our regular spring hours Thursday through Sunday (10am to 6pm) starting on February 5.