21. April 2013 · Comments Off on Weather Whys, April 21, 2013 · Categories: Graham Saunders, Weather Whys

April can be the cruellest month
What to write about this week? Spring planting, going to one of our many inland lake systems for camping and boating – hmmm. It is probably not a popular topic but the winter/spring storm that began on Wednesday and then caused highway closures and mainly shut down the city of Thunder Bay on Friday has to grab the spotlight this week.
April2013b
Let’s explore the when and whys first. I was watching the maps and radar of weather in the central United States early in the week. They featured a huge system with potential for strong winds, heavy rain, tornadoes and a direct feed of moisture from the Gulf of Mexico. It was predicted to move due north and then veer to the east, and part of the pattern had similarities to two situations last year that brought flooding to Thunder Bay in May and again three weeks later to Duluth.

The system was slow, vast and contained a variety of weather as it moved both north and east. Chicago received 100 to 175 mm of rain and some snow with extensive flooding as a result. All of Minnesota and Wisconsin experienced winter storm conditions, then Thunder Bay and the north shore of Lake Superior. Snowfall began in Thunder Bay late Wednesday; snow and occasional rain, freezing rain continued through Thursday. Friday extended the winter storm theme with strong winds, falling and blowing snow and blizzard conditions until into the evening.

Yesterday’s Chronicle-Journal had photos and articles about what became the beginning of an unscheduled long weekend. Even City bus service was halted in the afternoon because of severe weather and whiteout conditions.

How does this 48-hour storm compare with the past? The most formidable records belong to the 1950s. April 1950 has a scary snow total 79.2 cm, as a result of 15 snow days (1 cm or more).

The record daily of 24.1 cm belongs to April 6, 1956. Of course, snowstorms sometimes ignore calendar days and April 6 and 7 qualify as the greatest 2-day total with 32 cm.

Measuring snow and assessing events and trends should be a given. This is Canada after all.

Plowing roads, snow loads on roofs, winter accumulations and potential for flooding should be enough to justify careful measurement of snow amounts. The list continues if we consider resulting soil moisture, spring planting and planning for the forest fire season.

It can be a little complicated getting precise snow measurements. Moisture content can vary greatly and, as we witnessed many times recently, brisk winds can rearrange the depth of snow on the ground. In the good old days Environment Canada (EC) had detailed procedures: The observer will take 10 representative samples (avoiding obvious drifts and hollows) of snow on the ground and then divide by 10 to have an official measurement. This could be compared with a melted total to avoid glaring errors and/or instrument malfunction.

I occasionally harp on the Federal government’s policies of reducing monitoring and analysis of air and water toxins, crippling of the Canadian Ozone monitoring network and of course, the measurement of snow.

One of these policies is to stop the direct measurement of snow at the Thunder Airport after the first two weeks in April. Yes, it saves a few dollars and some years this can work. Last year the final snow in spring occurred in late March.

This year the airport total for April 1 to 14 was 34 cm, from five snow days. Snow was reported on 63 hours during April 15 to 19. There are two sites at the airport that measure precipitation and both have totals that are suspiciously low. For Friday one site has zero; the “CS” station lists 3.5 mm. In the future someone looking at these numbers would be puzzled about why much of Thunder Bay was shut down.

I made phone calls to some people who live near the Airport. My estimate (really a careful guess) is that the April total is 78 cm from eight snow days. If the forecast for 2 cm happens today, it would be an unofficial snow record for April. I think that the daily and 2-day records were tied (or slightly exceeded) by the 48-hour storm.

Be assured that all that snow was not your imagination no matter the EC numbers say.

Of course, if you really want snow, come out to rural locations. I have recorded 120 cm so far in April and wallowed through 85 cm early on Saturday to take 10 measurements. Gasp!

Postscript
I record the monthly global temps routinely (call me obsessive) via http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt

These numbers suggest that March 2013 was tied with 2006 for 8th place, i.e. 133 colder years.

On a more frigid note, Thunder Bay has a record low this morning and an almost yesterday.

This April is on track to be one of the coolest on record, but probably the 1950 mean temp of -2.2 C is secure.

In spite of the cool month here and central North America, April is likely to be in or near the top ten warmest, world-wide.

March
It was cooler or much cooler than average across central North America, most of Europe and European Russia. This phase of the Arctic Oscillation also contributed to much warmer than average and even record warm temperatures in northeastern Canada and southeastern Greenland. Many regions in China also recorded record warm temperatures. Several regions in central and northern Africa in the 0°–20°N latitude belt had record warmth. Most of northern Africa, along with northern South America and much of Australia, were also much warmer than average. Tasmania had record high temperatures. Argentina observed temperatures that were cooler to much cooler than average.

The cool/warm anomalies will almost certainly shift somewhat from the March pattern. For example, “Germany observed its fifth coolest March since records began in 1881 and second coolest in the past 50 years” but the last week or two has featured well above average temps, including 26 to 30 C.

I am thinking Tbay and area will warm slowly, then serious melting conditions beginning in early May. Ice fishing for a little longer.

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