Is This Weather Normal? – June 2019

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June in Terrace, BC was warmer than average and with average precipitation. For the year so far – now halfway through 2019 – weather in Terrace, BC has been warmer than average, and precipitation has totaled 70% of normal.

Temperature:

The average June 2019 temperature was 15.1°C, 1.3°C above the 1971-2000 baseline climate, the 20th warmest June on record. The month started with temperatures below average, but not abnormally so, and then finished above average (Fig. 1).

Figure 1: Daily average temperature for June 2019 in Terrace, BC (dotted red line). The solid red line shows January-May 2019 temperature. The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation. Note that there are three days of missing temperature data (June 17, 18 and 19).

For the year so far, we’ve had a warmer than average January, colder than average February then March through June above average (Fig. 2). This has led to a year-to-date average temperature of 5.6°C, which is 1.1°C above the 1971-2000 baseline climate, the 21st warmest on record.

Figure 2: 2019 average monthly temperature for Terrace, BC through June. The dotted blue curve is 2019, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

Precipitation:

Precipitation during June 2019 totaled 58mm, 2mm more than the 1971-2000 baseline climate. Precipitation for the year has totaled 386mm, 70% of normal (Fig. 3).

Figure 3: Cumulative precipitation – where total precipitation (green), rain (dark blue), and snow (light blue) are added throughout the year. Solid lines show the 1971-2000 average. Dotted lines show the 2019 totals to date.

For the year so far, temperature has been above average in all months except February, with May tying the all-time record for that month. Terrace has seen some return to more normal precipitation in recent weeks, but this isn’t enough to recover from the longer-term deficit.

Is This Weather Normal? – May 2019

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May 2019 in Terrace, BC was hot and dry:

  • Record tying heat
  • Much drier than average

Temperature:

The average May 2019 temperature of 14.2°C is tied with 2015 for the highest average temperature for the month, 3.8°C warmer than the 1971-2000 baseline climate. Average daily temperatures stayed above average for the entire month with some days at the beginning and end of the month approaching daily records (Fig. 1).

Figure 1: Daily average temperature for May 2019 in Terrace, BC (dotted red line). The solid red line shows January-April 2019 temperature. The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation.

The temperature pattern for the year shows an interesting stair-step pattern, as we have switched from one pattern of atmospheric circulation to another almost on a monthly basis (Fig. 1). This has led to well above average temperatures in January and May, well below average temperatures in February, and near average temperatures in March and April (Fig. 2).

Figure 2: 2019 average monthly temperature for Terrace, BC through May. The dotted blue curve is 2019, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

Precipitation:

May 2019 precipitation totaled 19mm, 39mm below the 1971-2000 average, which is the 7th driest May on record. After a return to average precipitation for April, conditions returned to significantly drier than average in May. Precipitation for the year to date totals 328mm, 66% of normal (Fig. 3).

Figure 3: Cumulative precipitation – where total precipitation (green), rain (dark blue), and snow (light blue) are added throughout the year. Solid lines show the 1971-2000 average. Dotted lines show the 2019 totals to date.

Check back in early-July for the June update and a half-way-through-2019 synopsis!

 

Is This Weather Normal? – April 2019

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April 2019 weather for Terrace, BC was about as normal as can be:

  • Slightly warmer than average temperature
  • Total monthly precipitation nearly identical to the baseline climate

Temperature:

April was the 31st warmest April on record, averaging +6.7°C, which is 0.5°C warmer than the 1971-2000 baseline climate. Temperatures stayed relatively consistent through the month, starting above average and falling a bit below average by the end of the month (Fig. 1).

Figure 1: Daily average temperature for April 2019 in Terrace, BC (dotted red line). The solid red line shows January-March 2019 temperature. The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation.

Temperatures for the year show the warmer than average January, colder than average February, warmer than average March and now the nearly average April (Fig. 2).

Figure 2: 2019 average monthly temperature for Terrace, BC through April. The dotted blue curve is 2019, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

Precipitation:

April 2019 precipitation was 73mm, nearly identical to the 1971-2000 baseline climate average of 74mm. This return to normal precipitation was a much needed, slight respite from the recent dry months. Cumulatively for the year, even with an average April, precipitation is at 69% of normal (Fig. 3). With April complete with no measurable snowfall, we can determine that the total snow in Terrace, BC for the winter months of 2019 was 118cm, which is 53% of normal.

Figure 3: Cumulative precipitation – where total precipitation (green), rain (dark blue), and snow (light blue) are added throughout the year. Solid lines show the 1971-2000 average. Dotted lines show the 2019 totals to date.

Is This Weather Normal? – March 2019

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The weather in Terrace, BC in March 2019 was abnormally dry. The main weather stories discussed below in more detail are . . .

  • March temperature was about a degree warmer than average
  • March 2019 was the 4th driest on record
  • Total February-March 2019 precipitation set a record low

Temperature:

March was the 27th warmest on record, averaging +3.1°C, which is 0.8°C warmer than the 1971-2000 baseline climate. Temperatures stayed abnormally cold during the first weeks of March (continuing from the cold February), but a change mid-month led to higher than average temperatures for the second half of the month (Fig. 1).

Figure 1: Daily average temperature for March 2019 in Terrace, BC (dotted red line). The solid red line shows January-February 2019 temperature. The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation.

The average monthly temperatures through March show the warmer than average January, colder than average February, and warmer than average March (Fig. 2).

Figure 2: 2019 average monthly temperature for Terrace, BC through March. The dotted blue curve is 2019, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

Precipitation:

The main weather story for March 2019 is the lack of precipitation. March 2019 was the 4th driest on record, totaling 30mm, 33% of normal (90mm). Cumulatively for the year, precipitation is now 63% of normal, with 237mm of precipitation compared to an average of 376mm. Snowfall to date is 55% of normal, and rainfall to date is 65% of normal (Fig. 3).

Figure 3: Cumulative precipitation – where total precipitation (green), rain (dark blue), and snow (light blue) are added throughout the year. Solid lines show the 1971-2000 average. Dotted lines show the 2019 totals to date.

March precipitation only tells part of the story of recent dry conditions in Terrace, BC and the larger region. When combined, February-March 2019 precipitation set a record low, with only 41mm of precipitation, 20% of the average of 203mm (Fig. 4).

Figure 4: 1913-2019 total precipitation for the months of February and March. The long-term average is in black and dashed. There are two years of missing data (1919 and 1955).

This winter dry spell follows the driest July-October on record – continuing the drought in northwest BC and southeast Alaska.

Links:

Drought in Alaska (Drought.gov)

In Southeast, Alaska is seeing its first extreme drought ever recorded, climatologists say (Anchorage Daily News)

BC Drought Map (BC Government)

BC snowpacks near 40-year lows prompting drought fears (Global News)

Is This Weather Normal? – February 2019

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February 2019 weather in Terrace, BC was abnormal in two ways – cold and dry. The warmer-and-wetter-than-normal January ended abruptly on January 31st, when a dramatic change in pattern brought in colder and drier conditions that lasted through February and March.

Temperature:

February temperature was the 6th coldest on record, averaging -6.1°C, which is 4.8°C colder than the 1971-2000 baseline climate. Temperatures plunged at the beginning of February to well below normal, then approached and reached average conditions by the end of the month (Fig. 1).

Figure 1: Daily average temperature for February 2019 in Terrace, BC (red line). The black line shows the 1971-2000 average. The two gray lines show plus/minus one standard deviation.

The temperature story in 2019 (so far) is one of a much warmer than average January, followed by a much colder than average February (Fig. 2). This difference from one month to the next isn’t abnormal. It’s related to circulation patterns in the atmosphere, particularly the location and direction of the polar and subtropical jet streams here in the northern hemisphere. The jet streams direct storms and act as a kind of barrier between colder air to the north and warmer air to the south. How the jet streams curve (Rossby waves) determine how far south colder air moves, and how far north warmer air moves, in addition to guiding the direction of storms. What is abnormal, however, is how these waves in the jet streams seem to be getting stuck in place, resulting in persistent weather patterns, a process that is hypothesized as likely being caused by global warming.

Figure 2: 2019 average monthly temperature for Terrace, BC through February. The dotted blue curve is 2019, the 10 red lines are the ten warmest years on record, every other year is in gray. The black line is the long-term average, and the error bars mark plus/minus one standard deviation.

Precipitation:

Precipitation in February (or the lack thereof) led to the 2nd driest on record, totaling 11mm, which is 111mm less than the average February precipitation of 122mm, or 9% of normal. This lack of precipitation can be seen graphically by the flat lining of the curves in the cumulative precipitation graph (Fig. 3). Other than a minor snowfall event later in the month, there was no precipitation in February. This February dry spell has resulted in total yearly precipitation to date moving from above average after the warm/wet January (115% of normal), to below average after February (71% of normal).

Figure 3: Cumulative precipitation – where total precipitation (green), rain (dark blue), and snow (light blue) are added throughout the year. Solid lines show the 1971-2000 average. Dotted lines show the 2019 totals to date.

February is an important month for snowfall in the Coast Mountains, building up a snowpack that is later available as liquid water during the spring/summer melt season. The near record setting dry February of 2019 does bode well for a recovery from the ongoing drought (Fig. 4).

Figure 4: 1913-2019 total precipitation for the month of February. The long-term average is in black and dashed. There are two years of missing data (1919 and 1955).

Links:

The jet stream, explained (National Geographic)

Jet streams (North Carolina Weather Office)

Global Warming Is Messing With The Jet Stream. That Means More Extreme Weather. (Inside Climate News)