Very, Very Cold May

The cold weather earlier this week prompted many inquiries as to the relative unusualness of having snow and temperatures so cold in the middle of May.  Fargo did set a daily record cold maximum temperature Monday at 40 degrees.  Old record was 44 set in 1890.  May snowfall is also rare, but not without precedent.  I would describe such weather in our region as rare, but not unusual; the sort of thing that happens every few years or so.  The most unusually wintry May weather on record in the Fargo Moorhead area was in 1907.  There was measurable snow in Fargo on four separate days; the 2nd, 13th, 14th, and 19th; for a total of 4.2 inches.  The first ten mornings in May were all in the 20s (except for May 2 when it was 17).  There were three more hard freeze mornings on the 14th, 20th, and 27th.      Meteorologist John Wheeler

Drought Beginnings and Endings

 

It was just one week ago that it started raining.  Rain over the seven days since has been plentiful enough to eliminate all concern about it being dry.  It is interesting to note that our weather condition can switch from dry to wet in such a short time.  On the other hand, it cannot switch from wet to dry so quickly.  Of course, it can stop raining tomorrow, but the lingering effects of recent rain will keep the soil soggy and the grass growing for some time.  The winter drought began last September 5.  That was the day after the last heavy rain of 2014.  We were in a drought through the fall because the drier weather caused us no problems.  The drought really began to manifest itself this spring with agriculture’s need for germinating rainfall along with a rash of grass fires.  Now suddenly, all that is over.  I wonder when the next drought will begin.  Tomorrow, perhaps?

Meteorologist John Wheeler

Warm Days and Rain

 

The average daily high temperature is not meant to be a reflection of what the temperature is supposed to be.  Rather, it is the average of all the daily highs over a period of record.  So with that in mind, the average daily high has now reached 70 degrees for the first time since September.  There have already been 17 days with a high temperature of at least 70 degrees this year.  The first was back on March 15.  It happened 11 times during a warm, dry April.  The warmest has been 87 degrees on May 2.  We had a lot of warmer than average afternoons from mid-March through early May due to the early snowmelt and exposed dry soils.  Now that the ground is wet, it will become a little harder to get so many above average afternoon temperatures.  Unless, of course, it stops raining again and the ground becomes dry.   Meteorologist John Wheeler

 

Tornadoes and Climate Change

Is our warming climate effect the threat of tornadoes and severe thunderstorms?  From the political sides of this debate, this question can be quickly and easily answered either “Yes!” or “No!” depending on the politics.  In the real world, the answer is a lot trickier.  The trend across the United States in recent decades is a decrease in the overall number of tornado days along with an overall decrease in the quantity of tornadoes.  But coupled with this decrease in bad storms is an increase in those few terrible tornado outbreak days, those days when dozens or even hundreds of tornadoes causing staggering property damage and loss of life.  So although severe storms are not exactly increasing, their variability is.  Some of this statistical clustering is skewed by the year, 2011, when several huge tornado outbreaks swept the Midwest and South.  Ongoing research offers no consensus yet of how tornadoes will be affected by climate change in the future.

 

Meteorologist John Wheeler

Shower vs. Rain

I had an inquiry earlier this week about the difference between a rain shower and just plain rain.  The classic meteorological definition is that a shower is brief and/or intermittent whereas rain is steady.  But there is no specific time limit for when a shower crosses the threshold and becomes just rain.  For most of us in the business of forecasting, a shower differs from rain by being convective in nature.  This means that showers are caused by smaller scale updrafts of air and so are briefer or more intermittent than a general area of rain which is caused by a general, gradual rising motion over a large area.  But here, also, there is no cutoff at which rising air is of too large of a scale to be considered a shower-making updraft.  In general, if it is brief, short, or longer but highly variable in intensity, it is a shower.     Meteorologist John Wheeler

From Dry to Wet

It took one storm exactly two days to take eastern North Dakota and western Minnesota from too dry to plenty wet.  This is often how it works in spring because of the fact that average precipitation through fall, winter, and spring is just not that much.  The six months of November through April produce just a fourth of our average annual precipitation.  So if those six months are very dry and we get just half of the average, we can make it up with one good rain storm like the one Sunday and Monday.  Warm season precipitation is the important stuff.  If we were to go from May through October with half of average rainfall, the moisture deficit would be more than eight inches which would cause much more of a problem and would be much harder to make up.  So the weather picked a good time to go dry this fall, winter, and early spring.       Meteorologist John Wheeler

 

Is Drier the New Average?

All this talk about below average precipitation the past few months begs a discussion on what it means to be average.  The weather is not “supposed” to be average or even near average.  The weather goes from above to below average all the time and sometimes by a lot.  In fact, what we call average is always changing.  Our weather and our climate are not static.  It gets wetter and it gets drier.  It gets warmer and it gets colder.  These things vary day by day, month by month, year by year, century by century, and so on.  In fact, the accepted, so-called “climate normals” are actually the average of the previous complete three decades.  Every ten years, what call “normal” or “average” is adjusted to reflect the latest decade in order to remain current.  For more than 20 years, precipitation has been generally wetter than in the past, creating a new “average.”  Sooner or later, perhaps now, the weather will likely become consistently drier again.

 

Meteorologist John Wheeler

Big Hurricane Absence

TIn the nine years since Category 5 Hurricane Wilma struck South Florida in October of 2005, there has not been a single major hurricane (Category 3 hurricane or stronger) to strike the U.S.  This is the longest absence of landfalling major hurricanes since records began in 1851.  Although Atlantic hurricane activity has been, overall, below average, since 2005, there have been many major hurricanes.  It is just that they have missed the U.S. mainland.  There were two very strong Category 2 hurricanes in 2008 that missed being Category 3 by just a few miles per hour.  And, of course, there was the Hurricane Sandy disaster in the New Jersey/New York area in 2012.  But Sandy was not a typical Category 1 storm.  It had a major hurricane caliber storm surge even though its winds had weakened just prior to landfall.  So this absence of big hurricanes is more of a statistical oddity than a change in hurricane patterns.   John Wheeler

Why So Windy Here?

April usually has the highest average monthly wind speed of any month of the year.  This April, the average wind speed ended up as 12.9 mph which is slightly below the long-term average for the month.  Nevertheless, it sure seemed windy in April.  The Red River Valley is one of the windiest places in the U.S. for two basic reasons.  Our location keeps us close to the Polar Jet Stream most of the year so there are plenty of fronts, highs, and lows to give us an ever-present air-pressure gradient.  Our flat and relatively treeless terrain offers little in the way of friction.  So we have a near-constant forcing (pressure gradient) and there’s nothing to slow the wind down.  April also offers bare, black soil which creates strong updrafts on warm afternoons which tap into stronger winds aloft and some of that energy is brought down due to turbulence.  This is why the afternoons are so often windy in spring.    Meteorologist John Wheeler

 

April in Review

The month of April in Fargo Moorhead was statistically warmer and drier than average.  The average high temperature for the month was 61.3 degrees, which is 5.5 degrees above average.  The average low was 32.9 degrees which is just 0.2 degrees above average.  So the average temperature of 47.1 degrees is 2.8 degrees above average.  The coldest temperature of the month was 15 on the 23rd and the warmest was 82 on the 30th.  April 14 was perhaps the strangest day of the month with a morning low of 31 degrees followed by an afternoon high of 80.  Total precipitation was 0.90 inches which is .46 inches below average.  Just a trace of snow was recorded although trace amounts of snow were observed on four separate days.   Meteorologist John Wheeler