June Temperatures

June temperatures were close to average.  The average high was 77.5 degrees which is 0.1 degree above the three-decade mean.  The average low was 56.8 degrees which is 1.9 degrees above the three-decade mean.  This continues the trend observed over recent years of having the low temperatures warmer than the high temperatures, relative to the long term average.  This is another representation of our local climate being wetter than in the past.  The increase in rainfall leads to higher humidity and more clouds, all of which has a bigger impact on temperatures at night and less of an impact in the daytime.  The increase in average humidity also leads to fewer really hot days.  June had two days with highs in the 60s, 15 with highs in the 70s, and thirteen with highs in the 80s.  The warmest day last month was 89 on June 21. The coolest day was 66 degrees on June 6.  June had 12 mornings with lows in the 60s, 15 with lows in the 50s, and three with lows in the 40s. The coldest temperature was 44 degrees on June 8.  The warmest night was 69 degrees on June 27.   Meteorologist John Wheeler

June Wet and Stormy, Kind Of

June was a wet and stormy month.  Rivers are high from Manitoba to Tennessee.  Almost every evening on the national news there is coverage about all the severe storms this summer.  But the national tornado count on the Storm Prediction Center’s Annual Storm Summary web page shows that the last year to have had so few tornadoes through July 1 was 2005.  What about all the rain?  It has been wet but nowhere nearly as wet as it was in 1993.  June was a bad month in the Great Plains and Midwest for storms.  But June was certainly not record bad and it wasn’t really even unusually bad.   Instead, network news is just covering the heck out of stormy weather.  It is riveting and extremely popular.  Weather is good for ratings.  And while the coverage is well-intended and truthful, the viewers should not be persuaded by the sheer volume of storm coverage into thinking this summer is out of the ordinary.   Meteorologist John Wheeler

High Humidity Makes Storms More Chancy

When the weather becomes humid, it is intuitive that there is an accompanying increase in thunderstorm activity.  But trying to forecast the timing and location of storms during humid weather is often very hard.  Storms do well in humid environments.  In addition to helping it rain, the evaporation and condensation process adds tremendous amounts of energy to the atmosphere, making storms explosive.  But storms also need a trigger; something to get them started.  Usually when we get our most humid summer weather, the fronts, lows, and other dynamics are weak.  This leads to forecasts of widely scattered storms, possibly severe, and some with very heavy rain.  And if people hearing the forecast gloss over the qualifying, “widely scattered,” they can get the impression that heavy rain is a certainty.  In reality, these humid weather patterns produce a few heavy storms and a lot of fine weather over the rest of the area.    Meteorologist John Wheeler

 

Humidity Facts

Here are a few sticky thoughts to keep the sweaty weather stuck in your mind for a while.  Humid air may feel heavy, but dry air is actually denser and heavier than humid air.  Humid air we get here in the North usually comes from the Gulf of Mexico.  But that air can actually pick up humidity on its way due to evapotranspiration of corn and bean fields.  The relative humidity percentage is a percentage of saturation, not a percentage of humidity.  The condition of 90 degrees and 90 per cent humidity is a condition rarely found on Earth. On a humid, 90 degree day, the relative humidity is usually around 40 to 50 per cent.  The 90 per cent humidity happens in the morning when the air is cooler. The relative humidity is usually higher in winter but we don’t notice it in the colder air.   Meteorologist John Wheeler

I Knew It Was Cold Here

An article last week in Nature Climate Change identified the few places around the Northern Hemisphere most prone to extreme weather.  Specifically, the study identified those places most likely to have stalled out large-scale jet stream waves as these are the mechanisms for too much rain, snow, cold, heat, etc.  For cold air anomalies, we are in a bad spot.  It turns out, the eastern half of North America is most vulnerable to long-term cold air outbreaks.  The worst flooding occurs in western Asia.  Drought is most prevalent across central North America, Europe, and central Asia.  Heat waves are most likely over western North America and central Asia.   Meteorologist John Wheeler

Good Sun, Bad Sun

Get too much sun and you can get a sunburn, which is painful.  But of greater concern from sun exposure is the risk of skin cancer.  But exposure to sunlight also has known health benefits.  Specifically, exposure to sunlight (and UVB rays in particular) is known to trigger production of vitamin D3, an enzyme which helps our bodies fight cancer.  New research is suggesting that slathering our bodies with the cheapest sunscreen available may actually be a double negative.  Many inexpensive sunscreens block UVB rays (which cause sunburn but also spur vitamin D3 production) but do nothing against UVA rays (which cause melanoma).  Perhaps a common sense approach to sun exposure is called for.  Avoid sunburn by not spending too much time in the sun.  Know your limits and be aware that some people can tolerate less sunlight than others.  Finally, read the labels of sunscreen and use it sensibly.   Meteorologist John Wheeler

Daytime and Nighttime Storms

There are two times of day when thunderstorms are most likely to happen over eastern North Dakota and western Minnesota, and they are related to two distinctly different weather patterns.  During spring, early summer, and early fall, the most likely time for thunderstorms is in the late afternoon and early evening.  Near the hottest time of the day, thermals rising off the warm grounds are at their strongest and this may be just enough to kick off a few thunderstorms.  During July and August, we tend to get more thunderstorms after midnight.  When our weather is at its hottest, the upper levels of the atmosphere are often warm as well, making it harder for just the thermals to initiate storms.  But at night, here in the Northern Plains, storms can get a little boost from something called the Nocturnal Jet Stream; a river of air a few hundred feet above the ground which blows from south to north causing a convergence of air which enhances rising motions in the atmosphere.  Of course, it is possible for a thunderstorm to happen at any time of day.  But suppertime and after midnight are the most common times in our region.   Meteorologist John Wheeler

Wet Year in Minneapolis

Average precipitation (rain and melted snow) in Minneapolis is 30.61 inches.  This is about eight inches more than our average annual precipitation in Fargo Moorhead of 22.58 inches.  Following a four inch rain on Thursday, the official Minneapolis weather station at the main Minneapolis airport has now received over 25 inches of precipitation since the start of the year.  This is more than four inches more (to date) than in any year on record, with records going back to the 1870s.  With half the year still to come, the annual precipitation record of 40.15 inches set in 1911 is in jeopardy of being broken.  Even with all the rain lately, Fargo Moorhead precipitation to date is about eleven and a half inches.  This is about 14 inches less than what has fallen in the Twin Cities.    Meteorologist John Wheeler

Where Does the Water Come From?

When it rains here in the Northern Plains, where does the moisture that makes the rain come from?  Actually, there is enough moisture in the air for rain most of the time.  Storm systems tend to make the most of available moisture because of convergence (air flowing together from different directions).  Also, slow-moving storms are able to generate more rain than ones that quickly pass.  But some weather systems are just better at making rain than others and a lot of this has to do with how much water vapor is available for rain.  If you follow air streamflows into our region, you will see that source regions of that moisture include both the Pacific Ocean and the Gulf of Mexico.  Storm systems really laden with moisture usually have some sort of connection to these regions. A lot of the time, it is the Gulf that brings us the moisture, but sometimes we get very moist air from the tropical regions of the Eastern Pacific.       Meteorologist John Wheeler

Soccer in the Jungle

Manaus, Brazil, is hosting Sunday’s FIFA World Cup match between the teams from the U.S.A. and Portugal.  Manaus is a city of two million people located at the confluence of the Negro and Solimões River, both important tributaries of the Amazon. The city has been populated since the late 1600s, so it is certainly metropolitan.  That being said, Manaus is actually located 900 miles inland from the Atlantic Ocean well within the Amazon rain forest.  One travels to Manaus by plane or boat.  One does not drive there from Rio de Janeiro.  The weather is that of a tropical rain forest.  Temperatures are usually in the 80s with dew points in the 70s. Usually there is very little wind.   There are frequent thunderstorms, often with heavy rain.  The stadium is a brand new, 40,000 seat arena.  It is open to the weather over the pitch but the roof is designed to keep most of the spectators out of any rain.  John Wheeler