Sweating In the Humidity

When we humans are exposed to any combination of hot temperatures or high humidity, we become uncomfortable.  The amazing human body is able to acclimate somewhat, given enough time and exposure.

But hot and sticky weather always leaves us feeling, well, hot and sticky.  It is obvious why we have trouble keeping cool in the heat, but humidity is more complicated.  The external human body temperature is usually in the lower 70s Fahrenheit.  So when the dew point is around 70, moisture that forms on the surface of the skin (sweat) is much slower to evaporate and provide the cooling from evaporation.  We sweat but the sweat just makes us wet instead of evaporating and cooling us off.

Either way (heat or humidity), our bodies are in a constant state of perspiring and we need to drink extra water to stay hydrated internally.

Meteorologist John Wheeler

El Nino

Friday, July 31, 2015

El Nino continues to make weather news.  This change in atmospheric and sea-surface conditions in tropical regions of the Pacific happens every few years or so, but the one building now has the look of being a strong one.  El Nino’s impacts in the middle latitudes are more pronounced during the colder months.

What will the impacts be here?  It depends on other factors, of course.  This is weather which is highly dynamic.  But a strong El Nino can be statistically correlated to a stormier fall season, a much warmer than average winter with below average snowfall, and a colder but drier than average spring.

But it is important to understand that other factors can overwhelm the El Nino signal.  Of particular interest this winter is a large region of unusually warm water in the northeastern part of the Pacific Ocean.  What role this will play is interesting but unknown.

Meteorologist John Wheeler

Just Not That Hot

Our short summers give us little time to acclimate to sticky weather.  So if you find yourself complaining about the humidity, you are entitled.  But this summer, there has been as much hot air coming from the mouths of the complainers as from the weather, itself.

Through July 28, only four days have reached 90 degrees this summer, one in June and three in July.  It will take a serious stretch of hot weather in order for Fargo Moorhead even to achieve its average of 13 days at or above 90.

The average temperatures in June and July have been marginally above the long term average due mostly to slightly above average nighttime temperatures.  But, again, there has been very little in the way of truly high humidity.  Overnight lows have been mostly in the 60s these past few weeks with a few 50s and a couple of 40s thrown in.  We have mostly been spared those hot, sticky nights when dew points in the 70s keep the temperature from becoming comfortable.

Meteorologist John Wheeler

The Fuel for the Fire, But Not the Cause

Wednesday, July 29, 2015

This past Sunday (July 26) was a perfect example of how warm and humid air is an ingredient, but not necessarily the key ingredient for severe thunderstorms.  It was 90 degrees Sunday afternoon with dew point temperatures in the mid 60s.  It was also almost perfectly sunny without even the slightest threat of a storm.

Warm and humid air is fuel for thunderstorms.  Specifically, it is the thermodynamic energy release when evaporated water is cooled to condensation within the updraft of a developing thunderstorm that makes them explode ferociously.  On Sunday, there was plenty of fuel.  But there was no trigger.  Depending on atmospheric conditions, a warm and humid day may yield anything from scattered weak thundershowers to blue skies unless there is something to trigger the storms.

The trigger can be a front which causes a confluence of surface air or a combination of cold air aloft and stronger winds aloft which increases instability and/or encourages rising motions.  Without the trigger, instead of stormy weather, it is just warm and humid.

Meteorologist John Wheeler

 

Warmer, Yet Not So Hot

There is an interesting trend regarding our summer temperatures.  Over the past few decades, the summertime average temperature for Fargo Moorhead has risen slightly.  However, there is an opposite trend of there being fewer days with high temperatures in the 90s and 100s.

From 1980 through 1989 there were 15 days in the 100s.  But in the 26 years since 1989, there have been just four days in the 100s. Meanwhile, the average temperature has risen, particularly the average daily low temperature.

What gives?  More humidity and more rainfall yield warmer nights which raises the average temperature but also allow for fewer really hot days which are more likely when the soil is dry.  Prior to 1990 when there was generally less rainfall, there were more hot days even in a cooler climate.

Meteorologist John Wheeler

Planet Kepler-452-b

Monday, July 27, 2015

The latest NASA reports of a potentially Earth-like planet in a potential habitable zone it its solar system is as exciting to astronomers as it is to science fiction fans.  Kepler-452-b is 60 per cent larger than Earth and likely has an atmosphere thicker than ours.

The planet’s year lasts 385 Earth days and it has been in this “habitable zone,” where temperatures would allow for liquid water, for six billion years.  This implies that life like we understand it is possibility there.

This newly discovered planet is 1400 light years away from us in the constellation Cygnus, making any kind of travel from here to there (or there to here) impossible except in science fiction.

Meteorologist John Wheeler

Not So Hot

In our part of the country, many people associate temperatures of 90 degrees or higher as being a sort of statistical boundary between our regular warm summer weather and what is considered “hot.”  Fargo Moorhead experiences an average of about 13 days a year at 90 degrees or higher.  The greatest number of 90 degree days was 39 in 1988.  Last summer there were only three.

Days of 100 degrees or hotter have historically occurred at a pace slightly lower than once every two summers.  However, these hottest of hot days are tied closely to soil moisture and there have been so many wet summers in recent years that 100 degree weather has become rare.  Since the summer of 1989, there have only been four days of 100 degree heat. The last was July 20, 2012.  Previous to that, there were two century days in July of 2006, and one in June of 1995.

Meteorologist John Wheeler

 

A Bit of Heat

Technically, the peak of the average temperature in Fargo Moorhead is in the middle of July when the average high is 83 and the average low is 60.  Invariably, there are many days warmer than this in any summer, but this is the peak of the daily averages, which are smoothed out by years of averaging.

In any given year, of course, the hottest part of the year is related to the way the Jet Stream moves air around and also to soil moisture as our hottest days often coincide with a period of drier weather which allows the top soil to dry out so that solar energy goes more into heating up the ground and not so much into evaporating water.

There is an average of about 13 days a year with high temperatures of 90 degrees or higher.  Temperatures of 100 degrees or higher happen, on average, less than once every two years.

Meteorologist John Wheeler

The Dog Days

The Dog Days of Summer are here.  Ancient Romans referred to this stretch from July 24 through August 24 as the “dog days” because the star, Sirius, the brightest star in the sky, rises and sets very close to the sun.

Astronomers in many ancient cultures including early Egyptians, Greeks, and Romans noticed the correlation between this and the latter days of the summer when the heat is hard to escape.   Sirius is called the “dog star” as it is part of the constellation Canis Major, (The Big Dog) which follows Orion, the great hunter in the night sky.

Technically, our warmest days on average here in the Fargo Moorhead area are from the middle of July through the early part of August although in many other parts of the world the hottest weather occurs at other times.  Of course, ancient weather observers had very little science to go on and the inaccuracies of these ancient explanations actually add to their charm.

Meteorologist John Wheeler

El Nino 2015-16

A very strong El Nino appears to be developing in the Pacific Ocean. El Nino is a reversal of weather conditions across the tropical Pacific.  Areas near South America get warmer and wetter while areas near Australia become very dry.  This affects the weather around the world by deflecting the Jet Stream.

But the effects around the world (including around here) are hard to predict because other large-scale patterns also influence the storm track.  The biggest concern for our area would be the potential development of a blocking pattern which could bring either persistently wet weather or drought, depending on the shape of the Jet.

At present, a large region of anomalously warm water off the coast of Oregon, Washington, and British Columbia, adds to the uncertainty.  If the strong El Nino continues to develop in conjunction with this warm blob, it could mean a very interesting winter for some parts of the world.

Meteorologist John Wheeler