Eerily Eemain?

A lot of climatologists are talking about the Eemian Period lately.  The Eemian is the name for the last great warming prior to the last glaciation.  It happened about 125,000 years ago.  According to ice cores and fossil records of the time, Earth was a few degrees warmer than the present period (The Holocene) and sea levels were about 20-30 feet higher than today.

The recent discussion revolves about a finding of a sudden warming late in the Eemian period that may have been related to a rapid ice melt and a sudden associated sea-level increase.  The thinking is that some of the glacial areas on Earth today are melting faster than the climate models have predicted, suggesting that the sea level rise in the next few hundred years could possible come faster and sooner than expected.

Not all climatologists agree with this idea.  The one part of this that concerns me is that there is more carbon dioxide level in the atmosphere today than there was in the Eemian.

Meteorologist John Wheeler

Humidity: It’s an AM/PM Thing

If you get your current weather information in the morning, you should know that the morning relative humidity is not a useful indicator of how humid the weather will be today.

In fact, the relative humidity is fairly useless as an indication of humidity discomfort because it tells us not the percentage of humidity, but the percentage of water vapor saturation.  The temperature is usually cooler in the morning and the relative humidity is usually 80 to 100 per cent because cooler air saturates more readily.  Later in the day, it might be 20 degrees warmer, and even with the same mass of water vapor in the air, the relative humidity usually is around 30-50 per cent.

The dew point temperature is a much better measure of humidity discomfort.  Air with dew points in the 60s and 70s feels increasingly humid.

Meteorologist John Wheeler


Season’s Wobbles

Someone asked the other day why it is warmer in the summer even though the sun is closer to us in winter.  First of all, yes, the sun is actually closer to us in winter.  Earth’s orbit around the sun is elliptical, not circular.

Winter is colder in the Northern Hemisphere because Earth’s Axis of Rotation points the Northern Hemisphere away from the sun in winter, giving us shorter days, longer nights, and more oblique solar radiation.  In the Southern Hemisphere, the sun is actually closer during the summertime.  But instead of having hotter summers and colder winters, the Southern Hemisphere is more temperate because there is a higher percentage of the surface covered by the ocean.

The Axis of Rotation slowly wobbles like a spinning top every 26,000 years.  Half of that time, the sun is actually closer to the Northern Hemisphere in summer.

Meteorologist John Wheeler


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