Early Warm Days Don’t Have the Humidity

Those early warm days of spring are a different kind of warm day than what we get in the later spring or summer. It’s about the dew point. Early in the spring, there is very little humidity available this far from the Gulf of Mexico. Air comes either from across the Pacific across the Rockies where it loses much of its moisture or it comes from nearby where there is little moisture available. The temperature may 70 or 80 degrees for a couple of hours in the afternoon, but it has warmed from a morning low in the 30s or 40s and likely as not will cool down that much the next night. Warm days in April are very much like typical winter days in the desert. The 76 degrees we experienced Easter Sunday was accompanied by an afternoon humidity of 18 per cent. When we have warm days in summer, even the days which are not particularly humid, there will be a lot more humidity present in the air than there was Sunday. John Wheeler

What Is Average?

Halfway through April and it is looking like another colder than average month.  December, January, February, and March have all been significantly colder than average.  April will likely make five months in a row.  Last October and November were also colder than average but only by an insignificant fraction of a degree. September was warmer than average but the summer months last year were only slightly warmer than average.  Average is only the average of the past.  There is no rule that weather has to conform to averages either by remaining near average or by swinging equally one way and then the other.  In this sense, our weather is non-linear, which means it does not converge to an average over time.  We present weather averages only as a way to roughly compare.  For most weather records, what we call, “average” is only the average of the past three full decades.  So what constitutes average weather actually changes over time as our climate goes through changes.      Meteorologist John Wheeler

Late Springs Good for Sinuses

Being one who suffers from the summer catarrh (hay fever), I have one reason to dread the budding of trees in spring.  Tree pollen; the elms in particular; have always brought a sudden change in how well (or poorly) I feel in the spring.  When I moved to Fargo back in the 1980s, I noticed that the hay fever symptoms would come on in a rush just as the elms were leafing out, which usually happened around the fifteenth of April.  That was then; this is now.  Most years now the elms leaf out a week or so later than mid-April.  Although our local climate has warmed slightly since my arrival in 1985, it has not warmed consistently.  The spring season in Fargo Moorhead has actually grown colder on the average. In our country, a snow storm or cold snap late in the springtime is to be expected once in a while.  But these spring surprises have become routine and spring cold snaps have tended to last longer than in the past.  Meteorologist John Wheeler

Total Eclipse of the Moon

Monday night(April 14-15), if the sky is cooperative, there will be a total lunar eclipse visible in its entirety all across our region.  At approximately midnight, the moon will enter the outer penumbral shadow of Earth, resulting in a slight dimming.  About an hour later, near 1 am, the moon will enter the full shadow of Earth resulting in the beginning of the partial phase of the eclipse.  From approximately 2 am through 3:20, the eclipse will be total.  The partial phase will end around 4:30 am, and the last of the penumbral shadow will have passed by 5:30.  So the entire eclipse will happen during the night, resulting in a good show if the sky is clear.  During the partial phases, a portion of the moon will be in total darkness. During the full phase, the moon will be dark but faintly colored with shades of red or orange caused by light coming from the edge of Earth.  Later this year, on the afternoon of October 23, we will be treated to a partial solar eclipse, when the new moon will actually cover up a portion of the sun.   Meteorologist John Wheeler

Ancient Weather Record?

Two scholars at the University of Chicago’s Oriental Institute have translated an ancient Egyptian inscription on a six-foot stone block which seems to be a 3.500 year old weather report. The writing on the block refers to rain, darkness and “the sky being in storm without cessation, louder than the cries of the masses.”  This is now believed to be the oldest weather report ever found. It is possible that this terrible weather may be a result of the Minoan eruption of Thela in the Mediterranean Sea, on the island now known as Santorini.  The Thela eruption is thought to be one of the strongest and most devastating volcanic eruptions of the past several thousand years.  Climate scientists have found evidence of sudden and severe climate change throughout the Northern Hemisphere, including tree ring data in Greenland, bristlecone pines in California, and reports of crop failures in China.  Such massive volcanic eruptions can change climate by ejecting huge amounts of sulphur dioxide into the upper atmosphere where it blocks sunlight for years. Meteorologist John Wheeler

AMO / NAO

March was the sixth month in a row with below average temperatures across the Lower 40 states, according to satellite data.  The satellite-based report resolves global temperatures based on infrared measurements of the atmosphere from the surface up to an altitude of about five miles above sea level.  March was the seventh consecutive cooler-than-average month in Fargo Moorhead, although October and November were only marginally below average.  Interestingly, this is in contrast to most of the Northern Hemisphere, which has been generally warmer than average during this winter and spring,  As explained in this space yesterday, the warmer locations are mostly over the oceans, particularly the Atlantic Ocean, which is undergoing a period of warming known as the Atlantic Multidecadal Oscillation (AMO), a weather pattern which at times can allow for sharp intrusions of Arctic air into central and eastern North America and Europe. Meteorologist John Wheeler

Cold Winter, Mild Winter

A new study recently published in “Environmental Research Letters” shows that the extremely cold winter just experienced across the central and eastern U.S. is likely due to a natural variation is Atlantic sea surface temperature known as the Atlantic Multidecadal Oscillation (AMO). The positive phase of the AMO (a phase of warmer Atlantic temperature) when combined with the negative phase of another circulation pattern, the North Atlantic Oscillation (NAO), a stronger than usual semi-permanent low pressure system near Iceland, results in a much greater frequency of arctic air intrusions into the central and Europe. The AMO changes over decades whereas the NAO changes over periods of weeks or months. The study found that the present positive phase of the AMO when combined with the positive phase of the NAO is likelier than average to yield a mild winter, which could explain our recent run of winters being either extremely cold or extremely mild. This suggests we should expect the winter variability to continue for another decade or two.         Meteorologist John Wheeler

Why Spring Snow Melts Quickly

Snow that falls in late March and April tends to melt quickly. There are several reasons for this. Average temperatures are much higher this time of year than in winter. In April, it is difficult to keep air below freezing for very long even in a cold snap. Sunlight strikes the Earth with much more intensity in spring than in winter, so solar radiation contributes greatly to the melting process in spring. But the biggest reason is the snow, itself. Old winter snow pack is cold. Having been on the ground during our subzero winters, the temperature of the snow inside a deep, old snow drift is usually well below 32 degrees at the end of winter. It can be quite a process to warm old winter snow up to 32 degrees so it can melt which is why those early March mild days melt very little snow. But freshly fallen spring snow is usually barely below freezing to begin with, so it warms to 32 very readily and then melts quickly. John Wheeler

The Last Blog Post

Today is my last day at WDAY/WDAZ, so the following is my last blog post….

 

One of my favorite quotes is from Stephen Hawking. “Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at.  It matters that you don’t just give up.”

Not to downplay the rest of the quote, but my favorite part is  “to look up”.  In our modern society we tend to look down at our phones more than the sky.  With many of us living in urban areas, buildings and trees often block our view of the sky, plus at night, lights severely limit the number of stars we can see.  This region offers a full suite of weather, plus, outside of city limits, a spectacular view of the heavens.

My hope is that we all find time in our busy schedules to at least occasionally look up and enjoy the view as the sky rarely disappoints.

California Tornadoes

Saturday, March 29, 2014
A storm system in California Wednesday produced a number of mostly small and relatively weak tornadoes. Social media resonated with non-meteorologists making claims about weird and changing weather. However, California has a history of tornadoes. Though not as common as in the Great Plains, California gets tornadoes almost every year. They usually happen in winter and spring when powerful low-pressure systems move in from the Pacific Ocean with strong rotation. California tornadoes tend to be weaker than in the Great Plains because California weather rarely sets up with contrasting temperature and humidity conditions like what we often get in the Plains around frontal systems. The states with the fewest tornadoes per square mile are Alaska and Hawaii. John Wheeler