A Gift from August

August, long renowned for its heat, arrived overnight behind a cold front, bringing cool, misty weather to central Missouri.  Ahead of that front, heavy rain fell across Columbia, a welcome dose of moisture during this long, brutal summer.

While we certainly appreciate that a dramatic change in weather has arrived with the new month, there is little doubt that the heat will return as the front heads east.  But, for now, the cool respite will facilitate some much-delayed yard work.

Since it is the last meteorological month of summer, August invites us to look ahead to the glorious season of autumn.  Unfortunately, climate change is pushing back that transition and, before long, August may represent the midpoint of a prolonged summer season. 

Return to Humidity

When we left Hays, Kansas, just before dawn this morning, it was already 75 degrees F, down from 99 degrees F the afternoon before.  Fortunately, as we traveled east, cloud cover persisted and the temperature  remained stable.

Even better, by the time we reached Junction City, rain began to fall, persisting throughout our journey across the Flint Hills.  Holding the temperature in the low 70s F, the rain was also psychologically beneficial after almost a month of intense sunshine and dry heat along the Front Range.

Beyond Topeka, however, the sun returned and the temperature gradually climbed into the upper 80s by the time we reached Columbia, augmented by Midwestern humidity as we entered a southerly flow from the Gulf of Mexico.  The moist air will feel good for a few days before I begin to miss the semiarid climate of Colorado. 

An Unfair Monsoon

Following two weeks of bright sunshine and severe heat, the annual Southwest Monsoon finally reached the Front Range urban corridor earlier this week.  Its scattered thunderstorms have dropped flooding rains in some areas while other locations (including our Littleton farm) have received little, if any, precipitation.

Such is the nature of the Monsoon.  Unlike the widespread, upslope rain and snow storms of spring, this river of moisture is less predictable.  Of course, between now and early September, most of us will receive some vital precipitation but the gift will likely be uneven, reflecting the effects of our varied terrain and the mountain wall to our west.  But we'll take what we can get.

Life is not fair, nature is not fair and the Monsoon can be frustratingly unfair. 

Trump's Environmental Ignorance

As almost 900 wildfires rage across the vast northern forests of Canada, Pacific storm systems direct some of the smoke into the Upper Midwest and Northeastern U.S.  Of course, this angers Our Dear Leader and it is one of the reasons that he threatens to impose a 50% tariff on our neighbor.  In his opinion, the Canadian government should be doing more to control the wildfires.

Our warming climate is primarily responsible for this widespread disaster, reducing snowfall and rain across the Great Northwoods.  Unfortunately, Trump and his Cabinet do not accept the "hoax" of climate change, choosing to cut emissions regulations, withdraw funds from green energy projects and encourage the rebirth of coal-fueled power plants.

Of all his disastrous policies imposed upon our country, Trump's disdain for environmentalism may have the greatest long-term effect.  Hopefully, the private sector will resist this folly and ignore his repeal of established environmental laws.  After all, they know by now that a Blue Wave is coming in November. 

Mother & Destroyer

The Sea is the mother of all life on Earth, which first evolved in her realm about 3.6 billion years ago.  It would not be until 450 million years ago that some species became terrestrial but a fabulous diversity of life still inhabits Mother Sea, much of which has yet to be discovered by humans.

Nourishing and sculpting terrestrial ecosystems with her weather systems, she also destroys habitats and human developments with coastal hurricanes, severe inland storms and flooding rains.  Indeed, as our climate warms, these destructive events will intensify.

Furthermore, as her component oceans open and close, earthquakes, tsunamis and volcanism alter terrestrial landscapes and destroy regional life; the recent earthquakes in Venezuela demonstrate a risk that stretches across the globe.  The Sea, an essential component of Life on Earth is both generous and destructive; we could not live without her but often succumb to her power.  

Thousand-Year Floods

Following episodes of severe flooding, as occurred in southeast Missouri and southern Illinois yesterday, references are made to a "thousand-year flood," indicating that such an event is expected no more often than every thousand years.  Of course, such an expectation is based on meteorological data that has accumulated over the past Century or so.

Unfortunately, we are now in a different atmospheric environment, courtesy of global warming that was triggered by the Industrial Revolution.  Earth's seas and atmosphere are steadily warming, saturating the air that moves above the Continents and archipelagos.  Storms, ignited by atmospheric clashes along an energized jet stream, often drop copious amounts of rain and, should the storms "train" across the same areas, severe flooding occurs.

Such destructive floods are becoming more common and will only increase in frequency as our climate continues to warm.  Efforts to reverse that trend are not currently sufficient, especially in the U.S., and we ignore the risk of living on floodplains and barrier islands.  "Thousand-Year Floods" have become annual events. 

Extreme Weather & Climate Change

Weather extremes have characterized most of the U.S. this year.  This week's flooding across the Southeastern States has been record-breaking as some locations have received almost three feet of rain.  Ironically, some of the deluge has occurred in areas that had been plagued by drought for many months.

Farther north, severe thunderstorms with tornadoes, high winds and large hail have repeatedly raked the Great Plains and Upper Midwest.  This weekend, another round of severe weather will develop across the High Plains, moving through the Ohio Valley and the Mid-Atlantic Region over the following days.

Extreme heat, warm oceans and a powerful, unruly jet stream combine to produce these dangerous weather conditions.  More than typical, seasonal storm systems, we are witnessing the effects of a warming climate.  Though its effects may vary over the years, these extreme weather events will surely become more common and efforts to reduce damage and deaths will be imperative. 

The Central American Gyre

From May to June and from September to November, a large, relatively weak zone of low pressure settles over Central America, coinciding with the rainy seasons in that region.  Of little consequence itself, this gyre may interact with tropical waves arriving from the Caribbean or from the South Pacific.

This interaction may produce tropical depressions which, under the right conditions, may develop into tropical storms.  Of course, if wind shear does not intervene, these storms may then become hurricanes, either in the Gulf of Mexico or along the west coast of Central America.

This meteorological sequence is often responsible for Gulf of Mexico tropical storms and hurricanes that develop early and late in the Atlantic Hurricane Season (June to November).  Typically, a tropical depression develops in the southwest Gulf of Mexico and moves northward; if high pressure has settled over the Gulf, suppressing wind shear, the depression becomes a tropical storm or hurricane as it moves across the warm Gulf waters.  According to current forecasts, such a development may occur later this week.  

Light Show on the Great Plains

Arriving in Hays, Kansas, late yesterday afternoon, I saw a thunderstorm approaching from the south.  After crossing the east side of town, it eventually merged with a large cluster of thunderstorms over Russell, about 25 miles east of Hays.

From my room, I was treated to a broad view of the Great Plains to the northeast and watched as the Russell storms spread northward and eastward.  Once the sun set, the lightning show was spectacular, with some cloud-to-cloud strikes radiating back toward Hays.  Consulting the weather radar, I found that a chain of severe thunderstorms stretched from Wichita, Kansas, to the Black Hills of southwestern South Dakota.  In addition, a mass of storms in northeast Colorado extended the turbulence westward; indeed, as was evident on Flight Aware, cross-country air traffic was funneled north of the Black Hills or south of Wichita.

The light show from this massive band of storms continued late into the evening, well past my usual bedtime.  But one of nature's most awe-inspiring spectacles was well worth a modest loss of sleep. 

 

March in May III

Following a round of thunderstorms yesterday, it is chilly and raining in Metro Denver today, the product of an upslope flow behind the potent cold front.  High temperatures today will be in the 40s F and our overnight low is expected to fall into the 30s.

I would complain about the clouds, the rain and the chill but they are just what we need as we hope to recover from a prolonged drought and nearly snowless winter.  The thirsty plants on our Littleton farm are surely relieved by the March-like weather and are resident birds are as active and as noisy as usual.

This cool, wet interlude will last another day or two but it seems the stagnant weather pattern that brought us the drought has broken down.  Bring on an unrelenting Southwest Monsoon!

Addendum:  The title of this post reflects the fact that March-like weather is not uncommon in May along the Front Range urban corridor; the title has been used at least twice before over the history of this Blog. 

A Snowstorm in May

It is not rare for snow to fall along the Colorado Front Range during the month of May.  An unruly spring jet stream, significant changes in elevation and the presence of a storm system crossing the Desert Southwest are the usual ingredients.

The current snow storm, which began yesterday, developed as a deep atmospheric trough (dip in the jet stream) allowed cold, Canadian air to drop southward along the Front Range while counterclockwise winds, around a low pressure center in New Mexico, pulled in Gulf of Mexico moisture from the Great Plains.  This upslope flow dropped two feet of snow in the mountains, a foot of snow in the foothills and rain changing to snow along the Front Range urban corridor.

This welcome moisture will likely have a limited effect on the State's drought and on Metro Denver's water shortage but it is surely welcomed by the regional flora and fauna.  Perhaps the greatest benefit of the storm will be to diminish the threat a wildfires across the eastern slope of the Front Range as the annual fire season gets underway.  Early and prolonged Southwest Monsoons and normal to heavy mountain snowpacks over the coming years are needed to end the drought. 

Frustrated by Virga

Anyone who lives in an arid or semiarid environment is familiar with virga, precipitation that evaporates in dry air before reaching the ground.  Viewed from a distance, it resembles a curtain, hanging from the bottom of a rain or storm cloud but not extending down to the terrain below.

During our current drought along the Front Range, many of us check the local radar when rain is expected.  Watching the green or yellow blobs move toward and then over our neighborhood, we anticipate a downpour.  In many cases, however, we stay dry or receive only a light drizzle, a victim of virga.

This phenomenon is enhanced in Metro Denver when storms arrive from the south or west.  As the air descends from higher terrain, it warms up and dries out and precipitation evaporates as it falls into the lower, drier layer of the atmosphere. 

Heading West

Following a stormy night in Columbia, we headed west this morning.  A steady north wind had brought down clear, cool, dry air behind the storm front, perfect for traveling.

Farther west, in eastern Kansas, plumes of smoke rose from the Flint Hills as the annual burning of grasslands was underway.  Designed to remove invasive plants and to nourish the pasturelands, one wonders about the carbon load released into the atmosphere.

And what wildlife did I encounter today (you might ask)?  Easy: turkey vultures, great-tailed grackles and dead raccoons.  But we did see thousands of cattle!  We'll complete our journey to Colorado tomorrow. 

Damage Watch

As a powerful Pacific storm system spun its way along the U.S.-Canadian border yesterday, its cold front stretched from the Upper Midwest to the Southern Plains, producing a broad swath of tornadoes, severe thunderstorms, large hail, high winds and torrential rain.

Millions of Americans, ourselves included, were glued to their TVs and computer screens, waiting to see if their community would be damaged or spared.  Even before this storm system arrived, severe flooding had developed in Wisconsin from storms deflected northward by the Southeastern ridge.  Here in Columbia, tornado sirens blared by mid evening as a twister passed just south and east of our city.

Meanwhile, on the back side of the system, cold air plunged southward, bringing snow to the Northern Plains and, finally, to the Front Range of Colorado.  As the storm pushes eastward in the coming days, its severity will diminish as its forward speed increases; nevertheless, more flooding and wind damage is expected before it heads out to sea. 

The Southeastern Drought

Due to a persistent atmospheric ridge over the Southeastern U.S., storm systems arriving from the Pacific have been shunted across the Upper Midwest, Great Lakes and Northeastern States.  As a result, severe drought has developed within that ridge; indeed, much of Georgia and Florida are in extreme drought.

A stable jet stream arc, from the Southern Plains to the Ohio River Valley and across the Mid-Atlantic region has produced the ridge.  Within its dome, air is sinking and heating up, impairing cloud formation, negating precipitation and drying out the soil.  As one might expect, the incidence of wildfires has increased significantly.

Fortunately, a potent storm system is forecast to arrive within a week, displacing the ridge and bringing much needed rain to the Southeastern States.  An early tropical storm or two would be nice as well but an El Niño pattern in the Pacific is expected to dampen this year's Atlantic Hurricane Season; on the other hand, El Niños tend to produce more precipitation across the Southern U.S. 

Greenery Rising

Yesterday afternoon, as a steady south wind brought warm, humid air into central Missouri, I rescued our Beetle from the garage and headed for the country.  Escorted by turkey vultures, sailing along in the cloudy sky, I did not encounter many birds or mammals but I was taken by the greenery, ascending from the lush grass, through the shrub lines and into the trees.

Our recent warm, wet weather had produced the transition from winter browns to these many shades of green, the product of chlorophyll, the fuel of life on Earth.  Absorbing carbon dioxide and releasing oxygen, green plants sustain our atmosphere, long threatened by the burning of fossil fuels.

Of course, the leaves themselves feed a wide variety of life forms, from microbes to insects to mammals, ourselves included.  Following the fickle weather of March, this explosion of greenery in April is always a welcome spectacle. 

The Kona Low

Severe flooding across Oahu, Hawaii, is the product of an unusually potent and persistent Kona Low.  The latter is a center of low pressure that typically develops northwest of the Hawaiian Islands during the winter months, sweeping tropical moisture across that archipelago from the southwest.

Held in place by an atmospheric trough (a dip in the jet stream), this "cutoff low"generally persists for a few weeks, producing a typical rainy season.  This year, the Kona Low developed relatively late in the winter but its strength and persistence has led to the torrential precipitation and record flooding.

Of interest, this atmospheric trough over the Pacific is tied to the persistent atmospheric ridge over the Desert Southwest, which has fueled the severe heat that is currently spreading eastward across the U.S.  Climatologists believe that both extremes demonstrate the effects of our warming climate.

A Dome of Summer Heat

Having produced record high temperatures across the Desert Southwest over the past few days, a ridge of high pressure is expanding eastward and will set records across much of the U.S.  Within this dome, air is sinking, heating up and drying out.

Unlike our usual summer heat waves, during which high humidities moderate the temperature and keep nocturnal lows relatively warm, this dry, desert heat will cause unusually high afternoon temperatures while permitting overnight lows to fall into the 40s and 50s F.

Here in Missouri, we will experience afternoon highs in the 80s F for the next few days with overnight lows in the low 50s.  Spring is just beginning and this taste of summer will fade quickly; on the other hand, this atmospheric dome may portend warmer springs as climate change progresses. 

A Heart of Darkness

Heading east across the High Plains yesterday, my pickup was buffeted by strong, south winds from Goodland, Kansas, to Hays.  Since the air was warm and dry, no clouds raced across the deep, blue sky and I could not readily explain the cause of the intense wind.

This morning, as I continued eastward, those potent winds were still blowing and strands of clouds appeared overhead, all pointing toward the northeast.  These strands thickened and darkened as I entered more eastern regions of the Great Plains, indicating that Gulf of Mexico moisture was being drawn northward by the wind.

Then, as the highway climbed atop the Flint Hills of eastern Kansas, broad views unfolded to the north revealing dark skies that stretched across the horizon, topped by towering cumulonimbus clouds.  This was the heart of the pinwheel-like storm, beneath which heavy rain and probable hail were pelting the ground.  Quite a spectacle from a safe distance. 

Moisture Arrives

It is a cool, damp, gray day along the Front Range with snow in the mountains and scattered showers across the urban corridor.......just what we need after a warm, sunny winter.  Of course, a foot or two of snow would be even more welcome but we'll take whatever moisture we can get.

This isolated atmospheric disturbance is currently centered over the Colorado-Wyoming border, where some thunderstorms have developed.  Unfortunately, the respite won't last long and sunny, warm weather is forecast for the next couple of days.

March is the snowiest month in Metro Denver and we can only hope that this year's snowfall is at least average.  Then again, entrenched weather patterns often take a while to break down, leading to droughts or floods.  This is, after all, a semi-arid ecosystem even though the sprawling development suggests otherwise.