Hurricane Polo floods the Southwest

One of the strongest hurricanes to ever form in the eastern Pacific, Hurricane Polo has weakened to a Category 3 storm before crossing the northern Baja Peninsula.  Nevertheless, its copious moisture has and will continue to drench the Four Corners Region.  Flash flooding is expected to occur due to the mountainous terrain, the torrential downpours and the hard, non-absorbent, desert soil.

A cold front, approaching from the northwest, will intensify the flow of moisture from Polo, sending it through the Four Corners States and across the Great Plains; the Southern Plains will receive most of the rain as moisture flows in from both the Sea of Cortez and the Gulf of Mexico.  Though that area has been in a prolonged drought, too much rain over a short period of time will flood the streams while offering limited drought relief.

Furthermore, powerful waves, spreading north from Polo, will rake the coast of Southern California, exacerbating the damage recently caused by Hurricane Marie.  Meanwhile, the Atlantic Basin remains quiet as a Super El Niño suppresses tropical development in that oceanic region. 

Snowpack Rescue

A series of Pacific storms will pummel the Cascades and Sierra Nevada for the next few days and  produce flooding along the West Coast.  Over the next week, the snow is forecast to spread throughout the Intermountain region, including the mountains of Idaho, the Great Basin, the Wasatch Front of Utah and the Rocky Mountain corridor.

Snowfall has been far below normal throughout most of the American West this winter, endangering its varied ecosystems and the water supply of its cities.  These storms are expected to significantly boost the mountain snowpack across that region, a welcome development as we approach March.

Of course, higher elevations of the West can generally expect more snow through the spring and peak snowmelt does not generally begin before mid-late May.  Hopefully, this vital recovery will continue until then. 

California's Wet Christmas

As the latest Pacific storm spins off the coast of Northern California, a flow of moisture is moving onshore from San Diego to the Pacific Northwest.  Having already endured several storms, the soil west of the mountain ranges is already saturated and the risk of flash-flooding and mudslides is high, especially in the burn areas.

Once again, the Sierra snowpack will be augmented, a welcome development for the regional water supply but a potential source of river flooding in the spring.

Aggravating this stagnant weather pattern is a dome of high pressure that is producing unseasonably warm weather across most of the U.S.  Here in central Missouri, we reached a high of 67 degrees F today and expect spring-like conditions for another three days.  Merry Christmas to all who celebrate the holiday!

Cut-Off Lows

The series of Pacific storms that have brought flooding rains to Southern California have been produced by "cut-off lows," not energized and driven by the jet stream.  As a result, they have meandered eastward, devoid of powerful winds or strong thunderstorms.

Currently, one of these storms is centered over Kansas and its counterclockwise winds are pulling up moisture from the Gulf of Mexico.  A band of steady rain stretches across Missouri, eastern Kansas and eastern Nebraska, a welcome development for this drought-plagued region.

Meanwhile, another cut-off low is spinning off Southern California, sweeping more rain into that water-logged area.  Unless and until an atmospheric trough drops southward to boost its energy, it will likely arrive here by mid week.  We'll take whatever moisture it brings. 

Southwest Deluge

Over the past week, a deep atmospheric trough off the West Coast directed heavy rain and high winds across Northern California, Oregon and Washington.  Then, its southern portion split away and strengthened off the coast of Southern California; this "cut-off low" is now sweeping torrential rain across San Diego, Los Angeles and the adjacent mountains.

Prolonged, heavy rain will be especially problematic in the burn scar areas, likely producing mudslides and landslides.  On the positive side, the Southern Sierra Nevada may receive up to three feet of snow, a welcome, early addition to the vital winter snow pack.

After pummeling Southern California, the storm is expected to move across western Arizona and southern Nevada before dumping significant snow in the mountains of Utah and Colorado.  Unfortunately, a second Pacific storm system may form in its wake, augmenting the potential for widespread flooding across the arid landscapes of the Desert Southwest.

Western Heat

An atmospheric ridge, stretching from the valleys of California to the Wasatch Front, will allow heat to stream northward today.  Many areas will experience afternoon highs above 100 degrees F, breaking records for the date.

Since most areas affected by the heat lie in desert areas, this event is easy to ignore.  But the early date and the extreme conditions are just another sign that climate change is altering the seasonal transitions that we have long come to anticipate.

Fortunately, the extreme heat will be short-lived as a Pacific front come ashore with its rain and cooler air.  Then again, a long, hot summer surely lies ahead. 

Rain threatens Southern California

After a prolonged drought and devastating wildfires, rain will return to Southern California over the next few days.  Unfortunately, it is expected to be too much precipitation within too short of a period.

A Pacific storm is approaching the West Coast, initially directing its stream of moisture toward northern and central California, adding to the Sierra snowpack.  By tomorrow, this band of precipitation will shift southward, unleashing heavy rain across the Los Angeles basin and its surrounding highlands.  Flooding is expected throughout the region and the rain will likely trigger mudslides in the burn areas.

While winter is the rainy season in Southern California, it is arriving too late to prevent wildfires and too soon to allow the burn scars to heal.  Unfortunately, climate change is expected to intensify both drought and flooding across our country and around the globe. 

Disasters, Risk & Questions

As the California wildfires reach epic proportions, we mourn the tragic loss for so many residents and businesses and, if we can, donate to relief efforts that might ease the pain of those affected.  We have seen such disasters before but not to this extent.

The same might be said for losses related to floods, hurricanes, mudslides and other natural disasters.  As we know, the frequency and severity of these events will significantly increase as our climate warms.  Yet, once the immediate danger subsides, we humans insist on rebuilding in high risk zones: dry forest canyons, barrier islands, floodplains and coastal lowlands, among others.

The drive to restore one's home and community is understandable but how many rounds will occur before we abandon these areas?  Santa Ana winds, severe hurricanes, extensive flooding, prolonged drought and wildfires will continue to occur and their effects will only worsen.  Perhaps it is time to face reality and restrict construction in high risk terrain; while some disasters, such as tornados, might ravage any city or community, others are predictable, based on regional weather patterns, ecology and topography. 

Flashback Post LXI

The current explosive wildfire in Malibu Canyon, like most wildfires in Southern California, was triggered by an ignition source, extremely dry foliage and Santa Ana Winds.  The latter were discussed in a post back in November of 2007.

See: Santa Ana Winds 

Crisis in Southern California

A friend of mine, who owns property in San Diego, enlightened me on an ongoing environmental and public health crisis along the southernmost coast of California.  Each year, 10 billion gallons of raw sewage (residential and industrial) enters the Pacific Ocean via the Tijuana River.  A known and increasing problem for almost a Century, this pollution has not been significantly addressed by either the Mexican or U.S. Governments.

Spreading northward along the Imperial and Coronado Beaches, the marine pollution poses a health threat to humans and wildlife alike; indeed, these scenic beaches are now officially closed most of the time due to hazardous levels of bacteria in the water.  Though not documented, one can imagine that industrial chemicals also pose a threat, contaminating the water, sand and air.

When we learn that neighboring Governments cannot cooperate to remedy a local, fixable disaster, it is hard to imagine that humans can adequately address global crises such as climate change.  For a concise overview of this tragic scenario, including its medical, environmental and economic consequences, watch The Big Dump documentary on YouTube. 

Atmospheric Rivers

As storms (low pressure systems) move west to east across the country, we can usually identify a long "tail" of thunderstorms or heavy precipitation that curves southward and then southwestward from the center of low pressure.  This is the clash zone between warm, humid air to the east and drier, cooler air to the west.  In the Northern Hemisphere, winds swirl counterclockwise around the storm's center and thus move northward and northeastward ahead of the trailing front.

Along the Pacific Coast of the U.S., these winds pull in copious moisture from the ocean; when the low pressure is especially intense, this flow (referred to as an atmospheric river) can drop prodigious amounts of lowland rain and mountain snow on the Coastal States.  Furthermore, if the storm is stationary or slow moving, extensive flooding may occur; as our climate and oceans warm, these events will likely become increasingly severe.

Such a scenario is currently developing off the California Coast, near San Francisco.  The storm is intense enough to justify a Hurricane Warning with winds expected to gust over 70 mph atop the highlands. As the storm comes ashore, the plume of moisture will move southward, from the Bay Area to Southern California.  Widespread, severe flooding is expected.

See also: The Pineapple Express 

Rogue Waves

As most Americans have likely seen on videos by now, a rogue wave struck the coast of Ventura, California, this week, injuring 8 persons and flooding the neighborhood.  Though such waves have been reported for centuries, they were not documented until the mid 1980s.

Defined as a wave that is at least twice the height of surrounding waves, the cause for this destructive, natural phenomenon remains controversial.  Most oceanologists point to a merging of waves with the transfer of energy to a single wave, induced by a complex interaction of surface winds and ocean currents.  One confusing observation is that rogue waves often move against or across the direction of the prevailing wind.

Predicting this phenomenon is currently beyond our ability, just another reason that beachcombers, seafarers and coastal residents must respect the power of the sea.  Whether climate change will augment the formation of these waves is unknown but it seems to be energizing most other weather-related catastrophes. 

Hilary Churns toward the Southwest

Having formed in the warm Pacific waters off Mexico, Hurricane Hilary rapidly intensified into a Category 4 storm and is churning to the NNW.  Expected to weaken in cooler waters off the Baja Peninsula, the storm may still retain Tropical Storm status when it enters Southern California; if so, it will be the first to do so in 84 years.

While high winds may cause damage, the primary concern with Hilary is widespread flooding.  Directing a steady flow of tropical moisture across much of the Desert Southwest and Great Basin, the storm will likely drop up to 10 inches of rain in mountainous areas; while 2-3 inches is forecast for most of the region, that is a year's worth of precipitation for many desert locations.

Like so many "natural disasters" over the past few years, this unusual weather event reflects our warming climate.  Warmer ocean waters and higher sea levels will produce havoc across the globe, primarily for coastal regions but, at times, far inland. 

The Rebirth of Tulare Lake

As European settlers spread across North America, prairies, wetlands and bottomland forest were cleared to provide space for agricultural fields.  One such victim was Tulare Lake and its adjacent wetlands in the southern portion of California's Central Valley.

Canals, levees and dams were used to drain the lake and marshes for the planting of various crops.  In addition, groundwater was pumped in to irrigate those crops, causing the lake bed to sink even lower.  This process "worked" for most of the past 125 years; then, global warming ushered in the torrential rain and heavy mountain snows of this past winter.

Tulare Lake has been reborn and will expand further as the spring snowmelt peaks in the Sierra Nevada.  We can tame Mother Nature for periods of time but she always has the final say (assisted in this case by our use of fossil fuels). 

California Flooding

Over the past two weeks, much of Northern California has received a foot of rain and many feet of snow have fallen in the Cascades and Sierra Nevada.  Coastal and river flooding as well as mudslides in burn scar areas have plagued the region.

Unfortunately, another Pacific storm, centered off British Columbia, is directing its plume of tropical moisture into the same area and two other storms (one over the western Aleutian Chain and the second east of Japan) are lined up to produce the same "atmospheric river" during the next week.  Whether the persistent onslaught of rain and snow will end with those storms remains uncertain.

While they are providing relief from the prolonged Western drought, these potent storms will deliver too much moisture over too short a period of time.  Widespread flooding will likely worsen and is expected to spread into southern portions of the State as well.  Relatively warm water in the Northern Pacific, a product of global warming, is surely responsible for the relentless precipitation.   

Nature's Gift to the West

During this Holiday Week, a strong Pacific storm, centered off British Columbia, swept copious moisture across the drought-plagued landscape of the Western U.S.  The persistent onshore flow produced heavy snow (measured in feet) along the Cascades and Sierra Nevada and steady rains across the lowlands of California and the Desert Southwest.

As it pushes inland, the storm will also bring heavy snow to the mountains of the Great Basin and Rocky Mountain corridor before stretching out across the Northern Plains.  On its heels, another Pacific storm will drag in additional moisture, further enhancing mountain snowpacks throughout the West.

After years of "sub-normal" precipitation, especially in the Four Corners region, relief has arrived.  Time will tell if this snow machine will remain active through the winter and what effects global warming will have on the American West.  While we wait to find out, continued efforts to conserve water and reduce demand make sense. 

La Nina douses the Western Fires

A La Nina weather pattern has developed in the Eastern Pacific Ocean.  Strong trade winds across the equatorial region push warm surface waters to the west; this leads to upwelling of colder water off the west coast of the Americas.

In a typical La Nina year, precipitation increases in the Pacific Northwest (including the northern half of California) and mountain snowpacks are generally deeper across the West (excluding the Desert Southwest).  Evidence of this pattern is currently unfolding as soaking rains fall from San Francisco to Seattle and heavy snows coat the Cascades, Sierra Nevada and Great Basin Ranges.

The La Nina precipitation will likely bring an end to the Western Fire Season but will offer only modest relief from the prolonged drought that grips most of the American West.  Our warming climate will surely exacerbate the drought and might even prevent the formation of future La Ninas.

Joshua Trees

Returning to Colorado, we drove east on Interstate 15 across Southern California and Southern Nevada.  Just short of the California-Nevada border, the highway climbed across a ridge and, near an elevation of 4000 feet, Joshua trees appeared in abundance.

Also known as the yucca palm, the Joshua Tree is native to the Mojave Desert of the Desert Southwest.  It is relatively fast growing and may reach 50 feet in height; flowering occurs in late winter or early spring (if weather conditions permit) and these hardy plants disperse by seed or suckering.  The yucca moth is the primary pollinator.

For some of us, the term Joshua Tree will always be associated with U2's best album (in my humble opinion), but, for most, it will bring to mind the distinctive, top-heavy denizen of the otherwise bleak Mojave landscape. 

Leaving North America

As we drove across Southern California yesterday, my focus was on the traffic and the scenery.  I knew but did not consider the fact that we were leaving North America.

Of course, we did not depart the Continent but we did leave the North American Plate.  As we descended through Cajon Pass on Interstate 15, we crossed the San Andreas Fault and changed tectonic plates.  Indeed, Greater Los Angeles and San Diego are on the Pacific Plate, destined to break away from the North American Continent in the future.

During our brief human lives, we witness hints of tectonic activity, usually in the form of earthquakes and volcanism.  But, except for those who live in southern and central California, it is not everyday (if ever) that we Americans leave our home plate. 

Westward from Flagstaff

Leading westward from Flagstaff, Arizona, Interstate 40 passes through a scenic landscape of meadows and ponderosa pine forests.  Beyond Williams, the highway leaves this lofty terrain and descends into a broad swath of open parklands and low ridges; covered by juniper shrubs; this attractive ecosystem generally ranges in elevation from 3000 to 4000 feet.

Nearing Kingman, the highway drops further into the bleak landscape of the Mojave Desert, bordered by high but treeless ranges.  Three hours later, during which we crossed the Colorado River south of Needles, California, we finally escaped the Mojave west of Barstow; we then followed Interstate 15 westward to Cajon Pass and descended into the Los Angeles basin.

One cannot fully appreciate the dimensions and severity of a desert without driving across it; even today, with our modern, air-conditioned vehicles, it is a tiring experience.  We can only begin to imagine the challenges endured by those who used horses and wagons to make the journey.