astronomy, geography, geology, weather

THEWEATHERMOGIL:: When geology and meteorology meet

In the Earth-Space Science arena, we often discuss meteorology, hydrology, oceanography, astronomy and geology. In recent years, a curious blend of meteorology and astronomy, known as “Space Weather,” has emerged. The National Weather Service, now routinely issues “Space Weather” forecasts that address parameters such as the solar wind and the transport of electromagnetic surges toward Earth and our orbiting spacecraft. While not weather, as we know it Earth, its impacts are more weather-focused (electricity) than astronomy-based (planetary motions).

Another, not-so-unusual, relationship involves geology and meteorology. At the Earth-atmosphere interface, mountains and coastlines affect wind flow; mountains can lead to rain-shadow effects (wet on one side of the mountain and dry on the other); changes in elevation and/or the mountains themselves can lead to intense thunderstorm rainfall and flash flooding; and terrain, even without a mountain presence, can help to channel precipitation runoff into narrow canyons or waterways and lead to significant localized and/or deadly flash flooding.

Add volcanoes to the mix and now the geologic events themselves can cause meteorological impacts. The recent eruption of the Pavlof volcano in the Aleutian Island chain is a prime example (Fig. 1).

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First, any heating of the exterior or near exterior of a volcanic mountain (which in northern climes is often ice and/or snow covered), can lead to rapid snowmelt and cause avalanches, mudslides and/or flooding. It is easy to see the effect that melting has in this image of the Pavlof volcano (Fig. 2).

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The main risk from volcanoes happens during and following an eruption. Based on the force of the ejected air and gas cloud, volcanic dust and particles can be lifted to altitudes high above the Earth’s surface. The Pavlof eruption of last weekend was relatively “tame,” sending ash only four to five miles aloft. The eruption of Mount Pinatubo (June 1991) sent ash so high that it reached well into the stratosphere, where ash was still detected years later.

The eruption process, once started, resembles the convective process of regular thunderstorm formation. In fact, volcanic clouds, as they grow from the eruption, often look like “dirty” thunderstorm clouds (towers, anvils, precipitation, virga and/or “fall” streaks, lightning and sometimes waterspouts). Fig. 1 and Fig. 3 typify what volcanic thunderstorms look like.

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In the short-term, volcanic ash and dust can lead to significant aviation impacts. In 1982, British Airlines Flight 9, flying at 37,000 feet, entered an ash cloud near Jakarta, Indonesia. The flight crew was not aware that such an ash cloud was in their flight path. As a result, the plane’s four engines “flamed out” and the plane started a growingly steep descent. The pilot was able to restart the engines, but not until the plane had descended to 12,000 feet. Following another “flame out” of one engine, the pilot was able to safely land the plane. A review following the incident demonstrated that the ash cloud was associated with an eruption from Mount Galunggung, some 110 miles southeast of Jakarta.

A similar experience occurred in late 1989 following an eruption of Mount Redoubt, AK. Here, a KLM flight, carrying 231 passengers to Anchorage, suffered a drop of several thousand feet following a “flame out” of its engines.

Since the ash cloud plume from the recently-erupted Pavlof volcano extended several hundred miles into Alaska (Fig. 4), flight operations at Alaska Airlines were put on hold (41 cancellations) on Monday. With the volcano eruption lessening, and the threat level lowered accordingly, flight operations at Alaska Airlines are expected to resume yesterday.

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As noted by Alaska Airlines spokeswoman Bobbie Egan, and most likely echoed by every airline executive worldwide, “We just simply will not fly when ash is present.”

Now, the United States Geologic Survey (USGS) routinely monitors volcanoes for all types of hazards and issues advisories or alerts for a wide range of target audiences. The USGS and other agencies use a sophisticated array of sensors to track earth movements, changes in lava distribution and aircraft to monitor actual or imminent eruptions. In the U.S., NOAA routinely provides satellite support, helping to track any ash clouds and monitor their density. Worldwide, a total of 9 Volcano Ash Advisory Centers (VAACs) provide such support for international aviation. The bottom line is that flight cancellations rather than emergency landings or actions are now the rule.

Although the Pavlof volcano has calmed down a bit and alert levels have been lowered, Pavlof and several other volcanoes worldwide remain on active USGS monitoring lists.

© 2016 H. Michael Mogil

Originally posted 3/30/16; updated 3/31/16

geography, weather

THEWEATHERMOGIL:: It’s all about source regions

March has been a mostly mild month across much of the U.S. That’s because upper-level and lower-level winds have been blowing primarily from the west, southwest or south across the Nation. Yes, there have been occasional bursts of chillier air, and these come on the heels of winds from northwest, north or northeast.

This is an important factor in the weather forecasting world because winds from certain directions carry air from certain “source regions.” “Source regions” are large geographical areas that help certain temperature and moisture characteristics develop in the lower atmosphere.

Consider the Gulf of Mexico. It’s a large, relatively homogenous, region filled with “bathtub-like water.” Hence, heat and moisture from it’s waters can create a warm and humid air mass above it. Similarly, air that sits over an icy landscape becomes cold and dry (cold air cannot hold much moisture).

Once formed, these air masses (large geographic regions with similar temperature and moisture characteristics) can move. When they do, significant changes in local weather conditions, possibly far-removed from source region origins, can take place.

Today, a storm system is exiting the Great Lakes, allowing a little chilly air to move southward into the U.S. (Fig. 1a). But, west and southwesterly winds are already coming into play across the western Plains states. These will initially spread warm and dry air northward through the Nation’s mid-section. As the winds across the rest of the Plains states and Mississippi River Valley become southerly, warm and moist air from the Gulf of Mexico will be drawn northward. This will set the stage for yet another bout of severe weather as the week unfolds. In fact, NOAA’s Storm Prediction Center is indicating a large region of severe storm potential on Mar. 30 from Iowa southward to Louisiana (Fig. 2).

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However, by the start of April, a very chilly air mass will charge southward from Canada, thanks to a significant shift in upper level winds (Fig. 3). By Apr. 2, cold air will cover the region from the northern and central Plains states to the Northeast and Middle-Atlantic (Fig. 1b).

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Then, winds return to westerly across the U.S., until around Apr. 8, when another significant system is expected to race into the Northeast, bringing another brief period of cold temperatures into the Great Lakes and Northeast. Leading up to this Canadian air mass intrusion, another Gulf of Mexico air mass will help set the stage for severe storms across parts of the eastern half of the Nation.

© 2016 H. Michael Mogil

Originally posted 3/28/16

weather

THEWEATHERMOGIL:: Welcome to spring and some spring snowstorms!

It’s only a couple of days into spring and the big weather news involves SNOW. In fact, we are talking about a lot of snow.

Wisconsin is bracing for a foot of snow or more across central and eastern sections between now and Thursday. The northeast corner of Colorado (including the Denver metro area) is on tap for about a foot of wind-driven snowfall. Blizzard warnings have been posted here, as well as in nearby areas of Nebraska and Wyoming (Fig.1). Look for some major airport and highway travel delays in these areas.

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The culprit behind this “out of whack” weather is a low-pressure system that has formed over the western High Plains (Fig. 2) and is expected to move to near Detroit by late Thursday. To the north of the system, heavy snow and gusty winds will be the rule. To the south of the system gusty, warm and dry winds will lead to a high fire danger across the southern High Plains. Then, to the east, with more abundant Gulf of Mexico moisture, showers and thunderstorms will begin to develop later today. According to NOAA’s Storm Prediction Center, some storms may reach severe limits today from Missouri southward to eastern Texas and tomorrow across parts of Tennessee and Alabama.

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Behind this storm system, another low is expected to head southeastward and spread a swath of snow across parts of the northern Plains later this week. If that’s not enough “Spring” weather, yet another storm is expected to affect Colorado by the middle of next week.

In the wake of each of these storm systems, chilly air will spread southward.

So, if you live in a region that includes the Intermountain West, the central Plains and the Great Lakes, think Spring, but expect Winter!

© 2016 H. Michael Mogil

Originally posted 3/23/16

weather

THEWEATHERMOGIL:: Almost all the weather, all at once

This morning’s national watch-warning map (Fig. 1) shows almost all the weather you’d ever want to see, all at once. Some extreme weather hazards (e.g., hurricane, severe weather, flash flooding and blizzard) are absent; however, just about everything else, “weather,” is expected to occur somewhere across the 48-states.

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Wind advisories and high fire weather alerts (on the west side of a strong high-pressure system) cover much of the Central Plains and parts of the Mississippi River Valley; on the east side of the high (and within the high), frost and freeze alerts had been posted for early today. We won’t be seeing these again, so far south and east, anytime soon.

A storm system coming out of the Rockies is expected to spread snow across the north-central Plains eastward to the Upper Peninsula of Michigan by tonight into Wednesday. As expected, the winter weather advisories from this morning, were upgraded to winter storm warnings today. Some parts of Wisconsin may see eight inches of snow or more.

Out west, a potpourri of wind and winter weather scenarios is scattered across highly variable terrain.

Stay tuned. More swings and extremes in weather are on the horizon.

© 2016 H. Michael Mogil

Originally posted 3/22/16

weather

THEWEATHERMOGIL:: Spring has arrived or has it?

Spring (astronomical spring, that is) officially arrived over the weekend and the weather pattern is definitely taking on a springtime appearance (well, sort of)! Temperatures may be above average in many places, but don’t discount winter, just yet.

During the past few days, many forecasters focused on the potential for a significant snowstorm across parts of southeastern New England. Right now, it appears that mostly light snow will affect that area, with heavier amounts further north along coastal Maine. In the storm’s wake, milder air will quickly return to the region.

However, the real Spring news involves the development of a northern tier storm track (Fig. 1) and yo-yo weather across the southern Plains. Severe weather potential, however, appears to be limited during the next few weeks.

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NOTE: As with any outlook spanning a two-week period, weather conditions and patterns can shift for many reasons. Always monitor the latest short-period forecasts.

A series of storm systems is expected to develop across the western High Plains and race toward the St. Lawrence River Valley in eastern Canada. Depending upon the track, these storms will bring a swath of snow to their north. Right now, Wisconsin, Michigan and parts of Iowa, Minnesota and Illinois seem to be in the target zone. Some places in Wisconsin could get a lot of Spring snow!

In addition to the storms, an arctic cold front is expected to move southward from Canada and stall just south of Wisconsin toward the end of the month. This could set up a multi-day overrunning snow event for the area.

The same arctic front may disrupt the otherwise warm, dry and windy pattern (one that favors a high fire danger) across the Central and Southern Plains. Instead, a snow event (along with some potential for freezing rain), could stretch from Colorado across the Plains states. This could become a cruel April Fool’s day joke for many.

Otherwise, California’s wet El Nino period could be over, as a strong upper level ridge persists along the West Coast.

© 2016 H. Michael Mogil

Originally posted 3/21/16

weather

THEWEATHERMOGIL:: Big chill enroute

As the risk for a significant New England snow event wanes, attention is now being focused on a major cool-down across the East and the South. In places where temperatures have been running well above seasonal averages for most of March, tumbling temperatures are now in many forecasts. As of late this Saturday afternoon (Mar. 19, 2016), frost and freeze watches, warnings and advisories covered a fairly large region across the Southern Plains into the Tennessee Valley and also across parts of the western Carolinas (Fig. 1). Look for these to be extended eastward and southeastward during the next 12 to 24 hours.

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The culprit is an upper level low located over the northern Mississippi River Valley this afternoon (Fig. 2). That low should move into the Ohio River Valley by Sunday, allowing colder air from Canada to infiltrate the eastern half of the U.S. (Fig. 3). Linked to this, a large surface high-pressure system will move into the Southern Plains, allowing a northerly wind flow across a large part of the eastern U.S. (Fig. 4).

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Temperatures that were running some 10 to 15 degrees above average for the past week to ten days (and about seven to 10 degrees above average for the month of March) will drop to some seven to 10 degrees below seasonal values by Sunday and Monday. For example, the seasonal average for Birmingham, AL is 56 degrees. Tomorrow (Mar. 20, 2016), the average for the day is only expected to be 46 degrees.

© 2016 H. Michael Mogil

Originally posted 3/19/16

"Life", politics, weather

THEWEATHERMOGIL:: Super Tuesday primary weather, not so super in three states

“Super Tuesday,” perhaps the biggest single day of primary election year voting, has arrived. Twelve states have Republican primaries or caucuses; ten states have Democratic primaries (with American Samoa holding a caucus). Six of the primary states are in the Deep South, with three states (Alabama, Georgia and Tennessee) in the Southeast and three (Oklahoma, Texas and Arkansas) across or near the southern Plains. As noted over a week ago, many of the southern “Super Tuesday” states are expected to experience some weather impacts – either rain and/or severe weather (Fig. 1 and Fig. 2).

What are the Super Tuesday states?

Both Democrats and Republicans: Alabama, Arkansas, Colorado, Georgia, Massachusetts, Minnesota, Oklahoma, Texas, Vermont and Virginia.

Republicans only: Tennessee primary and Alaska caucus.

Democrats only: American Samoa caucus.

The southeastern part of the Nation will be faced with the risk of locally heavy rainfall and possibly severe storms (reminiscent in some ways of the Super Tuesday tornado outbreak of Feb. 5 – 6, 2008). Arkansas and the eastern parts of Oklahoma will have a chilly morning rain, followed by cloudy skies (Fig. 1 and Fig. 2). Texas will be warm to start, with a cool down as the day unfolds. Alabama and Georgia will see wet weather later today and tonight, as primaries wind down. Otherwise, the weather should be mostly “good,” across the remainder of today’s primary landscape territory.

After today’s primaries and caucuses, I’ll provide periodic updates during the next week or so to keep the weather in focus as additional key primaries take place. Then, look for a continued period of updates for the next three months, thanks to a spate of primaries that doesn’t end until June 14.

Regardless of your party affiliation or political beliefs, I encourage you to use your right and responsibility to vote. I will be voting in the Florida primary on Mar. 15, regardless of the weather.

© 2016 H. Michael Mogil

Originally posted 3/1/16