Joe’s Weather Blog: The atmosphere in 3D + earthquake info (SAT-4/25)

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Good afternoon…a look at the satellite pictures and radar images then a look at the surface weather map shows a classic example of how the atmosphere works when there is a storm. More on all that in the discussion part of the blog + some interesting information regarding the devastating and disastrous earthquake in Nepal as well.

Forecast:

Rest of today: Periods of showers with lots of clouds…readings only in the 50s this afternoon for most areas…warmer towards the SE and well east of KC

Tonight: Cloudy skies and cooler with lows in the 40s

Tomorrow: Morning clouds giving way to sunshine and nice conditions with a steady east wind at 15-25 MPH. Highs in the 60s

Monday: Lots of filtered sunshine. Highs 60-65°

Discussion:

I thought today with it being rather dark and dreary I’d have you put on your thinking caps and do a brief little meteorology lesson.  The lesson today is thinking about the atmosphere in 3D.

Here is the current surface weather map…showing an area of low pressure (denoted by the closed isobars [lines of equal barometric pressure]) just east of the KC area… (click on the image to make it larger)

pmsl

OK so we know that there is a low pressure area on the surface towards central MO…

As we go up in the atmosphere however, it’s different. The lower pressures are tilted typically towards the W or NW of the surface low position. Here is an approximate figure for you…via the University of Wisconsin

 

The green represents the surface while the thin gray lines represent the flow of air up towards about 18,000 feet or so.

Notice how the storm there is lagging behind the surface low pressure. The word divergence means that the air at that level is moving outwards…when that occurs the air below is moving upwards to replace the air that’s being moved outwards (if that makes sense). Hence an area of low pressure at the surface develops.

You can often see the circulations of the upper level lows by looking satellite animations…here is a close up of the KC area

Here is a broad view…

The upper level storm is pretty much right on top of the KC area…

This upper level storm represents a pocket of colder air aloft…as shown by the dip in the gray lines in the above map. When temperatures are cold aloft and warmer at the surface the air rises (almost all the time during the day). When the layers are colder/warmer at the same time the air rises faster. When moisture is present (obviously today) you get a lot of clouds and you get rain in pockets…

If you look closely this afternoon you can actually see the radar returns rotating around the upper level feature…

 

Where there are pockets of more unstable air across central MO, the updrafts will grow more vigorously and turn into thunderstorms, some of which may contain hail.

Anyway this stuff is pretty neat if you look at the big picture.

This slow moving system will continue to allow moisture to hang around through the night into early tomorrow morning…it should move far enough away to allow sunshine to break through tomorrow afternoon.

The only issues after tomorrow is the amount of cloud cover early next week in the form of high clouds. Another upper level storm will be dropping southwards through the western part of the country and this will drop into the southern Rockies before passing to far south of KC to give us any rain…but it will bring a considerable amount of mid and mostly upper level moisture up our way from the SW part of the country. This means a lot of thick cirrus clouds filtering out the sunshine through Tuesday.

The only issue for the forecast really is trying to figure out how warm it will be on MON>TUE then the temperatures after that as we warm up. It appears we’ll be dry for quite some time in the region. I still expect below average temperatures through Tuesday before we try and make a run towards 80° by Friday.

Meanwhile in addition to the meteorology lesson today, now lets delve into geology.

There was a devastating earthquake in Nepal last night. It was measured as from 7.8-7.9. So far well over 1000 have lost their lives and many more deaths are expected to be revealed as recovery operations continue there. I was re-tweeting information regarding all this @fox4wx earlier this morning.

According to the British Red Cross…upwards of 6.6 million people potentially were exposed to this quake.

A full summary from the USGS with updated geological information is here...

Here is a small section of the report…

“The April 25, 2015 M 7.8 Nepal earthquake occurred as the result of thrust faulting on or near the main frontal thrust between the subducting India plate and the overriding Eurasia plate to the north. At the location of this earthquake, approximately 80 km to the northwest of the Nepalese capital of Kathmandu, the India plate is converging with Eurasia at a rate of 45 mm/yr towards the north-northeast, driving the uplift of the Himalayan mountain range. The preliminary location, size and focal mechanism of the April 25 earthquake are consistent with its occurrence on the main subduction thrust interface between the India and Eurasia plates.

Although a major plate boundary with a history of large-to-great sized earthquakes, large earthquakes on the Himalayan thrust are rare in the documented historical era. Just four events of M6 or larger have occurred within 250 km of the April 25, 2015 earthquake over the past century. One, a M 6.9 earthquake in August 1988, 240 km to the southeast of the April 25 event, caused close to 1500 fatalities. The largest, an M 8.0 event known as the 1934 Nepal-Bihar earthquake, occurred in a similar location to the 1988 event. It severely damaged Kathmandu, and is thought to have caused around 10,600 fatalities.”

end

We’ve heard about a lot of earthquakes in OK over the last couple of years…most of those are in the 3-4 magnitude range. This one was close to an 8. The difference in magnitude and energy released though is vastly different.

Yes this earthquake released almost 4 MILLION times more energy than what usually happens in OK. Amazing.

The overriding theme with this blog…are layers…there are layers in the atmosphere and there are layers and plates of the earth’s crust. When one layer collides into another layer on the earth…there are quakes…when one layer of the atmosphere is vastly different than another layer you get changing weather!

Joe

 

 

 

 

 

 

 

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