Written by on September 29, 2009 in Rest of Europe with 1 Comment

>– By Mark Vogan

After an interesting video by AccuWeather’s Angelica Campos on the remarkable hot summer South Texas has endured and yes, even for this normally hot place, this summer has been outstanding in the “hot summer” department and here’s why…

Some stats Angelica shared:

The lack of rainfall and intense heat has led to several South Texas counties having thier worst drought since 1950.

  • June 2009 produced 10 consecutive days at or above 100 in Austin. Averaging between 100 and 107 degrees.
  • July saw 23 days above 100.
  • August saw 21 days above 100.

Laredo averaged 5-7 degrees above normal everyday throughout the June through August period.

Interestingly I found there wasn’t major heat records broken. i.e. for the month or all-time. That being said, Houston and other areas in the upper Texas coast saw their warmest as well as drist ever June. But despite the relentless blowtorch that’s baked the Rio Grande Valley this summer and this will probably go down as the hottest recorded summer for communities down there, it’s not the actual high’s that’s breaking records but more the longivity of the intense heat. Afterall there hasn’t been the 110s or 115-degree days that Texas can get, but more day after day of relentless 100 to 108-degree days that’s the record breaker. Otfne even in this part of the world, you will get days of cooler temps in between hotter ones.

So, why am I saying all this? Well. When I take the entire nation into all this and you see just how cool June, July and August was across much of the country, you ask, well how was it such a hot summer across a region that is NORMALLY hot and dry?

One of my theories about the significance of the 2009 summer is that if it wasn’t for the exceptionally cool summer across the vast majority of the country, we simply wouldn’t have seen the type of record hot and dry summer over south Texas this year.

Why? the same way we wouldn’t have seen a new all-time temperatures recorded at Seattle (breaking the old record by three degrees) and Portland which hit 107 ( 1-degree shy of the all-time record).

It’s NOT because the earth is warming more and more that we witnessed this relentless heat in South Texas and the blowtorch of the century in Seattle but quite the opposite. I believe that cooler air and lower thickness values that covered much of the US east of the Rockies meant that the “normally” larger coverage of warm, tropical air was suppressed at a much more southerly latitude than normal and was able to penetrate into areas normally cooler. i.e. the Canadian High that covered much of the plains and east diverted and suppressed the tropical high, therefore stopping it’s normal progression northward towards the pole. Normally each and every summer, the United States is under a sub-tropical high pressure system. As the sun migrates northward in spring and summer towards the pole, a band of sub-tropical high pressure follows the sun’s migration north and thus brings a hot and sunny summer to much of the United States, but a cold winter and spring meant that the Canadian high had dominance because cooler air was stronger than it has been in many years. When the sub-tropical belt pushes north but is supressed and stopped in it’s tracks but a stronger Canadian high, it must go somewhere so it’s cen redistribute heat away from the tropics. If stopped and it cannot spread outwards, the pressures must rise vertically, increasing the verticle temperature profile of the atmosphere and this results in wamrer surface temperatures as well as a stronger evaporation of soils and the surface, therefore resulting in worsening drought conditions.

The normally hot summer in South Texas is 90s to low 100s and the high pressure is usually spread out across a much broader scale of the lower 48, but since the Canadian high had dominace of US airspace, the subtropical ridge was forced to not only raise pressures higher into the atmosphere and warming the air aloft but it was forcing the high pressure belt to find a path of least resistence. It found a weakness in the western side of the Canadian high and therfore pushing high pressure and high heat up the West Coast bringing record heat to the Pacific Northwest, interior western Canada and Alaska.

This set up brought atmospoheric opposites since the atmosphere must find a way to balance itself out. Air must go somewhere, it doesn’t just disappear, therefore Minnesota felt more like Manitoba while Seattle and Portland felt more like Las Vegas and Phoenix. To pull such concentrated cold air so far south from it’s origin, it’s only natural to think that warm air must surge north well away from it’s origin to even things out. Just in the same way high and low pressure together forces winds to blow, so the atmosphere can find Equilibrium.

When the cold air that stationed itself from the Rockies to East Coast strengthened and record cold was witnessed, so the hot air was strengthened. Seattle’s new all-time record was recorded when a reinforced surge of remarkably cold air was forced south from Canada on a northerly flow as the jet stream was of an unusual meridional alignment. Seattle and Portland topped the 100s whilst east of the Cascades high’s topped near 110 to even the low 110s with pressure heights in the 590dc range just east of Seattle and Portland, suddenly the Pacific Northwest had air that was forced north from the Four Corners at the same time air from the tundra was forced south into the Rockies and N. Plains. As Seattle and Portland saw scorching downsloping off the Cascades as unusually strong thickness values were recorded over eastern Washington and Oregon and a thermal low was over the Puget Sounds and Willmette Valley ( the perfect set up for all-time heat along the coastal plain) snow was falling over Colorado and high’s were stuck in the 50s and 60s in the heart of July!

The Texas heat and persistency of brutalising heat was because the normal sub-tropical ridge was squeezed and had nowhere to go, so upwards it went, building a protective shield from outside weather! This dominant feature then increased the drought and the feedback was firmly established. As the subtropical ridge surging around the Canadian high and enhanced perhaps by the El Nino, persistent sunny, hot weather brought unusually dry conditions to Alaska and western Canada and this produced 91-degree heat in Fairbanks and the 90s into the Arctic. Even the Arctic Ocean coast saw 81 degrees at Tuktoyaktuk, home to last years Ice Road Truckers.

Ultimately the earth is cooling and with cooling and greater dominance in colder air, we will see suppressed subtropical ridges in summer. The sun that migrates north as summer starts, builds and migrates the subtropical ridge with it, following the sun. But if winters become colder and the colder air covers more area of the atmosphere, the sub tropical ridge will become supressed, but it must go somewhere to redistribute the excess heat away from the tropics, where it goes, is where there is a weakness in the stronger cold pools that linger after the winter is over. That means the warmth goes where it normally doesn’t, If it doesn’t go somewhere, then the pressures rise ever higher into the atmosphere, what results is record breaking surface temperatures. That is exactly what happened in Seattle this summer… Global Warming is not the cause for blistering heat from Laredo to Seattle to Fairbanks or the severe drought in South Texas …

Even as winters grow colder, we may actually see some stunning “heat records” established in the coming years even though summers may grow cooler in the broader scale. This summer is another piece of the puzzle. The signs are there to be seen. We only have to open our eyes!

Thanks for reading.

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  1. JamieD5 says:

    >I dislike the fact that you make predictions based on localised, and temporary anomalies in weather. I guess I should leave you to it as everyone is entitled to an opinion.
    I could put my money on it that snowfall and glacial extent are decreasing in certain regions. I would not declare global warming based on such regional deviations. Indices such as the global mean temperature series are sensitive measures of climate change, but are non specific.

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