Weather Around The World This Week: All (Mostly) Clear On The Western Front

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A more settled weather pattern over the U.S. A cold front could bring severe weather to tornado alley; low pressure takes a more northerly route. 5 a.m. 4/22/14 analysis courtesy of NOAA

A more settled weather pattern over the U.S. A cold front could bring severe weather to tornado alley; low pressure takes a more northerly route. 5 a.m. 4/22/14 analysis courtesy of NOAA

As Decoded Science promised last week, the weather pattern over North America has calmed down, and much of the United States is now enjoying spring. But the change of seasons can bring on new problems.

Extreme Air Pollution Possible In Shanghai And Beijing

The air in many cities in China is barely breathable under the best of conditions. With high pressure forecast to settle over eastern China, the cities of Shanghai and Beijing could experience serious air pollution in the next couple of weeks. Currently readings are only in the unhealthy range, which is relatively good, comparatively speaking.

Air pollution is partly a function of the amount of pollutants created locally; but it also has to do with the prevailing weather pattern. Stagnant high pressure systems allow pollutants to build up, with little ventilation. These conditions prevail around the globe most noticeably in the zone near 30 degrees latitude. Los Angeles, Phoenix, Beijing, and Shanghai are in or near this zone.

The Chinese government has begun to acknowledge the pollution problem and is shutting down some of the worst polluters, but China is still building a coal-fired power plant every day.

European Heat Wave

The extremely warm winter that has prevailed in Europe this winter was interrupted in Germany by ten days of cold from April 9-18. Berlin, like London, has experienced whole months this winter with not a single day below normal. The forecast is for continued warm weather until the end of the month and then a transition to much colder weather. Color Decoded Science skeptical about the latter.

The Lull Before …….. ?

The hurricane/typhoon season in the northern hemisphere hasn’t started and the southern hemisphere’s tropical cyclone season is coming to a close. This week, with only a single tropical system in evidence — though a significant one — is a good time to clarify terminology:

  • Hurricane: a tropical system in the North Atlantic, Gulf of Mexico, and eastern North Pacific (east of the International Dateline)
  • Typhoon: a tropical system in the western North Pacific
  • Tropical Cyclone: A tropical system in the southern hemisphere, notably the Indian Ocean, but also the South Pacific.

All of the above are characterized by winds in excess of 74 miles per hour. Tropical systems with lower wind speeds are classified as follows:

  • Tropical Depression: a closed low pressure system with winds below 39 miles per hour.
  • Tropical Storm: a low pressure system with winds between 39 and 74 miles per hour.

In addition, typhoons, hurricanes, and tropical cyclones are rated according to wind speed.

  1. Category One: winds 74 to 95 mikes per hour.
  2. Category Two: winds between 95 and 115 miles per hour.
  3. Category Three: winds between 115 and 135 miles per hour.
  4. Category Four: winds between 135 and 155 miles per hour.
  5. Category Five: winds over 155 miles per hour.

Storms of category three, four, and five are classified as major storms.

The Search For MH370

Tropical Cyclone Jack, the lone tropical system this week, is in the Indian Ocean. It is heading for the MH370 search area, but will weaken to a depression before it gets there. Nevertheless, large swells and low visibilities may hamper search operations.

Precipitation forecast for the next week. Heavy rain on the Pacific coast and rain connected with thunderstorms in the heartland where tornadoes are possible. Forecast courtesy of NOAA

Precipitation forecast for the next week. Heavy rain on the Pacific coast and rain connected with thunderstorms in the heartland where tornadoes are possible. Forecast courtesy of NOAA

Looking Ahead

Winter-like weather will continue in the extreme northern parts of the United States and higher elevations in the west this week. Elsewhere, spring will increasingly be in evidence, as the polar vortex grudgingly relaxes its influence.

The northwest coast will have significant rain, centered on Oregon, and there will be severe weather outbreaks in tornado alley and surroundings. The best chance of tornadoes will come on the weekend and early next week, as a strong cold front pushes slowly east.

Enjoy the spring weather whenever you get it. Summer is coming with a new set of weather problems: hurricanes, hail, and heat waves — things only a meteorologist could love.

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