04.15.10

Can You Say Eyjafjallajökull?

Posted in General News at 10:58 am by Rebekah

Air space has been shut down indefinitely across Great Britain, Ireland, Scandinavia, and a few other parts of western Europe, including at London Heathrow, Europe’s busiest airport (see BBC, CNN, MSNBC)

A large volcanic eruption in Iceland has spewed ash towards Europe, causing a safety hazard for aircraft (the ash can get sucked into an aircraft’s engine and cause the engine to fail).

A friend of mine and fellow OU grad student (from England, incidentally) told me a few weeks ago that a volcano in Iceland started erupting on her birthday, March 20.  She shared a website with a “volcano-cam” where we could watch Eyjafjallajökull spew ash and lava.  Eventually the poor camera gave out (we theorized that it got “lava-ed”), and a new webcam took its place (unfortunately this new one was farther away and did not give quite as good of a view — if interested, you can see it at the link above).

The following image from the UK Met Office shows the projected coverage of the ash by 7am British Summer Time (0600 GMT) tomorrow, at which time the airports hope to re-open.

And here’s an interesting satellite loop, from EUMETSAT, showing the plume of ash heading for Europe (the ash is the dark, reddish-colored area coming from southern Iceland).

Click to play.

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04.14.10

Where Have All The Tornadoes Gone?

Posted in Storm Chasing, Weather News at 9:38 pm by Rebekah

Mid-April in Tornado Alley.  Only 93 tornado reports so far.

Over the last 30 years, there were on average 191 tornadoes between January 1 and April 15.

Over the last 10 years, there were on average 237 tornadoes.

Over the last 5 years, there were on average 338 tornadoes.

Tornado reports have, on average, gone up over recent years, but that is due in large part to increased tornado awareness, increased storm chasers and spotters, and increased tornado detection through Doppler radar.

But that’s not the point.

The point is that this year is below average.  Take a look at the plot below, from the Storm Prediction Center.  This graph shows the trend in local storm reports (LSR) of tornadoes in the U.S.  Values may be a little higher than the actual tornado count (some tornadoes may have been reported more than once).  The last five years are shown, as well as the current year up through April 12.

Now look at the graph below (click to enlarge), also from the Storm Prediction Center.  This plot shows annual tornado trends; if you’re curious as to how exactly the trends were calculated, see the website on the bottom of the figure.  Basically, the red line is the maximum tornado count in a single year and the pink line is the minimum tornado count in a single year.  The other lines show tornado trends in quartiles.  Currently, 2010 is in the all-time lowest 25th percentile, near the minimum.  That’s how slow this year is in terms of storms and tornadoes.

One thing to note, however, is that in 2004, there was an all-time record of over 1800 tornadoes in the U.S.  From January 1 to April 15 of 2004, only 91 tornadoes were reported.  As of today, April 14, 2010, 93 tornadoes have been reported this year.

Currently the weather pattern over much of the U.S. is more summer-like than spring-like, with few good troughs digging into the central or southern Plains…however, all this just goes to show that storm chasers shouldn’t be too worried about this season yet (and sane citizens of the Plains shouldn’t get too excited yet)…

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04.13.10

World Wide Weather #3: Rio de Janeiro, Brazil

Posted in Non-US Weather, Weather News at 5:19 pm by Rebekah

This week’s featured city, in my series on global weather and climate, is Rio de Janeiro, Brazil (click for a Yahoo! maps link).

Rio de Janeiro, Brazil. Courtesy of Wikipedia. Click to enlarge.

Located in southeast Brazil, on the Atlantic Coast, Rio is home to about 6.2 million people (approximately 14.5 million in the metro).  Rio de Janeiro, Portuguese for “River of January”, was the capital city of Brazil until 1960, when Brasília became the capital.  Near the Tropic of Capricorn, Rio is the main tourist destination in the Southern Hemisphere and will host the final match of the 2014 FIFA World Cup and the 2016 Summer Olympics (the first city to host the Olympics in South America).

A few more facts about Rio de Janeiro (from Wikipedia):

  • Time zone: Brasília Standard Time (UTC-3) or Brasília Daylight Time (UTC-2)
  • Elevation: 0 to 3,350 ft above mean sea level
  • Climate zone: Tropical savanna (hot/wet summers, mild/dry winters)
  • Average high temperature: 86 °F (30 °C)
  • Average low temperature: 68 °F (20 °C)
  • Record high temperature: 109 °F (43 °C)
  • Record low temperature: 45 °F (7 °C)
  • Average annual precipitation: 43 inches (1,090 mm)

Recent/current weather: Last week Rio de Janeiro and surrounding areas were hit hard by heavy rains; reportedly the heaviest rain in nearly 50 years.  Rio de Janeiro received about 11 inches of rain within 24 hours on Tuesday/Wednesday.  Massive flooding and landslides have sadly resulted in the deaths of over 200 people, and have left thousands without homes.

What caused the rain?  One big reason has to do with the low-pressure system sitting off the southern Brazilian coast last week (see figure, below).  In the Northern Hemisphere, low pressure turns counter-clockwise and high pressure turns clockwise; however, in the Southern Hemisphere, low pressure turns clockwise and high pressure turns counter-clockwise.  Thus the strong low-pressure system produced southerly and southeasterly winds in the Rio area, bringing a lot of tropical, moist air from the south Atlantic onshore.  Steep terrain around Rio de Janeiro also contributed to the rainfall, as warm, moist air can produce clouds and rain as it rises up a hill or mountain.

Surface analysis of South America on 7 April 2010, at 12Z (9am Rio de Janeiro time). Map courtesy of INMET. Note the 1004 mb closed low off the coast of Brazil, and the 1028 mb closed high off the coast of Argentina. Green arrows denote approximate wind direction. Click to enlarge.

As the low left the area, it was replaced by a high, which is bringing more easterly winds to Rio (this is the typical wind direction in the tropics).  As Rio de Janeiro’s coast primarily runs east/west, these easterly winds are assisting in producing some rain, but not nearly as heavy of rain as was associated with the low.  In addition, highs are associated with sinking air, so naturally there should not be as much rain.

For more information on Rio de Janeiro, here’s a link to Wikipedia.

For weather maps and information on current and forecast Rio de Janeiro weather, see the Instituto Nacional de Meteorologia (INMET, i.e., Brazil’s National Institute of Meteorology — warning, it’s in Portuguese!) or Weather Online UK (great collection of weather maps and models for all over the world).

Next Tuesday I’ll take a look at the climate and weather in another part of the globe.  As always, if you have any comments or suggestions for future cities, please leave a comment on this post!

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Website / Blog Updates

Posted in General News at 1:18 pm by Rebekah

In case any of you, faithful readers, have been wondering what happened to me, I have been pretty swamped the last couple of weeks with classwork — hence the lack of blog posts and website updates.  Weather (especially severe weather) has not been too exciting here lately, though, so I have been spending time getting stuff done before the chasing season really sets in.

I did just update the photo of the week (it’s a photo of a pileus cloud that I saw on my last chase, on April 6th) over on my website (see link on the right of the page).  Later this afternoon, after I get a bit more work done on a class project, I hope to update chase logs and photos for this year and to write the next feature post on global weather.

Hint: it’s the home of the 2016 Olympics…

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04.06.10

Chase #3

Posted in Storm Chasing at 12:12 pm by Rebekah

Supercells are possible today in eastern Kansas and northern Oklahoma…the trough will be moving over Colorado/New Mexico today, and dewpoints along the dryline in central Oklahoma are forecast to be in the mid 60s through 00Z (7pm).  CAPE values of 1500 to 2000 are forecast in a narrow region along the dryline, and storm-relative helicity may be above 200 in central Oklahoma.  Models show precipitation breaking out by 5pm in eastern Kansas and northern Oklahoma…if storms remain discrete, large hail and a few tornadoes are possible.

Target area: Ponca City, Oklahoma towards possibly Bartlesville Oklahoma and northward into Kansas

Will be leaving around 2pm…

You can track me at Spotter Network once I am on the road.

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