08.24.10

World Wide Weather #14: McMurdo Station, Ross Island, Antarctica

Posted in Non-US Weather, Weather News at 6:20 pm by Rebekah

This week’s post in the global weather and climate series features McMurdo Station, Antarctica (click for a Yahoo! maps link).

Russian icebreaker leading an American container ship to McMurdo Station on Ross Island, during Operation Deep Freeze 2006. Mount Erebus is in the background. Courtesy of Wikipedia.

Located on Ross Island, on the shore of McMurdo Sound, McMurdo Station is a US Antarctic research station at 78 °S. Ross Island is home to about half a million Adélie Penguins and one active volcano, Mount Erebus. The largest community in Antarctica, McMurdo Station is capable of supporting up to 1,258 people. The population in summer is around 1,100, while in winter it is less than 200. McMurdo is 2,200 miles due south of New Zealand.

A few more facts about McMurdo Station (weather data from Antarctic Connection):

  • Time zone: New Zealand Standard Time (UTC+12) or New Zealand Daylight Time (UTC+13)
  • Elevation: 78 feet above mean sea level
  • Climate zone: Polar desert
  • Average high temperature: 7 °F (-13 °C)
  • Average low temperature: -5 °F (-20 °C)
  • Record high temperature: 49 °F (9 °C)
  • Record low temperature: -59 °F (-50 °C)
  • Average annual precipitation (liquid water equivalent of the snow): 7.5 inches (190 mm)

Current weather: Currently it is winter in the Southern Hemisphere, although spring is on its way. The temperature at McMurdo right now is -6 °F, with light snow falling.  The sun has just risen. Weather Underground says the sun rises as 10:37 am NZST today and will set at 3:16 pm. Tomorrow will be 22 minutes longer.

McMurdo, unlike Amundsen-Scott, which I described a couple of months ago, is not in the middle of a continent of ice at over 9,000 feet high. Weather extremes are not quite as bad as at the South Pole, and the temperature gets a little warmer. However, once the sun sets in the winter, and Ross Island becomes connected to the continent by ice, temperatures can plummet.

Most of this week will be clear with highs between -5 and -11 °F and lows between -31 and -40 °F (over 50 °F below next week!).

You can see the current and forecast weather at McMurdo on the Weather Underground page here.

For more information on McMurdo, here’s a link to Wikipedia. For information on Ross Island, here’s another link to Wikipedia.

Next Tuesday we’ll be back to looking at the weather and climate 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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08.23.10

Hurricane Danielle and Soon-To-Be Earl?

Posted in Tropical Weather, Weather News at 6:14 pm by Rebekah

Danielle was upgraded to hurricane status this evening, with peak sustained winds of 75 mph (satellite image from CIMSS, taken at 2145 UTC, or 5:45 pm EDT).

The National Hurricane Center is forecasting that Danielle will reach Category 3 status (111 to 130 mph), peaking around 115 mph, on Wednesday evening.

Here’s a model intensity forecast again from Weather Undergound:

Danielle remains no threat to land; she should start recurving back north and eventually east by the time she gets east of Bermuda (NHC forecast track below).

Meanwhile, back where Danielle first formed, just south of the Cape Verde Islands, another disturbance is starting to organize. This area of low pressure is also in a favorable area for development, and the NHC believes there is a 40% chance of this system becoming a tropical cyclone within the next 48 hours.

Models show that this disturbance could become a tropical storm in the next few days, if it can hold together that long.

The next name on the Atlantic storms list is Earl.

In the eastern Pacific, Tropical Storm Frank is struggling with wind shear just southwest of Mexico, but is expected to become a weak hurricane after a couple days, once he gets into an area of weaker shear. Frank is not a threat to Mexico, but is forecast to move parallel up the coast towards the northwest.

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08.22.10

Tropical Storm Danielle

Posted in Tropical Weather, Weather News at 3:59 pm by Rebekah

Tropical Depression 6 has just been upgraded to Tropical Storm Danielle.

Some vertical shear and dry air will prevent Danielle from strengthening as fast as was previously expected, but it is still expected to become a hurricane by Wednesday afternoon.

Danielle is moving towards the northwest at present, but is forecast to turn to the west-northwest as it will be steered by a subtropical ridge to its north.

Model intensity forecast, from Weather Underground:

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08.21.10

Norman Microburst

Posted in Severe Weather Post-analysis, Weather News at 11:50 pm by Rebekah

A microburst on the northeast side of Norman this evening left over 500 homes and businesses without power.

I received a trace of rain and heard a bit of thunder at my apartment on the north side of town, but looked at the radar and saw what I thought was just a small, weak thunderstorm. The wind blew a little bit, but only gusted to 32 mph at the airport.

On my way to a School of Meteorology get-together, I saw the road was blocked as a power pole was laying down in the road. Another power pole nearby was snapped about a third of the way up, and all of the traffic lights in that area were either not working or blinking red.

I noticed later that a local storm report for north Norman at 7 pm local time (CDT) read: “FROM 650-700PM NUMEROUS REPORTS OF DAMAGE BETWEEN 12TH AND 24TH BETWEEN ROBINSON AND ALAMEDA. 4 INCH DIAMETER LIMBS DOWN, POWER POLES SNAPPED, SHINGLES BLOWN OFF HOUSES.”

Here’s what the Oklahoma City TWDR (high-resolution radar) looked like at 6:51 pm CDT (from Weather Underground).

It doesn’t look like anything special, but now take a look at a base velocity image for the same time.


Note the area of orange and green between Norman and Hall Park (circled). This is a pretty classic microburst signature.

Negative numbers (green and blue colors) mean the wind is blowing towards the radar (location marked at the white “+” in the upper left), while positive numbers (yellow and orange) mean the wind is blowing away from the radar.

In this case, fairly strong winds are diverging over a small area between Norman and Hall Park. The radar estimates winds of 36 knots moving towards the radar and winds of 64 knots moving away from the radar, equating to 100 knots (115 mph) wind shear over about a 2 mile distance.

A microburst is a small column of rapidly descending air, which hits the ground and spreads out fast. A microburst is a type of downburst that occurs over a very localized area, defined as 2.5 miles in diameter or less. Microbursts/downbursts can occur as a thunderstorm is dying, and are capable of producing straight-line surface winds of over 150 mph.

Finally, here’s a meteogram from the Norman mesonet station, showing how several meteorological parameters have changed over the last 24 hours.

Note several things (this station is near the airport, and not quite on the northeast side of Norman):

  • rapid drop in temperature between 6 and 7 pm (when the storm rolled through)
  • increase in dewpoint at the same time, when it began to rain
  • increase in wind speed and fluctuations in wind direction
  • pressure rise

Also, take a look at the solar radiation plot–the gray area shows the maximum amount of solar radiation that we could be receiving this day, while the orange area shows the amount of solar radiation we actually did receive.

The orange area dips down whenever clouds pass over, and goes back up when it gets sunnier. Now note what happened just as the sun went down–the actual solar radiation was HIGHER than the maximum possible solar radiation! What’s up with that?

As I went out tonight, I saw everything bathed in orange. The sun was just going down, but the storm was to my southeast and the anvil was covering the sky. The sun was on the horizon, so the low beams of the sun bounced off the clouds just right and back towards earth, providing us with more solar radiation than we would have otherwise received.

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Tropical Depression 6

Posted in Tropical Weather, Weather News at 4:02 pm by Rebekah

Last night I posted on a tropical disturbance off the Cape Verde Islands that had the potential to become a hurricane within a few days.

Within the last hour, this system has become organized enough for the National Hurricane Center to upgrade it to Tropical Depression 6 (TD6). The above map shows the NHC forecast track. They have it becoming Tropical Storm Danielle sometime tonight, and a hurricane by Monday afternoon.

The NHC discussion on TD6 mentions “the NHC forecast is close to the SHIPS/LGEM models…showing a large powerful hurricane over the central Atlantic Ocean in a few days.”

Here’s a model intensity forecast for TD6 from Weather Underground, showing the results of 4 different models. Keep in mind that forecast intensity is not always very good very far out.

Category 1 hurricanes have winds of 74 to 95 mph and Category 2 have winds of 96 to 110 mph.

Stay tuned.

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