03.29.11
Posted in Non-US Weather, Weather News at 8:00 am by Rebekah
This week’s post in the global weather and climate series features Nairobi, Kenya.
Nairobi skyline, from Wikipedia
Nairobi, just south of the equator, lies on the Nairobi River in south central Kenya. Kenya borders Lake Victoria and the Indian Ocean. Founded as a rail depot in 1899, Nairobi quickly grew and became the capital of British East Africa in 1907.
Today, Nairobi is the capital of and largest city in Kenya, as well as the largest city in east Africa. The population (2009 census) is 3.1 million. Well off financially, Nairobi welcomes many tourists each year. The primary tourist destination is the Nairobi National Park, including giraffes, lions, and rhinos. Nicknames for the city include “The Green City in the Sun” (from the vegetation and warm climate) and “Safari Capital of the World” (from the popular safari tourism).
A giraffe in Nairobi National Park, bordering the city of Nairobi in the background. From Wikipedia
A few more facts about Nairobi (from Wikipedia):
- Time zone: East Africa Time (UTC+3)
- Average elevation: 5,450 ft (1,661 m)
- Climate zone: Subtropical highland
- Average high temperature: 74 °F (23 °C)
- Average low temperature: 54 °F (12 °C)
- Average annual high/low temperature range: 69 to 78 °F (21 to 26 °C) / 50 to 57 °F (10 to 14 °C)
- Average annual precipitation: 40 inches (1,024 mm)
Weather: As Nairobi is near the equator, the city experiences fairly warm daytime temperatures throughout the year. However, the city is over a mile above sea level, so nights can be quite cool.
The rainiest months of the year are March through May and November through December.On average, the months of July and August each receive less than one inch of rain.
We’re going into the wettest month; April receives, on average, 8.6 inches of rain over 16 rainy days.
This week is forecast to be especially warm for the area, with highs in the low 80s and lows near 60 °F. Rain is in the forecast for Tuesday through Thursday (it has already been raining there for at least the past week).
For weather maps and information on current and forecast Nairobi and Kenya weather, see the Kenya Meteorological Department, Weather Underground and Weather Online UK (global maps and models).
For a bit more information on Nairobi, here’s a link to Wikipedia.
Next Tuesday I plan to take a look at the climate and weather in another part of the globe. As always, if you have any suggestions for future cities, please leave a comment!
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03.28.11
Posted in Weather Education at 8:00 am by Rebekah
Last week in the weather education series we looked at weather satellites. This week we’ll wrap up meteorological measurements with lightning detection networks.
This discussion will be limited to two lightning detection networks: the U.S. National Lightning Detection Network (NLDN) and the 3D Lightning Mapping Array (LMA).
National Lightning Detection Network
The NLDN, established in 1989, is a network of over 100 sensors spread across the United States (there is also a similar lightning detection network in Canada, and together the networks are called the North American Lightning Detection Network).
Put simply, the sensors detect electromagnetic radiation from lightning ground strikes (cloud-to-ground, or CG flashes). The time of the strike, strike location, current magnitude (i.e., strength of the strike), current polarity (e.g., positive or negative), and number of return strokes is recorded for each observed CG flash. The strike location is determined by triangulation.
Map of the NLDN sensors. There are two types of sensors indicated on the map.
3D Lightning Mapping Array
There are currently three 3D lightning mapping arrays (LMAs) in operation in the U.S., all set up under the direction of New Mexico Tech. The LMAs are located in New Mexico, central Oklahoma, and northern Alabama.
My work in the lightning research department at the University of Oklahoma has dealt extensively with the Oklahoma LMA, run by a group in the National Severe Storms Laboratory.
The OK-LMA consists of 11 stations in west central Oklahoma, each of which is equipped with a very high frequency (VHF) antenna, to detect the radiation produced by the lightning, and a time-of-arrival sensor, to determine time and location information about the VHF radiation points from both intracloud (IC) and CG lightning flashes.
We can then use this VHF data for various purposes, such as finding out where and when the lightning flash initiated. This was a large part of my research for my M.S. degree.
The plus symbols show the location of each LMA station in Oklahoma, the orange circle shows the range of the 3D LMA, and the yellow circle shows the range of the LMA for just 2D data (the inner, pinkish to blue circle is the range of the polarimetric radar KOUN).
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Next Monday we will move on to weather maps!
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03.27.11
Posted in Uncategorized at 8:00 am by Rebekah
Which state do you think has had the most tornado reports so far in 2011?
You might be surprised.
Here’s a map from the Storm Prediction Center showing the location of tornado reports in the U.S. so far, not including the few Georgia tornadoes from yesterday (keep in mind that this is a preliminary map, and not all tornadoes are reported, just as not every report turns out to be a tornado):
The answer is Louisiana!
Louisiana has had 28 tornado reports. Tennessee came in second, with 23 tornado reports. Alabama and Iowa are tied at third, with 18 tornado reports.
For more state statistics on severe weather reports, check out the Storm Prediction Center’s Annual Report Summary for 2011:
http://www.spc.noaa.gov/climo/online/monthly/2011_annual_summary.html
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03.26.11
Posted in Severe Weather Forecast at 8:00 am by Rebekah
I feel like I’m the only storm chaser who has only chased one day so far this year. I know that’s not true, but a number of chasers have already bagged multiple tornadoes and storms.
To be fair, there really haven’t been any good setups yet in my early season chase region. Before April (or really even May) I don’t like to spend too much gas money on risky setups outside of southern Kansas to northern Texas (including the Panhandle), and I don’t usually chase east of I-35 (at least in Oklahoma).
So the question remains: when will the next good chase setup present itself for the Southern Plains?
The following 500mb map from 00Z last night (from the Storm Prediction Center) shows rather weak shortwave troughs in the Northwest into the southern Rockies and in eastern Canada, while there’s perhaps a bit of ridging going on in the south central U.S. Not too exciting.
The GFS and NAM models (model observations are based on 00Z runs) do show that the trough in the West will begin to strengthen and dig further south tomorrow. By Monday evening, the models show the trough over Utah with an elongated surface low over northeastern New Mexico and the western Texas Panhandle.
The GFS is a bit more bullish on moisture, as south of the warm front (along the Red River), dewpoints are in the mid- to upper 60s in central into eastern Texas, while the NAM only has these dewpoint values along the Texas Gulf Coast.
The GFS solution for Monday is a bit interesting, but still not enough to tempt me, unless it starts to look better and perhaps sets up a tad further north and west. Also, it looks like the moisture depth will be pretty shallow.
00Z GFS 72-hr forecast for surface pressure and dewpoints, valid 00Z Tuesday (Monday evening), from TwisterData
By Tuesday evening, the GFS shows the trough will have moved on to Missouri. Tuesday may wind up a bigger severe weather day for the lower Mississippi River Valley.
On Wednesday, the GFS indicates another trough may be digging into the southern Rockies, but the model indicates that moisture will be even worse than on Monday, so the chance of storms appears slim at this point.
It also looks like after the Wednesday system, northerly winds will prevent us from getting much moisture return any time soon.
There may be another slim chance or two for severe weather the following week, as some meager moisture may be present in Texas, but it still doesn’t look any good and is too far out to say anyway.
One thing I would bet on, though: I would bet that there will be a good Southern Plains chase day or two (maybe the first outbreak) while I’m in Florida the third week of April. However, I know it won’t bother me as there will always be more tornadoes…but there will only be two more shuttle launches!
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03.25.11
Posted in Astronomy, Photography, Space Shuttle at 8:00 am by Rebekah
When I go down to Florida next month to view the launch of Space Shuttle Endeavour (STS-134), I would like to watch as much of the launch as possible through my own eyes, rather than through a camera lens.
I want to take photos and videos of the launch, though, but I don’t want to mess with too much stuff (i.e., adjusting multiple tripods as the shuttle goes up).
Enter the idea of a tripod plate that will mount to one tripod but allow multiple cameras/camcorders to be attached.
I know you can buy these, but they can be pretty pricey, and I figured it might be better and cheaper if I just made one to suit my own purposes.
I’m sure there are better ways of doing this, but here’s how I built my tripod plate for less than $12 and in about 30 – 45 minutes.
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- Supplies (prices listed are from Lowe’s):
- hardboard pegboard (3/16 inches by 2 feet by 4 feet) – $4.92
- four 3-prong T-nuts (1/4 inch – 20 thread; 7/16 inch barrel height) – $2.30
- four bolts (1/4 inch – 20 thread; 40 mm long) – $3.53 (I only used 3, but they came in a package of 4…also, I’ll probably be getting shorter bolts soon as these are a little long for the width of the board)
- Measure pegboard and use a pencil to draw the size (I started with 16 x 24 inches, to leave a margin of error, but may cut a bit off later)
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- Cut it out
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- Insert a T-nut into the center of the board; the bolt in the tripod’s quick-release plate will screw into this nut. I used a knife to make the desired hole a bit wider, then used a hammer to pound in the T-nut
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- Place T-nuts in other desired holes in the board, for cameras and camcorders
- Screw bolts in the other side of the holes (using an Allen wrench, if necessary), through the T-nuts and into the screw holes on the camera devices, and that’s it!
A few thoughts:
- Make sure the weight is distributed right; my tripod plate leans very slightly to one side, but is better as I pan the tripod head up. I have thought about attaching some sort of weight to the plate to balance it out, but it’s not too bad so I may wind up leaving it.
- My bolts are a little long; as you can see, they stick out the bottom a fair ways. I will probably look for shorter bolts before going to Florida. While these bolts may be alright, the camera/camcorder may wind up rotating a tad when you move the plate up and down. However, this could also be an advantage, as I might want to move the camera/camcorder from side to side a bit.
- I thought I might to need to build a back for the plate, to give some support to the cameras/camcorders as the plate tilts up. However, the T-nuts and bolts are more than sufficient to keep the camera devices from sliding around, so this may not be necessary.
- I still might want to cut more off the back end of the board, but I like that it’s big enough to have the camcorder LCD screens open and long enough to support a longer camera lens (I will be putting a longer, telephoto lens on for the launch).
I’ll still have to do more testing, and practice using it, but so far I’m pretty pleased with my new tripod plate. Now I should be able to take photos (I can use my remote control for my DSLR), HD video, and possibly stream video with another camcorder, all while only adjusting one tripod!
I’ll let you know how it goes after the launch!
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