Grabbing a NOAA weather satellite download

NOAA has a set of older LEO weather satellites that send an analog signal of the the sensor data they receive, one line at a time, and these are easily listenable with modest equipment. I picked up this image from NOAA 18 this morning, just by chance (I had just come in from listening to the ISS repeater and happened to leave the SDR listening on 137MHz). Recording via SDRSharp, WFM modulation, 35kHz bandwidth, gain at 30-40dB with a short vertical monopole indoors. Decoded with the appropriately named https://noaa-apt.mbernardi.com.ar/

Today's sunny and windy weather

Click to enlarge to medium size. The link below goes to the really big image.
Today's weather in Chicago as seen from above via the MODIS imager on the Terra satellite. It was sunny and very windy with winds out of the southwest. It looks like you can see some dust streamers coming out off the lakeshore. Click on the link below for the huge 5200x6000 image with 250m resolution.

http://ge.ssec.wisc.edu/modis-today/index.php?satellite=t1&product=true_color&date=2010_09_07_250&overlay_sector=false&overlay_state=false&overlay_coastline=true§or=USA3&resolution=250m

Credits: http://ge.ssec.wisc.edu/modis-today/credits.html

Haze and smoke from western Canada

Haze and smoke visible in on the visible satellite image for this afternoon might give the less humid weather the next few days in Chicago a tinge of non-clarity.

http://www.osdpd.noaa.gov/ml/land/hms.html

Can you stand it? Cloud footage running backwards

I'm going to be honest:

I can't stand anyone running cloud video footage in reverse. This drives me crazy; whether it's my physics and chemistry of the atmosphere classes or just my sensibilities but whenever I see it it drives me crazy (c.f. Survivor this season). If the cloud droplets are evaporating or condensing the wrong way, anyone with meteorological experience (or someone who has watched Koyaanisqatsi) will call shenanigans. Convection has a distinct look to it; as well as evaporation; and when producers try to reverse the video it shows.

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Las Vegas precipitation

Las Vegas received more rain last week, 1.69 inches, than it did in all of 2009, when it received 1.59 inches. The "average" is about 4 inches annually. If the rains continue into a full El Nino style winter, the area will bloom green in spring with the normally brown/gray mountains turned into green.

Source: http://www.lvrj.com/news/breaking_news/Rainfall-expected-to-taper-off-today-82379942.html

Redoubt volcano: image of the week

This is definitely the image of the week for the Redoubt eruption.


This is from a Japanese weather satellite staring at the Western Pacific, and the volcano is near the limb of the Earth from its perspective.
Picture Date: March 26, 2009 17:30:00
Image Creator: Dehn, Jonathan / NWS

Raft

My time has been taken up with four friends of mine who are building a raft. Building a raft to travel from Chicago to New Orleans. I've been helping out as my schedule allows, although I took a few days off recently to help out on moving the preassembled parts from the backyard of a Hyde Park apartment to the Croissant Marina on the Little Calumet River. (This marina is a great spot--amazing for the friendliness, the methane purgers on the other side of the river, and the barges passing silently by). The weather gods have not been kind though. The majority of the water on the Little Calumet is effluent, and this weekend Chicago received the highest one-day precipitation event ever, AND the remnants of Hurricane Ike, in two separate rain events. In the scheme of things, it was so bad they opened all the normally closed locks that keep the Chicago river and canals from flowing into Lake Michigan. So, our previous spot at the marina is now covered in combined sewage and storm output by ten feet. It put a damper on the weekend for a lot of people; a lot of people are flooded out of their basements and apartments. Ryerson Observatory reports almost 11 inches of rain in the past seven days.

While we now have a 16ftx32ft raft, we still need to mount the 35hp motor and construct the cabins and hammock supports for the travelers. Try this link for construction photos. You might be able to see it without a facebook account--I'm just dumping stuff without much editing.

When in doubt, blame the instrument: It wasn't the lightning.

The WGN Weather blog shows a video from Bucktown of the intense thunderstorm of August 6th here: http://blogs.trb.com/news/weather/weblog/wgnweather/2008/08/incredible_viewer_video.html, but they claim that the nearby lightning strike at the end of the video actually produced arcing close to the camera. That wasn't the case. The "arcing" is actually an artifact of the CCD sensor in the video camera. To understand what's going on, you'll have to deal a little bit with the physics of CCDs. In silicon, incoming photons will excite electrons out of a lower energy state and into the "conduction" band where it can then migrate through the material. You can call this liberating the electron. In a CCD control voltages create zones where these freed electrons are trapped in the silicon until they are moved out and measured. Those zones are best known as pixels. Depending on the type of CCD, when the exposure is over, the electrons are moved pixel by pixel in columns to be read.


Intensely bright sources of light will produce so many electrons that they will overwhelm the control voltage and flood out of the pixel and into the surrounding pixels and circuitry, producing spurious effects. You've probably seen these effects -- it starts showing up at 1:57 in the Yeah Yeah Yeahs video for Maps for example, or in the SOHO image above (it's Venus doing the blooming).
In this case the electrons flow out and down the columns that the electrons would normally be read. The Sun is a great source of column bleeding in a lot of videos online: see this one, for instance. Or bright stars--here is a weak version (it's the faint vertical column, not the diagonal streaks):


Since it's difficult to control all the sources of light in any possible photo scene, the CCD manufacturers have ways of trying to mitigate the overflowing electrons. One technique is to put drainage canals around the pixels and dump the electrons. This is good, but the extra space for drainage costs you some light sensitivity and light measuring accuracy.


Another problem can develop while you are moving the electrons off the CCD to be measured--if you have a shutterless camera, then light is still hitting all the pixels and can still cause overflow problems. One technique (used a lot for video cameras, at least in the old days) is to make the CCD twice as big with half of the chip covered up. At the end of the exposure you quickly move the electrons in the lit part over to the dark part and then leisurely read them out. This helps, but you can still have those overflowing electrons come down into your dark area.

So, in the lightning video, you can see that the extremely bright strike produces too many electrons in the CCD of the camera, and they flow 1. into the dark frame-transfer area and 2. down the columns (the vertical bleeds).
You can see at least one of these effects in some of the other strikes in the video.

In case of weather emergency in Chicago

Rely on WFLD, Fox 32, for your severe weather information. Do not expect the otherwise stellar Tom Skilling at WGN to give you info until well after the threat passed you by. This is born out by the south suburban tornado in June and yesterday's severe weather, which I watched out the window while downtown during round 1 and in Hyde Park during round 2. Telling the bartender to switch to WGN offered no new information other than the county was under a tornado threat--and that was obvious from watching the Cubs game. Watch the line organize here.

Why you shouldn't stop a sports game because of weather

Tom Skilling writes in the WGN Weather Center Blog:

The rain ended, and the game continued on a sloppy field.
With the Pittsburgh Steelers leading the College All-Stars 24-0 late in the
third quarter the heavens opened up again as severe thunderstorms struck.
Winds gusted to 64 m.p.h. as the rain fell in torrents. The game was
stopped, but as the players left the field unruly fans ran out and knocked
down both goal posts. Even though the rain let up the game was cancelled. It
was the last College All-Star game ever played.

Football is the sort of sport that shouldn't let weather get in the way of the game. I guess the fans agreed. Kudos to WGN for the last two sentences--a tale to remind ourselves of true grit and/or moral turpitude.

Sudden cold front temperature change

A fantastic wind shift and cold front passage last night dropped temperatures by twenty degrees Fahrenheit in the course of a few minutes. As is common here, the cold front used the lake as an expressway south to accelerate and end an otherwise warm and humid Memorial Day. As experienced by me, a quiet warm night suddenly grew loud as the trees shook, then a blast of cold air blew through my open windows in a gust. Another account.

This data is from the Ryerson weather station.
--Timestamp--- Temp Humid Dewpt Wind HiWind WindDir
20080526 19:30 80.6 57 63.9 8 18 247
20080526 20:00 79.8 58 63.7 6 15 247
20080526 20:30 79.0 61 64.4 5 13 270
20080526 21:00 78.2 63 64.6 4 13 247
20080526 21:30 77.6 66 65.3 5 11 247
20080526 22:00 76.8 67 65.0 5 11 247
20080526 22:30 76.1 69 65.2 4 11 270
20080526 23:00 54.3 73 45.8 10 35 270
20080526 23:30 51.9 78 45.3 18 41 0
20080526 24:00 48.8 82 43.6 18 33 0


One of the few storms that popped up on the warm side earlier that evening
Is this cloud from the cold air bumping the warm humid air up and out of the way?

Weather on campus

The Ryerson Astronomical Society got SG funding for a weather station on campus, to get accurate weather data (which is really important in the spring with lake breezes freezing the lakefront while Midway is warm). We finally overcame all obstacles last night and have the station live at http://sagan.uchicago.edu/. I believe we have other delivery vectors to set up, so it can be seen at the Reynold's Club TV screen and such.

Freezing rain

I went out Saturday evening into the freezing rain because I was out of vermouth. Actually I was out of good vermouth, which is as bad as being completely out. So a trip to the good wine/spirits store ensued despite the worsening weather. Earlier in the day there had been a intense but short burst of snow that left a half-inch everywhere. Then it started sleeting, and when I left my apartment it was raining. I thought innocently that the liquid water was good, as it would melt the snow. But as I continued I realized the rain was a silent evil--it was freezing rain, icing anything it hit. Running my hand over a car window showed the rain was freezing as soon as it hit the glass. It's beautiful in addition to being evil as the trees began glazing over--even fallen, rotting leaves were gorgeous, covered in a glossy encapsulation. A flat glass covering a light became scalloped with ice so well that it appeared as if the glass was installed that way, and it wasn't obvious until I saw the flat glass on another pane.

The WGN Weather blog has a description of the processes and temperature profiles that define what precipitation you get in a winter storm such as Saturday's. In nearly all precipitating clouds the precipitation starts out as ice crystals. Depending on how the temperature increases towards the ground you can get snow, rain, or some bizarro type. The storm started cold--it was cold from the top to the bottom, and so the precipitation was all snow. As the storm progressed warm air from the south increased in the midlevel altitudes, melting the snow, but the air close to the ground, where the wind velocity is not so high, was still cold, and the rain droplets (ex-snow crystals) refroze to fall as sleet. Then, as the warm layer got thicker, there wasn't enough cold air to refreeze the rain, leaving it liquid and falling to the ground (which still was below freezing) as freezing rain. Finally later in the evening the cold air on the ground was whisked away and we had just a cold, but liquid, rain.

Snow tracks

Today's visible NOAA satellite image of the Chicago region showed the remnants of two snow bearing systems, one a big snow system on Friday night, which moved from the SW to NE, the other a set of lake effect snows extending southeast from Lake Michigan into Indiana. The lake effect can be seen here.
The image is courtesy of the University of Wisconsin's Space Science and Engineering Center, which provides great images for those of us near Madison.