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Springing Along

The past few weeks have proved a questionable spring. Temps failing to reach 60, frozen precipitation, a sun missing in action….can’t rely on Midwest weather to be on a consistent time-table.

At least two of these mentioned will be absent this week. Perhaps the most justifying, rain and warmer weather will arrive.

Rain is no stranger so far this Spring. A nice dose of 2+ inches across the region last week has us well above normal for the year(yellow line). Rain is again in the forecast for the week. Rainmakers will appear on Monday/Monday Night, as well as heading into Thursday when conditions may threaten for some severe weather along the Michigan/Ohio border. This will need to be looked at as the week progresses. Through next Saturday, a good two inches of rain could fall in already saturated areas, so flooding will again be possible.

Grand Rapids climate graph of 2013 so far.

At least the precipitation will be in liquid form. Sleet was reported in southern Michigan on Sunday, and Central Michigan University campus had a delayed start on Friday thanks to a sleet/freezing rain combination Thursday evening. That event may have been worse had the days leading up to the storm not been above freezing. Ground warmth did a good job at fighting off ice accumulation on surfaces. Trees don’t harbor this ability as well, and ice on the branches was evident while out and about on Friday.

Warm weather will filter into the region with our rain producing pattern. A ridge will amplify over the Midwest, and the warm air will be allowed to travel north. However, with that transport is the mentioned moisture. Temperatures will start in the lower 60s for Monday, and top out in the mid/upper 60s on Thursday. Once we have our stormy day on Thursday, the associated cold front and trough will bring in some cooler spring air, but still above freezing during the day. Yay progress! Hang in there!

Severe Weather Tips

As daylight becomes longer and temperatures get warmer, we move into our yearly cycle of weather changes. Snowstorms become rain and thunderstorms, and there is plenty to take note of as we head into another year of severe weather.

As produced by National Weather Service offices around Michigan, April 7-13 is Severe Weather Awareness week!

Earlier in March, I was remembering the unique events that launched Spring 2012 into a craze. We had record temps into the 80s, and multiple tornadoes tear across eastern Michigan. It was a very interesting start to the year, and it kept you on your toes for forecasting and figuring out just what the heck is going on up there! While Spring 2013 is moving in like a lamb, that lion could be waiting right around the corner, and being prepared is a priority.

Greg’s Tips for Severe Weather

NOAA Weather Radio
This is the single most valuable thing you can have for warning during a stormy day! We absorb weather through many sources these days; internet, TV, radio, word of mouth. When the winds start brewing and the power goes out, many of these reliable sources are cut down. Even if you have a backup generator, chances are your media services(internet/cable TV) will not be powered in your area. Having a battery-powered weather radio can keep you up to the minute warnings and weather information. The warning signal usually beats web updates by a few minutes as well. Weather Radios are also a hero at night if the house is asleep and dangerous weather is near. Keep them charged with batteries nearby!

Know Your Surroundings
This goes along great with the weather radio. While forecasters may get as specific as calling out road names and cities where the storms are near, you should also know the County names surrounding your location. Storms typically move West to East, sometimes SW to NE, sometimes NW to SE. Bottom line, know where you are relative to where the storm is. If you think a dangerous storm is going to miss you, do not take it for granted. Supercell thunderstorms are known to waver on path, and sometimes can change direction. Be prepared for anything!

Skywarn Classes (http://www.nws.noaa.gov/skywarn/)
These are great chances to learn about weather a little more in detail, and refined to severe weather scenarios. They are free, and usually run by a few forecasters from your local NWS office. That means they are run by the folks that track and watch for storms on a daily basis and know what to look for. You will go over everything from how to report weather threats to authorities, to determining if that ominous dark cloud is a wall cloud or shelf cloud(important!). Usually there is a great Spotter’s Field Guide that is handed out for quick reference, there is an online PDF version available here. Once you have learned this material, you become a very valuable resource to forecasting as you are an eye witness to the weather in your area. As useful as that is, always make sure your safety is first! NEVER put yourself in danger to get a report.

Know Your Clouds
As mentioned previously, knowing the difference between clouds can mean loads for the weather to expect. Low flying scud could prompt you to call it a wall cloud(precursor to tornadoes), but is that cloud rotating as well? Is is attached to the base of cloud above it? How about those shelf clouds that take up the entire horizon? Much of this is detailed in the Skywarn classes, but this is something that can help you out in a fix, and impress others.

Example of a wall cloud just SE of CMU campus back in May 2011.

Heed Warnings
“Yea, that storm is way far from my house, I don’t need to pay attention.” Always take note of Watches/Warnings. Along those lines, know the difference between a Watch and a Warning.

Severe Thunderstorm Watches and Tornado Watches mean conditions in the atmosphere are favorable for that type of weather to develop, so be ready for storms later in the day, or within the next couple hours.

Severe Thunderstorm Warnings and Tornado Warnings mean a severe storm has been spotted/identified, and is tracking along the specified path.  Take appropriate action immediately if you are in the track of the storm.

Again,
Watches = be ready for storms soon/later in the day
Warnings = take action immediately if you are identified in the path of a storm

A disclaimer I must make about the blog; Greg’s Weather Blog is not a good source for immediate severe weather forecasting! Please do not rely on this page for up to the minute information on storms! Head to http://www.weather.gov for that, and type in your Zip Code to find yourself quickly and any Watches/Warnings that are in effect.

Take care out there!

Tracking Down Fallstreak Holes (with some VIIRS Day/Night Band imagery)

In mid January, I went on a bike ride around town due to pleasant temperatures in the mid 50s. On my way back, I looked up at a progressing layer of altocumulus to see a giant bald spot.

Fallstreak hole!

I pondered for a little while over what it was, but I had a suspicion. As the shape held together, I knew it was a fallstreak hole! These are pretty rare but certainly catch the eye since it is a good patch of blue sky surrounded by a deck of cloud.

I knew planes were a common trigger of these because of the air mixing they cause flying through a cloud layer. Just 15 minutes ago I saw a low plane fly by and I wondered if it was caused by that. Once I got home I looked at a visible satellite view and spotted a pretty good train of fallstreak holes across central Michigan. They seemed to be on this lip of altocumulus cloud, ahead of thicker stratus clouds associated with a tracking low pressure system. With this pattern, I doubt a plane would have caused these holes. But it will remain a mystery.

Since I lost that specific image of the visible satellite view. I went digging.

NOAA CLASS (Comprehensive Large Array-Data Stewardship System) is a great resource for looking at archived satellite images. Anything from popular GOES imagery to the new Suomi VIIRS satellite images can be ‘ordered’ and downloaded. It is a large site, and it takes a little while to understand it and navigate. However once you get that crisp satellite image, you’re hooked!

Anyway, a week later I went to CLASS and started narrowing down my search results (you can easily get bogged down in hundreds of thousands of images if the search isn’t spot on). I selected the region over the Great Lakes/Michigan, and selected a time period of 2 hours around when I saw the hole from the ground. I ordered the 800mb file and got it downloaded.

The VIIRS images are .h5 files, so they must be viewed in a compatible program. I found HDFView to be a simple, free utility. What did I get? An image of some place with a bunch of clouds on it.

Where in the world am I?

Now the search features on the website had me select a region on a map to narrow down where I want an image, so I knew I must be somewhere in the upper U.S. A few features on the image stand out, so we can to match these up with a map with boundaries on it.

Looking at the details of the surface on the bottom left, it has a good consistency and it appears to have cracks on it, so this was possibly a frozen-over lake…a large one. At this time I still believed it to be a usual North at the top image. But was this really true? I went to Google maps and started searching for clues. That other patch of undisturbed white in the middle of the image almost looks like Lake Michigan, but that can’t be right. It is definitely another body of water however. Where am I?! Am I even on Earth? Then I had a breakthrough. Matching the coast line of that large lake, I noticed how there was a sharp point that pointed towards this other vertical ‘lake’. Sure enough things became clear, I was holding the treasure map upside down. This stock image was flipped 180 degrees (possibly because of ascending and descending orbits of the polar-orbiting craft, similar to MODIS), and the large lake I am looking at is a frozen over Hudson Bay with adjacent Lake Winnipeg.

Mystery almost solved!

Locating Lake Winnipeg, I cruised east and there was the upper portion of the mitten. Thunder Bay is pretty recognizable on the north-eastern tip.  These images are high-resolution, so you can zoom in a get nice details. Bingo, there’s our fallstreak holes! This was taken at roughly 2:19 pm EST, so it was about 20-30 minutes before I saw the hole over Mount Pleasant.

Zoom in towards the lower right hand side shows northern Michigan peeking through the clouds.

This was a really cool find, and will definitely be using this method to document past weather events in the future!

Three views of Hurricane Issac in the Gulf of Mexico. One of the great abilities of having an archive of data, is to revisit notable event dates.

When Big and Little Combine… (Feb 7-8, 2013 Snowstorm)

A progressing shortwave, similar to our recent clipper systems, will cut down from Canada Wednesday and merge/phase with a longwave trough moving across the continental U.S. This interaction will ensure moisture transport from the deep south into the Great Lakes region, amplifying precipitation amounts in the area. In this way, it is different than our previous shots of snow.

This is a good example of how tricky weather can be. This past weekend, the storm was little more than a trace-3″ disturbance, now it threatens to bring triple that amount to some locations of the state. Quite interesting to see models not show agreement, and then all of a sudden snap in line with each other. Euro had this solution previously, and the GFS/NAM had come into agreement by Tuesday morning. This actually falls near a date back in 2008 when much of mid-Michigan had a 1-2 punch of snowfall:

On February 6, 2008, a snowstorm hit most of Southeast Michigan. Widespread amounts ranged from 6 inches across central Livingston, Oakland and Macomb Counties to greater than 10 inches for all of the Flint (11.3 inches at Bishop Airport), Tri Cities (12.0 inches at Tri Cities Airport)and Thumb regions. Areas across the southern Saginaw River Valley were dumped with 16 to 18 inches of snow from southwest Saginaw to Birch Run to Vassar. -Detroit/Pontiac National Weather Service

Accumulation wise, central Michigan and lower Michigan look to be in the cross-hairs for persistent snow beginning Thursday morning and continuing through to Friday morning. There is some discrepancy between the GRR(Grand Rapids) and DTX(Detroit/Pontiac) forecast offices. as to what the heaviest snow amounts will be. My experience is that GRR likes to over estimate snow accumulations, and DTX likes to hold a conservative line on accumulations. Typically with winter storms, you get little pockets of the high accumulations, but they are not as widespread as the forecast covers. These higher amounts will also depend greatly on how consistent the early snowfall is. Therefore, I believe isolated areas across mid-Michigan will receive 9″ or 10″, but most locations across mid-Michigan will see 6-8″. Along the I-94 corridor, a good swath of 3-6″ seems like a good bet as they will get high intensity snowfall, but for a shorter duration. With warmer temperatures moving into the region, this snow will have a wetter characteristic compared to lighter dry snows this past week.

Snow will begin to trickle in Thursday morning for central Michigan. Snow should then continue through the day, intensifying in the afternoon. Overnight, snow will be at the strongest. This leaves little time for morning commuters to have  a clear surface, and roads will likely be covered and treacherous  Further south in the state, the initial snow will not begin until the afternoon/evening on Thursday, thus lower amounts are expected. However, once the main portion of the system is over the region, heavy snows will be occurring  and accumulation rates will be high enough to cause transportation issues.

The Detroit forecast office has a great briefing of timing, expectations, and other facts about the storm available to view in a PDF document online here.