Feeds:
Posts
Comments

Posts Tagged ‘warm front’

Assignments #4

Assignments:

First of all, notice the weather. Record your observations for us to discuss.

Then, because the more you know the more you notice, study the next chapter(s) in your books.

Eric Sloane’s Weather Book ch 4-5

These two chapters are so short, you can read both. Since you have 14 chapters, we’ll be doubling several times.

Chapter 4

Sloane compares isobars — lines going along the spatial geography of similar barometric pressure — to elevation lines on a topographic map. Since you probably haven’t seen topo maps, that may not be a completely simple idea, but I think he explains it well. After you read the chapter, find a newspaper or other printed weather source and find the isobars. Bring a copy to class so we can look together at the maps and be sure everyone has the idea clear.

Chapter 5

Sloane describes the Coriolis effect. Be sure to study the cartoons — notice that he divides his drawings between the folktales and some unexpected observations. Sloane’s cartoons have lots of information. What does he say about riverbanks? Is there a place near Sioux Falls where you can get a picture of a riverbank eroded on the right more than the left? (On the river’s right as it comes downhill.)

I think you will appreciate Sloane’s drawing of the sledder who slides to the right going down the mountain, and then, aiming to the right, finds himself in a left spiral as he goes into the circular valley. Look at it very carefully, so you can remember how it works.

While we’re talking about unexpected Coriolis effects, go to this website: http://tafkac.org/science/coriolis/coriolis_force_tyson_debunking.html

The whole thing is worth reading, but scroll down maybe 1/3 of the page for a little piece on an engagement between the British and the Germans during World War I, near the Falkland Islands. (You can do a word search for “Falkland” if that’s an easier way to find it.) What happened here?

Chapter 4: Storms and fronts

page 47-48 — if your book is two pages off, sorry. First two pages of chapter 4…

So what is a front? Very simply, it’s the front portion of a mass of moving air. Weather people talk about a front as if it were some kind of object – it’s just the front end of the incoming weather – and being in front, it’s where the action is.

Notice the interesting story about Benjamin Franklin’s investigations of a storm. He was a first-rate scientist and gave up that career to serve our country. Thanks, Ben.

page 49

Cold front, warm front, occluded front. The warm and cold fronts are easy. The occluded front is more of a challenge. He says that cold fronts don’t often catch up with warm fronts, but then what’s that on page 56-57 where that’s what’s on the map? Anyway, the point is that cold fronts travel faster, so… So I don’t know how often, but sometimes.

pages 50-51

What’s the Beaufort number for winds at 100 mph?

pages 52 – 53, then 54 – 55 (or so)

(I discovered in class that we have different page numbers.]

Anyway, Williams has a two page spread on  a warm front moving across the US, followed by a cold front. Take some time with this diagram. Then he has another two-page spread on the same storm becoming an occluded front.

pages 56-57

More discussion of weather that travels and of the interaction between upper and lower winds. Notice that the cold front seems to have caught up with the warm front…

pages 58-59

This is an inset piece on a specific storm which added high tides to its fury. In an interesting interplay between water and air, between meteorology and astronomy, the storm hit at the very time when tides were high anyway because of the positions of sun and moon. Really, you never know what’s going to be important in a storm.

pages 60-62

The chapter ends with a discussion of the interaction between upper and lower air during a storm. Upper and lower winds do not always go the same direction.

Advertisements

Read Full Post »

Cold front, Warm front

There’s a family camping trip this weekend, and most of you are going, so of course everyone wants to know about the weather. Guess what. I can’t predict the weather!

But I can tell you a few things.

First off, you remember how cold it was last week, when I was getting well into Corey’s story? Remember how bright the skies were? Brilliant blue all day and sparkling stars all night? That’s the sky when cold air has moved in – really clear.

Then the blue, daytime skies gradually got paler, meaning full of high cirrus that you couldn’t really see, but it scattered the sunlight. Then we had a day that it clouded all over; and the next day it rained, all day, but pretty gently. That’s your basic warm front pattern, meaning the pattern of weather when the front end of a warm package of air moves in. We’ll study it more later on.

Anyway, now the warm air is here, and it’s going to lift up some of the moisture in the soil and keep the air full of humidity. So when the weather man says it will be clear or partly cloudy and mostly warm, I believe him. That’s what to expect if a big package of warm air has just arrived. The only thing that could change it would be a sudden cold front (they’re pretty much always sudden) and I don’t expect that.

Why not?

Well, look at the map of the jet stream. (You have to feed in the year, the month, and the day and how many hours apart you want your images. If you tell it to start in August (21 days ago) and ask for 21 days with 6 hour intervals, you can get a really amazing animation.) It looks like a bunch of otters and things swimming around the northern part of the globe. (I thought the jet stream was like a river or a swaying band, but it’s more like various sizes of graceful diving and slithering creatures moving along in an invisible stream that keeps changing course. Every now and then, a mouse runs in from some southern tributary.) Right now, there is no jet stream activity near us. The cold air we had is a Loch Ness monster way out to the east (headed for Loch Ness, maybe) and other segments of the jet stream are way up in Canada or way west near Seattle. The jet stream is the main way that big pockets of cold air come our way. Maybe it’s the only way; I don’t know.

Anyway, no otters of cold air in the vicinity, not even a baby one. I hope the sky is clear enough for star-gazing, but it won’t be the best sky.

Well, but maybe it will. When you start out with star-gazing, it can be confusing to have so very many stars. (Which one is she pointing to?) And the moon rises very late this week, so that won’t be washing out the starlight. I think we’ll have a good time.

 Song of the Sky II

I found the story of the generals in Guy Murchie’s Song of the Sky. It’s near the end, page 393-404 – 12 pages. It’s a month before the Battle of the Bulge, and this pilot’s got “18 American generals” who’ve been consulting with General Marshall at the Pentagon. As I said, the clouds close in earlier than expected, along with very high winds, just as they complete the Atlantic crossing, and they can’t see a thing. Suddenly they’re over Norway instead of England, so they come back south, still blind, pick up the signal from their airport about 4 hours late and then the pilot realizes they don’t have the fuel to get there. He needs to remember the radio frequency for pilots in distress looking for any nearby airport; he’s never used it. “O God, help me.”

“4220”

“Thanks.”

He contacts the airport and prepares to land, but runway is in blackout and the tower almost forgets to turn on the landing lights. One engine sputters out. The lights come up. The second sputters as they land. The last two shut down at the end of the runway, five hours late and 80 miles north of London.

On such fine thread was the fate of the world hung.

I bet they never put that much brass into one airplane again.

Read Full Post »