ThompNickSon

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About ThompNickSon

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    http://home.earthlink.net/~nickthompson/naturaldesigns/

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    Central MA/ Santa Fe, NM
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    I am a retired evolutionary psychologist who wrote some about the philosophy of my field. Apart from my lifetime interest in the weather, having grown up near the Worcester Tornado and the Massachusetts hurricanes of the 50's, I have a general interest in the philosophy of analysis and prediction.
  1. So, here is another example of a forecast of showery weather due to an elevated COLD pool. BY THURSDAY THE COLD CORE IS DIRECTLY OVERHEAD. SO WEDNESDAY IS A TRANSITION FROM STRATIFORM TO CONVECTIVE...THURSDAY MAINLY CONVECTIVE. SUFFICIENT INSTABILITY BOTH DAYS TO INDICATE A CHANCE OF THUNDER. I will try to remember to post a skewT on Thursday, if this thing verifies. The synoptic situation is an upper low to the west of NE which will spawn a coastal low for Wednesday and move over NE bringing with it said "cold pool". The result is chilly showery weather. Like elevated mixed layers (which are warm, but very dry) an elevated cold pool seems anomolous because relatively cold air is relatively dense. I assume, therefore, the air in a cold pool is conditionally cold ... i.e., it's cold relative to what the air below it will be when heated by the sun on thursday. (Cold here, always refers to "potential temperature".) Hence the prediction of convective showers. N
  2. Dear Calm_Days, While I have your attention, I am wondering if you or anybody else had had any thoughts about my query concerning elevated COLD pools. We have one of those bearing down on us in Massachusetts right now, and the prediction is for cold clear nights and showery cool days. As usual, I wondering, if they are colder (we are talking POTENTIAL temperature, here, remember) than the layers below them, why do they stay up. I assume that the answer is that they are condition unstable; i.e., only with the heating of the atmosphere during the day do they become more dense than the layers below. If you (or anybody else) feels that this question is answered above, and I have forgotten, please point me to the answer. N PS: I am NOT in NM at the moment.
  3. Calm Days, I would hate to see you change the thread as long as this line of thought has anything to do with the prevalence of EML's in the US and their relevance to severe weather here. Let me try and restate, for your correction, what I take that relevance is. In my original post that accompanied the opening of this thread, I wondered at the persistance of EML's. You seem to have identified pockets of dry air, that come off the high deserts of Asia and persist indefinitely, out over the Pacific. Tracking these packets across the Pacific led you to wonder about the "seams" between the satellites and how they are filled in with pictures of different characteristics, because these fill-ins were making it hard for you to track these dry pockets all the way from ASIA to the US. Do I have all of this right. Please correct me firmly if I do not, so that I don't confuse subsequent readers. Thanks for your help, N
  4. Ok. So you guys have convinced me that Hot Dry Pools (EML's) can overlie Warm Wet Pools because you have demonstrated to me that moisture is not as important factor in determining the bouyancy of air as is temperature. But you have yet to explain to me how Cold Dry Pools can overlie Warm Wet ones. So, here is a case in point. I am Western MA and I am told there is a dramatic cold pool aloft. The weather is showery with alternations of sunny weather, popup showers, and alto stratus blow off, presumably from the showers. Here is the morning skew T from Albany, just west of us. (If I can manage to post the darn thing.) I will try to post the afternoon one when its circulated. Notice that the potential temperature of that overlying airmass is 10 degrees C colder than that of the air mass below it. Why don't they flipover. Does anybody know of a chart that shows lines of equal buoyancy for different temperature and dewpoint combinations. I suppose there would have to be a different one of those for every millibar level Oh, gosh! I really don't know what I am talking about here, do I? [sigh] N
  5. I wonder if some body could help me visualize the geometry of this situation. Attached is the progged map , . And here is the relevant synoptic discussion: ALL MODELS INDICATE A JET MAX OF 80 KT AT 300 MB PASSING OVER NJ WHICH PLACES SOUTHERN NEW ENGLAND IN THE LEFT FRONT QUADRANT... A POSITION FAVORABLE FOR RISING MOTION. IN ADDITION...AN ELEVATED MIXED LAYER WILL BE PRESENT WITH 500-700 MB LAPSE RATES AROUND 7C/KM. THUS...WITH THE WARM FRONT APPROACHING...THE BAND OF THUNDERSTORMS THAT WILL BE APPROACHING THE BERKSHIRES AROUND DAYBREAK SHOULD CONTINUE TO PROGRESS EASTWARD...ESPECIALLY OVER SOUTHERN NH AND NORTHERN MA...PERHAPS EXITING THE REGION AROUND NOON OR 1 PM. LOW LEVEL WIND FIELDS WILL BE STRENGTHENING DURING THE MORNING...TO 30-40 KT AT 5000 FT...AND THIS MEANS THAT ANY REMAINING STORMS COULD PRODUCE STRONG TO POTENTIALLY DAMAGING WINDS BEFORE EXITING NORTHEAST MA. The warm front is to the south roughly parallel to teh mason dixon line. A trough is to the west. I cannot make a picture of how a warmfront and a eml relate. Presumably there is warm most air over NE; but presumably also, there is warm DRY air. Can anybody else make a picture out of this? N
  6. we are awaiting relieving thunderstorms in western massachusetts. Having a hard time getting them started. Here is the skew T from Albany, this morning. Is this a "doubly capped" atmosphere? http://www.spc.noaa.gov/exper/soundings/14072312_OBS/ALB.gif N
  7. Thanks, again, PyroCu, Another very informative post. I will get into the AMS material straightaway. Thanks also for the term, "conceptual model." Has anybody written about "Conceptual Models in Meteorology"? How they work? Advantages and hazards? N N
  8. PyroCu, Thanks, as always, for your well thought out response. If the Banacos paper is the one I am thinking of, I think I have already gone through it a couple of times. It is splendid. However, time for me to look through it again. If there are other resources that can be reached on the internet for free or nearly free, please let me know. I know about the NOAA tutorials, and Haby's material, but probably naive beyond that. I am kind of bending my own thread, here, so feel free to ignore what follows. snip ----------------------------------------------------------------------------------------------------------------------------------------------snip Obviously, fluency with the equations is important, but haven't you known students who are fluent with the equations but lack any grasp of what is going on? I once talked to to a commercial pilot about the weather. I suddenly realized during the conversation that he conceived of the atmosphere in terms of routes and rules, but didn't really grasp the three-dimensionality of it. He didn't have -- to use the language I used above -- adequate "model" of the atmosphere. Now, I should have been more careful in my use of that term, because I gather, for meteorologists, "model' means, in effect, a very large set of inter-related equations. That's not the use I intended. In many sciences, and in philosophy of science, "model" often refers to a thing or process that you understand well that you bring to bear on a situation you don't understand so well "Cold Front" and "Warm Front" are "models" originally borrowed, presumably, from military science. Now, I gather that many meteorologists feel that "models" in my sense are scientificly frivolous, and they should be used -- if ever -- only for communication with the public. But many good scientists and philosophers of science argue that such "model"s are unavoidable in scientific thought, that inexplicit "models" have their dangers, and that it is best to make one's "models" explicit. It is this conception of scientific thought that you see working as I try to understand EML's and Cold Pools. end snip ------------------------------------------------------------------------------------------------------------------------------------------ end snip No need to respond to the above. I am enormously grateful for the help you have given me so far, and we don't need to talk about "meta-science." All the best, N
  9. Sorry, I went backwards. So, the two soundings I posted were for 7pm on the 17th and 7am on 18th? The tornado, according to news reports, was on the ground a 9pm. Hard to imagine anything scarier than a nighttime tornado. N
  10. thanks, the wxman, Here for others to see is that skewT. It would be fabulous if some of you wise folks could comment on other features of this sounding. 0000Z is about 7 am in Iowa, right? The second image is the same station 12 hrs later. The cap has increased. Again, love to hear some wise comment on that. Thanks, all. N.
  11. Dear PyroCu, To avoid me being confused, let's always insert the word "potentially" to modify any parameter where we are referring to the properties of a packet of air relative to its surroundings (or how it would feel if it were brought down to us) and the word "actually" to refer to how it would feel to us if we were taken up there with it. So, for instance, the air at high altitudes, ahead of a warm front is actually cold, but potentially warm. We agree that its potential warmth is what determines its behavior, right? So I am going edit your message below in accordance with these understandings. You follow along and see if I got it right. My additions are in red. Readers should be aware that PyroCu had nothing to do with the red bits. At the risk of driving everybody nuts, allow me to pursue for a moment the cold pool "model". A pool, to be a pool, has to be restrained by an impervious medium of some sort. So, pursing that idea, what could be the medium that contains the cold pool? Now, a mature extra tropical cyclone, as you make clear, generates energy by advecting potentially warm, moist, air over potentially cooler, dryer air. In so doing, it wrings the moisture out of it making it potentially even warmer. Since a mature low is a spiral, in wraps this air around itself. So we have a circle of warm, dry air up there? Could that be the container of the pool, in some sense. Or: here's another thought. Does the fall of moisture out the layer that is wrung out carry so much heat out of the advected air that it becomes potentially cold? It would have to carry away not only the realized latent heat of the wrung out moisture, but also the original potential heat that existed in teh airmass at the beginning of the process. Ok. Bad idea! Forget the "cold pool" model. Let's work with a wash-basin model, for a minute. When I stir the water in the washbasin, the water level falls in the center of the whirlpool. That happens even without pulling the plug out of the basin. ILet's say that an extra tropical cyclone works that way. Because (unlike a hurricane) it is cyclonic all the way up, it's center is evacuated at high levels of the atmosphere and therefore "cold". OK, now I am in trouble. Is it potentially cold or just actually cold. If we returned the packet to 1000mb, it would not be cold, so it it's not; But if we returned the entire circulation to the surface, it would still be evacuated, and therefore would prove to be potentially cold.. But not by comparison with an average airmass spinning at the same speed. Ok. Another bad idea. Well, anyway. Thanks for helping me think about it.
  12. Dear PyroCu, Many, many thanks for your post. I will respond to the technical points in a minute, but here I want to make a broader point, inspired by your last comment. I taught a technical subject for many years but I grew up in a publisher's family, so I used to tell my undergraduates that "they couldn't really say they understand something until they could explain it to their roommates." If you have some freshman meteorologists you would like to sick on me, I am all for it. As a retired person I deeply miss those sorts of interactions with students who are struggling to master a field; so, seriously, if anybody wants to pass on to me some students the project of getting an old dumb guy to understand hydrostatics, I would be grateful to them. Now I DON'T want to turn this thread (which has brought together so many good, thoughtful, patient comments) into a thread on philosophy of science, but I genuinely am curious about what it is to UNDERSTAND something. I think that understanding something is not just being able to work the equations. Before you understand something you have to have a workable MODEL of it. Models, formal and informal, are everywhere in meteorology and they interact in all sorts of interesting ways, because meteorologists, perhaps even more then doctors, are experts who have to make themselves understood by The Public. "Pool" is already a model; "cap" is a model. When you suspend a pool overhead, you violate the model of a pool (cf Fukishima). The modeler may or may not intend those violations, but s/he has to deal with them. In my experience, the lack of an adequate model can lead smart people into error. I think you will see some of that in our discussion here on EML's where there is confusion between a dry line and a cold front. That leads the writer to assign to the dryline both the role of a cold front (undercutting, lifting) and the role of a warm front (capping) and miss the singularly important point that it is the warm air (potentially warm, remember) running out ahead of the dry line at mid-altitudes that makes the plains states' atmospheres so dangerous. The dry line IS a warm front, of sorts, although, admittedly, a very strange one. Thanks again, N
  13. Thanks again, Calm Days, for another stunning WV loop. If you learn anything that connects the vigorous anticyclonic flow in the pacific with the severe weather in the US, please post it. I have not had time to do my homework about hydrostatic balance, so the following may not be worth an answer. But just in case: I like to think in terms of potential temperature. So when I speak of warm air, it is air at any altitude which, if it were brought down to the surface, would be warm. Or, to put it another way, air that is relatively warm, relative to the mean temperature of air at the same altitude. Similarly with "dense" or "heavy" air. So, from my point of view the following question comes to mind: How is saying that something is caused by hydrostatic balancing different from saying that something is caused by the fact that things that have a greater potential density tend to fall, and things that have a lesser potential density tend to rise. So the mystery is how do things ever get out of hydrostatic balance in the first place. Now we know "hot pools" form at the surface. that's the whole story of heating at the surface building up under a cap. But how do cold pools form in higher levels of the atmosphere? I am in correspondence with a very kind professional meteorologist who gave me a brief and technical description about how cold core lows form cold pools. Unfortunately, I did not understand it. But, by analogy with the "hot pools" that form below a cap, I would be tempted by a theory that, say, dry warm air brought to the top of the atmosphere by the process of convection and wringing out of its moisture, if it stays there long enough, radiates enough heat to become "heavy" , and then, "falls", giving us the snow flurries for which the NE can be famous in the winter. But then I would need something analogous to a cap, to keep it from mixing down as it warmed cooled (!-nst). All of this is, of course,mere madness, but I haven't had time to work out a sane version. All the best, N
  14. Ok. People keep banging that into my head and I think I am finally getting the point. Water vapor does not make THAT much difference. However, then, given that cool air is heavier that warm air, other things being equal, what keeps it up there? Perhaps this will help: Boston is said to be under a "cold pool" at the present. Here is a recent sounding from Chatham, south of Boston. I assume the cold pool is the layer from 850 to 600 mb where the red dotted line exceeds the red solid one. Before I read your comment I was inclined to explain the fact that it stays up there to the fact that the dewpoint is rising over that same range ... the air is getting moister with altitude ... a characteristic of EML's as well. The weather here, 70 miles west of Boston, is characterized by broken strato cumulus with some fractocumumulus below. Can you help me see how this sounding relates to my clouds?
  15. Dear PyroCu, I am glad to have you state so baldly what I have always assumed, but never could quite get anybody else to assert, that if there is less dense air over more dense air, it will overturn immediately. Nice to have that one in the bank. However, I still wasn't clear, after I read your post, if you were agreeing or disagreeing with my notion that that a cold pool could only be less dense than warmer air below it by virtue of being moister. (By "warmer" and "cool" of course, we are speaking of altitude-relative temperature). n