Ask a Pro Met

[LocoAko]

Both of them were professors of mine at UW, and they were both exceptionally good teachers.

Both of them play in the same cover band called "The Sundogs" (Martin in front and GP on the right):

Cool dudes.

Wow! I'm sure my classmates will get a kick out of learning that. (lol @ "The sundogs").

They did make it quite accessible and a bit "friendlier" than Holton, especially considering the nature of the material.

[isohume]

Thanks guys, much appreciated! I have some calculus background so I think I can comprehend the intro to dynamics. I'v heard bad things about the Hulton book lol not necessarily knowledge wise but a rigorous and tedious read.

Yeah I hear that all the time, but Holton is the truth...the Bible so to speak, which all others interpret from. lol

[Conclue]

Thanks guys, much appreciated! I have some calculus background so I think I can comprehend the intro to dynamics. I'v heard bad things about the Hulton book lol not necessarily knowledge wise but a rigorous and tedious read.

Yeah i have both of those books suggested from school and I would suggest the "Intro to Mid-Lat Dynamics" over Holtons for simplicity purposes. If your a master of vector calculus and great with understanding differential equations by all means Holtons is *thee* book, however for simplicity purposes (in terms of avoding long derivations and their explanations) the other book is great.

"Atmosphere, Weather & Climate" by Roger G Barry and Richard J Chorley may be a good read for you as well. This covers the larger spectrum of the atmos sciences but goes into very good conceptual detail about various aspects of the atmosphere. I got it for a class but never really read into it deeply, only a few chapters here and there for studying. It's actually a book I want to read start to finish because from what I've read it explains complicated processes in a very non-mathematical sense, providing physical reasoning and explanation without choking the life out of you with equations like Isohumes siggy. LOL I get them, but they give me a headache, LOL.

[isohume]

Yeah i have both of those books suggested from school and I would suggest the "Intro to Mid-Lat Dynamics" over Holtons for simplicity purposes. If your a master of vector calculus and great with understanding differential equations by all means Holtons is *thee* book, however for simplicity purposes (in terms of avoding long derivations and their explanations) the other book is great.

"Atmosphere, Weather & Climate" by Roger G Barry and Richard J Chorley may be a good read for you as well. This covers the larger spectrum of the atmos sciences but goes into very good conceptual detail about various aspects of the atmosphere. I got it for a class but never really read into it deeply, only a few chapters here and there for studying. It's actually a book I want to read start to finish because from what I've read it explains complicated processes in a very non-mathematical sense, providing physical reasoning and explanation without choking the life out of you with equations like Isohumes siggy. LOL I get them, but they give me a headache, LOL.

Lol! Math is the most concise and unambiguous way to describe something in nature. It's the language of science.

[clskinsfan]

I was wondering if there is any correlation between fall storm tracks and storm tracks for the winter? If storms have a tendency to track up the east coast during the fall. Does that tendency carry over into winter?

[johnstown]

I understand what model output statistics is..e.g. MAV vs MET. How does GMOS(MosGuide) compare to MAV/MEX guidance? Is it true that MAV is more reliable than MosGuide in the short term, but MosGuide is more reliable than MEX in the long term?

[usedtobe]

I was wondering if there is any correlation between fall storm tracks and storm tracks for the winter? If storms have a tendency to track up the east coast during the fall. Does that tendency carry over into winter?

I don't think there is much of a relationship at least in Sept and October. as the wavelengths are different so the tropical forcing being located in the same place in October gives a cold look to the east but by late dec and Jan gives a warmer look. You can see that by looking at the MJO composites for the different phases and comparing the Sept-Nov ones to the Dec-Feb ones. Others may have a different take on it. Of course the mjo forcing moves which is part of the basis for thinking Dec will flip to cold as the forcing moves into phases 8 through 2 which probably would shift the storm track back towards the east coast again before the mjo moves back into a warmer phase and again help shift the storm track back to the west providing the nao doesn't go massively negative.

[isohume]

I understand what model output statistics is..e.g. MAV vs MET. How does GMOS(MosGuide) compare to MAV/MEX guidance? Is it true that MAV is more reliable than MosGuide in the short term, but MosGuide is more reliable than MEX in the long term?

Like any other regression MOS product...mosguide will be better at the main climo sites than the surrounding regions between them. The adjmos and mosguide were designed to account for complex terrain btw sites by incorporating adjusted raw model data and it will therefore have the same biases as it's particular parent model...the nam, gfs, etc. These adjusted mos products are mainly used to help populate or blend into GFE grids. I'm not sure how they can be accessed outside of that program, but I haven't really looked.

[Big O]

I am from Texas, and in the past I have heard mention of the McFarland Signature being a prelude to severe arctic intrusions in my area. I have three questions:

1. Can anyone explain this signature pattern?

2. Are there any analog years that support such a pattern or is it merely transitory?

3. What teleconnection phases support the development of such a pattern?

Thanks in advance.

[usedtobe]

I am from Texas, and in the past I have heard mention of the McFarland Signature being a prelude to severe arctic intrusions in my area. I have three questions:

1. Can anyone explain this signature pattern?

2. Are there any analog years that support such a pattern or is it merely transitory?

3. What teleconnection phases support the development of such a pattern?

Thanks in advance.

Here's a paper on it.

http://www.srh.noaa.gov/ssd/techmemo/tm88.htm

[clskinsfan]

I don't think there is much of a relationship at least in Sept and October. as the wavelengths are different so the tropical forcing being located in the same place in October gives a cold look to the east but by late dec and Jan gives a warmer look. You can see that by looking at the MJO composites for the different phases and comparing the Sept-Nov ones to the Dec-Feb ones. Others may have a different take on it. Of course the mjo forcing moves which is part of the basis for thinking Dec will flip to cold as the forcing moves into phases 8 through 2 which probably would shift the storm track back towards the east coast again before the mjo moves back into a warmer phase and again help shift the storm track back to the west providing the nao doesn't go massively negative.

Thanks for the info. Some of the models are trying to forecast a strong west based -NAO for late November early December. Could get interesting I guess.

[Ottawa Blizzard]

I was wondering why it is possible for cities like Minneapolis, Toronto, Ottawa and Montreal to (under the right conditions) be just as hot as New Orleans and the Carribean in the summer, but much colder in the winter. Sometimes, a city like Minneapolis can get hotter than New Orleans in July, but it's next to impossible for New orleans to be as cold in January.

[okie333]

I was wondering why it is possible for cities like Minneapolis, Toronto, Ottawa and Montreal to (under the right conditions) be just as hot as New Orleans and the Carribean in the summer, but much colder in the winter. Sometimes, a city like Minneapolis can get hotter than New Orleans in July, but it's next to impossible for New orleans to be as cold in January.

In the summer, the days are longer in the north than in the south. The opposite is true in the winter.

EDIT: Oops I'm not a pro met, but here's the answer anyway.

[isohume]

I was wondering why it is possible for cities like Minneapolis, Toronto, Ottawa and Montreal to (under the right conditions) be just as hot as New Orleans and the Carribean in the summer, but much colder in the winter. Sometimes, a city like Minneapolis can get hotter than New Orleans in July, but it's next to impossible for New orleans to be as cold in January.

Haha...it doesn't have to do with longer days. If you used that logic, you'd have to account for the signif decreased sun angle and weak insolation at higher latitudes as well. Anyway, in the summer...large scale semi-permanent ridges help maintain strong subsidence or deep warming at the higher latitudes, which allows (at times) sfc and llvl flows out of the s and sw, or a waa regime to persist for several days. As long as the upper ridge is strong enough the higher latitudes can warm to levels warmer than the surrounding regions due to a stagnant capped off airmass. In the winter when nly heat fluxes subside due to the lessening sun angle, cold air from the north (trofs) drop south in response. Generally, the more nly the location, the colder the polar/arctic air will be...as some measure of weak solar heating and more days of waa exists across the lower latitudes and allow for airmass mixing/modification.

[snowlurker]

What exactly are short waves? I'm beginning to understand that long waves are representations of the relative placement of ridges and troughs, but I don't have a feel for what short waves are and why they are so important for unsettled weather.

[isohume]

What exactly are short waves? I'm beginning to understand that long waves are representations of the relative placement of ridges and troughs, but I don't have a feel for what short waves are and why they are so important for unsettled weather.

Short waves are pockets of energy or cold pools which propagate through the mean long wave flow. The are what they sound like...atmospheric waves with a lower magnitude than long waves. They are important in the genesis and maintenance of disturbed wx as they create increased upward and downward motions either through dynamical or thermal processes. Basically, they can significantly increase the strength of a llvl feature as omega (upward motion) becomes deeper and perhaps coupled with the upper s/w forcing.

[snowlurker]

Thanks! If you can think of any resources (i.e., books, articles or web sites) at a weather hobbyist level for understanding the interaction of short waves with llvl features in storm development, I would be grateful. Weather makes so much more sense to me when I understand the basic physical process.

[Metsfan]

Quick question to the mets. I am graduating Stony Brook University in december with a B.S. in Atmospheric and Oceanic sciences, and I am wondering where I could look for job postings. Thanks. Also, is a B.S. enough as for education? Is there a need to go further?

[griteater]

Thanks! If you can think of any resources (i.e., books, articles or web sites) at a weather hobbyist level for understanding the interaction of short waves with llvl features in storm development, I would be grateful. Weather makes so much more sense to me when I understand the basic physical process.

There's a lot of good info here - http://www.theweatherprediction.com/

[isohume]

Quick question to the mets. I am graduating Stony Brook University in december with a B.S. in Atmospheric and Oceanic sciences, and I am wondering where I could look for job postings. Thanks. Also, is a B.S. enough as for education? Is there a need to go further?

That's a complicated question and folks have varying ideas about it and rightfully so. If you're looking for intern spots with the NWS, you need to go here:

http://www.usajobs.gov/ ...type in 1340 for "What".

[ArtRosen]

Is there any radar signiture differenc between a single vortex tornado and a multi vortex one?

[Ellinwood]

Is there any radar signiture differenc between a single vortex tornado and a multi vortex one?

No, but usually a storm has to be fairly organized to produce a multi-vortex tornado, so when you DO have one it's usually associated with a good hook-echo signature.

[meteorologist]

Quick question to the mets. I am graduating Stony Brook University in december with a B.S. in Atmospheric and Oceanic sciences, and I am wondering where I could look for job postings. Thanks. Also, is a B.S. enough as for education? Is there a need to go further?

This may be of help:

http://www.weatherknowledge.com/become.html

[Chinook]

I read years ago that the GFS had a cold bias and a progressive bias, implying the polar jet was over-represented. I also read that the ECMWF has a less-than-progressive bias and a warm bias, also it tended to be not progressive enough with lows in the SW USA. Is this still true? Now that we have a trough in the western USA, I am starting to wonder again about long-range stuff for the West.

[Chinook]

Like any other regression MOS product...mosguide will be better at the main climo sites than the surrounding regions between them. The adjmos and mosguide were designed to account for complex terrain btw sites by incorporating adjusted raw model data and it will therefore have the same biases as it's particular parent model...the nam, gfs, etc. These adjusted mos products are mainly used to help populate or blend into GFE grids. I'm not sure how they can be accessed outside of that program, but I haven't really looked.

Isohume,

I have occasionally looked at MOS guidance, but I don't do it every day. I wonder some times why the GFS MOS and MEX MOS are different systems, although they seem to have the same high/low values for the first couple of days, as these are the only days the GFS MOS covers. I wonder about the computation of highs/lows and so forth. It must be based on 2-meter temperature from the model and other predicted variables, such as upper atmosphere temperature values. I am just curious. Sometimes I use the NOAA ARL web site to get direct output on 2-meter temperature, wind, and precip.

[dtk]

I read years ago that the GFS had a cold bias and a progressive bias, implying the polar jet was over-represented. I also read that the ECMWF has a less-than-progressive bias and a warm bias, also it tended to be not progressive enough with lows in the SW USA. Is this still true? Now that we have a trough in the western USA, I am starting to wonder again about long-range stuff for the West.

I always struggle to answer these kinds of questions/comments because people tend to overgeneralize "model bias". You need to be more specific about what portion of the atmosphere you are talking about, what lead time you're interested in, and even be specific about which geographic regions you're curious about.

With that caveat, the GFS certainly doesn't have the documented "cold bias" it used to have. If you look at the long term trend, just in terms of NH 500 hPa height bias, you can see for the past two years the GFS actually has a warm bias:

http://www.emc.ncep....H500mb_day5.png

The figure isn't labeled well, but the interval for the x-axis is yearly. The time series shows bumps toward warmer bias around 2007, and then again in 2010. Both of these jumps correspond to significant implementations (2007 was a model coordinate change and DA overhaul, 2010 was a resolution increase and physics overhaul). This is also demonstrated in the figure here:

http://www.emc.ncep....00mb_dieoff.png

These plots also show that the ECMWF model does tend to have a small, warm bias (in this hemispheric metric). Keep in mind that this doesn't mean that either of the models has the same bias at the surface (or other regions of the atmosphere for that matter).

I believe the issue you bring up with the ECWMF model over the SW US has more to do with long-duration, cutoff type events (I don't think it is accurate to say that the model is always "not progressive enough" with any low over the SW US). In fact, I'm not certain this is even an issue with recent versions of the model (they do very regular, fairly frequent upgrades)

[isohume]

Isohume,

I have occasionally looked at MOS guidance, but I don't do it every day. I wonder some times why the GFS MOS and MEX MOS are different systems, although they seem to have the same high/low values for the first couple of days, as these are the only days the GFS MOS covers. I wonder about the computation of highs/lows and so forth. It must be based on 2-meter temperature from the model and other predicted variables, such as upper atmosphere temperature values. I am just curious. Sometimes I use the NOAA ARL web site to get direct output on 2-meter temperature, wind, and precip.

The MEX and MAV are very similar as they both use the raw GFS output to help initialize their regression schemes. There are differences tho...like temporal resolution and the MAV is initialized 4 times a day while the MEX only twice. The MOS equations calculate their own 2-meter temps that are totally separate from the raw model 2-meter temps. These are bases on the station climo variables at a specific site that produced those temps previously using a statistical regression scheme. Historically, MOS is hard to beat, especially for raw llvl model output variables. MOS is the standard by which NWS forecasters "compete" against and attempt to add value to when conditions warrant.

[AtticaFanatica]

Is there any radar signiture differenc between a single vortex tornado and a multi vortex one?

No, but usually a storm has to be fairly organized to produce a multi-vortex tornado, so when you DO have one it's usually associated with a good hook-echo signature.

You can pick out multiple vortices in high resolution data from mobile radars, but it's pretty unlikely in 88D data.

[H2Otown_WX]

I'm curious as to why phases 7 and 8 (I think) of the Madden-Julian Oscillation are favorable for east-coast cyclogenesis?

[isohume]

I'm curious as to why phases 7 and 8 (I think) of the Madden-Julian Oscillation are favorable for east-coast cyclogenesis?

The MJO can help to enhance upper level divergence (even llvl convergence) and can create a more favorable large-scale storm environment as it passes east across the tropics. Due to the the large scale nature of the MJO and depending on the ENSO phase, it creates north and southward moving atmospheric waves (Rosby Waves) in it's wake analogous to a ship's wake. When the MJO crosses the Atlantic...it is usually weaker and harder to identify through OLR as large scale convection is usually not associated with it...but the northward moving and divergent rosby waves can and do reach the eastern conus and help to enhance the overall storm environment by allowing for a stronger east coast trof and a colder airmass pushing south. Generally, this enhanced interaction is more probable in the late fall and winter under near neutral ENSO conditions.