Hand Analysis Questions

[CZandbergen]

In attempt to hone my forecasting skills I have been doing a hand analysis of surface maps each morning. I create the map in DA and then attempt to figure out what is going on just using the station plots. I also have automated upper air charts that I use to help with my hand analysis as well. After I finish my analysis I compare it to the NCEP front data and see how close I got or if I have a different take.

One thing I have been struggling with is identifying surface troughs. This morning is the perfect example. SE KS and NE OK have had convection the last two mornings due to a trough of low pressure and I can't for the life of me identify it using the station plots or upper air charts. However NCEP depicted them both mornings. My question is using the charts below, what features should I be looking at to see the trough that is in eastern OK?

My hand analysis for 1300Z http://zandbergen.smugmug.com/gallery/8847863_weX8E#586384909_ryJD3-A-LB

NCEP output http://zandbergen.smugmug.com/gallery/8847863_weX8E#586385742_3RGyh-A-LB

12Z 200mb http://zandbergen.smugmug.com/gallery/8847863_weX8E#586385742_3RGyh-A-LB

12Z 500mb http://zandbergen.smugmug.com/gallery/8847863_weX8E#586382563_F3whM-A-LB

12Z 700mb http://zandbergen.smugmug.com/gallery/8847863_weX8E#586382614_6Wz9K-A-LB

12Z 850mb http://zandbergen.smugmug.com/gallery/8847863_weX8E#586382597_fUdEg-A-LB

Any help is appreciated.

 

[Tim Vasquez]

I haven't looked specifically at that situation but sometimes NCEP is kind of ambiguous with trough markings -- I've seen them used for drylines, outflow boundaries, squall lines, wind shifts, and all kinds of things. I wouldn't get too hung up on differences between your analysis and theirs. If SPC has any human-generated surface analysis products posted (from MCDs, etc) those would be a good alternate source to check, and I would consider differences between their analysis and yours to be more significant than differences with NCEP.

For convective forecasting it would actually help to have a much finer, detailed map at a zoomed scale. The more plots you can look at, the better. The maps you plotted are excellent for showing the big picture with a top-down emphasis -- i.e., it reveals the synoptic scale mechanisms driving the weather patterns on this particular day and suggests the rough orientation of upper-level patterns. But for mesoscale forecasting you have to look at mesoscale maps. Convergence of surface winds and thermal boundaries would be the key mechanisms to look for; troughs mean nothing specifically to storm forecasting, but they are often co-located with fronts and convergence axes and those can be significant to a chase day.

Tim

 

[CZandbergen]

Thanks Tim, that helps. This seems to be one of those things that the more you do it the more you actually see is there. And I agree about the fine scale. I have a meso scale map that I use with crowding turned way up that is really helpful.

 

[Jeff Duda]

I noticed on your hand drawn surface analysis no isobars. I bet if you did a pressure analysis and drew them in you'd see the trough more easily.

 

[Mike Johnson]

I noticed on your hand drawn surface analysis no isobars. I bet if you did a pressure analysis and drew them in you'd see the trough more easily.

agreed. Isobars (usually 2 mb resolution for me) are the first thing I analyze. That should be yours as well. The surface troughs and fronts are easy to pick out. The isobars can help you find some of the more subtle boundaries where they develop kinks. Analyze temps as well. I do a hand analysis every shift except one (don't have time...grrr). PM me if you need assistance. I'll be happy to share some of my work.

 

[Jason Boggs]

agreed. Isobars (usually 2 mb resolution for me) are the first thing I analyze. That should be yours as well. The surface troughs and fronts are easy to pick out. The isobars can help you find some of the more subtle boundaries where they develop kinks. Analyze temps as well. I do a hand analysis every shift except one (don't have time...grrr). PM me if you need assistance. I'll be happy to share some of my work.

Mike, I would really love to come out there sometime and watch you do a hand analysis from start to finish. I'm not sure if that would be allowed, but I'd love to experience someone doing it firsthand.

 

[CZandbergen]

agreed. Isobars (usually 2 mb resolution for me) are the first thing I analyze. That should be yours as well. The surface troughs and fronts are easy to pick out. The isobars can help you find some of the more subtle boundaries where they develop kinks. Analyze temps as well. I do a hand analysis every shift except one (don't have time...grrr). PM me if you need assistance. I'll be happy to share some of my work.

Guys thanks for the feedback as this is a learning process for me. The problem I have with trying to analyze isobars is there don't seem to be enough surface plots with a barometer reading to be able to accurately interpolate the isobars. Any advice on how to handle that?

 

[Jeff Duda]

The problem I have with trying to analyze isobars is there don't seem to be enough surface plots with a barometer reading to be able to accurately interpolate the isobars. Any advice on how to handle that?

There are enough data points on your surface map (the top link) to be able to do a reasonable surface pressure analysis. I was taught in my synoptic class that to be truly accurate, you can only draw contours when you have data on both sides of where one would be. However, if you don't have enough data, then either speculate the location of the isobar by dashing it or just leave a spot open if there truly is no data there. In my mesoscale class, I was taught that you can skimp on the accuracy a little by trying to fill in every spot by making assumptions if need be. You can still dash lines if you want, but you do have enough data on your plots to do a pressure analysis.

 

[Jeff Snyder]

CZ -- it looks like your upper-air maps are making the analysis using only 7-8 sounding locations. You can't really do much of an analysis with such few data if you use an analysis technique to relies solely upon the data (as opposed to an analysis technique that uses a background field in addition to the observation data). Try creating a plot like -> http://www.rap.ucar.edu/weather/upper/upaRAOB_500.gif, and you should end up with a graphic that gives you enough data to hand analyze. Even if you want to do an objective analysis via a computer (and D.A.), you'll want all the available sounding data.

 

[CZandbergen]

Again thanks for the help guys. Does anyone have a link to a surface hand analysis so I can see how to properly get the isobars down? I found one at the SPC site, but it is too low res to really be helpful.

Thanks again.

 

[Jeff Duda]

Try this tutorial: http://profhorn.meteor.wisc.edu/wxwise/contour/index.html