The Definition of a Triple Point

[STurner]

First off is the triple point where the dryline is seperated by warm moist air at the surface and cold air aloft. Is this a pretty good area to target when chasing tornadoes? Is finding a triple point pretty difficult or is it usually pretty obvious? Are there any advantages or disadvantages regarding the triple point? Just hear it discussed quite a bit when chasing and wondering if its a very important area when chasing tornadoes. Also chasers have fun the next few weeks to a month and be careful. I wish I could be there with you but I dont have any money to chase.

 

[Paul Knightley]

A triple point is defined as the meeting point of 2 other boundaries, such as a cold front and dry-line; a warm front and cold front; a warm front and dryline, etc etc.

They are favourable for thunderstorm development due to the enhanced lift given to air parcels in the area. In addition, surface winds can be backed near it, enhancing low-level shear.

 

[Darren Addy]

An example: (It is a surface feature)

 

[dentonsachs]

I chased a supercell that was very foreign to me the other day. A Low topped supercell, associated with a upper-level low, this cell produced a fairly high base, slight rotation, and even a small funnel at one point. This was extremely perplexing to me, and wondered about the frequency of these, and exactly how they form, are they always associated close to a low pressure area?

 

[Connor McCrorey]

My first tornado was on 3/26 this year, a day that was very much a triple point chase. A warm front set up along the Red River, while a dryline formed a few counties west of I-35. The cap was very strong that day, but extra lift near the triple point got two lone supercells going a couple of hours before dark. They then rode just south of the warm front, producing tornadoes and hail to the size of baseballs.

 

[Rich Thompson]

Shane,

In case you're wondering, the "triple" point refers to the intersection point of 3 different air masses. In most chase situations, the triple point refers to the warm front-dryline intersection (usually cool north, warm south, dry west), or the dryline-cold front intersection (warm east, dry southwest, cool northwest).

The intersection of boundaries can be a favored area for thunderstorm formation because focused low-level lift erodes the cap from below.

Rich T.

 

[Drew.Gardonia]

how do you identify where exactly the triple point is? do you look at a weather map with the cold front and warm front boundaries are? i've been hearing this term a lot the past week and still trying to understand what the triple point is and how to identify where it's located. Could some post some examples please?

thanks!

 

[Andy Jackson]

Here Drew, here's a hint from a tornadic event back in 2008:

Where the blue, red and purple fronts meet that's the triple point, usually it's around the center of the surface low pressure.

I recommend looking at past events and seeing how the surface maps progress throughout the day and you can start to see what happens. Try this site: severe events.

 

[Jeff Snyder]

We often use the term "triple point" to refer to the intersection of only two fronts or boundaries, even though the TP strictly refers to the intersections of three different airmasses (as Rich noted). This can be a dryline abutting a warm front (continental polar airmass ahead of warm front, maritime tropical south of front and ahead of dryline, and continental tropical behind the dryline), or a cold front abutting a warm front (not-terribly-cool cP N of warm front, mT south of warm front, and cP behind cold front). In the first example, the separation between the cP N of the warm front and the cT behind the dryline is often marked by a cold or stationary front; in the second example, there may be a front of some sort separating the not-terribly-cool cP N of the warm front with the relatively cold cP airmass behind the cold front. In either case, we're not very concerned about this particular front or boundary, since it's typically well removed from the potential instability in the warm / moist sector.

Of course, actual surface analyses may reveal a much more complex situation with multiple fronts (perhaps multiple warm or cold fronts, an occluded front, and one or more drylines), so it can be tricky at times! In Andy's example above, the "triple point" that chasers are most likely to refer to the intersection of the hot/dry (cT), warm/moist (mT), and cool/dry (cP) airmasses in northwestern Kansas (marked where the dryline meets the warm front). Here, we see that there *are* three airmasses "intersecting", even though there are only two boundaries involved. There looks to be another triple point back in extreme northeastern Colorado, but that is typically not going to be of interest to chasers considering the air ahead of the cold front is warm but dry (e.g. more characteristic of a cT airmass).

 

[Mike Kovalchick]

"There looks to be another triple point back in extreme northeastern Colorado, but that is typically not going to be of interest to chasers.."

If I'm not mistaken that particular triple point earlier in the day was associated with the F3 Windsor, CO tornado. It caught a lot of chasers with their pants down including my own.

 

[Jeff Snyder]

"There looks to be another triple point back in extreme northeastern Colorado, but that is typically not going to be of interest to chasers.."

If I'm not mistaken that particular triple point earlier in the day was associated with the F3 Windsor, CO tornado. It caught a lot of chasers with their pants down including my own.

Evidently mine as well! You are correct, it appears. I couldn't see the dewpoints in the upslope region north of the warm front in the image linked to in a previous post. Looking at surface obs at 19z (see HERE), you can see that some low-mid 50 Tds did reside N of the warm front in far northeastern Colorado. Although these weren't the 60s that were in the true warm sector across KS, they were high enough to get the job done on the high terrain!

 

[Matt Hunt]

how do you identify where exactly the triple point is? do you look at a weather map with the cold front and warm front boundaries are? i've been hearing this term a lot the past week and still trying to understand what the triple point is and how to identify where it's located. Could some post some examples please?

thanks!

Yes, you can look at a map that displays the boundaries, but typically the maps updated hourly (which you need when you're actively chasing) aren't going to plot the fronts on them. The dryline is the easiest, as you can see clearly here:

http://www.twisterdata.com/index.ph...nding=n&output=image&view=large&archive=false

Right through central TX would be the dryline where dewpoints around 20 are right against dewpoints around 60. Probably my favorite site to use for real-time data is the COD site: weather.cod.edu. Here you can view the visible satellite and turn on the mesoanalysis on top of it with layers for dewpoint, MSLP, and temperature which will show you the dryline, surface low, and warm/cold fronts. A lot of times you'll be able to see it clearly on the visible satellite as well.

On my April 19th chase I was also using the plots to see the location of the warm front. If I remember correctly it was 81 in St. Louis, and something like 58 in Quincy, IL, so clearly the warm front was between the two! Surface low was to the west, and that's where storms fired, and rode the warm front. Perfect example of a triple point storm initiation.

 

[Jamie Winterstern]

We often use the term "triple point" to refer to the intersection of only two fronts or boundaries, even though the TP strictly refers to the intersections of three different airmasses (as Rich noted). This can be a dryline abutting a warm front (continental polar airmass ahead of warm front, maritime tropical south of front and ahead of dryline, and continental tropical behind the dryline), or a cold front abutting a warm front (not-terribly-cool cP N of warm front, mT south of warm front, and cP behind cold front). In the first example, the separation between the cP N of the warm front and the cT behind the dryline is often marked by a cold or stationary front; in the second example, there may be a front of some sort separating the not-terribly-cool cP N of the warm front with the relatively cold cP airmass behind the cold front. In either case, we're not very concerned about this particular front or boundary, since it's typically well removed from the potential instability in the warm / moist sector.

Of course, actual surface analyses may reveal a much more complex situation with multiple fronts (perhaps multiple warm or cold fronts, an occluded front, and one or more drylines), so it can be tricky at times! In Andy's example above, the "triple point" that chasers are most likely to refer to the intersection of the hot/dry (cT), warm/moist (mT), and cool/dry (cP) airmasses in northwestern Kansas (marked where the dryline meets the warm front). Here, we see that there *are* three airmasses "intersecting", even though there are only two boundaries involved. There looks to be another triple point back in extreme northeastern Colorado, but that is typically not going to be of interest to chasers considering the air ahead of the cold front is warm but dry (e.g. more characteristic of a cT airmass).

Is there such thing as hot/moist?

 

[rdale]

Here are the airmass types - https://cimss.ssec.wisc.edu/wxwise/class/frntmass.html

 

[J. Mike Sheard]

Wasn't a triple point responsible for the storm that produced 5-22-11 Joplin? if not did it fuel it in some way.