Texas Fall 2013

[sooner101]

Radar looking very interesting out west

[Meteorcane]

Radar looking very interesting out west

Yeah some light-moderate snow showers in between Amarillo and Lubbock.

[joshskeety]

I can tell you this much if I were a met, I would quit looking at the models when I saw this and start using my training if I had to report.. These kind of screw ups and too many of them just look at the surface, but don't look why to find the anomaly..

Reality says that -30c dewpoints at 850 and -5c at the surface is a little awkward.. It screws the whole model up and suppresses any moisture in the air and surface precip maps..

We will know for in the next run. If obs show -30c dewpoint at 5,000 feet I will feint.. I can't believe that..

[sooner101]

Radar looking very interesting out west

Yeah some light-moderate snow showers in between Amarillo and Lubbock.

Buddy of mine in Lubbock just told me the snow is "crazy" out there right now.

[joshskeety]

The 3z SREF will be out in about an hour and a half and we will know then if the NAM has sh** the bed with this supposed magically -30c cold dry dewpoints...

[joshskeety]

According to the NAM.. Sleetorama '13 has turned into Vergaorama '13...

Dont worry kids, I don't believe it..

[TrekkerCC]

[snip excellent discussion above]

A bit much??? -5c Dewpoints, MAYBE -10c dewpoints, but -30c? Especially when even east it has -15c? With wet grounds and temps got up near 40 today? Yea.. No doubt there are issues with it.. And probably have been over the past 3-4 runs..

This is exactly why it seems to be going overly nuts on not allowing the atmosphere to moisten.. Yea, the dewpoint at 5-6,000 feet has MAGICALLY hit -22 F in a few hours...

So, until this resolves, and where this anomaly lies, I would stick to the Euro models for the next few runs..

Josh, I think I can help you a bit where the NAM got the crazy dry air from. It appears like there was an error or anomalous readings on the weather balloon sounding FWD sent up.

If you look at the 900mb to 881mb portion of the atmospheric column on the skew-t when you plot the 00z FWD sounding - you will see (and I'm using text listing of the readings to get a more exact understanding of what happened with the sounding) that the dewpoints are up to -33 Celsius in the region of 900mb to 881mb. It tracks well where the NAM thinks that there is "super-dry" air. So the NAM is reporting it accurately - it just the actual data from FWD sounding may be suspect. I guess it's best to check around to other upper air sites to see if there is similar spikes on their soundings. If there are similar spikes on other soundings nearby then likely the layer of super-dry air is real, if not, then it likely just erroneous data. I haven't done a check yet to detect similar dewpoint spikes in nearby upper level soundings (if the spikes do exist). I do note that other than the spike on the actual FWD sounding - the rest of the column is dry but not super-dry.

edit: I just checked the OUN sounding as well. It has similar super-dry layer as well (up to -44C dewpoints). The layer on the OUN sounding that is super-dry is around the 850mb level. So I believe the layer is real.

[Meteorcane]

[snip excellent discussion above]

A bit much??? -5c Dewpoints, MAYBE -10c dewpoints, but -30c? Especially when even east it has -15c? With wet grounds and temps got up near 40 today? Yea.. No doubt there are issues with it.. And probably have been over the past 3-4 runs..

This is exactly why it seems to be going overly nuts on not allowing the atmosphere to moisten.. Yea, the dewpoint at 5-6,000 feet has MAGICALLY hit -22 F in a few hours...

So, until this resolves, and where this anomaly lies, I would stick to the Euro models for the next few runs..

Josh, I think I can help you a bit where the NAM got the crazy dry air from. It appears like there was an error or anomalous readings on the weather balloon sounding FWD sent up.

If you look at the 900mb to 881mb portion of the atmospheric column on the skew-t when you plot the 00z FWD sounding - you will see (and I'm using text listing of the readings to get a more exact understanding of what happened with the sounding) that the dewpoints are up to -33 Celsius in the region of 900mb to 881mb. It tracks well where the NAM thinks that there is "super-dry" air. So the NAM is reporting it accurately - it just the actual data from FWD sounding may be suspect. I guess it's best to check around to other upper air sites to see if there is similar spikes on their soundings. If there are similar spikes on other soundings nearby then likely the layer of super-dry air is real, if not, then it likely just erroneous data. I haven't done a check yet to detect similar dewpoint spikes in nearby upper level soundings (if the spikes do exist). I do note that other than the spike on the actual FWD sounding - the rest of the column is dry but not super-dry.

You would hope the Data Assimilation scheme the NAM uses (I think NDAS, which uses 3DVAR if I remember correctly), would have snuffed those erroneous obs out, considering how different they were then its background analysis. Then again Radiosonde dewpoints are usually pretty accurate so I imagine their variances are quite low which weights them fairly heavily.

[joshskeety]

[snip excellent discussion above]

A bit much??? -5c Dewpoints, MAYBE -10c dewpoints, but -30c? Especially when even east it has -15c? With wet grounds and temps got up near 40 today? Yea.. No doubt there are issues with it.. And probably have been over the past 3-4 runs..

This is exactly why it seems to be going overly nuts on not allowing the atmosphere to moisten.. Yea, the dewpoint at 5-6,000 feet has MAGICALLY hit -22 F in a few hours...

So, until this resolves, and where this anomaly lies, I would stick to the Euro models for the next few runs..

Josh, I think I can help you a bit where the NAM got the crazy dry air from. It appears like there was an error or anomalous readings on the weather balloon sounding FWD sent up.

If you look at the 900mb to 881mb portion of the atmospheric column on the skew-t when you plot the 00z FWD sounding - you will see (and I'm using text listing of the readings to get a more exact understanding of what happened with the sounding) that the dewpoints are up to -33 Celsius in the region of 900mb to 881mb. It tracks well where the NAM thinks that there is "super-dry" air. So the NAM is reporting it accurately - it just the actual data from FWD sounding may be suspect. I guess it's best to check around to other upper air sites to see if there is similar spikes on their soundings. If there are similar spikes on other soundings nearby then likely the layer of super-dry air is real, if not, then it likely just erroneous data. I haven't done a check yet to detect similar dewpoint spikes in nearby upper level soundings (if the spikes do exist). I do note that other than the spike on the actual FWD sounding - the rest of the column is dry but not super-dry.

edit: I just checked the OUN sounding as well. It has similar super-dry layer as well (up to -44C dewpoints). The layer on the OUN sounding that is super-dry is around the 850mb level. So I believe the layer is real.

Yea, Im looking at it too.. Here is what I am thinking... They are admitting some sort of erroneous air balloon data, which most definitely happens, but to see that kind of spike is just jaw dropping.. And since the soundings are based on the NAM run and we aren't actually looking at the weather balloon's themselves I still think there is a major issue going on here.. I mean, I could be all wrong, it certainly is possible, but I have not run across it before where you literally get a sharkstooth in sounding instead of a gradual curve from one layer to the other.. To me, I would take out that sharks tooth and curve it and that is most likely what the dewpoint actually is.. Connect the 2 points where the sharks tooth in the sounding is..

Times like this, Im glad Im not getting paid to come out with a solution.. Wish the NWS was more forthright with what the error was... But so sayeth Uncle Sam.. lol

[downsouthman1]

This appears it will be a rather impressive convective banding type wintry precip event. In areas where the column is sub-freezing, a decent amount of snow should fall. My fears are for most areas, as the column won't be below freezing for most of this event, meaning that the convective precip will accumulate in forms we don't like. Sleet & freezing rain. Because of the convective nature of the precip, it will basically be thunderstorms that produce bouts of heavy freezing rain & sleet. I've seen this before & it's not fun. My hope is that we can get the entire column cool enough quick enough, far away enough from the ULL so that the precip changes over earlier to snow. If we have to wait for the changeover until the ULL is actually close, we are in trouble fellow Texans.

[TrekkerCC]

[snip excellent discussion above]

A bit much??? -5c Dewpoints, MAYBE -10c dewpoints, but -30c? Especially when even east it has -15c? With wet grounds and temps got up near 40 today? Yea.. No doubt there are issues with it.. And probably have been over the past 3-4 runs..

This is exactly why it seems to be going overly nuts on not allowing the atmosphere to moisten.. Yea, the dewpoint at 5-6,000 feet has MAGICALLY hit -22 F in a few hours...

So, until this resolves, and where this anomaly lies, I would stick to the Euro models for the next few runs..

Josh, I think I can help you a bit where the NAM got the crazy dry air from. It appears like there was an error or anomalous readings on the weather balloon sounding FWD sent up.

If you look at the 900mb to 881mb portion of the atmospheric column on the skew-t when you plot the 00z FWD sounding - you will see (and I'm using text listing of the readings to get a more exact understanding of what happened with the sounding) that the dewpoints are up to -33 Celsius in the region of 900mb to 881mb. It tracks well where the NAM thinks that there is "super-dry" air. So the NAM is reporting it accurately - it just the actual data from FWD sounding may be suspect. I guess it's best to check around to other upper air sites to see if there is similar spikes on their soundings. If there are similar spikes on other soundings nearby then likely the layer of super-dry air is real, if not, then it likely just erroneous data. I haven't done a check yet to detect similar dewpoint spikes in nearby upper level soundings (if the spikes do exist). I do note that other than the spike on the actual FWD sounding - the rest of the column is dry but not super-dry.

edit: I just checked the OUN sounding as well. It has similar super-dry layer as well (up to -44C dewpoints). The layer on the OUN sounding that is super-dry is around the 850mb level. So I believe the layer is real.

Yea, Im looking at it too.. Here is what I am thinking... They are admitting some sort of erroneous air balloon data, which most definitely happens, but to see that kind of spike is just jaw dropping.. And since the soundings are based on the NAM run and we aren't actually looking at the weather balloon's themselves I still think there is a major issue going on here.. I mean, I could be all wrong, it certainly is possible, but I have not run across it before where you literally get a sharkstooth in sounding instead of a gradual curve from one layer to the other.. To me, I would take out that sharks tooth and curve it and that is most likely what the dewpoint actually is.. Connect the 2 points where the sharks tooth in the sounding is..

Times like this, Im glad Im not getting paid to come out with a solution.. Wish the NWS was more forthright with what the error was... But so sayeth Uncle Sam.. lol

Tthe dryness on the sounding and NAM is not an error - the 850mb(ish) layer has a super-dry pocket. I went, using twister-data to look at soundings from previous runs, and you can see that the NAM develops a super-dry pocket like we see on the FWD sounding. NAM might be overdoing the strength of the pocket with tonight's run, but it looks "real" to me.

[weatherdude1108]

I haven't been studying models like most folks on here, but I would say for the Austin metro area, based on casual observations and historical trends, my loose prediction is occasional cold light to moderate rain on Sunday, changing to an occasional sleet mix in the middle of the night Monday morning.

Rain off and on most of Monday, then rain with a few flurries/sleet pellets mixed in Monday night into Tuesday morning, turning to all rain late Tuesday morning. Rain tapering to drizzle with peeks of Sun towards dusk Tuesday.

May have a few issues with slush on the overpasses, but the roads in contact with the ground will be fine. I think there is sufficient ground warmth with how early in the season it is, and the fact that it was in the 80s and 90s within the past week for a few days heating the ground, which could help to act as a kind of a latent geothermal conductor onto the surface during this cold snap, reducing icing risk.

I think the main issues or annoyances will be the leftover sand on the bridges, scattering dust everywhere and all over your vehicle with traffic passing over it once it dries up.

Anyway, my two pesos. Probably way off, but can't hurt to try. Every storm/event is different.
All I know my work may close Monday if we get freezing drizzle! Hope so!

[downsouthman1]

Let's not get to absorbed by these soundings. The moisture & lift is currently showing up in an extremely widespread fashion on all the radars out west. As this pushes in, it will overcome the dry air. Keep in mind that we're right on the edge of the timeframe where the models are less important than trends & we should not underestimate what we see in the WV loops & radars.

http://www.wunderground.com/wundermap/? ... ving&hur=0

http://www.atmo.arizona.edu/products/wx ... 0mbwv.html

http://www.ssec.wisc.edu/data/geo/index ... thod=flash

[joshskeety]

Tthe dryness on the sounding and NAM is not an error - the 850mb(ish) layer has a super-dry pocket. I went, using twister-data to look at soundings from previous runs, and you can see that the NAM develops a super-dry pocket like we see on the FWD sounding. NAM might be overdoing the strength of the pocket with tonight's run, but it looks "real" to me.

Im using Twisterdata as well and have seen those, but again, that is why I think the NAM has gotten dryer and dryer because prior to 4 runs ago, this "anomaly" was not there, nor did it forecast it.. In fact, not even close.. I think this has been on the past few runs.. I think the column gets dry.. 5c to 10c dewpoints, but I highly doubt the -30c dewpoints, especially after the surface is so moist and the temps were higher today..

Reality is, the obs for 0z show relatively normal.. it starts on the 3h, on the previous run it started on the 3h as well.. Something is wrong with that..

[TrekkerCC]

Let's not get to absorbed by these soundings. The moisture & lift is currently showing up in an extremely widespread fashion on all the radars out west. As this pushes in, it will overcome the dry air. Keep in mind that we're right on the edge of the timeframe where the models are less important than trends & we should not underestimate what we see in the WV loops & radars.

http://www.wunderground.com/wundermap/? ... ving&hur=0

http://www.atmo.arizona.edu/products/wx ... 0mbwv.html

http://www.ssec.wisc.edu/data/geo/index ... thod=flash

Yes. I mean the atmospheric column is going to moisten as the moisture from the pacific streams in. It should not be a problem for the atmosphere to moisten up and precipitation to fall. I just was a bit shocked at how dry the 800 mb dry pocket was - I hadn't been really looking at the model soundings the past few days.

[joshskeety]

Let's not get to absorbed by these soundings. The moisture & lift is currently showing up in an extremely widespread fashion on all the radars out west. As this pushes in, it will overcome the dry air. Keep in mind that we're right on the edge of the timeframe where the models are less important than trends & we should not underestimate what we see in the WV loops & radars.

http://www.wunderground.com/wundermap/? ... ving&hur=0

http://www.atmo.arizona.edu/products/wx ... 0mbwv.html

http://www.ssec.wisc.edu/data/geo/index ... thod=flash

I have seen Virga storms in Virginia so big that not a drop of anything fell and looking at the radar you would of thought we had 6 inches of snow by now..

If there really are -30c to -35c it won't be as easy to break that as you think.. It will eat up much of it..

[joshskeety]

Watch the surface obs at Abilene in the next 1-2 hours.. That will tell the story.. If they don't report sleet/snow by 1-2AM CST, then its pretty much Virga as Abilene supposedly has the -30c dry column as well...

[joshskeety]

Freezing rain reported in San Angelo.. But they were outside of the "dry column" a tad, I think Abilene will be our best bet to see what will happen..

[sooner101]

Where are you getting your reports?

[joshskeety]

:uarrow: Where are you getting your reports?

Looking for them on Twitter..

This was posted 55m ago..

Texas Storm Chasers ‏@TxStormChasers 55m

RT @wall_cloud: Freezing rain just began in western #SanAngelo. Stay off the roads tonight and tomorrow. It's gonna be slick! #txwx