Texas winter wx thread (2009-2010)

[sphelps8681]

Need help to read/understand map. When I go the link above and pull a map of a particular day it shows at the bottom of the map a color bar. What do the colors represent? And I also wanted to know about total snow based on precip amount. What i mean, if it says .50" of precip how much snow is that. I have lived in Texas (Houston, Lumberton) my whole life so I have not seen much snow. Does snow amount stay the same at .50" or is it different? I know this must sound stupid, so please forgive me. And what is the possibility Beaumont/Lumberton will see snow?

Thanks,

Susan

[wxman57]

I'm new to this board but not new to weather, been looking at computer models since I was 13. Been lurking for the past week or so but decided to chime in. Any comments on the 12z GFS? I know this is to be taken with a grain of salt but the IPS meteostar forecast at Fort Worth... http://wxweb.meteostar.com/sample/sampl ... ext=kftw... shows 0.56" of precip on the 27th at 00z with an 850mb temp of -7, and 0.30" of precip on the 27th at 12z with and 850mb temp of -12. That could easily result in 5-10" of snow. Not to mention the low temperature of 1 above zero it shows the morning of the 30th!

Just remember that the precip on those charts occurs BEFORE the chart is valid (previous 6 hours). So just because you see green shading in areas of sub freezing air doesn't mean that precip will be falling at the same time the air is cold enough for snow. You have to check the map after that to see if precip was still occurring when the previous map was valid. For the first event (this morning's GFS), it looks like the precip is ending as the air gets cold enough. Could be some snow in northern TX, though. For the event the 12Z GFS is predicting on the 27th, it looks like cold air is in place when the precip starts.

But the GFS is swinging so wildly back and forth with each run, I won't have much confidence in its projections for next week until maybe next Monday.

[msstateguy83]

I would also go as far as to say if anyone disagrees please say so, but I think this could
be something on terms that the northern plains, great lakes region is acustom to seeing
NOT the southern plains of ok & tx, iam talking that extreme i think its reality now and COULD cripple travel, business,exc for days on end in the tx/ok region due to heavy snow & or ice and just the extreme cold temps as the gfs is hinting... this could be one for the books!

edit: i agree with not much faith in general in the gfs what has upped my confidence level on this setup
is the euro in play with this and been showing the general pattern change, for a setup of a dump of arctic
air down into the southern plains region and the gfs as was said is coming more,more into line with that...

[wxman22]

VERY interesting but i would wait to atleast Sunday/Monday before i got excited about anything....

[wxman57]

Need help to read/understand map. When I go the link above and pull a map of a particular day it shows at the bottom of the map a color bar. What do the colors represent? And I also wanted to know about total snow based on precip amount. What i mean, if it says .50" of precip how much snow is that. I have lived in Texas (Houston, Lumberton) my whole life so I have not seen much snow. Does snow amount stay the same at .50" or is it different? I know this must sound stupid, so please forgive me. And what is the possibility Beaumont/Lumberton will see snow?

Thanks,

Susan

Susan,

The color bar on the bottom of the map represents an accumulated liquid precipitation amount for the PREVIOUS 6 hours leading up to the valid time of the map. It doesn't mean that precip is occurring at the time the map is actually valid (when temps may be cold enough for snow, for example).

As for the conversion from liquid amounts to snow depth, that depends on how wet the snow is. For the event on the 4th of December, we calculated general conversion rates of about 3 or 5 to 1. Meaning each inch of liquid precip would produce 3-5 inches of snow. So a half inch of liquid precip might mean 1.5 to 2.5 inches of snow. It really depends on the airmass, though. Sometimes the conversion is as high as 10 to 1 (or more). Down here in Houston, figure around 5 to 1 as an average, though.

[jasons2k]

Update from Jeff Lindner:

Next Week:

GFS shows large scale high latitude blocking developing over the US west coast into N Alaska with varying degrees of intensity and position of the downstream US trough. Strong ridge is forecast to build into the Yukon region of NW Canada where current air mass surface temperatures are in the -20’s to -30’s. A polar vortex over SE Canada appears to retro-grade W over the Great Lakes region helping to carve out the downstream trough. All this points toward some or all of this very cold arctic air to be potentially unleashed southward next week into the US. Will not get bogged down in the details yet given the uncertainty in the trough position…however one must remember that such cold dense air masses tend to keep moving once they start moving. Feel the best course of action remains to go toward the colder side of guidance and below climo for much of next week based on the upper level pattern and not the surface features in the guidance. May need to hit it much harder around the 23-24 as this is when the arctic boundary may arrive and really tank temperatures, but confidence in how cold this far out is very low.

[richtrav]

:uarrow: Welcome!

Same shows 13-28F for Houston on the 29th! ACK - NO!!

http://wxweb.meteostar.com/sample/sampl ... text=kiah..

I'd like to see some more snow too, but geez, that's just sickening cold. Might have to worry about the fan palms with such a sceanrio. I don't want to even think about it yet as the GFS tends to do this in the long range.

Jason

Yes I saw their even more ridiculous numbers this morning, and the more I look at their progs for other cities the less credible I find their numbers to be. They now have DFW down to the 1-3F range IIRC. Well, ok, fine, but some common sense checking shows how flimsy those numbers are. Look up the predicted minima for Cut Bank or International Falls: they're only about 5 degrees colder! That alone should raise some serious red flags about their forecast. Near-zero record cold in Dallas has to come from somewhere, and readings barely below 0 in Cut Bank or Int'l Falls ain't gonna do the trick.

On the bright side though I'll get to scare my cold-paranoid friend in Austin yet once again (I've done it so many times courtesy of that site) when I send him today's forecast. Gosh I've used that site so many times the past couple of years to scare the tar out of him I almost feel a little guilty doing it Just about every winter they predict a good strong 10-12 degree freeze event for Austin and every time he falls for it

[southerngale]

Btw, I've seen a lot of new members joining and posting recently, particularly quite a few new Texas posters. Welcome to all of you!

OT: Hey is dem' Saints gonna beat dem' Cowboys in the dome on Saturday night? As they say in NOLA "GEAUX SAINTS, BLESS YOU BOYS".

We're about to hand the Saints their first loss.

CC, you're not going to believe some computer model, are ya?!

I'm telling y'all IT IS COMING, BABY!! WHOO-WHOOO ... the Polar Express will be pulling out of the station shortly. The 12z GFS just continues the chorus we have had for days now.

Meanwhile, I'm lacing up my shoes and grabbing the football. It's "game on" for next week. Where's Lucy? Oh Loooo-ceeeee!

[cctxhurricanewatcher]

Ha, ha, ha!!!

I just looked at the Accuweather Pro snowcover model and from Dec 26 to January 1, it keeps snow cover from a line from Baffin Bay to Laredo northward ! A good 80% of the lower 48 has snow cover.

[HockeyTx82]

Ha, ha, ha!!!

I just looked at the Accuweather Pro snowcover model and from Dec 26 to January 1, it keeps snow cover from a line from Baffin Bay to Laredo northward ! A good 80% of the lower 48 has snow cover.

Wow, can you post a link?

[cctxhurricanewatcher]

Ha, ha, ha!!!

I just looked at the Accuweather Pro snowcover model and from Dec 26 to January 1, it keeps snow cover from a line from Baffin Bay to Laredo northward ! A good 80% of the lower 48 has snow cover.

Wow, can you post a link?

It's on the Accuweather Pro Site.

If that verifies (which it won't), then we'd be talking about some very historic stuff here along with the temps.

[Ntxw]

Is it just me or the gfs showing more than one storm for north texas? One in and around Christmas and one just before new years

[Brent]

Ha, ha, ha!!!

I just looked at the Accuweather Pro snowcover model and from Dec 26 to January 1, it keeps snow cover from a line from Baffin Bay to Laredo northward ! A good 80% of the lower 48 has snow cover.

[sphelps8681]

Need help to read/understand map. When I go the link above and pull a map of a particular day it shows at the bottom of the map a color bar. What do the colors represent? And I also wanted to know about total snow based on precip amount. What i mean, if it says .50" of precip how much snow is that. I have lived in Texas (Houston, Lumberton) my whole life so I have not seen much snow. Does snow amount stay the same at .50" or is it different? I know this must sound stupid, so please forgive me. And what is the possibility Beaumont/Lumberton will see snow?

Thanks,

Susan

Susan,

The color bar on the bottom of the map represents an accumulated liquid precipitation amount for the PREVIOUS 6 hours leading up to the valid time of the map. It doesn't mean that precip is occurring at the time the map is actually valid (when temps may be cold enough for snow, for example).

As for the conversion from liquid amounts to snow depth, that depends on how wet the snow is. For the event on the 4th of December, we calculated general conversion rates of about 3 or 5 to 1. Meaning each inch of liquid precip would produce 3-5 inches of snow. So a half inch of liquid precip might mean 1.5 to 2.5 inches of snow. It really depends on the airmass, though. Sometimes the conversion is as high as 10 to 1 (or more). Down here in Houston, figure around 5 to 1 as an average, though.

Thanks so much for the info. That makes it easier to understand.

Susan

[shibumi]

Jason

Yes I saw their even more ridiculous numbers this morning, and the more I look at their progs for other cities the less credible I find their numbers to be. They now have DFW down to the 1-3F range IIRC. Well, ok, fine, but some common sense checking shows how flimsy those numbers are. Look up the predicted minima for Cut Bank or International Falls: they're only about 5 degrees colder! That alone should raise some serious red flags about their forecast. Near-zero record cold in Dallas has to come from somewhere, and readings barely below 0 in Cut Bank or Int'l Falls ain't gonna do the trick.

On the bright side though I'll get to scare my cold-paranoid friend in Austin yet once again (I've done it so many times courtesy of that site) when I send him today's forecast. Gosh I've used that site so many times the past couple of years to scare the tar out of him I almost feel a little guilty doing it Just about every winter they predict a good strong 10-12 degree freeze event for Austin and every time he falls for it

Actually richtrav that seems like good thinking but it is not....every time we get a really cold shot (think 1989) in fact we are COLDER than the temp in northern plains....you don't have to get a continuous drop in temps with latitude....the air displaces and travels south......if it isn't reinforced they have return flow and can actually warm quite dramatically WHILE we are below freezing way down south....so the model actually makes sense....

[shibumi]

Ha, ha, ha!!!

I just looked at the Accuweather Pro snowcover model and from Dec 26 to January 1, it keeps snow cover from a line from Baffin Bay to Laredo northward ! A good 80% of the lower 48 has snow cover.

Once again, whether from MSN or Accuweather or any other source out past 10 days, they ALL use the GFS and either print out actual model data or data leaning towards climatology as you approach Day 15.

It has nothing at all to do with the site you get the info from...it isn't 'theirs'...just the graphics...

[Portastorm]

Is it just me or the gfs showing more than one storm for north texas? One in and around Christmas and one just before new years

No, it is not you ... the 0z and 12z GFS runs have shown two winter storms for North Texas: one around Christmas and the other about five days later.

[Ntxw]

Good then im not crazy, given all this "hype" I think this arctic blast may be just enough to overcome that darn omega block in Austin

[jasons2k]

Jason

Yes I saw their even more ridiculous numbers this morning, and the more I look at their progs for other cities the less credible I find their numbers to be. They now have DFW down to the 1-3F range IIRC. Well, ok, fine, but some common sense checking shows how flimsy those numbers are. Look up the predicted minima for Cut Bank or International Falls: they're only about 5 degrees colder! That alone should raise some serious red flags about their forecast. Near-zero record cold in Dallas has to come from somewhere, and readings barely below 0 in Cut Bank or Int'l Falls ain't gonna do the trick.

On the bright side though I'll get to scare my cold-paranoid friend in Austin yet once again (I've done it so many times courtesy of that site) when I send him today's forecast. Gosh I've used that site so many times the past couple of years to scare the tar out of him I almost feel a little guilty doing it Just about every winter they predict a good strong 10-12 degree freeze event for Austin and every time he falls for it

Actually richtrav that seems like good thinking but it is not....every time we get a really cold shot (think 1989) in fact we are COLDER than the temp in northern plains....you don't have to get a continuous drop in temps with latitude....the air displaces and travels south......if it isn't reinforced they have return flow and can actually warm quite dramatically WHILE we are below freezing way down south....so the model actually makes sense....

I would add you have to look at the timeframes. Yes, often, the southern plains will get colder as the high moves south, and clockwise flow around the center of the high will induce a W or SW flow in the northern plains. I have seen it in the 30's in Texas and 70 in Montana with a chinook wind; it's not all that uncommon. Also, if there is a snowpack, the airmass won't modify as much, and you won't need -20 in North Dakota to equal teens in DFW.

With an airmass coming straight down the plains, you can ignore the ABQ number. It is west of the front range which blocks such airmasses - use Trinidad - Amarillo - Liberal to track upstream trends in this type of setup.

All that said, I'm not panicking just yet. It's still WAY to early to hit the panic button....

Still, I know what's possible. I saw, firsthand, 19F in Tampa in 1983, -1F in Dallas in 1989, 3F in Savannah, GA in 1986, and 16" of snow in Birmingham in 1993. All this in my relatively short 36 years. If there is one thing I have learned, it's 'never say never'...

[srainhoutx]

Well I see the activity has picked up abit and even wxman57 is posteding. I go to the Doctor and miss all the excitement. Hey Portastorm, are you hiding Lucy from the model runs. Folks, I know we have been talking for sometime about a big pattern change (seems like forever) and now the guidance is catching on to all the players that have been discussed since the beginning of this Topic. Welcome new members and I suggest that you take some time and read back early on in the discussion. Long Range forecasting is an interesting science. Hopefully many have learned a few things along the way. Just a bit different than tracking Tropical Systems, isn't it.