October 2013 pattern and discussion

[Snowless in Carrollton]

If KATL can drop to 32 tonight it will be the earliest fall freeze since 1965.

That surprises me a little actually, considering the first freeze on average is at the end of Oct or early Nov. I know I had a freeze in the middle of Oct 2000 i believe it was, and Atlanta is further north than I am.

[VanillaDream]

The only thing I dislike about them using KATL as the official temperature of the metro area is the fact that it is so close to the airport and is usually 5-10 degrees warmer than the real temperature in the metro area.  For instance, I am at 43 right now (Of course, I am about 30 miles further north) and KATL is at 50.  It always irritates me how the local news stations base there forecasts off what models show for KATL...knowing that its 95% of the time warmer by several degrees than surrounding areas.  

 

I noticed CBS Atlanta now has there 7 day forecast broken up into regions...which I think is much more representative of each climate area in the metro area

Knowing how poorly KATL does with freezes that depend on good radiational cooling (850's are +2 to +3 C), I'm thinking only a very low chance for KATL to make it to 32...maybe 5%. That would require about a 24 degree drop from today's high. The past tells me to not expect it. However, 35 is quite impressive for sure. 35-36 sounds reasonable.

[dsaur]

I just figure in a 3 to 5 degree lower difference than the heat island up the road.  The airport has it's own climo, but it is what it is, and official readings for Atl come from there.  I'd rather they set up a station at Piedmont Park, at Buckhead, at Vinings, Conyers and Carrollton, and average them with P'tree City, lol.  But I guess it would equal the airports average over time, so what the heck   I made 38 twice, and if tonight is colder I could see 35, or maybe freezing.  The tv said I'd see 28, but that's a stretch, though it wouldn't amaze me if it did.  P'tree City, and I see  colder nights than the airport all the time.  Tony

[GaWx]

I feel confident ATL can get to at least 34 and if the winds decouple then 32 is totally possible.

 

At 11 PM, KATL is 42/30. I'm sticking with my prediction of 35-6. I don't see a 32 happening regardless of winds. Again, we're talking ATL airport, which doesn't radiate well at all.

[dsaur]

Larry, I'm at 36.9 at 1pm, but my dp is over freezing saith the Experiment Station.  T

[DaculaWeather]

29.9  here in Gwinnett County at 6:04, I'll hit my low around 7:30 -8am

[1300m]

At 11 PM, KATL is 42/30. I'm sticking with my prediction of 35-6. I don't see a 32 happening regardless of winds. Again, we're talking ATL airport, which doesn't radiate well at all.

Looks like 35 will be the low. However, wind was almost definitely the problem - a 7-9mph wind during the last few hours made all the difference considering clear skies, the low dewpoint and also surrounding stations readings that had lighter winds. If winds had gone calm or only 2-3mph for the last hour or two, the low would have most likely been 32-33 with the dewpoint at 30.

[DaculaWeather]

Yea, it's already started heading back up here... I had a low of 29.0F at 6:55 am this morning. I hit 32F at 12:47 am this morning and still at 30 degrees. Nice little freeze.

[CAD_Wedge_NC]

At 11 PM, KATL is 42/30. I'm sticking with my prediction of 35-6. I don't see a 32 happening regardless of winds. Again, we're talking ATL airport, which doesn't radiate well at all.

 

I see that Fulton County airport had their first freeze....

[GaWx]

Looks like 35 will be the low. However, wind was almost definitely the problem - a 7-9mph wind during the last few hours made all the difference considering clear skies, the low dewpoint and also surrounding stations readings that had lighter winds. If winds had gone calm or only 2-3mph for the last hour or two, the low would have most likely been 32-33 with the dewpoint at 30.

Maybe so but it didn't happen and I think is a big part of the problem with KATL. I believe it is rare that winds go near calm there for a sig. length of time, even with surrounding stations having near calm winds. In other words, the setup (high overhead) was a really good radiational cooling night setup. Many surrounding stations responded with near calm winds. Yet, KATL winds never went even close to calm and temp.'s still stayed 5 degrees above the TD. If you were to examine records for clear, low TD nights with light to calm winds at surrounding stations, I'm sure you'd find that KATL is nearly 100% of the time warmer than most surrounding ATL stations by several degrees. I've been following it for 30+ years. That's why I was so confident in predicting 35-36. The point is that on rad. cooling nights, katl is not rep. of the Atl area and that is easily predictable.

I've heard that one of the reasons KATL has a problem getting near calm winds may be that the sensor is located above the six foot level and that also the planes stir things up too much. I can't verify these things right now. However, besides the winds, I assume some warming due to the nearby runways is probably a factor on nights like these.

OTOH, when there is a cold advection/windy clear night, KATL usually gets just about as cold as any of the surrounding stations, including FFC!

[GaWx]

I see that Fulton County airport had their first freeze....

 

Yeah, Fulton County airport, a different airport from KATL, almost always goes several degrees colder than KATL on radiational cooling nights. This is no surprise at all.

[WidreMann]

There will be a reprieve for a week or so, but definitely not torching. Models in the past couple of days are showing another block building in the Pacific. AO/NAO hold + but I think that may change as we move into Nov as building heights from the Pacific move into the arctic and displace the PV toward NA.

The Euro sort of neutralizes the AO, but the NAO is crap, and the Pacific isn't great. That's fine for early November, but I hope it's not a sign of things to come.

[jburns]

I've heard that one of the reasons KATL has a problem getting near calm winds may be that the sensor is located above the six foot level and that also the planes stir things up too much. I can't verify these things right now. However, besides the winds, I assume some warming due to the nearby runways is probably a factor on nights like these.

 

 

I thought anemometers were supposed to be 10 meters above the ground.  

[GaWx]

I thought anemometers were supposed to be 10 meters above the ground.  

 

If so, I didn't know. I thought that all of the instruments were normally near each other. Regardless, I recall hearing that KATL's temp.'s may be skewed because of the thermometer being way above the 6 foot level.

[Cold Rain]

The Euro sort of neutralizes the AO, but the NAO is crap, and the Pacific isn't great. That's fine for early November, but I hope it's not a sign of things to come.

Robert posted on his facebook page a couple days ago that the Pacific and Atlantic is looking much better lately and much better than last year. I guess we'll see how it turns out.

[Cold Rain]

Welp, it looks like the ol GFS is slowing down the Halloween rain threat and keeps it dry for many. Good news and par for the course for the GFS.

[SN_Lover]

Why are some so down in the dumps? There are some good signs showing up already.

 

Notice how snow-cover is more east than last year. Also https://www.facebook.com/photo.php?fbid=720198404676884&set=a.358160627547332.99358.356106867752708&type=1&theater

 

edit: cold rain, i just saw your post after i posted this. haha Robert is pretty good at winter forecasting. 

[jburns]

If so, I didn't know. I thought that all of the instruments were normally near each other. Regardless, I recall hearing that KATL's temp.'s may be skewed because of the thermometer being way above the 6 foot level.

 

 

I found it.  Took some digging.

 

 

The standard exposure of wind instruments over level, open terrain is 33' (10 meters) above the ground (WMO 1971). Open terrain means the distance between the wind sensors and the nearest obstruction is at least ten times the height of that obstruction.

 

 

http://www.novalynx.com/reference-applications.html

 

 

I read your original statement as being the wind gauge was skewed due to being higher than 6 feet.  If we are talking thermometers, then 5' is considered the standard.  I see now by rereading that it seems you may have been referring to the lack of calm winds due to mixing affecting the temperature gauge because it is too high.  lol  Every time I read the below it seems to say something different.

 

 

"I've heard that one of the reasons KATL has a problem getting near calm winds may be that the sensor is located above the six foot level and that also the planes stir things up too much. I can't verify these things right now. However, besides the winds, I assume some warming due to the nearby runways is probably a factor on nights like these."

[dsaur]

It's the breaking wind ground effect .  The cold air settles to the ground, and is thick like molasses.   The light winds can't push it, so they die down.  Plus, the ground causes friction that causes the wind to die down even further.  So the nearer to the ground on a still night, the less wind affects the temp gage.  But up at 20 feet the wind may be blowing up a storm, leaving 10 feet to be the balance between no or slow wind, or big wind.  Now, if the instruments are operated by people who are breaking wind, the data changes in unexpected ways.  People at airports drink lots of coffee.  Coffee causes many to become flatulent.  So airport flatulence could also be a reason to move the official data elsewhere!  And methane would also cause the temps around an airport to rise...that and all the  burning kerosene.  Now, the runways hold the heat of the sun, so that coupled with airport flatulence cause increased winds, and extra heat.  Skewing the data even further.   A big, cow less field in the middle of the city might give a better reading. Thus I vote for Piedmont Park. T

[1300m]

At 11 PM, KATL is 42/30. I'm sticking with my prediction of 35-6. I don't see a 32 happening regardless of winds. Again, we're talking ATL airport, which doesn't radiate well at all.

Maybe so but it didn't happen and I think is a big part of the problem with KATL. I believe it is rare that winds go near calm there for a sig. length of time, even with surrounding stations having near calm winds. In other words, the setup (high overhead) was a really good radiational cooling night setup. Many surrounding stations responded with near calm winds. Yet, KATL winds never went even close to calm and temp.'s still stayed 5 degrees above the TD. If you were to examine records for clear, low TD nights with light to calm winds at surrounding stations, I'm sure you'd find that KATL is nearly 100% of the time warmer than most surrounding ATL stations by several degrees. I've been following it for 30+ years. That's why I was so confident in predicting 35-36. The point is that on rad. cooling nights, katl is not rep. of the Atl area and that is easily predictable.

I've heard that one of the reasons KATL has a problem getting near calm winds may be that the sensor is located above the six foot level and that also the planes stir things up too much. I can't verify these things right now. However, besides the winds, I assume some warming due to the nearby runways is probably a factor on nights like these.

OTOH, when there is a cold advection/windy clear night, KATL usually gets just about as cold as any of the surrounding stations, including FFC!

ATL is an ASOS station that is maintained by the NWS, so I'm certain it meets all the same standards as other ASOS stations. It may be a local effect results in winds being higher there, and if so that would be the reason ATL reads warmer on nights like last as you alluded too, but winds do matter which I interpreted you to say didn't in the first quote.

Also, not trying to knock you, but I really don't think forecasting 34 vs 35 honestly has any skill to it - when you know how ASOS stations measure temperatures. In order for a low to count the station has to measure it 3 times over a running 10 minute window. It is highly likely the temperature made it down lower than 35, but obviously it didn't do it 3 times in a running 10 minute window. There really is no such thing as high confidence in forecasting the low at an ASOS station in my opinion and that comes from many years of experience and frustration with just that!

With all that said, I do understand forecasting to a stations tendencies though, which unfortunately each station has and that is what you were doing and good job!

[FLweather]

There will be a reprieve for a week or so, but definitely not torching. Models in the past couple of days are showing another block building in the Pacific. AO/NAO hold + but I think that may change as we move into Nov as building heights from the Pacific move into the arctic and displace the PV toward NA.

Agree and maybe just a couple weeks at the max if that.

Before switching back to a cold pattern in or near the first full week of Nov.

The Euro sort of neutralizes the AO, but the NAO is crap, and the Pacific isn't great. That's fine for early November, but I hope it's not a sign of things to come.

 

 

 

 

 

 

Honestly the temporary pattern we're going to be entering is nothing really extreme. Its going to be average temps for the most part.

 

Really at this point and time teleconnections are kinda useless. They have been bouncing from one extreme to the other just about every day. Considering the recurving trop systems in the west pacific recently also which has strengthen the upper ridge out west has also left pretty cold SST near Japan. Which would be indicative  of a decent broad ul trough over that region as well and colder than previous years. Also notice from last couple years this year it is alot warmer near Greenland.

 

But the point being the warm up is only temporary. I believe this early in the year sst help make up the overall pattern and considering what we have had thus far will only continue that. But even though the models have and will continue to show alot of variablity next week or so eventually should get cold again with a deep trough in the east early to mid Nov. But we shall all see how things work out between now and 2 weeks from now.

 

10/24

http://www.ospo.noaa.gov/data/sst/anomaly/2013/anomnight.10.24.2013.gif

10/21

http://www.ospo.noaa.gov/data/sst/anomaly/2013/anomnight.10.21.2013.gif

10/17

http://www.ospo.noaa.gov/data/sst/anomaly/2013/anomnight.10.17.2013.gif

 

Could be worse .

2012

http://www.ospo.noaa.gov/data/sst/anomaly/2012/anomnight.10.25.2012.gif

Alot worse.

2011

http://www.ospo.noaa.gov/data/sst/anomaly/2011/anomnight.10.27.2011.gif

[NC_hailstorm]

Think we get a front through here Friday,need a little rain.

[FallsLake]

Still some uncertainty for the weather on Halloween. For folks in Central NC we need to be rooting for the euro. GFS would not be too bad but there would at least be showers around (especially in the Triad). For areas away from central NC, it would seem that western NC, SC, and then running sw towards Alabama might be in the cross-hairs for heaver precip. Still some time to see how this pattern sets up.

Part of long range from RAH:

MODEL SOLUTIONS CONTINUE TO BE STUBBORN AS FAR AS TIMING WITH THE

FRONTAL SYSTEM AT THE END OF THE WEEK IS CONCERNED. THE GFS

CONTINUES TO BE MUCH FASTER WITH THE SYSTEM AND THE ECMWF HOLDING

STEADY WITH THE SLOWER SOLUTION. ONE CONSEQUENCE OF THIS IS THAT THE

GFS IS NOW STARTING TO PUT IN DOUBT THE DRY FORECAST FOR THURSDAY

NIGHT ESPECIALLY IN THE TRIAD. THE NEW SOLUTION BRINGS MOISTURE OUT

OF THE SOUTHWEST ATLANTIC SPURRING SHOWERS WEST OF US HIGHWAY 1 BY

THURSDAY EVENING AND CONTINUING OVERNIGHT THURSDAY NIGHT AS RAIN

ASSOCIATED WITH THE MAIN FRONT MOVES INTO THE FAR WESTERN PIEDMONT.

THE ECMWF ON THE OTHER HAND...KEEPS THE HIGH PRESSURE A LITTLE BIT

CLOSER TO THE COAST...EFFECTIVELY KEEPING NC DRY UNTIL THE FRONTAL

SYSTEM MOVES IN TO THE WESTERN PIEDMONT EARLY FRIDAY MORNING. WILL

BOOST SLIGHT CHANCE POPS THURSDAY NIGHT A LITTLE IN RESPONSE TO THE

GFS SOLUTION BUT HOLD OFF MAIN PRECIPITATION UNTIL CLOSER TO 12Z

FRIDAY. LOW TO MID 70S FOR HIGHS WITH LOWS FRIDAY NIGHT ONLY

DROPPING TO NEAR 60.

[GaWx]

With all that said, I do understand forecasting to a stations tendencies though, which unfortunately each station has and that is what you were doing and good job!

 

 Thanks!

[NCSNOW]

Think we get a front through here Friday,need a little rain.

I've seen some dry autumns around here and this one ranks up there. Climo wise this is the driest time of year but there is no denying we have fallen into a totally different pattern over the past 8+ weeks. Wouldn't be surprised to see this dry trend continue right on through the winter. Fridays front is looking less and less promising qpf wise as time draws near.

[Cold Rain]

Looks like Halloween will be dry for most of us. Certainly welcome news for the kiddies.

[SN_Lover]

Looks like the GFS tires to detach a small portion of PV but fails to do so as the model goes into truncation. Maybe if the vort max moves fast enough downstream we might get a cutoff with the trough to the north becoming negatively tilted and lifting faster. Pretty boring pattern for us though if your a winter/cold fan. 

[NC_hailstorm]

I've seen some dry autumns around here and this one ranks up there. Climo wise this is the driest time of year but there is no denying we have fallen into a totally different pattern over the past 8+ weeks. Wouldn't be surprised to see this dry trend continue right on through the winter. Fridays front is looking less and less promising qpf wise as time draws near.

Yeah it's been dry around here too.

Been watching the SOI it's really been tanking the last 10 days or so,going negative today on the 30 day average.This usually is a good sign for precip down the road but we'll see,November is a dry month too on average.

[griteater]

Looks like Halloween will be dry for most of us. Certainly welcome news for the kiddies.

Euro 1, GFS 0?  Or does the win go to the blend?

[FallsLake]

Euro 1, GFS 0?  Or does the win go to the blend?

I will say that the GFS saw the wet pattern way out (past 10 days); and did not waver much. Once the euro caught on to the pattern it did present the better solution.