Denver Day 1

What a challenging forecast today! A wide spread in forecast models was present (mid 60s to lower 50s) and an interesting challenge when it came to the winds.

I checked out the MOS numbers yesterday to see how the NAM and GFS were performing, and it turns out the NAM most for Monday was forecasting a high in the lower 40s while the GFS was forecasting a high in the middle 50s. In the end the high was 51...in the middle. Today the GFS MOS was foreasting a low of 32 and a high of 55, while the NAM was going with a low in the lower 20s and a high of 51. Now, the spread wasn't quite as great on the MOS today as compared to yesterday, but the RAW GFS was still forecasting highs in the mid 60s! It is just amazing how the RAW numbers can be so different than the MOS at one single location.

In the end I went with a high of 55 and a low of 31. Why? Well it all came down to the model performance yesterday and the dewpoint this evening. The NAM did horrible yesterday for its forecast for today. Additionally, the 12Z NAM MOS was saying the high today should have been in the lower 30s....which it obviously wasn't. This immediately made me question the NAM MOS numbers. Additionally, the dewpoint was too low as compared to the current dewpoint temperature, which was leading to a much lower low. However, the GFS did much better than the NAM on its forecast for Monday and the GFS had a correct current dewpoint. Additionally, I did not expect the dewpoint to drop all that much today, but rather hold constant through the night. Thus, my final numbers. Hopefully it works out, but we shall see!

The winds are also a big challenge. The MOS numbers are fairly low around 9 knots while the RAW shows a late increase in wind speed just before dusk to 16 knots. Today around 5/6pm we saw this increase in wind speeds occur. I am not fully sure why...I will have to look into it. But the same thing looks to happen tomorrow, so I leaned towards the higher numbers and went 13 knots. The highest wind speed on Monday was 14 knots as of the 5 pm Climate Report. The high was 51 and the low was 27.

Week 2 After Thoughts and Week 3

Wow, well I was totally wrong about this week. Each system that tried to pull out towards the east lost its energy and dried up, leading to a completely dry week! It did rain Monday, but that wasn't a forecast day so it doesn't count. The GFS was way too wet in the long term last weekend!

And now we move on to Denver where the snow will be flying over the weekend. Luckily we won't have to deal with the snow this first week (at least). Temperatures should warm up nicely for the week. Denver will bring many different challenges compared to Charleston with the primary challenge likely being larger temperature swings. If we can get a strong front to move through the area we could possibly see highs in the 70s followed by lows in the 20s. Anything is possible in Denver. The next week doesn't look like a prime example of this, but the NWS does have highs on Thursday in the 60s with lows near 30. I look forward to the challenge and I hope I can score a little better than in Charleston. I really got punished on my forecast for Thursday. I know why I went 67 for my low and I understand why I ended up going 88 for my high...but I wish I had more time to look at the forecast. Work is a bit more important than a forecast contest, so I only really looked at it for about 10-15 minutes. I should have realized that strong southwesterly flow would lead to stronger heating and the MOS numbers would recognize that well. Oh well! On to Denver!

First week and thoughts about week 2

Charleston has been a rather dull city so far. The only real challenge was the low Tuesday night because it ended up being a midnight low and the winds....which didn't pan out as high as I had hoped on Friday. Temperatures seemed to follow the 850 mb temperature rules and were very close to MOS, with both the NAM and GFS being very accurate.

However, things should change for week two. Two or three systems have the potential to impact the area. The first will be remnants of Olaf streaming across the south and stalling in the southeast on Tuesday followed by a strong cold front on Wednesday. Thursday we might have a break between systems before a new cold front impacts the area late Friday. (Or at least that is what the models are currently indicating.) This will result in some high scoring opportunities! I wouldn't be surprised to see a winner for this city easily up near -8 or -9 if this much rainfall pans out. I will try and remember to blog on Monday about the possibilities for Tuesday. It will be interesting to see how the moisture from Olaf impacts the area. I see some opportunities to undercut guidance this week and possibility some 6Z lows. Should be a fun week!

Day 1 and 2

So yesterday I decided it was best to go a little below MOS Guidance (80F/80F,59F/58F) due to some cold 850 mb temperatures and MOS having difficulty with cold fronts and often going too warm. We will see how that works out, but as for now its ok. I don't see it reaching 80 today.

For tomorrow the 12Z MOS guidance is currently 79F and 53F for both models, which makes the day fairly easy. I am not surprised to see the models drop the high a bit considering 850 mb temps will be even colder tomorrow. No rain is in the forecast and winds should be lighter than today. A deep trough has set up over the eastern US with northwest flow over the area allowing for temperatures to drop easily tonight. MOS has winds coming down to 4-6 mph tonight, which isn't ideal for perfect radiational cooling, but still pretty good. Dewpoints will be in the upper 40s to lower 50s. This seems like a situation where going just above guidance makes sense....but I will have to look at more data to make sure that is the way to go. It's tough to go against such good model consensus. Cloud cover should be minimal tomorrow and tonight.

One More Time:

Actual numbers for Sunday:

Low Saturday night: 72
High Sunday: 86
Max sustained winds: 24 mph, 21 knots
850 mb temps Sunday: 15C
Forecasted on Sunday (NAM): 16.5C Potential: 88F
Forecasted on Sunday (GFS): 16C Potential: 88F


MOS Forecasts:

GFS 00Z 9/28/09

HIGH Monday: 90 Winds 14 knots
LOW Monday night: 62
HIGH Tuesday: 81 Winds 10 knots
LOW Tuesday night: 52

NAM 00Z 9/28/09

HIGH Monday: 89 Winds 15 knots
LOW Monday night: 63
HIGH Tuesday: 80 Winds 10 knots
LOW Tuesday night: 54

RAW NAM 00Z 9/28/09

HIGH Monday: 89 Lower, Upper Winds 22, 29 knots
LOW Monday night: 61
HIGH Tuesday: 77 Lower, Upper Winds 16, 18 knots
LOW Tuesday night: 52

RAW NAM 18Z 9/27/09

HIGH Monday: 90 Lower, Upper Winds 25, 34 knots
LOW Monday night: 61
HIGH Tuesday: 77 Lower, Upper Winds 18, 19 knots
LOW Tuesday night: 52

Weather Challenge Begins Soon

I am going to start writing about the Weather Challenge on this website for the foreseeable future. I want to write out some of my thinking without giving my numbers away, so if you are in the challenge please feel free to read this, but don't expect to get actual numbers. For now, I am just going to jot down the MOS numbers for the next couple of days to see some trends and look at actual numbers compared to the forecast numbers. Doing this gives you a little hint as to how well MOS is doing for this forecast location with the current airmass. However, if a different airmass moves into the area the first day of the forecast, doing this can often cause you to react incorrectly. So don't take the trends as a golden rule, it doesn't always work...but it can be handy. The first city is Charleston, SC:

KCHS:

GFS 18Z 9/26/09

LOW Saturday night: 73
HIGH Sunday: 87 Winds 12 knots
LOW Sunday night: 64
HIGH Monday: 90 Winds 14 knots
LOW Monday night: 62


GFS 00Z 9/27/09

HIGH Sunday: 88 Winds 12 knots
LOW Sunday night: 65
HIGH Monday: 90 Winds 14 knots
LOW Monday night: 61


NAM 00Z 9/27/09

HIGH Sunday: 87 Winds 15 knots
LOW Sunday night: 64
HIGH Monday: 89 Winds 12 knots
LOW Monday night: 61

RAW NAM 00Z 9/27/09

HIGH Sunday: 86 Lower, Upper Winds 19, 25 knots
LOW Sunday night: 68
HIGH Monday: 88 Lower, Upper Winds 17, 31 knots
LOW Monday night: 60

Ummmm...

I can't find anything very interesting out there right now. A trough-ridge-trough pattern is set up over North America right now with with some decent heat pumping into the high plains. The high temperature today on the 14th of September was 94 degrees in Philip, SD. Not unprecedented (the record high is 104F), but still hot! Normally when you hear of heat in the 90s in South Dakota you would expect warm or hot temperatures further south within a building ridge in the central US. However that is not the case at the moment as a cut off upper level low has been stuck in the southern Plains for quite a few days now leading to heavy rainfall from Kansas through Texas into the Deep South. Dallas recorded 4-7 inches across the entire city a couple of days ago and Wichita recorded 3-6 inches last Tuesday. This rain has been very beneficial to the drought stricken areas in Texas and generally for much of the southern Plains. Highs have been in the middle to upper 70s in Wichita for the last week! Wonderful temperatures considering it could easily have been much worse if this low had not become cut off.

But this pattern can't last forever, and the cut off low is slowly moving east in some weak westerly flow aloft. Eventually the low will be picked up (maybe not for another 4-5 days in the southeast!) and taken out leaving behind pleasant, slightly warmer, conditions for the southern Plains. A great weekend is in store for much of the central United States!

In other news, the GFS is starting to hint at strong troughs beginning to move into the US once again indicating the start of the fall season. In one run the GFS even had the 522 line at 500 mb all the way down into the Great Lakes in 10 days! It has since backed off, but this is just a sign of the changing of the seasons. Often the GFS likes to bring down strong troughs in the 10-16 day period only to back off as the event comes closer to the present day. The new GFS 00Z is still coming in, so as of now I am not sure what the model is showing in the most recent run.