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February storm threat discussion


Ellinwood

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I was defending two friends and didn't realize it was a joke.

Not to pile on so much, but I didn't see it as a joke either. In the time I was at NCEP, I know those guys at the medium range desk have a tough job much of the time. Especially given how the guidance has been this winter! I never was on the "hot seat" in terms of having to put a forecast on the line like that, but I can still respect the years of expertise they bring to the table. Nobody is there to say "how can we hype up the snow weenies..mwaaa ha ha<insert Dr. Evil laugh>!!" They're professionals, making the best judgement that they can with the information available. Sometimes, it's really tough to sift through what that information is telling you. (Having done some forecasting years ago, I know well what that's like).

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You ask and you shall receive. First, you're basically correct....and from a scientific (and design) standpoint, every member should be an equally likely outcome.

However, the GEFS system does have one quirk relative to the other major operational centers that can lead to some correlative skill characteristics by "member number" (albeit with a 24 hour lag). The GEFS initial perturbations are applied using something called an ensemble transform (rescaled) method, which for all intents and purposes is a variant of breeding. For each cycle (00, 06, 12, 18), there is actually an 80 member ensemble of short (06h) forecasts. Those 80 forecast perturbations are then rescaled (shrunk) to represent initial condition perturbations (they are also reorthogonalized). From the 80 initial perturbations, only 20 are selected and integrated out as part of the EPS. The problem is that the selection process isn't random:

00 UTC : members 01-20

06 UTC : members 21-40

12 UTC : members 41-60

18 UTC : members 61-80

I guess this was was chosen to try and maintain "forecast continuity". The naming convention for the products does not actually line up with the member number within the perturbation cycling. In other words, member NN" is not the same cycled "member NN" between each of the 4 cycles/day.

I suppose then it's possible through the breeding and selection process there could be relationships between the members (with a 24h lag though, not from cycle to cycle). This has become less likely now that they have implemented stochastic noise in the ensemble model integration.

Thanks guys. I was wondering about the names and if they were the same every run. I guess that explains why each run at least this year, seems to indicate a different outcome on the three temperature maps (days 1-5; 6-10; and 11-15) that accompany each run.

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weak low hardly any precip some light snow pa & ny........... ric and dc are warm +4 ~ +6

signal is there the details will take a few days atleast it's something to watch

It makes me worry a little about ice knowing how the euro warms up the 2m temps. Still it's so far out there in time, lots can change. It does support the HPC forecast idea.

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WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

0115 PM EST SUN 29 JANUARY 2012

SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)

VALID 30/1100Z TO 31/1100Z JANUARY 2012

WSPOD NUMBER.....11-060

I. ATLANTIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

II. PACIFIC REQUIREMENTS

1. FLIGHT ONE -- TEAL 72

A. P54/ DROP 8 (45.0N 166.0W)/ 31/0000Z

B. AFXXX 08WSC TRACK54

C. 30/1830Z

D. 17 DROPS AS PUBLISHED ON TRACK

E. AS HIGH AS POSSIBLE/ 31/0600Z

2. SUCCEEDING DAY OUTLOOK:

A. POSSIBLE TEAL C-130J MISSION FOR

P56/ DROP 9 (44.3N 151.0W)/ 01/0000Z.

B. POSSIBLE NOAA G-IV MISSION FOR

P56/ DROP 9 (44.3N 151.0W)/ 01/1200Z.

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hr 204 huge +pna nice -nao, big trough in the east

But no southern stream and the trough is too far east to develer much more than cold air unless the miller b delivers. It's a very cold look. There hasn't been much consistency except for the love of a potent arctic connected PNA pattern.

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day 10 has -16c dc -20 philly -AO -NAO +PNA the PV is just south of hudson bay and looks like some hint of a split flow

It is better and that's what's important. The strong -EPO look is really no longer there though the last 2 runs And the block is east of Iceland. It is serviceable though and we probably will get cold.

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It is better and that's what's important. The strong -EPO look is really no longer there though the last 2 runs And the block is east of Iceland. It is serviceable though and we probably will get cold.

It's not a bad pattern going forward,certainly better than anything we've seen so far this year.

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This has been a terrible winter so far. I can say for the early part of February in my opinion is the best I have seen so far this winter. I hope all models will come together for once and gives us the real oppurtunity too bring our shovels and sleds out. Most of all a smile on everyone's face and my daughters. I still believe we will get a good event before winters end. The real question is when? Right now I am being more positive then ever. If it's ice ice baby or frosty the snow man, I will take it!

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It still looks like you're going to have to wait until near the 10th or so, for a better risk of a more widespread storm other than a Miller B or overrunning. That's when the trough slides back west and those weenie analog dates appear like Will mentioned in the Medium Range thread. Seems like the time to watch for you guys, I think. The -NAO may not be around, but you may have enough amplitude out west and perhaps enough of a pseudo -NAO ridge poking into Greenland to help out.

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