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Roger J Smith

Call For Forecasts -- Predict 20 March Before 4 March

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Map workshop I -- submit your map for 20 March 12z

__________________________________________________________

The Murcie Boy forecast map thread (dealing with his maps for 1-5 February) set off a lively discussion about what was or was not possible in long-range forecasting. Basically, the challenge is to beat random chance at a time range greater than the 16 day GFS which, let's face it, has a big challenge doing just that (my estimate of its correlation with reality, 0.2, meaning slight improvement over random chance).

Think you're onto something that can do better? Test out your theory against others and the models, random chance and pure luck.

We might do this a few more times too. By the way, the RJS map in the Murcie Boy thread scored 0.4 against reality and wasn't much different at 22d than the GFS or ECM at 10d. So there is faint hope out there.

Here's the deal, this thread is about predictions not explanations of why you can or can't do this. Just cough up a map, it has to cover the grid defined by these four corners: 70N 20W ... 70N 20E ... 40N 20W ... 40N 20E.

That's basically a map with Iceland, the UK, Ireland, France, northern Spain, the western Med, Germany, and Scandinavia in it. Submit a map or fill out a grid that replaces the following co-ordinates with sea level pressures for 12z 20 March 2011.

GRID TO BE VALIDATED:

70N 20W 15W 10W 05W 00W 05E 10E 15E 20E

65N 20W 15W 10W 05W 00W 05E 10E 15E 20E

60N 20W 15W 10W 05W 00W 05E 10E 15E 20E

55N 20W 15W 10W 05W 00W 05E 10E 15E 20E

50N 20W 15W 10W 05W 00W 05E 10E 15E 20E

45N 20W 15W 10W 05W 00W 05E 10E 15E 20E

40N 20W 15W 10W 05W 00W 05E 10E 15E 20E

Replace each longitude above with a sea level pressure. reminder, these normally fall between 950 and 1050 mbs. You could picture "normal" as being something like this:

1010 1005 1000 0995 0990 0992 0994 0996 0998

1005 1000 0995 0990 0985 0988 0992 0996 1000

1002 0997 0990 0987 0985 0990 0995 1000 1005

1000 0999 0998 0996 0994 0997 0998 1003 1008

1003 1000 1002 1003 1004 1005 1005 1006 1007

1009 1006 1008 1009 1010 1011 1010 1010 1011

1015 1013 1014 1014 1013 1014 1013 1012 1012

And all submitted maps will be reduced to this grid for easy correlation analysis, so if you can't submit a map draw one up at home and read off the pressures at these grid points.

I've selected 20 March because there's a very high energy peak on my research model from events between 19 and 21 March. Also it's basically the spring equinox.

Note the two basic rules:

** fill out the grid -- if you submit a map, try to mark the isobars clearly and I suggest a 4 or 5 mb grid; and whether you submit a map or a grid, add any comments you want about the weather -- these won't count as the validation will be strictly correlation, but they may help the reader to get a picture of how your forecast plays out in terms of real weather.

** submit a map before 4 March 12z when the GFS will have its first stab at the forecast time from +384h.

All forecasts will be correlated and ranked, and compared to various days of GFS, ECM and other models as they come on stream before validation time.

Be there or be square.

I will submit a map in a few days' time.

Please, spare us any pessimistic diatribes already on file in the MB thread, we get it, this is difficult.

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Give me a map and I'll perfectly direct anyone, anywhere but I'm sorry Roger, I don't do the synoptic chart thing, makes my head spin. I hope this doesn't bar me from this exercise though...

The weather in the British Isles on 20th March will be dry, overcast, with temperatures average to just below but feeling colder in the gusting North to North Easterly wind.

Heavy rain and strong winds will follow in the next week.

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In order to keep some consistency, I propose everyone uses the same base map. I have included what I think will be a suitable one in this post, it should also allow direct comparison with that days Met O Fax chart which I would use as my 'yard stick'. If anyone finds a better one and there is general agreement, then we can go for that.

Now I don't do forecasts, let alone LRF's, but it might be fun to make one up as a complete and utter guess (without virtually any real knowledge, a placebo if you will) to see if a totally random chart can compete with people who actually know something or have an alternative method! :D

post-6667-0-15261000-1297845918.jpg

post-6667-0-15261000-1297845918_thumb.jp

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nice idea that Coast-I'm sure RJS will agree with that.

Not sure if I may have a go T+384 hours grief-hard to get things right for 3-7 days!

;

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And how does one 'draw' on the map and post it?

BFTP

I should imagine you can save it and print it. Then draw your detail then scan it and post it.... or you could use something like paint....

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I should imagine you can save it and print it. Then draw your detail then scan it and post it.... or you could use something like paint....

One needs decent equipment then, that's me out of it, no scanner etc. I'll do a Jethro then.

BFTP

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I would use Paint probably, don't have a scanner.

My approach to doing this SLP map will be using a progressive pattern of the Jetstream to conclude pressure locations, with the deeper pressures being situ close to strong arms of the jet....great idea this.

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And how does one 'draw' on the map and post it?

Use a simple standard programme like Microsoft Paint (ships with most versions of Windows OS) or similar, photo manipulation software. There are lots of freebies on the web.

I've risen to the challenge and produced this (which may, or may not actually be possible :lol: ):

post-6667-0-86089000-1297856094.jpg

I've even got a method, which I will reveal if I get even slightly close!!!!!!! All I can say is it doesn't rely on numbers, being in contact with the dead, seaweed, seagulls or salty sea dogs :winky:

If I had to pronounce my confidence in this forecast, I'd say low......

very, very low :doh:

post-6667-0-86089000-1297856094_thumb.jp

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post-6069-0-14016400-1297858206_thumb.jp

I go for raging zonality

Chances of varifing = 0% :rofl:

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I might have a go at this later. My method will be similiar to MB i.e just randomly select an archive chart and copy and paste. :whistling:

Just realised MB never did answer my questions which makes me think it was just a copy and paste forecast!

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Heres my guess, I am submitting it now as its based upon historical trends and IMO that's as good an idea as any other. It won't change between now and the 4th of March.

The general trend for the later half of march is for the HP cells to migrate from Scandy across the UK to re-inforce the azores, with a spell of unsettled weather for Iceland and for lower pressure near the med as African heat starts to move up.

post-6326-0-62948500-1297860624_thumb.jp

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The general trend for the later half of march is for the HP cells to migrate from Scandy across the UK to re-inforce the azores, with a spell of unsettled weather for Iceland and for lower pressure near the med as African heat starts to move up.

a014.gif

Interesting, now I'm starting to worry about my method!!

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There is no right or wrong answer IMO Coast, at least not yet ! :)

I think that somebody who thinks they can predict specific synoptics at 3 weeks out is fooling themselves, I am happy to make a fool of my self though.

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Thanks for all the above, the map is ideal (one or two data points are just slightly off-grid but we can extrapolate those). Maps submitted Feb 27 to Mar 4 could be influenced by existing GFS 16-day output which will tend to show up in correlations with that output on 4-5 March. Maps submitted after 4 March will have whatever interest value they provide by being at variance with said output, if somebody comes up with a slight variation on the existing model output, then that will probably have only slight interest.

I would advise anyone serious about participating to enter before 28 Feb just to be well out ahead of any trend that shows up in FI, thereby avoiding any inferences of copying the models.

If anyone wants to use my research data, the CET index value for March 2011 is -0.5 C (anomaly for all cases) while the shorter-term secular index value from lunar analogues is +2 C, and the postulated energy peaks are 19 March 20z and 21 March 00z. This will influence the shaping of low pressure according to said theory. What I attempt to do is first define the general circulation pattern, then shape lows and fronts into that pattern using the energy level agenda for timing.

We'll see if anyone in the group can demonstrate a reasonably high correlation using the grid points. I think 0.6 would be good and 0.8 excellent, 0.4 in practice turns out to be fair to middling.

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My stab in the dark is for a cheeky wee northerly similar to March 2007 post-9298-0-98417400-1297892767_thumb.jp

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Just a guess I have drawn up based on nothing in particular really!

post-7593-0-24677100-1297960529_thumb.pn

NW flow over the UK, windy in NE Scotland. Then the low complex near Norway drifting SE and filling allowing high to the SW to ridge N then E and link up with a high coming out of Scandinavia and build bringing an easterly flow to the south half of the UK then more so to the Continent. SW flow then beginning to affect the far NW. Just a totally random guess!

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Update to the forecast.

With angular momentum starting to edge upwards, and some suggestion of the MJO gaining some amplitude in early to mid March, I'm minded to go for phase 4 Global Wind Oscillation centred on the 5 day period 20/03/11.

Forecast:

post-2478-0-46721000-1298063431_thumb.jp

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Posting my entry for March 20 (12z) today, map is in 5-mb intervals ...

Pattern expected to be zonal with some blocking around Iceland, storm track across northern UK on 19th dropping south to central UK by 21st.

Map shows expected strong low (note 6hr positions for track) about 967 mbs near Shetland heading northeast, with remnant of earlier low drifting north west of northern Norway. A second low is developing with strong winds in its frontal systems, to the southwest of Valentia and this would track near or just across southeast Ireland towards Wales and central England over the period 20 12z to 21 12z. This may bring strong winds to southern England on the night of 20-21 and into 21 March. The earlier low would have brought strongest winds to northern parts of Ireland and into southern Scotland, northern England.

Anticipated errors if pattern is different ... a WNW to NNW upper flow would have strong disturbances embedded around Holland and southeast of Iceland. A strong blocking pattern would have deep low pressure near southern France and northwest Italy, as well as possibly northwest of Iceland.

Possible changes within the general framework of this entry, if timing is faster (meaning if timing line three is further east) the first of the two lows could be as far east as Norway-Denmark with the second low over the central or southern U.K. at map time. If timing is slower, would expect a deep low northwest of Ireland with a secondary near the western edge of the map grid.

The energy peak on 21 March is a very strong one in my research, and any well-developed systems at this time could produce severe weather.

East coast U.S.A. expected to see storm development slightly offshore near 39N 71W with a coastal nor'easter of rain trending to sleet and snow inland, and very strong winds. Error here would place the storm further inland to the northwest of predicted position, around PA-NY. Another significant low expected northeast of Newfoundland (this circulation hinted at on the map but centered back around 40-45W). A further low of interest may be in Texas and Oklahoma with severe storm development across the south central U.S. ... the east coast low would have originated from the Gulf of Mexico around 72h earlier but if its track further north, could also be a svr wx producer around the 16th to 17th.

Hoping to see a few more entries and then we await the slow and uncertain march through Fantasy Island to Reality Mainland.

post-4238-0-67244200-1298281426_thumb.jp

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Not sure if this has worked - never tried to attach anything to a post before, so here goes....

It has and here it is in .jpg format to view and compare:

post-6667-0-98727500-1298550646.jpg

post-6667-0-98727500-1298550646_thumb.jp

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