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Trom

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  1. I use that site too. The radar is good. They also use a combo of GFS and other models (albeit free ones) for their forecasts.
  2. My head office where I have to visit every few months is in LaCrosse Wisconsin currently -24C just before mid-day. Remarkably that's a warm-up for them. A lot of the time you just can't be outside as it's too cold. Issues with frostbite on exposed skin and cold air affecting the lungs. Mississippi freezes and people drive on it and go ice fishing.
  3. Wow big upgrade overnight for snow in the South London/North Surrey area from the Met. Double flake symbols instead of single and extension of the period at both ends. Was 6pm to 4am now showing as 5pm to 8am. I have my finger crossed that they're right.
  4. Interesting height rises to the NE late in the GFS run (day 15 posted) Could this finally be the impact of the SSW hitting the trop? Will need to see if this sustains in future runs and whether it gains any cross model support once it comes into the ECM 10 day timeframe. Thought it was worth posting given the reasonably bullish Met 6+ day forecast
  5. My firm has an office in LaCrosse Wisconsin. There's not a lot going on in most of Wisconsin other than corn and dairy. The temps get so low that it rules out being outside for any period of time as any exposed skin starts to freeze. I have been ice fishing on a frozen Mississippi. Massive cold period about to hit the mid-West in the next few days. LaCrosse will be -20C in the day and closer to -30 at night by the weekend.
  6. Yes, the operational is very close to the mean for 7 days out. Recent runs the op and ensemble means haven't been. Does this herald some consistency and perhaps less volatility on the ECM in future runs? Time will tell.
  7. I agree about the no panic it's just that I'd rather see a cold op supported by the ensembles rather than an operational that's at variance with it's ensembles. Hopefully, you are correct and the ECM op moves into alignment with the ensembles. My unease is also compounded by the fact that it's the ECM op that is so out of kilter with its ensembles and GFS output. Another way of viewing it that the volatility caused by Trop/Strat interplay is having a major effect on the reliability of the model output and that higher definition compounds this uncertainty. We did see all models struggle significantly with the quick trop impact last year. This year's been a more normal SSW impact (i.e. slower) but we know it's impacting shortly. Fingers crossed.
  8. Well partly and the fact that the initial input data is tweaked for the ensemble members (control excluded).
  9. I don't think you can ignore operating runs given they are high definition compared to the ensembles and controls low definition. The question is, especially on the ECM, what is the operational picking up on that the lower definition control isn't that causes the direction to be so different.
  10. I always think it's like a break in snooker. You know where the balls should roll but in essence, every break is different. The physics look simple but the outcome is surprisingly variable in snooker. The split SSW is like the white ball and the voretex the reds. You know the vortex will dissipate but exactly where and how remains an enigma.
  11. There were some interesting posts the other night stating that the GFS and parallel are currently experiencing difficulties and low verification stats. The argument was that the Federal shut down in the US means the models are running in auto mode with no intervention. The way automatic data is recorded has changed and due to the shut down the US models have not been adapted to this new system. So issues with initialisation data. This is compounded by the facts that the models need to be manually adjusted for known bias which isn’t happening right now Work has stopped on the GFS parallel. As Whitefox said the parallel is in a testing phase. This is where the model outputs are correlated against actual outcomes and the differences analysed (Root Mean Squared Error ‘RMSE’ for those of you who like regression models). The algorithms are then tweeked over the parallel period to reduce the RMSE and hence increase predictive accuracy. With the Fed shut down this is not happening. For those not hugely into stats RMSE is the standard deviation of the difference between forecast and actual outcome. Low indicating differences a small and a high RMSE indicating big dispersion between forecast and actual outcomes. The upshot is a delay to the parallel taking the place of the existing model and lower verification stats for both GFS and parallel in the meantime. This came from workers at the agency and there was a good article in the Washington Post https://www.google.co.uk/amp/s/www.washingtonpost.com/amphtml/weather/2019/01/07/national-weather-service-is-open-your-forecast-is-worse-because-shutdown/
  12. Well never given they are incorrect at T+0! Good use of perturbations is: 1. Look for how many support the operational run. 2. Look for clusters indicating possible trends. Individual perturbations not hugely useful as they are low resolution and start off with tweaked initial data. So I'm with you Froze. However, pointing that one out I think is more for the holey mother imagine if that came off point rather than anything else.
  13. It's worth noting that the models could not cope with the SSW last year (wave 2). I seem to remember that we had a huge period of volatility in the NWP until after the event. Then the change in the models, the week after the warming, was abrupt. It wasn't something we saw in FI that got closer and closer. So they really struggled with last years wave 2. If this pattern repeats this year then anything showing now for the post-warming period should be taken with a pinch of salt. The models appeared to be reasonable with the forecasting of the warming of the strat but all at sea with regards to the tropospheric impacts. The question right now is are we likely to see wave 1 or wave 2 warming. Wave 2 with it's sheering rather than pushing effect on the vortex gives us a higher probability of cold weather. I would also presume that the models find it harder to model the impact of wave 2 rather than wave 1 due to the more complicated variables of a split vortex (although that is just a hunch). The key variables for us right now are wave 1 versus wave 2 and the likely speed of tropospheric response.
  14. I seem to remember that last year the NWP struggled with the wave 2 event. I seem to recall it was significantly after the event that the models picked up the implication for the troposphere but when they did the impact was marked. Before the event and immediately afterward they did not cope at all well if my memory serves me well. I'm not sure how well they cope with a wave 1 event. Do they find a displacement easier to model than a total split? Anyway, I'd say patience is a virtue right now.
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