Nick F

Senior forecaster
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About Nick F

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    Specialising in severe weather
  • Birthday 08/09/75

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    South Norwood, London (home), Hounslow/Heathrow (work)
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    Weather - particularly thunderstorms, growing plants, walking, cycling, cooking and good food, wine.

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  1. Yes, with the EC high res and EPS/GEFS mean again singing from the same hymn sheet of pushing down the UK high and letting in the Atlantic once the SW Europe/NW Africa trough drops/fills, it seems a return of SWly flow to be the most likely path. This was picked up by the last Euro weeklies too. The block over Canada is just too far west to stop arctic cold air draining into a mean deep trough over the Atlantic. In a way, the high over the UK over the coming week is our downfall, because it can't build NE, N or NW, because of too much upper flow energy in this direction, so can only really sink or stay in situ. The wildcard is the SW/Europe trough is stubborn to relax and may even be re-inforced by a southerly tracking jet developing over the Atlantic - but this looks like a low probability atm, but not to be ruled out for now IMO. The positives I can see for longer term prospects into February, if you like cold and snow, is that the most likely return of SWlies may be brief, because the trop and strat PV is still forecast to be pulled toward Russia and the trop upper flow looks increasingly amplified upstream at day 10.
  2. A frustrating 12z GFS op, SW-NE aligned upper trough moving out across NW Atlantic is just very slow moving - so ends up with areas of low pressure sliding NE on the forward side of the trough towards Iceland which prevent the bitter cold up over Norwegian Sea and Svalbard sinking south and draws in milder Atlantic air toward UK eventually. Really need to see that upper trough digging a lot further south over the Atlantic with a negative tilt, like 00z EC, rather than positive tile laike 12z GFS.
  3. If anyone thinks GFS is top dog of the models, perhaps think again: Although the ECMWF may have been too keen on easterly for the UK, an easterly is still going to happen, just a lot further south. Remember GFS was slower than ECMWF to cotton on to the blocked pattern we are now entering, preferring the much flatter and more zonal pattern across Atlantic and UK, before backtracking. Be interesting which model comes out top with a rather complex trop pattern evolving over the coming few weeks .. couple that with a warming stratosphere setting up for possible SSW late Jan/early Feb. However, there is the chance that the warming may level off like it did in late Nov/early Dec - so we may need a second warming to break the PV. However, in the mean time, the MJO is probably driving blocky pattern for the rest of January, it's just where the block sets up which is causing problems for forecasting the medium range for now, the models perhaps again not factoring in the correct MJO signal? Realtime and CFS forecasts suggest the MJO will be motoring through 6/7/8/1
  4. Had a streamer of sleet for a good hour and half or more down here at work at Gatwick early afternoon, temp dropped to 2C in the sleet but now rising as the sun returns. Took these pictures of snow still lingering on Reigate Hill, Surrey by junction 8 of the M25 this morning:
  5. Just light snow here at Heathrow, just enough to dampen the ground, seems the heavier snow further east. Oh well, resume the hunt for next snow potential!
  6. Last time I witnessed 'thundersnow' was a frontal event on 28th Jan 2004' when a potent cold front and squall line raced south across the UK, think it was +4C ahead of front and -3C immediately behind, the cold air undercutting creating strong convective updrafts and lightning even well inland. Was spectacular when the rain suddenly turned to heavy snow too. Lightning on 28/01/2004 faxes
  7. Most likely after dark, yes, though wherever rainfall is heavy, evaporative cooling may lower the temperature enough to bring the snowfall level down quite quickly - settling is another matter too, the heavier the better as the ground will be wet.
  8. I think snow chances this evening for most of us that live at low-levels will depend very much on how quickly the colder and drier arctic air undercuts the rain from the NW - which will relate to how developed the wave low will be when it clears. If the wave is flatter than forecast by those models which are most keen on rain to snow at low-levels, then cold/dry air from the NW will be less inclined to undercut, deeper then game on. I use the partial thickness (850-1000mb) and dew points as a guide to snow potential to low-levels. Ideally need a 1290 dam or below for snow to fall, 1300 the limit with heavier precip. Also need dew point of 0C or below. Both 129 gpdm line and 0C dp lines lagging the precip to the NW at 6pm, so may still be rain by then apart from above 150m However, by 9pm, the 129 and 0C lines have caught up the rain to turn it to snow on back edge However, if we are deeper than 06z GFS, latest EURO4 from 06z nearly 10mb deeper at 6pm with developing centre of low, then we could see stronger snow signal as cold/dry air more likely to undercut from NW: 06z GFS 6pm EURO4 6pm So you can see why there is this uncertainty, even only 6-7hrs out.
  9. Milder blip on Sunday/Monday - especially in the west. But turning progressively colder again next week, this time from the east. This time next week looking a bit raw on 06z GFS max temps - with the increasingly cold and dry flow off a cold near continent: 850-1000 hPa (partial) thicknesses show well the cold and dry continental airmass advecting west
  10. Looking at some of the airport TAFs in the SE, Stansted (Essex) and Heathrow shows heavy snow forecast: Stansted: Temporary from 12 at 17 UTC to 12 at 21 UTC Visibility: 0600 m Broken clouds at a height of 200 ft snow TAF: EGSS 111704Z 1118/1224 28012KT 9999 SCT045 PROB30 TEMPO 1118/1121 30015G25KT BECMG 1210/1213 21007KT 7000 -RA BKN012 TEMPO 1211/1215 RA BKN008 TEMPO 1212/1217 09010KT BECMG 1215/1218 01015KT TEMPO 1215/1217 3000 RASN BKN004 TEMPO 1217/1221 0600 SN BKN002 PROB30 TEMPO 1217/1221 35023G38KT 0200 +SN BKN000 BECMG 1218/1221 29015G25KT 9999 NSW SCT045 Heathrow: Temporary from 12 at 16 UTC to 12 at 19 UTC Wind 24 kt from the North/Northwest with gusts up to 38 kt Visibility: 0500 m Broken clouds at a height of 100 ft heavy snow TAF: EGLL 111715Z 1118/1224 30012KT 9999 SCT045 BECMG 1203/1206 24008KT BECMG 1209/1212 8000 -RA BKN012 TEMPO 1211/1216 4000 +RA BKN008 BECMG 1212/1215 15010KT BECMG 1215/1217 32018G28KT TEMPO 1216/1220 0800 RASN SN BKN004 PROB30 TEMPO 1216/1219 33024G38KT 0500 +SN BKN001 BECMG 1220/1223 29012KT 9999 NSW FEW030
  11. 18z GFS indicates some leading edge snow as the rain pushes SE, but not supported on other models so far and probably change next run - too far out to forecast snow anyhow.
  12. My latest blog covers the risk of snow, ice, gales and coastal flooding over the next few days:;storyid=7895;sess=
  13. There are various ways of gauging MJO activity, other than using the more easier to understand RMM plots. tropical and ex-tropical interactions can be seen through the magnitude of the upper winds and the waves in them, as GP suggests, as shown on plot below: Found at: Also the velocity potential (CHI-200) charts can show the propagation of the MJO, if you know how to read them, but charts below do show eastward propagation of an MJO wave So the RMM plots we are used to don't always pick up the MJO activity well, as they may not filter out other modes, such as Kelvin and Rossby waves.
  14. Yes, I have been keeping tabs on Kyle MacRitichie's realtime MJO and 30 day CFS MJO forecasts - which have been propagating MJO out of COD, unlike the EC/GFS/JMA/UKMO, from phase 6 (today) through phase 7/8/1 later this month