Nick F
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Posts posted by Nick F
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And a 10% tornado risk
Deffo be virtual chasing this tonight - even though I have to be up early for work in the morning, can't miss a Moderate Risk and 10% tornado prob. over Tornado Alley
Virtual target: Ardmore, OK
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2 hours ago, Nick L said:
Where do you get the frontal analysis charts from, Nick?
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Thought I'd start a new thread for those who want to follow/post about severe storms and the live streaming of it across Tornado Alley over the coming weeks.
The next few days are looking quite active as a few upper troughs move east across the CONUS. Lee cyclones develop over the central/south Plains as upper trough emerges from the mountain west, drawing moisture north over the Plains which destabilizes as the upper trough moves east. The severe risk then shifting east of the Mississippi with the trough the next day, then another trough arrives from the SW U.S. and the cycle repeats.
SPC ENHANCED risk today for Oklahoma and N central Texas, lee low over W Oklahoma later with dry line extending south into NW/W Texas.
Cold front further west eventually overtakes the dryline and marches east with the surface low to be over eastern Oklahoma around midnight local time.
Supercells forecast to develop along dry line and in warm sector or towards low triple point. Uncertainties / concerns over quality of moisture return north across TX and OK for tornado potential. Dryline supercells could be high-based due to high temp to dewpoint spread, may have to follow dryline storms until moisture improves from the south and the temp-dew point spred falls, bases of any storms developing towards low centre moving over W to central Oklahoma around peak heating perhaps lower - where cloud bases / temp-dew point spread lower.
Nonetheless, any storms could have very large hail. Looking at models, HRRR breaks out storms around 22z just west of I-35 corridor, GFS and NAM similarly breaks storms out along I-35 corridor by 00z.
Think I would target just west of the I-35 to the south of Oklahoma City and see what happens along the dryline, maybe shoot northwest if storms look better near low centre and triple point.
A slight risk over lower Ohio Valley + Lower to mid Mississippi valley on Monday, not such great terrain for chasing with hills and forests and limited river crossings, but perhaps worth watching the streams
Back west to western Texas on Tuesday for an already ENHANCED risk, so could be a big severe day to follow.
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Warmer by day this weekend, a few spots in the north and west reaching 18C, but nights will be cold and frosty. Warmth more toward the SE early next week, before turning unsettled for all from mid-week
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Storm & Convective Forecast
Issued 2017-03-22 10:43:42
Valid: 22/03/2017 06z to 23/03/2017 06z
CONVECTIVE/STORM FORECAST - WEDNESDAY 22ND MARCH 2017
Synopsis
Upper-level trough extending SE across far western Europe will disrupt into a cut-off upper level low over the Bay of Biscay today. At the surface, an area of low pressure centred over Wales this morning will drift slowly south and fill, with associated slow-moving occluded frontal system lying across EIRE and central UK, while cold front moves slowly east across eastern England with an unstable Polar maritime (Pm) airmass edging east across Wales, Midlands, southern and western England later this morning and into the afternoon.
... S IRELAND, WALES, W ENGLAND, MIDLANDS and C/S ENGLAND ...
Clearer skies with sunny spells following cold front with its bands of rain moving east across England this morning coupled with increasingly cold mid-level temperatures towards the west will create steep lapse rates across the above areas with surface heating in sunshine. This will support the development of scattered heavy showers and isolated weakly-electrified thunderstorms into the afternoon and early evening, before diurnal heating wanes after dark and storm risk fades. Any showers/storms may produce hail, gusty winds and localised flooding. No severe weather is expected - given weak shear where strongest instability is indicated - coupled with cool surface airmass and shallow instability.
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-03-22 10:43:42Valid: 22/03/2017 06z to 23/03/2017 06zClick here for the full forecast
CONVECTIVE/STORM FORECAST - WEDNESDAY 22ND MARCH 2017 -
Storm & Convective Forecast
Issued 2017-03-21 10:04:05
Valid: 21/03/2017 06z to 22/03/2017 06z
CONVECTIVE/STORM FORECAST - TUESDAY 21ST MARCH 2017
Synopsis
Upper-level trough will move in towards western Britain today, with surface low pressure to the N and W, driving a strong cyclonic SWly flow across the UK. Cold air of polar origin spreading east with arrival of upper trough to the west will create an unstable / showery flow across the UK today, with a risk of hail and thunder almost anywhere.
... UK and IRELAND ...
A broad forecast for scattered thunderstorm potential across much of the UK and Ireland on Tuesday, as cold air spreads east aloft in association with upper low arriving to the west atop of surface which will be modestly warmed in clear skies - creating instability. Already a few t-storms over Scotland where lapse rates are steepest, but through the day chance of t-storms becoming more widespread as increasingly cold air spreads east aloft and diurnal surface heating increases. Despite 30-40 knts of deep-layer shear, cumulonimbus will tend to be fairly low-topped along with low dew points / warmth - which will tend to limit severe potential to negligible. Though showers/storms likely to align in bands with SWly/Wly streamlines bringing risk of localised flooding in the NW where they'll be most frequent. Also showers/storms maybe accompanied by small hail and gusty winds.
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-03-21 10:04:05Valid: 21/03/2017 06z to 22/03/2017 06zClick here for the full forecast
CONVECTIVE/STORM FORECAST - TUESDAY 21ST MARCH 2017 -
High pressure has brought fine and warm weather to southern areas, but a change to more unsettled conditions on the way and it could turn a lot colder next week.
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Think we went to Aspen Creek restaurant just a short walk down the road from the Best Western, Irving last time I stayed there a few years back.- was reasonably good I remember.
Always a novelty walking anywhere in the mid-west though, most locals drive even the shortest distances so they don't get hot and bothered out of their permanent air-con environments they live in half the year
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32 minutes ago, RobR said:
For those who miss TVN chasers, there is a new platform online, launched overnight and Brett and Brandon are streaming on it: https://livestormchasing.com/map
Thanks for the link, will be using that heavily when the severe storms return. Love the deep south / Alabama drawl of Brett Adair and co! Apparently already 4-5" of snow across parts of New Jersey and it's only just the start of the storm before the winds pick up.
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Southern areas will perhaps see 16C tomorrow, but if you want temperatures in the mid-to-high 20s head further than Spain and Portugal on Friday and Saturday.
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Possibility we may see more influence from the Azores high ridging NE next week, as the flow buckles in response to deep cold vortex digging S and E across eastern N America - bringing a return to winter across eastern U.S. from the weekend. That's what the 06z GFS op and 00z GEFS 5-10 day z500 mean points at, though 00z EC suggests Azores ridge visit more brief and confined to the south early next week, with unsettled conditions for the north. Certainly nothing particularly cold or wintry looking away from northern Scotland apart from the usual EC tease towards the end of the high res run.
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UK Severe Convective & Storm Forecast - Issued 2017-03-08 10:11:46Valid: 08/03/2017 00z to 09/03/2017 00zClick here for the full forecast
CONVECTIVE / STORM FORECAST - WEDNESDAY 8TH MARCH 2017 -
I will be one of the drivers on Tour 1 and this is the kind of supercell structure we'll hopefully see in just over 2 months time, a few tornadoes too will be nice!
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Looking south from my office in west London
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Some mammatus beneath a heavy shower moving across central London, looking from west London
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Might be a few rumbles, hail and gusty winds from the showers across southern EIRE, S Wales and S England this afternoon. Storm forecast issued:
Storm & Convective Forecast
Issued 2017-03-05 10:28:20
Valid: 05/03/2017 06z to 06/03/2017 06z
CONVECTIVE / THUNDERSTORM OUTLOOK - SUNDAY 5TH MARCH 2017
… EIRE, S WALES, S ENGLAND and E ANGLIA …
Upper troughing and associated colder mid-level temperatures will spread east off the Atlantic across the UK. Cold air aloft and diabatic warming warming of the moist surface airmass across southern UK, to south of surface low moving east, will create steep lapse rates – which will support scattered heavy showers and a few thunderstorms across EIRE, S Wales, S England and E Anglia this afternoon.
Modest deep layer shear of 20-40 knts and a few troughs in the westerly flow will organise showers/storms into bands. With drier air arriving in the mid to upper levels from the west, downward momentum of strong jet stream winds aloft will be enhanced in stronger convection which will have the potential to bring some locally strong wind gusts (50-60mph). Otherwise, showers/storms maybe accompanied by hail and may lead to localised flooding.
http://www.netweather.tv/index.cgi?action=convective;sess=5d497d5f63bc82233152f5ca1961b329
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UK Severe Convective & Storm Forecast - Issued 2017-03-05 10:28:20Valid: 05/03/2017 06z to 06/03/2017 06zClick here for the full forecast
CONVECTIVE / THUNDERSTORM OUTLOOK - SUNDAY 5TH MARCH 2017 -
Yep, quite an active cold front coming through, just been hit by a blob of heavy rain here near Heathrow ahead of the main convective rain band which is producing the odd sferic.
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What I find more intriguing was this unusually long-tracked supercell, which dropped a destructive tornado early on, that crossed nearly 600 miles over several states on Tuesday ahead of the same cold front that was further west over U.S. Plains back then
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So, the 18z GFS singing from the same hymn sheet as EC day 10. Ties in with the z500 ENS mean from both models shifting the mean upper trough from the west of the UK to the east of the UK by day 10. Now will it still be there in the morning, won't hold my breath ... but has support from London EPS for turning colder toward mid-month
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A look at the stats showing that winter 2016-17 was dry and mild for the UK overall, though there were some regional differences for each month
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Like the warmer parts of the year, looks like northern France and Belgium stole all the storms again, despite pretty cold uppers and relatively mild/moist surface airmass. French storms triggering along cold front which cleared southern UK overnight.
A look at the skew-ts and 12z radiosonde ascents though suggest airmass is rather moist all the way up to the tropopause across much of the UK today - which doesn't favour electrification of convection. So sferics been rather sparse today and convection messy.
Another chance on Tuesday for some convection with hail and the odd rumble of thunder in the cold polar NWly flow destabilised by weak surface heating in sunny spells.
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Virtual Chasing Thread - Spring 2017
in Storm Chase USA
Posted