SmartD
-
Posts
17 -
Joined
-
Last visited
Content Type
Forums
Blogs
Gallery
Events
Learn About Weather and Meteorology
Community guides
Posts posted by SmartD
-
-
Ex-Helene:
Good consistency from global models with ex-Helene tracking NNE over Ireland into the Iceland gap as a deepening system. This is consistent with the limited climatology for these types of transition in the NE Atlantic - Debbie(1961), Gordon (2006) and Ophelia (2017). Nb that all three of these systems produced damaging winds over Ireland/W/NW UK.
Study of the three previous storms suggests that transition produced a hybrid Shapiro-Keyser like structure similar to transitions in zonal flows and somewhat similar to wintertime rapid deepeners. However, this may not be reflected in Met Office analyses (ASXX) and in measures of rapid deepening (Sanders&Gyakum 'bomb' criterion). The hybrid structure typically consists of a deep warm core ('warm seclusion') around which exrtratropical-like conveyor belt features form. Analysis of simulations and satellite imagery ( Gordon & Ophelia) for the cases suggests they all produced sting jets soon after transition. By the time of 'landfall' over Ireland the surface wind field in the frontal fracture region was dominated by the cold conveyor belt jet with SJ(s) in close proximity above. A possible exception was Debbie where a SJ may have been reaching the surface directly in western Ireland. Typically this scenario produces extreme and damaging wind gusts over land.
-
1
-
-
1 hour ago, Sky Full said:
....Not being knowledgeable about the GFS, can anyone explain to me why the parallel model could vary so much from its older sibling?
The difference between the GFS OP and GFS FV3 para is striking. Likely it's due to the different handling of the trough to the west, but treatment of convection with ex-Helene may be an issue as well. Here is the pressure of the PV (potential vorticity) =2 surface T120 VT 12 UTC 18Z September. The filament of PV extending from the large scale trough west and north of the UK and curving back to the Azores is key to the evolution of ex-Helene and is handled differently by FV3 along with the trough-ridge itself which appears sharper and less progressive in the OP run consistent with the weaker development. Unfortunately I couldn't retrieve MSLP from the Para file but it produces a much weaker system farther east.
All the global models can struggle with trough extension- typically producing less sharp features than those verified, esp at T120. Therefore one should treat individual model solutions with a great deal of caution. However, on climatology grounds (comparing with Debbie (1961), Gordon (2006) and Ophelia (2017)) I would favour the western OP solution and this may not properly depict the intensity and trough interaction yet.
David
-
4
-
2
-
-
1 hour ago, knocker said:
It's apparent that there are two jet streaks around the upper trough. Is Helene getting a boost near the right exit of the easterly one? ...
Did you mean right entrance?. This solution for Helene resembles ex-Debbie (1961), ex-Gordon (2006) and ex-Ophelia (2017) all of which produced damaging winds over Ireland/western UK. At the estimated time of transition the storms were near the right entrance of a meridional jet streak on the flank of a trough. Composite anomalies for the 3 cases from the NNRP.
-
3
-
-
Blended WV & IR, GFS T+6 850hPa wind vectors (coloured by speed) and windspeed isotachs at 250 hPa valid 06 UTC.
-
2
-
-
Greetings- nice thread,hope you don't mind me butting in...David
As well as the tropical systems I think it's worth pointing out the conveyor belt of moisture affecting the NW UK. The pattern is just mobile enough to avoid very high accumulations over the Lakes and SW Scotland and the max in IVT (Integrated [water] Vapor Transport) is moving into the North Sea this morning. Radar accumulations suggest only ~50mm in 24hr in parts of the NW rather than the 100mm+ totals associated with 'Atmospheric River' flooding events.
IR image
https://aviationweather.gov/satellite
MIMIC Total Precipitable Water
IVT product courtesy Ben Moore,
http://www.atmos.albany.edu/student/bmoore/natlantic_ivt.html
-
5
-
-
We are also marking the 50th anniversary of the greatest windstorm in modern times around the west coast, known in the Pacific northwest U.S. states as the "Columbus Day" storm and in the Vancouver area of B.C. Canada as "Freda" (some call it typhoon, some hurricane, the confusion being based on which family the storm developed in, west or central Pacific). The reference cited below calls it Typhoon Freda. This storm hit the U.S. regions late on October 12, 1962 and reached B.C. around midnight (12-13 Oct).
http://docs.lib.noaa...094-02-0105.pdf
The dynamics appear very similar to the October 1987 storm applied to a more complex topography, the parallel mountain ranges near the west coast. As you can see from the reference, there was massive wind damage especially to the huge trees that grow in this region. Besides what you can read in the reference, there was a large-scale blowdown of large trees in Vancouver's Stanley Park.
From the weather records of Environment Canada, I found a report of a maximum wind gust of 126 km/hr from 160 deg at YVR, probably recorded around midnight to 0100h as the low centre (by then about 965-970 mbs) passed just west of Victoria BC.
While that is a relatively high value, gusts to 200 km/hr were implied by the damage done in Stanley Park which must have been better exposed to the gradient wind blowing out of Puget Sound.
Yes, this is a very interesting storm which appears to be in the extreme category (on landfall) as October '87.
David
-
http://www.see.leeds...ogical-society/
An open talk at School of Earth and Environment, University of Leeds.
Wherein Prof Browning will discuss the role of the 'Sting Jet' in the Oct'87 storm and report on the latest research into the role of mesoscale jets in the damaging 3 Jan 2012 windstorm.
Well worth a few hours of your time if you're in the area,
David
A reminder...
Results from a reanalysis simulation of the October 87 storm:
Out-going Long-wave Radiation (cloud top brightness temperature) at 18 UTC 15 October 1987, windspeed at 850 hPa.
OLR and wspd 850 hPa at 02 UTC 16 October. The area of winds > 50 m/s over SE England is the Sting Jet.
Diagnosed 10m gusts 02 UTC 16 October.
David
-
1
-
-
http://www.see.leeds.ac.uk/research/yorkshire-centre-of-the-royal-meteorological-society/
An open talk at School of Earth and Environment, University of Leeds.
Wherein Prof Browning will discuss the role of the 'Sting Jet' in the Oct'87 storm and report on the latest research into the role of mesoscale jets in the damaging 3 Jan 2012 windstorm.
Well worth a few hours of your time if you're in the area,
David
-
I suspect that you could very quickly lose me David-as an ex senior forecaster reading output from Keith and listening to an occasional lecture from him was about my limit, although his work into frontal activity, especially his early work around the Scilly Isles-Project Scilly I think led to an increasing awareness of conveyor belt fronts. That said I find it extremely interesting and your work certainly highlights the number of occasions when this type of frontal activity associated with the Ana cold front can and does occur.
For myself I had never noticed so vividly the radar effects which last night showed-it seemed a classic to me but I'm just an interested onlooker really. So your views will be avidly read on here David.
It is a rather specialised subject and there is not that much recent work from the UK to put it in context. Much of the recent research originates in the States. I think UKMO and other forecasters/nowcasters will have to think more about it though as Doppler becomes more available and the grid spacing of operational models goes to ~1km.
I am happy to answer any questions (as best i can!) about the paper if people are interested,
best,
David
-
sorry unable to help David-very subdued when it went through here so my AWS does not show anything like you request.
An interesting front mind you-I don't recall seeing what with quite such good characteristics-enjoyed reading the paper of yours with Keith Browning and I did understand most of it!
Cheers John,
it looks like the tendency last night was for the rain cores to be tilted down (the system-relative) wind., with less upright updraughts and a weaker gravity current flow compared to 24 sept 2007.
David
-
Hi all-
Global model output suggests this front on a convergent trough with a
pre-frontal low-level jet (~30 m/s) will form into a sharp ana-cold
front. Expected is a core/gap morphology with Line Echo Wave Pattern
characteristics. UKMO invent output (presumably processed 1.5 km var)
is predicting such-
http://www.metoffice...ent/weathermap/
There is a risk of localised damaging winds and brief tornadoes.
I would be grateful if reports of damage and unusual AWS readings
could be amended here. It is important that AWS users switch to high
frequency logging. 5 min logging is insufficient to record the frontal
passage.
Time frame is 18Z 24th to 06Z 25th all of England and Wales as the
front progresses eastwards,
thanks,
David
davidDOTwaghornATgmailDOTcom
I am still interested in seeing high-resolution (1 min) AWS records of this front eg with pressure kicks of =>2 hPa, strong wind gusts (>25 m/s, ~50 kt) and veer at frontal passage,
thanks,
David
davidDOTwaghornATgmailDOTcom
-
Evenin' All,
can I put in plea for AWS users to switch to high frequency logging as per my post here-
and am also interested in hearing damage reports (in the appropriate thread.)
BTW I should have written 'confluent trough' and 'appended' !
I'm interested in collecting AWS/damage records in support of very-high resolution modelling of this type of front. Further details see here-
http://www.abuhrc.org/newsmedia/Pages/news_view.aspx?news=29
Thanks,
David Smart
'waghorn'
-
Morning Waghorn and welcome to Netweather! :unsure:
You'll find we already have a storm report section and hopefully people can take advantage of the thread here to post reports and extreme/unusual data: netweather.tv
GFS has backed it off a little bit now, but if you look in the convective outlook at the post I made earlier, you will see there are indications for some strong convective gusts and more possible funnels and maybe a tornado.
Ah cheers! Thanks for tidying up after me,
D
-
Hi all-
Global model output suggests this front on a convergent trough with a
pre-frontal low-level jet (~30 m/s) will form into a sharp ana-cold
front. Expected is a core/gap morphology with Line Echo Wave Pattern
characteristics. UKMO invent output (presumably processed 1.5 km var)
is predicting such-
http://www.metoffice.gov.uk/public/pws/invent/weathermap/
There is a risk of localised damaging winds and brief tornadoes.
I would be grateful if reports of damage and unusual AWS readings
could be amended here. It is important that AWS users switch to high
frequency logging. 5 min logging is insufficient to record the frontal
passage.
Time frame is 18Z 24th to 06Z 25th all of England and Wales as the
front progresses eastwards,
thanks,
David
davidDOTwaghornATgmailDOTcom
RMS journal Weather- call for papers
in Weather and Meteorology Q&A
Posted · Edited by SmartD
A reminder that the RMS journal Weather is always on the look out for short papers/articles on recent weather events. Historical and articles of a climatological nature are welcomed as wel. Photographs of a meteorological nature or related to topical weather events are always of interest.
https://www.rmets.org/weather
A 'short research article' is less than 2000 words. The 'Spotlight ' slot is also available for very topical events. Support is available for submission and drafting and very often I can provide additional source material e.g. satellite/radar imagery.
David
davidDOTsmrtATgmailDOTcom