Model Outlook Thread (< 120hrs Only)

Deep Easterly

A new, clean and hopefully aggro free model thread.

A few new rules agreed by the mods.

1. Models within the 24hrs to 120hrs range to be discussed only. This is often considered the "reliable timeframe" of model watching, although anything past 76hrs can still change dramatically from run to run.

2. Again, this is not a forecast thread. Any major weather events that are forecast within 2 days will warrent their own seperate threads. This thread is just to spot any potential down the line.

3. Any posts that are off topic, dismissive of others, rude and just plain insulting will be deleted, and the poster banned instantly for a period at which will be at the discretion of the Mods. This is to prevent this thread from going down the same lines at the last 2 model threads; while 99% of posters abided by the rules, the 1% ruined that thread and the mods have decided not to tolerate abusive posts anymore, whether they claim to be on topic or not. This will be the only warning given. :)

Snowaddict

Evening all .

• All of the main latest outputs tonight, GFS - ECMWF - UKMO all have broad agreement upon a pretty deep depression being centred quite close to the west of Ireland on Saturday. This is currently for the T+72 timeframe, so details are still subject to change, however there is clearly a lot of potential there for some very high wind gusts.

• Further out towards T+96, there is broad agreement for this area of low pressure to track towards the general Icelandic region. There are differences between the main model outputs at this point as to the exact positioning of the area of low pressure, however all main NWP outputs are in broad agreement for a fairy cool to cold westerly to northwesterly airflow becoming established over the country on Sunday. The UKMO 12Z Chart below illustrates quite well the suggestion of a quite cold and brisk northwesterly airflow, with the chief area of low pressure tracking towards Iceland.

• At this point, with the isobars shown to be fairly tightly packed, there is some strong potential for fairly high wind speeds on Saturday in particular as the area of low pressure approaches the west of Ireland.

• Furthermore, it would be worth noting that on Sunday in particular, there is a suggestion of the possibility of wintriness over higher elevations. EDIT: The 18Z has now reached this T+84 timeframe for Sunday and it shows 522 dam air over parts of Ireland. Therfore, a good possibility of wintry precip over higher elevations. The chart below also reinforces the idea of a westerly to northwesterly airflow.

GFS 18Z T+84 (Sunday 14 Jan 2009)



Out into the T+114 timeframe for Monday and GFS 18Z (Following the pattern of recent outputs) suggests 522 dam heights over Ireland along with upper 850hPA temps of -7 to -8, which could be condusive to wintry potential. However, this is still outside the the T+72 timeframe so exact details very much uncertain at this point.



In summary, out to Sunday at this point, the latest NWP outputs show our weather to be staying very much unsettled, with the potential for even stormy conditions on Saturday. At this point, it appears that a colder westerly veering to northwesterly airflow will become established on Sunday.

Regards,
SA.

forkassed

Sub 528
sub -5 850's
Temperatures of -1 ish
Plenty of showery precipitation

Question..

It has been posted that all we can expect from this is rain/sleet at low levels due to maritime influence from the atlantic.Thats fair enough but are the showers more likely to turn more wintry (sleet to snow) as they cross land from west to east.

I know this is right on the outer limits of the timeframe involved and still uncertain but i wanted to use this chart as it has night time temps associated.

Danno

Good summaries there lads. I feel, at night time [Sunday Night] areas inland will get snow. I remember a very familiar setup in 2001 where a stream of showers moved in a line from Miltown Malbay to Tullow. The band was around 20 miles north-south, and delivered "nocturnal" snow here that was 3 to 5 inches deep. I remember working in Kilkenny city and they had nothing down past Jenkinstown and people north of Abbeyleix had nothing either. Now, that is not an IMBY post by any means, but just to point out that these setups can deliver (even locally at lower levels). Hopefully they will be more widespread this weekend.

Snowaddict

Morning all.

There is again this morning, a clear suggestion on the various NWP outputs of potential for some wintry type precip. This potential begins on Sunday and follows through to Monday.

Saturday:

The latest 00Z UKMO run suggests that a fairly deep depression, of 965 mb will come fairly close to the west of Ireland. Thereafter, it shows the track of this low pressure as heading northwards towards Scotland firstly, then tracking towards Iceland. This setup suggested by UKMO still has the potential to deliver some very high wind gusts.



For the same timeframe, GFS 06Z also has a deep depression of 965mb, but centred more to the northwest of Ireland with the low tracking towards the general Icelandic region thereafter. Again, if GFS is correct with this track then some fairly blustery conditions will develop, but not quite as windy as modelled on the latest UKMO run.

Although the exact track of that low is uncertain at this point, there is still the potential for very windy conditions to develop on Saturday.

Sunday

Moving on to Sunday and major NWP outputs this morning clearly show a cold westerly to northwesterly flow developing widely over the country. ECMWF T+72 chart shows this up quite well. The flow would be quite cold and with the upper temperatures being modelled as being condusive to wintry precip, there certainly is a possiblity of wintry type precip, especially on high ground. The flow will also be fairly brisk, making it feel quite cold.

Upper 850hPA temps are modelled on most outputs as being in the region of -5, somewhat more on others, slightly less on some others. However, there is general agreement at this point for a cold west to northwesterly flow being established, with fairly brisk winds. GFS and UKMO also model fairly similar setups as shown on the ECMWF below.




Monday:

Finally, for Monday and at this point, all major NWP outputs are strongly suggestive of a westerly to northwesterly flow over the country. Again, upper and surface temperatures are shown to be quite cold, with conditions being modelled as being condusive to wintry precipetation. Most outputs still show the flow as being quite brisk, so still feeling quite cold. ECMWF shows a shortwave development for Monday, however the flow still remains quite cold.



In summary, conditions are modelled as being quite unsettled up to Monday on the latest various NWP outputs. At this point, there is uncertainty as to the exact track of the depression on Saturday, however there is still the potential for very high winds. Furthermore, conditions are modelled as becoming quite cool to cold on Sunday and Monday, with moderate potential shown for wintry precip.

Regards,
SA.

Snowaddict

Interesting developments out to T+120 on this run.

The latest GFS run is modelling a vigirous area of low pressure centred to the south of the UK over the channel - a channel low.

This poses high wind potential if it were to verify, along with a wintry risk as there is cold air wrapped up with the system.

I would note however that this development is not shown on the other major NWP outputs, however a similar evolution is shown on the latest GME output.

An interesting development that needs to be monitored over the coming days.



Regards,
SA.

DOCARCH

Exciting stuff there SA! Potentially very wintery stuff on that last chart!

The air progged in the reliable timeframe [or even outside of it depending on how long it takes the atlantic m50 to get it here but get here it must when not blocked] looks like the air currently over the NE of North america.
The surface air from that is obviously going to be very modified to say the least after it's atlantic crossing.
Currently that air has been giving daytime maxes of -6c at sea level un modified.

Now think about this...When we have an easterly we often need air temps on the near continent as low as that to guarantee sea level snow.
Thats without the handicap of 3000+ miles of sea water to cross.

Gfs often overcooks or under cooks by a few crucial degree's what the 850 temps are going to be and that makes using that model alone when 850 temps have to lower in atlantic air [to compensate for the warm water modification] for guessing precip types at sea level tricky.

If we were Noaa we'd be using a blend of the 3 main models and mostly ECM.
Looking at that last map SA has kindly posted,thicknesses of 510 in the mid atlantic look too low to the trained eye.It just doesnt look right to me to have them that near us having traversed the mid atlantic.
But then thats GFS-it could be an over cooking.

528 would be borderline-too borderline.

Focus'ing in on the storm and it's northeasterlies and northerlies as it heads into southern Britain.It's an awfull pity that theres going to be no real continental air there with nice very sub zero dp's.
Without them,my excitement level would be contained wintry weather wise for the higher ground.

Villain

Met Eireann on Radio 1 said possibily plenty of wintry showers early next week, wait and see as usual

By excitement containment to higher ground-To clarify I meant snowyness there rather than wintryness.
I'd be expecting wintryness in that flow at sea level...just not too much snow if any.
Microclimates and local topography eg adjacency to higher ground with a windflow down off that higher ground will come into play in the right circumstances combined with obviously evaporative cooling/night time conditions to give a possible snow event on the lower ground.
It's all very marginal though,the devil being in the detail that just cannot be tied down too well at this point out from it.

Whats not on the side of snow fans , the missing factor is again on that tuesday gfs chart,the full strength of the polar maratime flow misses Ireland and heads into Biscay.
It then circulates around the low pressure routes up through France ,into England and then out to us mostly through topograpghy that will vary from well above freezing to only close to freezing in inland northern France/belgium perhaps to back to above freezing again in Britain and well above over the Irish sea.

Now to be Brutally honest,thats a big ask and you will need 850's and thickness's right.

Thats not good.

Supercell

The track that low takes is crucial I feel, will be paying very close attention to the positioning of it in future runs.
The dreaded NW isnt much good normally here in the east at this time of year but with the wind strength we may be in luck this time.

repr

Depending on the track of that low on Tuesday parts of Ireland and Northern Ireland could have a major snow event as we in prime position with the cold air.

ch750536

Noooooooooooooooooooooooooooo

Im overseas tuesday to thursday!

nacho libre

Supercell wrote: »

The track that low takes is crucial I feel, will be paying very close attention to the positioning of it in future runs.
The dreaded NW isnt much good normally here in the east at this time of year but with the wind strength we may be in luck this time.

who cares about you supercell- you've had enough this winter. as long as we in the west and north west get snow that is all that matters:pac:

repr

12z is a good run with wintry showers affectin Northern Parts startin on Sat evenin spreadin to most of Ireland Sunday up to Wednesday of next week.

Snowaddict

Afternoon All. I don't have much time this evening, but suffice to say that the 12Z GFS run yet again shows wintry potential beginning on Sunday and extending to Tuesday.

Upper 850hPA temps are modelled as being between -5 and -7, so definately quite marginal for low level snow, however given that these charts are now well into the sub T+120 timeframe, its looking good for at least some higher elevation wintriness next week.

The UKMO chart and FAX updates are very important tonight.

Saturday:

The latest GFS chart for Saturday again suggests a deep depression tracking fairly close to the western coast of Ireland. There is still the potential for very high winds in exposed parts.



Thereafter, there are indications of a cool to cold westerly to northwesterly airflow becoming established over the country. At T+63, GFS 12Z is suggestive of 522dam heights and upper 850hPA temps of -5 to -6.



Again, there is a clear suggestion on the latest 12Z output of the possibility of marginal wintriness early on Monday - T+93.



Furthermore, the latest GFS output has altered the idea of a channel low shown on the previous run. It now indicates this low travelling to the North East of Scotland and towards Norway. Out to T+120 and Ireland remains under a cold westerly to northwesterly airflow.



In summary, there is still strong potential for high winds this coming Saturday. GFS continues to show a colder westerly to northwesterly flow becoming established over the whole country thereafter, modelling some quite low - 522 dam heights and upper 850hPA temps of -7. These are quite low, given the long distance travelled by the cold air. As ever, further outputs needed, but high ground at least, does appear to be at the risk of some wintriness early next week, going on the latest GFS output.

Regards,
SA.

Snowaddict

The latest 12Z GME evolution is fairly similar to the GFS, albeit somewhat colder.

It also takes a deep depression very close to the northwestern coast of Ireland on Saturday, giving clear potential for some very high wind gusts for a period of time.



Thereafter, it models a cold northwesterly flow into Ireland and again displays wintry precip potential from Sunday through Tuesday.

T+72 (12Z)

The latest T+72 chart seems to suggest upper 850hPa temps of -8 into parts of Ireland this coming Sunday. This would be quite cold, again given the very long sea track of the cold air.



Continuing on out to Monday and Tuesday, it also shows a quite cold westerly to northwesterly flow over the country.

T+108 (12Z)



Out towards the T+120 timeframe and it is also suggestive of the formation of a low to the south of Ireland, with this low travelling over the UK quite swiftly. It also indicates some quite cold air wrapped up with this low.

At this time, various NWP outputs show different tracks for this potential low early next week. The tracking of the low is quite important as there is a good possibility of some quite cold air being wrapped up with it.

In summary, an unsettled, quite cold and potentially wintry output on GME out to T+120 today.

SA.

Snowaddict

Indeed, you are completely correct there, its just that I am airing on the side of caution at this point, given the source of the flow . I do agree though, things do look very interesting, with a very interesting 12Z output from GME today.

Regards, SA.

DOCARCH

Metcheck are showing heavy snow for Dublin for 9am Tuesday with 12.7mm of precip. That's approx 5 inches of snow:D

I know....don't all scream at me at once for referring to Metcheck, but I have nver seen them showing heavy snow for Dublin.

As long as we are all prepared for it to go t*ts up tomorrow.

Snowaddict

The latest UKMO charts are also indicative of what's being mentioned about the latest GFS and GME outputs.

They are showing a cool to cold northwesterly airflow becoming established over the country this coming Sunday. The latest outputs from UKMO also show a slightly different track for the first area of low pressure, for this coming Saturday, showing it developing just to the north of Ireland.

In summary, the latest UKMO run still offers the potential for high wind gusts for some parts over the early to mid part of the coming weekend and shows a quite cool to cold and potentially wintry flow thereafter.

SA.

Supercell

I dunno fellas, the Bracknell charts look like light hail showers at best here in the east to me. Hope I'm wrong.



Yes its going to be windy but I've seen this kind of chart many many times and all it seems to deliver is clear skies and at at best light hail and rain showers here in the east

Supercell

nacho libre wrote: »

who cares about you supercell- you've had enough this winter. as long as we in the west and north west get snow that is all that matters:pac:

Nacho minus 100 points from the weather league.

Snowbie

darkman2 has returned after a siteban issued by the admin for a legal threat in September. He/she has ignored a PM from me earlier and posts have been deleted and the user banned temporarily untill i can get an explanation from an admin.

LEIN

Models looking very tasty indeed but they never seem to deliver the goods to my area and I'm moving closer to the Irish sea coast line next month so my chances will be even smaller!

Snowaddict

Just thought I would write a separate post regarding Saturday. It should be noted that the deep depression is now further south and east on this run, with the centre of the depression coming extremely close to the coast of Ireland.

IMO, if this is to be the track of the low, then some seriously high wind gusts are possible, with an exceptionally dangerous situation along the west coast in particular.



These are also very high wind speeds being shown. If this trend is to continue, then I would expect that Saturday could be exceptionally windy for a time.

nacho libre

snow addict, are we talking about gusts in excess of 80mph in some western coastal aeras?

Snowaddict

nacho libre wrote: »

snow addict, are we talking about gusts in excess of 80mph in some western coastal aeras?

Hi Nacho Libre, there would be wind gusts approaching at least 70mph, likely in excess of this to be honest, if the low was to track and develop exactly as shown on the latest run.

Indeed, at this point, that low is becoming a major concern in my opinion.

Snowaddict

As mentioned above, Saturday has the potential of being exceptionally windy to stormy. Indeed, conditions could be quite dangerous and the development and track of this low needs to monitored very carefully.

Regarding the outlook out to 18Z Tuesday, GFS again models conditions that would be condusive to wintry type precip. A second area of low pressure, for T+105 on Tuesday, somewhat similar to the evolution on the 06Z output is shown on the 18Z GFS Operational Run. Again this also needs to be monitored, both in terms of strength of the low and the possibility of wintry precip assocaited with this possible development.



Latest UKMO Fax Chart T+96, Monday.

This chart shows the 528dam line well to the south of Ireland, with troughs embedded within the northwesterly flow. Again, something that needs monitoring.



In summary, it would appear that the coming few days will be very unsettled, with exceptionally windy conditions possible on Saturday according to the latest GFS 18Z Op output. Furthermore, Sunday and the early days of next week are still showing some possible wintry potential.

SA.

nacho libre

just saw the bbc weather there, if you are a snow lover it was a very encouraging forecast for monday:D. also, he was saying there could be gusts of 80 mph in exposed parts of scotland and northern ireland on Saturday. so all in all a period of interesting weather coming up this weekend.

Danno

Whoaaa, stop the press! What a difference a day makes... [Just finished the last of the Chrimbo gargle , (a bottle of baileys to be exact) so excuse this sudden outburst of JOY!!!]

Howly God, I have never ever seen such charts in all my life. It's like Canada has been tilted up from the west coast and everything on the east coast is going to slide into the Atlantic and glide over the ocean to us.

Who awoken the Atlantic, and what is their telephone number!!! :P

This is incredible, just incredible. And, all at under 100 hours.

Snowbie, Pat, SC, can I please, please, please go nuts now!!! :P :P :P

Danno

Deleted User wrote: »

http://www.wzkarten.de/pics/Rukm1441.gif Thats about as south westerly and realistic as one can be as regards whats ahead by the way. No amount of thrawling gfs ensembles for odd permutations hanges that.

Dare I say, but that is a FI chart, especially in the current set up! :pac: