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BrickFielder

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  1. BrickFielder
    At low levels we have moisture advection from out in the bay of Biscay whilst the fringes of the jet stream run across the south at high levels. At the surface we have a number of convergence zones which look to spark off convection. Steering winds and winds aloft suggest to me a possibility of back building convection which could give rise to localized flooding. With temperatures at best reaching around 16 degrees we should not expect very strong updrafts, but rear flank downdrafts and outflow boundaries could provided conditions for an isolated more potent storm. Forecast skewT's even from a conservative view could produce more instability than suggested by models, but there does seem to be very moist mid levels which could make convection messy. Overall cloud tops look somewhat limited, so we should not expect widespread thunderstorms and wind shear although having some directional shear at the very lowest level is pretty weak. Strong winds aloft may also shut down convection as tops shoot ahead of convection. Instability through the zero degree isotherm looks quite strong which could help to sustain some moderate hail. Slight chances of thunderstorms with main risks being hail and localized flooding.With very slack winds at the surface there is always the chance of some localized anomalies especially with a south feed of moisture (perhaps a hint of a low level jet on some charts as well). Something to keep a close eye on with an outside chance of a more severe isolated storm.
  2. BrickFielder
    Eumetsat Images show low pressure system to the north west of Ireland Currently which should sink south towards Northern Ireland. An area of vorticity wraps this low which should affect parts of Ireland from midday on wards. Eumetsat images also show a weak lobe of vorticity approaching the south west which should spread along the southern coast of England (affecting Wales now and south west soon) . This is not particularly well modeled so could pep up showers as it moves across. Low level winds show marked convergence zones initially along the m4 corridor and along the south coast but moving towards the south east from midday. Later convergence sets up across parts of Wales and the midlands. Forecast SkewT's show a marked temperature notch at 600Hpa as drier air comes in aloft and a lowering of the tropopause thus limiting convective height.Convection is likely to be better where the convective height is slightly lower. With temperatures on the low side still and limited cloud height it is likely that thunderstorms will be limited to Ireland and along the south coast. Key areas are likely to be Southampton to Reading from midday moving quickly eastwards during the early afternoon although mid to upper level cloud could limit convection. There is an elevated spout (very weak tornado) risk for the south east but particularly for parts of Ireland.In my opinion thunderstorms are likely to be very isolated today and not significantly severe although there is a risk of localized flooding.
  3. BrickFielder
    Looks like one of those days where forecasting is extremely tricky and I am not sure how much to trust the modelling. From Satellite images we can see the frontal system swinging up northward across the UK, but there is also evidence of a second front developing in what looks like a partial MCS. This is going to alter the times for cloud clearance and narrows the window of opportunity for thunderstorms to develop. Looking at the moment of the two centers of low pressure it looks like the weaker one to the west of the UK will slow down with the result that the deeper low to the south west of Ireland will not be pushed so far south and come closer to the UK. Generally speaking discreet thunderstorms require some sort of triggering mechanism whether that be cold air aloft, moist air at the surface,wind convergence, surface heating or orographic lift. I can see some wind convergence areas developing in very slack wind conditions. It is not clear however whether those convergence zones are modeled as a result of storm development or other conditions. Looking at the forecast skewT's we can see a very moist air profile all the way up which usually means rather messy convection. There is an area of increased low level wind speed shear towards the more south east and towards the east which could help storm inflow. Over all temperatures of 13 degrees in the sun do not generally indicate strong storms and I have doubts about some of the modelling. Assuming the modelling is mostly right then we should be watching East Anglia later this afternoon and perhaps the north midlands. My gut feeling is that post frontal convection is likely to be more limited to the south and perhaps south west generally with still a risk for East Anglia soon after frontal clearance. The modeled low level wind convergence bothers me in that it could indicate storms developing their own wind fields which makes severity of storms unpredictable.
  4. BrickFielder
    Winds from the north west are not often associated with thunderstorm or heavy shower potential and I pretty much agree with the forecast outlook. Having said that there are some interesting details we can explore which might prove interesting. As pointed out in the forecast wind convergence is key and without it convection potential is severely reduced. Compare the mid afternoon chart for rainfall and the chart for low level winds with convergence below and you should see a close match. Next up is the forecast SkewT charts which show cooler drier air moving in aloft which should act to increase the height of convection as the lifted tropopause moves south. This shows up more clearly on the comparison between the mid day and late afternoon forecast SkewT's for the west midlands below. This can often result in increased lift through the freezing zone and could increase the risk of hail. Sometimes just looking out the window and observing can tell you a few things as well. I notice this morning that lower level cloud seems to be moving along quicker than upper level clouds. This can just be an early morning effect, but forecast SkewT's are hinting at the same thing. This can mean that updrafts and downdrafts are clearly separated leading to stronger longer lived convection , along with localized inflow winds. Combining with convergence very weak tornadoes should not be totally ruled out. This does not mean that we should expect significant thunderstorms today and there are clear hints that the most we should really expect is some heavy showers. Mid level lapse rates are not that strong, day time temperatures will not result in fast building convection and the Overnight Nottingham Sounding shows some notches which could inhibit convection at certain heights if the atmosphere does not change.My best guess is that lightning will be pretty isolated if there is any at all today, but I would have some concerns about hail. Its always interesting to me just to explore some of the detail even if it is not a classic thunderstorm day.
  5. BrickFielder
    If it was a little deeper and a little slower moving I would be looking closely at this for storm surges. Here I am thinking about the Bristol channel and later down the British channel onto the continent. Storm surge models currently don't show too much to worry about though.
  6. BrickFielder
    Looks like the convective cap is a little strong to the south east, so little action possible there during the daytime. Comparing the Nottingham sounding SkewT from midnight last night and the forecast SkewT's show that temperatures of about 18 to 19 degrees will start surface based convection in theory so we might be relying on some heat island effects over large cities. EUMET Satellite images suggest weak mid level vorticity which would coincide with some drier air suggested on some SkewT's in the mid levels. Low level veering of winds is restricted to the cold front which is behind the convection and to an area to the north east where onshore winds may interact with an storms. Cloud tops look quite high from forecast SkewT's although the Nottingham sounding adjusted for daylight would limit heights a little. High level cloud could just limit temperatures where no surface based convection takes place. Key areas would be places like Leeds and York although lapse rates and cloud cover could prevent any storms at all.
  7. BrickFielder
    The MJO is a major contributor to the global weather patterns, so for those who want to understand a little bit more about it here is a brief overview of my current understanding of the MJO and Rossby and Kelvin Waves. First lets talk a little bit about waves or more specifically Rossby and Kelvin waves. These can occur both in the Atmosphere and in the Ocean and it is important to be clear about the difference between the two. Oceanic Rossby waves take the form of slight height changes in the sea and more apparent changes in the depth of the thermocline. These can take months or years to cross an oceanic basin and have there orrigin in anomalous atmospheric pressure patterns.In the North Pacific, for instance, a Rossby wave, after the 10 years or so that it takes to cross the basin, can push the Kuroshio Current northwards and affect weather on the North America continent. This might have happened already in 1993, the culprit Rossby wave being an effect of the 1982-83 El Niño.The important thing about oceanic rossby waves are that they are slow and westward moving. Kelvin waves move faster and eastwards taking about 70 days to cross the Pacific. See in the link below how an easterly wind anomaly at the equator can produce these waves and in the subsequent link how they are reflected to ultimately produce a pattern which has similarities to the el nino,la nina pattern. Oceanic Rossby and Kelvin wave Thory The Evolution of Oceanic Kelvin and Rossby waves The point here for me is that strong MJO events have large impacts of weather patterns and probably contribute to la nina and el nino events. We should note however that el nino and la nina tend to closely follow the volumes of warm water (20C+) at the equator so the MJO does not have it all its own way. Warm Water Volume and ENSO We recognise Rossby waves in the atmosphere as the long waves in the jetstream but there are also Kelvin waves in the atmosphere which travel eastwards around the world typically taking 40-50 days which show up as a pressure anomally. These lesser known waves may actaully play a most important role is triggering the MJO cycle. Perhaps we should just note that gravity waves are a different phenomenon and although Atmospheric Rossby waves are thought of as planetary waves I prefer to use this term for those waves in the Stratosphere, Mesosphere and Ionosphere. So onto the MJO events which have there orrigins in enhanced convection over the tropical western Pacific which create a low pressure which radiates rapidly eastward as a dry equatorial Kelvin wave over the eastern Pacific. It is blocked by the orographic barrier of the Andes and Central America for several days before propagating through the gap at Panama. After rapidly propagating as a dry equatorial Kelvin wave over the Atlantic, the sea level pressure anomaly is delayed further by the East African Highlands before it reaches the Indian Ocean and coincides with the development of enhanced convection at the start of the next MJO cycle. So we have a trigger which circulates the world over a set period (typically 50days) with one event triggering the next.Here we should note that the MJO Phases do not coincide with this circulation but reflect the eastward migration of convection once convection has been triggered. Once convection fires at the start of the cycle you will get a Rossby wave response with pressure troughs to the north and south of the area of convection. The low pressure will bring colder air in to the west of the convection killing of convection while eastward moving warm air spreads the convection eastwards. Eastwards of the low pressure systems will be strong anticyclones (high pressure) which will give strongly easterly winds at the equator. These pressure systems affect the mid latitude jetstream and hence the pattern across the north Pacific, the US and to some extent the North Atlantic and the UK. MJO Phase 2 or 3 weather pattern response MJO Phase 6 or 7 weather pattern response At the moment cool waters in the central pacific due to la nina are tending to damp down the eastward movement of convection while anomalous highs ahead of the convection will be acting to enhance la nina and slowly move it Westwards. Phase 5 through 8 of the MJO can result in a high pressure anomaly towards Alaska and a deep trough down into the central US. There are some suggestions that this high pressure towards Alaska ridges into the arctic region causing a displacement of the stratospheric vortex forcing the arctic oscillation to trend negatively. Perhaps I will revisit this when I know a bit more.
  8. BrickFielder
    I am not sure I really agree about the vortex at lower levels. Certainly there is some cold air and a deep circulation at 30hPa but it all looks pretty weak at 100hPa. Vorticity at the tropopause is very messy indicative of a weak vortex. Analysis out of Japan also shows a very weak vortex. Heat flux also looks to be fairly flat line. The thing about the average of zonal winds at this time of the year is that it is the average of years when both the vortex is still active and when it has already broken up. You would expect it to be above or below the average with average indicating a weak vortex at lower levels. There are indications though that it will strengthen and we might be in for a late break up of the vortex. We wait to see which way it goes.
  9. BrickFielder
    One of the key things about Spring and Early summer is that the jet stream begins to shift North. Typically in the region of the UK there is a northern arm and a southern arm to the jet and where ever they occur you often get wet and windy weather. Due to the low global angular momentum (la nina like) state of the climate then the jet stream is currently further south than it would normally be. This is born out by the ITCZ being relatively far south across Africa for this time of year. I tend to think that we get two periods of about a month of wet weather as the jet stream moves north. During la nina those months might be April and June with August and October being wet as the jet comes back south. During el nino those months may be earlier for instance March and April. Ideally you would want a transition from la nina to el nino during spring which would push the jet north quickly, limiting the about of wet weather. One of the best teams for predicting la nina and el nino are the Australians who tend to look at the SOI (Southern Ocean Oscillation Index) as a pre cursor to the state of equatorial water temperatures in the Pacific (which is what la nina and el nino are). During the last month we have seen a significant change and although this was enhanced by some strong activity through phase eight of the MJO it should be noted that the recently dominate pacific trade winds have been over come. I will take time for the MJO signal to travel around the world again and to some extent you might expect some change at this time of year, but I still see some significance that may not yet be reflected in the models.Warm water volumes should be declining somewhat now so a full on el nino seems unlikely but the changes seem to be significant even though global angular momentum is on the low side. Since the stratospheric vortex has never really recovered from the mid winter disruption we have had an unusually spring like late winter season with very little pattern blocking. Significantly the North Atlantic storm channel has been open for over a month and this has had an impact on ice formation to our north especially in the Barents sea area (yes I do know all the caveats surrounding the following chart but it goves an indicator). This is perhaps not good news for snow lovers for next winter in the UK although the snow fields of Asia may still be quite late clearing leaving us watching for a beast from the east as a source of cold next winter. Coming back to the storm channel being open and how weather patterns seem to be to be limited to a two month period then the current pattern should not have that much more to run. I put this down to the rossby wave lengths (number of undulations of the jetstream around the world) tending to change with time and season. In conclusion I am quite hopeful for a drier spring season than usual with temperatures beginning to catch with the norm from here on in. I am also rather hopeful that with plenty of cold air to the north due to the low angular momentum conditions and with the jetstream beginning to come north more quickly we may have an interesting storm season ahead (although it may be shorter than usual?). We might also see a Hot month mid summer instead of barely escaping the clutches of the jet stream last year. I reserve the right to completely change my mind though if the SOI changes, or the stratospheric vortex reforms, or any one of a number of variables change.
  10. BrickFielder
    My take would be that Low angular momentum means less energy going into the jet stream. This would suggest to me that during a low angular momentum period the jet stream tends to stay south and not arch northwards leading to high latitude anticyclones. This means that low angular momentum is not good for a particular type of blocking. Typically we get cold periods due to being north of the jetstream, but the Atlantic storm track is rarely disrupted. A strong la nina period which is associated with low angular momentum however means trade winds tend to be strong across the Pacific. This leads to a stationary anticyclone north of the equator which by nature of the fact it does not move can cause extra tropical blocking to its north. Unfortunately this type of blocked pattern is not often conducive to cold weather in the UK with I think high pressure in the north pacific, low pressure in north west Canada and high pressure again in north east Canada. All this does depend on the season and number of Rossby waves around the globe, hence why Glacier Point uses re- analysis to show the effect during any particular month. You might think that a strong el nino period would give you the opposite effect, but what you get is a strong jet blasting across the Atlantic with the UK ending up with a largely wet winter. You will get periods where the jet arches northwards but any anticyclone tends to get undercut or blown away by the strong jet. In contrast to the fixed anticyclone north of the equator in the Pacific you tend to get Thunderstorm activity (MJO) moving west to east across the equator, again not giving a very fixed pattern. The point about the QBO and its direction is that stratospheric anomalies tend to be transmitted down to the troposphere during a easterly QBO rather more than a westerly one. This is not well explained why in literature but seems to reflect the fact that north pole stratospheric winds (stratospheric vortex) may be pulling in the opposite direction to equatorial stratospheric winds (QBO). I also think the actual nature of the Stratospheric disturbance plays a part. Split vortexes tend to lead to a lot of blocking, displace vortexes lead to less blocking and completely disrupted vortexes give very little blocking, but tend to reinforce low angular momentum. We have actually gone through all three of these phases with different results.
  11. BrickFielder
    Current Analysi of the stratosphere. 5 Days out. From this I would take a strong signal for blocking in the northern Pacific and a secondary weaker signal for blocking in the north Atlantic. This kind of shows up on the GFS blocking maps. 8 DAYS OUT How does it compare to ECM and GFS forecasts. Clearly the strong signal is across the other side of the world and we are more likely to be influenced by GWO and as a downstream product of the strong signal in the pacific. GWO is now headed strongly into phase 1 and there are clear indications that Global Angular momentum is likely to tank. I see this as an indication that we are never going to be far away from being north of the jet stream, but indications are that we might just miss out on the really cold stuff. Spring weather with a misture of cold and mild seems in order.
  12. BrickFielder
    Events in the stratosphere are pretty unusual and the tropospheric response should be linked to the specifics of the type of event going on. To my way of thinking there are three distinct types of event that can occur in the stratosphere. 1) A split Vortex with both displaced southwards much like we have now. 2) A single vortex displaced southwards, much like we will have in a few days. 3) A complete disruption of the vortex which I think may be on the cards after that. Lets look at now. Temps and the vortex Signals for high pressure as a result Lets move on 5 days and we see one part of the vortex collapsing as they both rotate around. Unfortunately that collapsing bit moves nearer to the UK and seems likely to give us some more atlantic type weather untill early next week. Further out and that second part of the vortex collapses leaving just one part displaced southwards. Vorticty charts suggest here we could be in for another cold period with a risk of snow. Even further out and we have to start looking upward in the stratosphere for clues and you need to go almost all the way up to the 5hPa layer before you start to see any kind of vortex reforming. Giving very little vorticity in the stratosphere for a period. Meaning other signals will take priority over the stratosphere. Those signals will most likely involve the GWO which you would expect to head into phase 1 and 2 but seems to be stubornly stuck in 3 4 and 5. I am not really convinced about mountain torque reducing angular momentum which if I understand things correctly means as a cyclone crosses one of the great mountain ranges it transfers momentum to the earth ,taking it away from the atmosphere. My take on this would be although the mourtain torque is falling it is still positive and as such we still have some time before angular momentum falls away. Perhaps this is something for Glacier Point to elaborate on. Cyclically it looks like warm water ought to be on the decline in the Pacific, but we do have a stalled MJO in phase 6 so maybe this will come into play. SST's I think will have their day this year if things really calm down so we ought to be thinking about high pressure maybe to the north of the warm spots in the atlantic. The upshot of this is that models are likely to struggle a bit with the transitioning phases in the stratosphere and globally we might expect some high impact weather this year as a result of this event.
  13. BrickFielder
    There are times when the Global wind oscillation is not the whole story and I suspect we have such a period coming up. It is not that its wrong just that there can be some delayed actions from the patterns that occur as a result. First let us have a quick review of where we think we are. GWO shows we are drifting into phase 1, perhaps spiking as ed berry puts it is a better word although. Long Paddocks SOI figures show that the pacific trade winds have been somewhat intermittent, showing that the la nina phase at the moment is pretty weak. 1-Jan-2009 1012.26 1002.65 23.56 12.82 14.72 2-Jan-2009 1011.35 1003.55 15.03 12.60 14.81 3-Jan-2009 1012.38 1004.40 15.88 12.42 14.85 4-Jan-2009 1012.21 1004.95 12.49 12.91 14.89 5-Jan-2009 1013.74 1005.60 16.63 13.70 14.95 6-Jan-2009 1013.60 1005.70 15.50 14.38 14.93 7-Jan-2009 1013.45 1006.10 12.91 14.76 14.76 8-Jan-2009 1010.79 1005.40 3.68 14.37 14.57 9-Jan-2009 1008.14 1004.25 -3.39 13.78 14.37 10-Jan-2009 1008.39 1003.60 0.85 13.33 14.22 11-Jan-2009 1011.14 1003.20 15.69 13.47 14.21 12-Jan-2009 1011.61 1006.60 1.89 13.27 13.96 13-Jan-2009 1011.89 1007.60 -1.50 12.88 13.74 14-Jan-2009 1012.16 1006.90 3.07 12.94 13.56 15-Jan-2009 1013.66 1007.35 8.01 13.15 13.38 16-Jan-2009 1014.60 1006.00 18.80 13.44 13.33 17-Jan-2009 1014.59 1007.30 12.63 13.25 13.28 18-Jan-2009 1012.88 1007.60 3.16 12.60 13.20 This also coincides with a pick up in MJO activity as the wave finally comes round again. Phase 8 where the MJO is currently is usualy the end of the cycle and we might expect la nina and the trade winds to pick up again. Understanding what is going on Torque wise is rather more tricky. Moutain torque does not suggest any spectacular change in angular momentum, however as GP points out the frictional torque has picked up. Gut feeling tells me that the spike into DWO 1 will lead to a signifcsnt drop in angular momentum coming up (Read a blocked pattern). Normally I would guess that the current pattern is here to stay, but I don't think so and I think most of the models may be perfroming poorly at more than a week out. Ed berry suggest a transitional change and when he talks about winter storm developments focusing on the Plains I cannot help thinking mountain torque and sinking angular momentum. Now for the fly in thointment so to speak and here I am looking at the stratosphere forecasts. That looks a lot like a split stratospheric vortex and if that comes off then all bets are off. Current vorticity charts suggest a deep low for the central plains of the US, meaning winter will reallly start over there and a lot of energy will go into the jet stream as a result. High pressure ridging north in the Atlantic would not be an unexpected result although it does depend on how the jet reacts (it could just blast across the atlantic). Despite my inital argument that the stratosphere was spoiling things there is some symmetry between what the GWO tells us and the ECM stratospheric forecasts. Cooler northerly perhaps on its way then ?
  14. BrickFielder
    East asian mountain torque looks to be dropping off and I cannot quite see where the next reduction in angular momentum is going to come from. High pressure looks to cover the big mountain ranges in the short term, so I could see a bit of a stall in phase 4 or 5 as a result. Stratospheric modelling would appear to me to be divergent with weather modelling so am undecided beyond about 5 days out as to whether it will move into phase 7 and 8 at that point. I suppose the MJO going into phase 7 and 8 could disrupt the trade winds somewhat which might help to break the pattern. SOI (Southern Oscillation Index) has remained positive which would tend to indicate continued la nina conditions (east to west trade winds) over riding the MJO convective activity.
  15. BrickFielder
    That slightly tricky to answer. Lets try to answer the second question first. Fast, zonally oriented Rossby wave dispersion occurs in phase 5. (Amplified Jet) An extended Pacific Ocean jet stream and southward shifted storm track is observed in phase 7 (strong flat jet over the pacific) A retracted Pacific Ocean jet stream is a key feature in the total field is observed in phase 3 (Weak pacific jet) Phase 1 has enhanced subtropical jets and closed lows in the subtropics. Angular momentum being added usually results in a stronger jetstream I think. As for how angular momentum is measured and what level then I think it is from the winds at all levels up to 10hPa with those at the jet stream level being important. GP will probably have a few more details.
  16. BrickFielder
    Ok I will start a new thread for dicussions along this line and perhaps I will draw on some ideas expressed in the stratospheric thread and artic sea ice thread. I guess you would be the best person to explain all this GP but for those who don't know this thread is about global angular momentum and how it oscialltes up and down (Global Wind Oscillation) along the lines discussed by Ed Berry. Angular momentum is of course a measure of the turning force in the winds, so could perhaps be considered a measure of the strength of low pressure systems, but also relates to how much the jetstream undulates and how much blocking we have. The budget of angular momentum goes up and down as energy is lost as weather systems crash into mountains and increases as cold air meets warm. Each phase of increasing and decreasing momentum suggests different types of weather for the UK. Looking at the current GWO plot we see a liklihood of going into phases 3 and 4 based on how it usually cycles round. This implies increasing angular momentum as the various torques including mountain torque diminish (i.e those things which take energy out are not active). This is certainly true of mountain torque. For frictional torque and gravity wave torque then the jury is out. Overall it looks like global angular momentum is on the increase. The tendecy during december has been upwards. Short term I think we are looking at phases 3-4 and more of an Atlantic influence. What I am guessing at though is that low pressure systems crossing the US will increase mountain torque, equally the jet stream across india is not a weak flabby one which might increase asian mountain torque. The strong jet in the western pacific along with OLR charts suggest strong trade winds with a stationary high to the north east of Australia and convectional activity to the north west of Australia. So back to phase 1-2 fairly quickly I think afterwards. All maps are available in the link below. PSD Map room for AAM I am sure GP will tell us what he expects from the MJO and convectional activity in the pacific and how and if he expects rossby wave development as a result. It is those Rossby waves which in part will affect the stratospheric vortex and the low angular momentum could be linked to a more blocked pattern and sea ice build up to our north which I talked about in associated threads. What we should always remember though that this a complex interaction of parts of which the stratosphere plays a large part during the winter. Please note that this post and subsequent comments have been copied from the forum, so the dates/times of the comments are not correct.
  17. BrickFielder
    Bit of a ragged eye but there is still ongoing convection development around the eye. It appears to have pulled down some drier air so it might be a bit of a hybrid at the moment. Those people in Madeira or the Canary Islands or those traveling to those destinations should keep an eye on the forecasts.
  18. BrickFielder
    Looks like there will be some tornadoes embedded in the hurricane and reports of severe lightning in the eyewall. Radar imagery from KTLH shows a cluster of quasi-discrete supercells over Apalachee Bay moving northwest towards the Wakulla County coast. It is here that the supercell tornado risk appears focused during the next few hours as this convection moves ashore. Inputting the supercell motion (150 degrees at 40 kt) yields 240 m2/s2 0-1 km SRH per KTLH VAD data. Low-level shear will likely increase further and become more favorable for low-level mesocyclones and an EF0-EF2 tornado risk this morning with the persistent/more intense mesocyclones.
  19. BrickFielder
    No real evidence of an eye now as far as I can tell but there is deep convention in the south, which may lead to some re-organization. Many models taking just to the west of Ireland as a strong autumn storm. With no clear warm core most tropical characteristics will be lost although this could change (good chance of a little re-organization in my opinion) , but it will still be a significant storm for the Azores. There are a few outlier model solutions that take Helene over Cornwall as an Autumn Storm, but I think this is unlikely at the moment. The westward movement could be a little bit of a Fujiwarra effect from tropical storm Joyce. Some models show Joyce developing and following in behind Helene with a more eastwards movement heading eventually towards Portugal before dissipating. Looking at EUMetsat Satellite shots show Joyce not really developing in warm air and I don't really see it having a warm core. NHC seems to think Joyce can move into warmer air left from Helene and take on tropical characteristics. It is possible and it is even possible that Joyce could circulate back to off the coast of North Africa to reform. So I am not totally convinced by the westward movement suggested by the models and would not be surprised to see a little strengthening again of Helene based on convection in the southern quadrant. To summarize ,I have low confidence in the modelling , but don't expect hurricane like conditions for the UK. The prime risk is likely to be very heavy rainfall if at all based on current low confidence modelling.
  20. BrickFielder
    Extract from NHC Forecast discussion 16. I think discussion 15 suggested the baroclinic transition could see the storm increasing in size and becoming a significant autumn storm moving north eastwards. Modelling today might suggest that it will hold on to its warm core structure for longer than you might expect. I still think the Azores should be watching this one closely.
  21. BrickFielder
    Helene is pretty big with a ragged but quite well defined large eye at the moment. I would not be surprised if it is not close to a CAT 2. Bearing in mind that Isaac is dragging a band of very warm moist air across the North of Helene it is a bit surprising that models have Helene fading away in the mid Atlantic. It would not be the first time that modelling has a hurricane fading away when in reality it manages to survive quite far into the North Atlantic especially since this is forecast to start moving North quite quickly in a few days. If I was in the Azores or Madeira I would be watching this one closely.
  22. BrickFielder
    High Pressure building to its Northwest as it approaches the Seaboard, which makes GFS's loop the loop solution credible. Still too far out to really get any idea of whether it will make Landfall. ECM has it making landfall in the carolinas whilst CMC has it skirting and just missing the seaboard. Somewhere in between maybe ?
  23. BrickFielder
    The positioning of the potential trough out to the north west Friday evening could be interesting especially if it went down the Cheshire gap. Whenever I see a weather pattern setup like we see on Friday I always look for those little wind eddies developing to the south of Iceland (sometimes the southern tip of Norway as well) which can create shallow but quite potent little snow storms which can affect the UK (polar low). They don't tend to show up in the modelling until quite close to the time, and usually only occur when the arctic ice has moved further south. Worth watching the models closely even if its too far out for precise detail yet.
  24. BrickFielder
    OK so its not an ex hurricane and it will be weakening as it crosses England, so its just a bulk standard autumn storm. Except it has a warm core anomaly, which means it probably started its life in a similar region to Ophelia but as a failed tropical storm. Quote from Estofex Forecast (http://www.estofex.org/cgi-bin/polygon/showforecast.cgi?text=yes&fcstfile=2017102106_201710192030_1_stormforecast.xml) A gradually filling depression with a warm-core anomaly approaches Ireland during the night with a weakening gradient wind event along the S-periphery of the depression. This makes me nervous about the forecast modelling and a warm core anomaly approaching from this direction could actually reach the UK. If we assume that the modelling is correct then it looks like sustained winds of 40mph gusting to 65 mph which is no big deal. However this system is not coming up from the south west but moving much more eastwards than north eastwards as it crosses the UK. It puts the strongest winds up the Seven Estuary and into the midlands. 65mph gusts into the Midlands is a different proposition to coastal areas. It should be OK but it is unusual for this time of year. My biggest concern I think is the tide in the Severn which peaks at 13.5M at Bristol at around 9am which will be boosted by a half meter due to low pressure near by and topped up with a wind surge. A 14.5M tide in the Seven Estuary is around the point where we need to consider flooding risks for that area I believe. In addition to this we should see some squally showers over the region at the same time which will be enhanced by dry air aloft. This increases the risk of strong downdrafts from these showers and increases wind gust potential under these showers. (See Estofex forecast for additional detail) (25ms downdraft + steady 40mph wind gives gusting from showers over 80mph). The problem is I don't want to be a scaremonger and the risks from this storm on the face of it are not that severe. Even the risks from some of the concerns I have highlighted are low, so if you are a forecaster I would be watching very closely, but for the rest of us we can ponder unexpected outcomes and risks. My opinion would be that the risk of severe disruption is low from Storm Brian, even if I cannot put to bed my niggling concerns.
  25. BrickFielder
    Took one look at the satellite imagery this morning and saw the warm core has broken up, but noticed the jet wrapping the low and thought singlet. Estofex mesoscale discussion suggests their forecasters came to the same conclusion.
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