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BrickFielder last won the day on July 11 2010

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  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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 ?
  7. 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.
  8. 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.
  9. 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.
  10. Estofex forecast for those who have not seen it http://www.estofex.org/ Couple of quotes. A surge of dry low-stratospheric air wraps cyclonically around the cyclone's center, probably ending the stage of a potential offshore sting jet event. Downdrafts may bring severe wind gusts to the BL. What I am pondering is the forward speed of the storm which I roughly calculate to be 50mph (6 hours to traverse Ireland) which makes me question highest wind speeds of 80mph. Looking at forecast storm surge levels which range from about 1m to 2m then there seems to be some key risk areas like south Wales, but particularly the Scottish borders down to Liverpool (in addition to Ireland). What does concern me is that the jet stream pattern showing up on satellite images is deviating slightly from forecast (jet to the east of the storm is weaker than expected and the trough to the west a little sharper). Maybe a few twists and turns still to play out.
  11. Just coming into range of some shorter range models like the lightning wizard ones which can give some further insight into expected conditions. Wind gusts over 90 knots (100mph+) for southern Ireland for example. I have also being trying to assess the potential for embedded super-cells which could pose a lightning, hail or tornado risk as well. Looking at mid level and low level lapse rates and overlaps between the steepest lapse rates for both, then I don't think there is much of a tornado risk (perhaps a waterspout risk for southern Ireland coasts). The parameters for an embedded non surface based super-cell are not that good either despite what some charts suggest apart from very close to the center of the storm. There is some marked vorticity advection from the cold front and some weak instability which would have to be watched. Theta e and Thompson index values suggest some very heavy rainfall for Ireland and perhaps to a lesser extent from the cold front associated with it. Assessing whether there is a possibility of a sting jet scenario is also tricky, as there is rapid cyclogenesis caused by the Jetstream, but also an amount of frontal wrapping around the center of the low. Despite quite a narrow gap between the cold front and central core for a period and the jet streak over the cold front, I am not at the minute thinking a sting jet is on the cards. Some of these factors which I don't think will be applicable for the UK (convective potential) may not hold true for parts of Europe as it weakens and moves across the north of Europe, so European forecasters should probably keep an eye on events as well. Longer range modelling differences between some European models and GFS have shown differences in the handling of a trough down towards the Baltics with European models I think picking up the trend earlier. I think makes the eastward shift in the forecast from European models more likely. Ensemble members were a little confused about a low pressure system developing along the frontal boundary Saturday into Sunday which moves across to northern Europe late Sunday. This looks likely and is also part of the reason for the slight eastward movement.Its possible with the Baltic trough moving a little more south east than south than there could be further eastwards movement in the forecast, but its unlikely to be far at this forecast range. I not too happy though with the modelling of the transition to extra tropical and think the warm core will only breakdown just south of Ireland, increasing the risks of stronger gusting winds for southern Ireland.Looking at satellite pictures (eumetsat) then there has been a slight upper jet to the north of Ophelia slowly wrapping around to the west , which has caused the hurricane to spread out eastwards. This is causing some sheer and perhaps a little dry air to be drawn within, so we should expect a little weakening and perhaps a slight eastward shift again. While focus is drawn to Ireland we should note that with many trees still with considerable foliage across England then even moderate winds could cause some disruption. Equally some parts of the UK are already fairly water soaked so a strong deluge of rain could cause some localized flooding issues. Lastly a couple of forecast images from GFS which show how the storm will be wrapped by a small jet streak to its east, with divergence aloft ahead of that streak. Whether its a hurricane, hybrid or plain autumn storm, this probably means rapid cyclogenesis as it approaches Ireland (Deepening of the low).
  12. Looking at the storm as a hybrid between hurricane and extra tropical storm might give some different insights particularly looking at it as extra tropical. In this case we have a jet streak looping around the storm as it moves up from off the coast of Spain to France with divergence aloft ahead of the storm. This would suggest rapid cyclogenesis (deepening of the low) as it approaches the UK.As the storm moves near to the coast of Ireland that jet streak swings across England. Strongest winds for a hurricane are near the eye whilst the strongest winds from a non tropical storm are under the jet stream. Looking at the ECMWF 850mb winds shows wind strengths in excess of 70 knots at 850MB (That is 90mph winds at 5000 feet) across much of the UK. Now ECMWF brings the low closer to the UK than some other models and winds at the surface will be a lot less than that, but it is worth bearing in mind. So we must be careful not to assign purely tropical attributes to this storm.Having said that Southern Ireland looks to have the brunt of this according to current modelling.
  13. It is way too early for any sort of realistic forecast , but realistically the worse case scenario for Scotland is probably some Gale force winds and heavy rain. By the time the system reaches Scotland the storm will have transitioned from a tropical system with warm core (convection around a central low ) to your typical north Atlantic low pressure system. Once it is fully transitioned to extra tropical it should not be any worse than you typical autumn low pressure system. The only difference is that it might contain tropical moist air giving lots of rain, and as it interacts with the Jetstream it might deepen to give strong Gale force winds. The only question is really how and when the warm core dies and how the remnants of the storm interact with the Jetstream. Both of these should have happened by the time the remnants reach Scotland and most likely before it reaches the UK. There are some slight scenarios where southern parts of the UK and Ireland could be affected by unusually high winds and rain for this time of the year, possibly even near weak hurricane strength winds. Living in Scotland you are unlikely to experience much beyond your typical autumn low pressure system, with rainfall and flooding a more likely risk than abnormally high winds.
  14. Its quite an unusual path for tropical storm and forecast modelling will most likely change over the next week, but storms like this can produce a few unpredictable results. Hurricanes Gordon (2006) , Vince 2005, tropical storms Ana (2003), Grace (2009) come to mind. The prime concern does have to be for the Azores, but we should also consider what exactly happens when this type of storm goes extra tropical. Based on past observations the storm can become embedded in a frontal system and tropical aspects decay. Unlike storms which go extra tropical mid Atlantic as they lift out, what can happen is that the warm core shrinks in the front and tightens up before breaking up totally. The core moves quite rapidly up the frontal system and in its death throws can just about reach the southern UK bringing localized hurricane force winds. In effect the core tightens, shrinks and its rotation speeds up as it dies with a possibility of producing winds in excess of 100mph. In this particular case I don't think this will happen as the tropical storm is not strong enough and the core not warm enough with a result that the core dissipates long before it gets anywhere near the UK. So the prime risk to the UK would be tropical type rainfall and a particularly deep Atlantic low developing as the remnants move towards Iceland. Current modelling would suggest that western Ireland could experience some very strong winds next Monday afternoon and Northern England and Scotland a deluge of rain Monday evening. We should however note that ECMWF and UKMET moved things eastward in the last run.
  15. 06z forecast modelling looks a lot better than the overnight modelling. Suggests French storms will pass over the south east of the UK with further initiation of elevated storms south west and south later this evening trundling on through to East Anglia. Key area to watch would be around Exeter this evening. Not sure how far north storms will get as things move a little faster eastwards than previous thought.
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