Vorticity0123

The precursor low of the storm has indeed formed to the southwest of Iceland. Currently, there is a comma-cloud formation present at that area. The surface analysis of the KNMI (HIRLAM) shows the development of the system: The precursor storm is the 1005 mb low to the SW of Iceland Six hours later, the system is deepening quite rapid (to 995 hPa in the picture) located to the northwest of Scotland. However, at Thursday 6UTC (only six hours later), the low pressure area has attained a pressure of below 970 hPa This would mean a pressure drop of on average 4 mb/hr! (on this six-hour interval) The main reason for this event to occur is because the low pressure area is in the left exit of the jet stream1 The low pressure area is in this image on the extreme southeastern tip of Norway. For the wind analysis, the Hirlam wind output will be used: This is the wind map for Thursday 07 GMT. It shows that a rather severe 11 Beaufort (No BFT this time ) impacting the northwest of Schotland. This could result in quite heavy wind damage there. The wind map for Thursday 13GMT shows that the wind field has moved southeastward along with the low pressure area. It shows a 10BFT impacting the northern tip of The Netherlands and western Denmark. Because the wind is also northwesterly, there is a chance of rather extreme high tide occuring in the countries adjacent to the North Sea. One final thing i'd like to point out is that there is a storm warning of some sort (code yellow or code orange) for the northern part of Holland for 29(!) hours. The codes indicate a 3 hr span of wind gusts of up to 100 km/h, thereafter an 8 hr span of wind gusts up to 130 km/h, and finally another 19 hrs of wind gusts up to 100 km/h. The duration of the storm makes it even more dangerous. Sources: http://www.knmi.nl/ 1http://rammb.cira.colostate.edu/wmovl/vrl/tutorials/satmanu-eumetsat/satmanu/cms/racy/backgr.htm http://www.netweather.tv/?action=jetstream;sess= http://www.weeronline.nl/vakman-index/130/0

I'll try to give a more in-depth analysis of the wind field and possible flooding (along with the WRF-model). On Thursday afternoon, gales are expected to occur in the North Sea and possibly a small piece of eastern UK and northwestern Holland: As the wind is not that severe yet, and the wind is from the west-southwest, no severe flooding will be expected. Six hours later, a brisk west-northwesterly is shown. The average winds get up to 90 km/h in the northwestern part of The Netherlands: Still, the risk on flooding isn't very high at that point for the Benelux, as it is slightly in the shadow of the UK (regarding the wind direction). However, the threat for Denmark could be more serious, because water can be pushed up toward Denmark itself. Meanwhile, at Friday 00Z, the winds veer more toward the northwest, while reaching speeds up to 80 km/h. The risk for flooding for Holland is much higher at that point, as the wind is now fully from sea. The explanation is that the North Sea functions as a kind of "bathtub". The water is, when a severe NW'ly is blowing, being pushed into the Norht Sea. There, the water piles up to give an increase in height of the water.2 Accompanied with this, there is also spring tide (as indicated in my previous post), which increases the risk on flooding. This is because the moon is at it's "new moon" stage.1 One positive point is that the most severe winds aren't northwesterlies. Otherwise, the storm could have caused major problems. Sources: http://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=3&map=0 1: http://en.wikipedia.org/wiki/Tide#Tidal_constituents 1: http://www.kalender-365.nl/maan/maankalender.html 2: http://en.wikipedia.org/wiki/Storm_tides_of_the_North_Sea

Thanks for the merging!

As there will be a possible storm system developing next Thursday and Friday, an outlook for the storm is given below: The system is forecast to cause a possible 11BFT along the eastern UK, the Netherlands and Denmark on Thursday and Friday. This could possibly cause quite some damage in these countries. For illustration, the Hirlam (a short-term high-res model) output of pressure on thursday 12Z is shown below: It shows that a rather intense low pressure area (975 mb) drops from the north with a rather tight pressure gradient. For the wind speeds, the GFS 12Z on Thursday 12Z is given below: It shows an 11BFT over the North Sea, with a 10BFT scraping the easter UK and the north part of The Netherlands. Six hours later. there is still a 10 BFT along the northern part of The Netherlands and Denmark. On Friday 6Z, there is still a potent 8BFT in the northern part of The Netherlands, and a 9BFT in Denmark. Along with this wind, there will also be high tide accompanied by "springtide" (when the moon causes the tide to have a higher amplitude). As from the KNMI, this could cause alarm levels to be reached in the Netherlands (concerning flooding). This means that there is a rather severe risk on flooding occuring there. On top of this all, there is also snow forecast for the hills in the UK and the Netherlands: Below is the GFS 12Z forecast for snow on Friday morning: The amounts of snow falling are not very severe (only 3 cm max, may change somewhat in the short term), so the chances on a blizzard occuring are quite slim, luckily. Though the severity of the storm is not set in stone yet, the potential of the system makes it worth watching. Sources: http://www.weeronline.nl/vakman-index/130/0 http://www.wetter3.de/animation.html http://www.knmi.nl/waarschuwingen_en_verwachtingen/extra/guidance_meerdaagse.html

Note that the amount of easterly solutions consists only 5 of the 50 lines around monday. Most solutions are going for a south-southwesterly around that timeframe. Therafter, the scatter is so large that, in my opinion, no real conclusions can be drawn about that timeframe. EPS "pluim" of the wind direction forecast of Holland. The flow is indeed forecast to veer more to the south around Dec 10, but keep in mind that the average always go to south in the long term. This is because, for example, two EPS members with wind directions of 350 and 010 degrees, respectively (both almost fully northerly), give an average in the graph of 180 degrees (which is a southerly!) This indicates that the average will always converge to the middle of the graph, which is in this case 180 degrees. However, when one looks at the temperature "pluim" itself, one can clearly see that there are quite a large amount of members (around 40%, decreasing slowly with increasing timeframe) which sustain the cold up to tuesday. This shows that there are indeed some cold solutions, but I can't the link with the southeasterly winds. EPS "pluim" of the temperatures in Holland. Perhaps the cold solutions might have something to do with cold uppers being drawn into Holland from the southeast? For analysis, below is the upper temps chart of GFS 12z for 11 December (it showed a very cold solution for Holland at T+192, temperatures only reaching about 2 degrees at 12Z)) A quick analysis shows that there are indeed quite some cold uppers to the southeast of Holland, but this is way too far to actually reach Holland. Therefore, this is highly unlikely the right explanation. The only explanation I could come up with is that this might have something to do with the so called "radiation cold" (when the outgoing radiation is larger than the incoming radiation). Does anybody have another possible answer? Sources: http://www.weerplaza.nl/15daagseverwachting/?type=eps_pluim http://www.wetterzentrale.de/topkarten/fsavneur.html

As the possible cold snap is nearing, I'll try to give a summary of today's output (GFS and ECMWF) Unlike the 12Z run (which showed no ridging between Iceland and Greeland), the 18Z GFS shows the England High connecting to the Greenland high, which is a good thing regarding the amount of possible amplification of the ridge and trough (and as a result a more potent and persistent northerly). T+126 GFS 18Z However, at T+144, the GFS shows too much low pressure activity near the fragile high pressure area near Iceland, which in turn leads to a deamplification of the ridge. Also note that the low pressure area to the west of Spain (which just sits there for the next 6 days) also barely connects toward the low pressure areas to its north, resulting in a west-east oriented trough to the west of Iceland. T+144, GFS 18Z As for the ECMWF 12Z run, it also shows the connection between the Greeland and the England high, but it maintains the amplified version of the ridge somewhat longer. It appears like this is because the low over Nova Scotia isn't very deep (giving less energy being sent in between the ridges). However, the connection with the low pressure area west of Spain seems to be more firm. This results in a rather long north-south stretched through, which in turn allows the amplified ridge to remain in place for quite some time. T+144, ECMWF 12Z. And finally, for comparison with the 12Z GFS, the track of the low pressure area forecast near Newfoundland at T120 is shown below: It shows the low pressure area moving with a pressure near 990 hPa toward Europe, giving the high pressure connection no chance to build. Overall, there is still quite some uncertanity regarding the outcome, depending on a couple of low pressure areas which may interfere or not interfere. The presence/absence of one of those can create a major change in setup and therefore also have a large impact on the possible northerly in western Europe. It will be interesting to watch how it will unfold. Sources: http://moe.met.fsu.edu/cyclonephase/gfs/fcst/index.html http://www.wetterzentrale.de/topkarten/fsfaxsem.html

I hope this isn't already included, but the Canadian warning centre has verification stats for all models (I don't know how those statistics are compiled, though) The verification stats are for 1 day and 5 days in advance over the last few years. The yearly verification stats at T24h. The yearly verification stats at T120h. Furthermore, error growth charts can be found on the same site for each month. For example, the verification stats for the month October are as follows: And from the link below, error propagation charts of different months in 2013 can be found. http://weather.gc.ca/verification/error_growth_e.html Finally, the World Meteorological Organization also does research on model verification, and they might have some interesting articles as well: http://www.wmo.int/pages/prog/arep/wwrp/new/Forecast_Verification.html I hope this helped a little. Sources: http://weather.gc.ca/verification/monthly_ts_e.html http://www.wmo.int/pages/prog/arep/wwrp/new/Forecast_Verification.html

Alessia has found her new home, the Gulf of Carpentaria! She just really enjoys staying there. SSTS are abundantly warm for her to remain alive, the only threat being upwelling of cool deep ocean waters (though I doubt this will be the case as the ocean is not very deep in the Gulf). Currently, Alessia looks rather dishelved, with no deep convection associated with the system. Most of the convection dissipated around 11 UTC. However, knowing her, don't be suprised if one sees another burst of deep convection occuring. For a short review on the cyclone, the track of Alessia is posted below: Quite an extrordinary track Alessia has taken so far, with 3 landfalls and a tight loop in the Gulf of Carpentaria. However, as stated above, the cyclone is far from done yet, as it may regenerate in its very own Gulf, or near its birthplace, in the longer term, as the cyclone is forecast to move westward over the northern Kimberly coast. The forecast track, according to the AVNO model (I don't know how reliable it is) is as follows: If it makes the trip over northern Australia, the it would have regenerated for the third time (or fourth, depending on if it regenerates in the Gulf of Carpentaria for a second time). If this occurs, then Alessia could be one for the record books. However, the uncertanity is still very high, so no quick conclusions can be made right now. EDIT: Say hello to a healthy looking Alessia once again! First visible imagery show that the center is now fully tucked under a large burst of intense convection. This could help Alessia to spin up and become a depression once again! However, banding features are not apparent yet, and therefore, development is likely to be slow. Sources: http://polar.ncep.noaa.gov/sst/rtg_high_res/ http://www.nhc.noaa.gov/ http://en.wikipedia.org/wiki/2013%E2%80%9314_Australian_region_cyclone_season#Tropical_Cyclone_Alessia http://www.ral.ucar.edu/guidance/realtime/plots/southernhemisphere/2014/sh022014/

It is most likely that this low will indeed be renamed Alessia, once it regenerates. It would be quite extrordinary to have a cyclone have a double possibility of regeneration after interaction with land. The GFS has thrown in another solution regarding Alessia, as it develops it into a cyclone in the Gulf of Carpentaria. The cyclone then stalls for about 4 days, before moving back inland into the Top End. At T+66h, Alessia can be seen meandering near the east coast of Top End. While at T+120h, this system can still be seen sitting in the same place. And finally, at T+156h, Alessia can be seen moving inland (backward) again. Though this is only a model forecast with quite a big margin of error (only 100 km more to the west/east could make a very big difference regarding the intensity and possible cyclone), the GFS 06Z run showed the same solution. EDIT: As a big suprise, tenacious Alessia seems to have become a tropical cyclone again to the east of Top End, looking at the last visible loop. The imagery shows a pronounced blob of convection with some banding features to the north. Though BOM hasn't assessed this as a cyclone yet, and JTWC has chances of development still at the "low" category, I'm quite certain that this is a tropical cyclone. I think it won't be long before this system is once again recognized as a tropical cyclone. Quite an amazing cyclone! And finally, a quick look at the conditions. Shear values are currently very low around Alessia, and are forecasted to stay that way for the next day or so. Current SSTS are sufficiently warm to support a TC, with values up to 29 degrees Celsius. Overall, the future track of Alessia (which seems still very uncertain to me) will largely control its intensity. It will be some very interesting TC watching! EDIT 2: Although the cyclone does seem to be a TC on satellite imagery, TC intensity estimates argue against that, with only a T1.5 (25 kt) given. This would mean Alessia is at best a weak tropical depression. (as from http://www.ssd.noaa.gov/PS/TROP/tdpositions.html) Sources: http://www.ssd.noaa.gov/PS/TROP/floaters/02S/02S_floater.html http://www.wetterzentrale.de/topkarten/fsfaxsem.html http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDY00001.gif

TC Lehar is currently intensifying steadily while moving generally northeastward toward eastern India. Satellite imagery shows that Lehar consists of a large blob of deep convection with little associated banding features. Dvorak satellite imagery of Lehar, showing the intense blob of convection and the lack of banding features. There are currently no hints of an eye feature forming. This makes chances of RI occuring quite slim. CIMSS MIMIC imagery also shows that the cyclone has currently no well-organized inner core, with an elongation northwest-southeast. ]Mim MIMIC imagery of Lehar. The loop seems to be lagging behind a little. Until the inner core of Lehar becomes better established, no RI will occur. Shear analysis shows that Lehar is currently affected by 20 knots of shear from the southeast. This could explain the elongation seen in MIMIC imagery. However, shear tendency from CIMSS reveals that the shear has been decreasing somewhat in the last 24 hr, and it is forecast to decrease further in the next days, giving the cyclone an opportunity to establish a well-organized inner core. Current shear tendency analysis over the past 24 hrs. The current intensity is assessed at 55 knots, as from JTWC. The forecasted peak intensity of 100 kt still holds. The track forecast shows the cyclone making landfall south of Visakhpatnam, which will in this situation experience the strongest winds (northeast quadrant). However, the forecasted landfall is still 4 days out, so it will take some time until the exact landfall location is known. The forecasted track and intensity, as from JTWC. The forecast track and intensity do show quite some similarities with Phailin, which became a cat.5 TC in the bay of Bengal. The main difference is that Lehar is forecast to make landfall to the south of the location Phailin made landfall. The track of Phailin, a devastating cat.5 cyclone which made landfall as a cat.3 cyclone in Northeastern India this year. Unfortunately, the track of 05B takes it just to the north of the area Helen hit last week. This would increase the chances of heavy flooding over that area. Concluding, it will be a cyclone worth tracking, as it could potentially be quite a disastrous cyclone. Sources: http://tropic.ssec.wisc.edu/ http://www.nhc.noaa.gov/ http://www.usno.navy.mil/JTWC/ http://en.wikipedia.org/wiki/Cyclone_Phailin

The Bureau of Meteorology from Australia has a list of tropical cyclones and their occurence per month, between 1988-2003. It shows that there were no tropical cyclones at all which developed in the month of November. This means that TC activity in November is indeed quite unusual in the Australian basin. The frequencies of TC's per month are listed below: The last tropical cyclone existing in November is cyclone Anggrek (formed in October) in the 2010/2011 TC season. http://en.wikipedia.org/wiki/2010%E2%80%9311_Australian_region_cyclone_season Currently, Alessia looks quite disorganized, with only a burst of convection occuring over the center and no convective banding. The JTWC has upped the intensity to 45 knots. BOM still classifies the system as a cat.1 tropical cyclone (winds between 38 and 54 knots). Given its current satellite presentation, I don't expect Alessia to intensify beyond its current intensity. What i find quite strange is that some intensity models bring the system up to 80 knots, and one even to 150 knots. That doesn't seem quite realistic to me, but still nice to note. Sources: http://www.ral.ucar.edu/hurricanes/realtime/plots/southernhemisphere/2014/sh022014/intensity_late/ash02_2013112212_intensity_late.png http://www.bom.gov.au/cyclone/climatology/wa.shtml http://www.nhc.noaa.gov/satellite.php http://en.wikipedia.org/wiki/Tropical_cyclone_scales

Helen is about to make its landfall in mainland India. The landfall location has shifted somewhat to the north, because of unexpected continued northwestward movement according to the JTWC: The biggest threat with this system will be anomalous rainfall with the system. Currently the Indian basin is quite active. The image below (MIMIC TPW) shows the total precipitable water (a measure for humidity). Helen can be seen rotating just to the west of India. 30W (Yes, it stubbornly continues to hold on) can be seen moving westward to the west of India while slowly weakening. There is a lot of dry air behind 30W (low TPW values), which is probably impeding with development. However, the main area of interest lies over Thailand. One can see a slowly rotating column with very high TPW values near that area. That area is probably the next area developing in a TC in the Bay of Bengal. The JTWC notes about the AOI in Thailand that: Chances of development are currently in the medium category for the next 48h. The GFS forecasts this system to become a potent and potentially destructive cyclone making landfall at almost exactly the same area as Helen is about to do (though it is still 5 days away, exact landfall position may shift somewhat.) At T48, the cyclone can be seen as a still weak entity to the west of Thailand: However, at T120h, the system can be seen as a strong TS/weak hurricane about to make landfall at almost the same spot as Helen. Usually, the GFS has a bias to underestimate the minimum pressure (too low grid level). This means that the next area will be an area worth watching. Sources: http://www.usno.navy.mil/JTWC/ http://tropic.ssec.wisc.edu/# http://en.wikipedia.org/wiki/Precipitable_water http://www.wetterzentrale.de/topkarten/fsavneur.html

And that's the end of the consistency regarding Melissa. Models have made a quite significant shift to the right concerning the recurve of Melissa. Most of the models currently show the system moving up toward the Iceland/Greenland area, while just 12 hours ago, a track edging more toward Nova Scotia was forecasted. This is a good example of the flip-flop of the different models. The uncertanity is also reflected in the advisory of the NHC: For comparison: The EC shows the system moving as a seperate entity toward Spain (T96): (Melissa is the 1005 hPa low a couple hundred miles southwest of Newfoundland). While the GFS shows the system curving and becoming absorbed by the low pressure area just off Newfoundland. (T96): (Melissa is the low pressure area weakly discernible to the right of the Newfoundland low pressure area). The difference in outcome is that at T120 the EC shows a north-south block over Great Britain, while the GFS shows a more northeast-southwest oriented "blockade". Concluding, The uncertanity will remain for the next few days as the models flip-flop with the track. The coming days will be an interesting period of model watching. Sources: http://www.nhc.noaa.gov/ http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2013/al142013/ http://www.wetterzentrale.de/topkarten/fsecmeur.html

Agreed, Melissa appears to have lost its beautiful curved structure. And yet, it does seem to me that its current organization reflects more and more a tropical cyclone. This is actually the first time a moderate convective band has wrapped halfway the eastern semicircle, this close to the center.. The system might be in a process in decoupling from the long band to its far east. Indeed, this system seems to have quite a high chance to become the third hurricane of the 2013 hurricane season. The funny fact is, though, that Melissa has a lower MSLP than Humberto had on its maximum intensity, according to satellite estimates from CIMSS. Models have been trending toward a more tropical structure of Melissa in the future, with the GFS now forecasting a symmetric warm core to develop, before extratropical transition begins. Note that on this graph, C is the starting point where the system is at the beginning of the model run, while A is the starting point of the system, when it was firstly recognized by the GFS. What's also very interesting to note (from the perspective of Europe), is that Melissa is now forecast to remain a seperate entity during the next 5 days. This will definitely have quite some impact on the models in 5 days, thus decreasing the certanity in that timeframe. As from the NHC: Sources: http://tropic.ssec.wisc.edu/real-time/storm.php?&basin=atlantic&sname=14L&invest=NO&zoom=4&img=1&vars=11111000000000000000000&loop=0 http://en.wikipedia.org/wiki/2013_Atlantic_hurricane_season (for the lowest pressure of Humberto) http://moe.met.fsu.edu/cyclonephase/gfs/fcst/archive/13111812/20.html http://www.nhc.noaa.gov/text/refresh/MIATCDAT4+shtml/182053.shtml

In the last few runs, the models have become in better agreement on the cyclone curving back toward Greenland, while 2 days ago half of the models were forecasting the cyclone would continue its recurve toward Spain. Though the hurricane models are still struggeling on the definite track (the angle of the recurve is far from set in stone), all models (except the LBAR) agree on a curve back toward Greenland, and therefore enhancing Warm Air Advection toward Greenland. My knowledge about that phenomenon is quite lacking, but it seems to me that the fact that this system came from the tropics (and containing a warm core), will imply a quite vigorous WAA event Greenland. The GFS is actually forecasting the core to remain warm in its tour toward Greenland (though it will become much more shallow during its extratropical transition). A note for caution is that the models haven't initialized Melissa as a subtropical cyclone yet in the 12z runs, and therefore, the forecast track (and the future when it nears greenland) could change quite strongly in the near future. And finally, an analysis of how close FI is actually in this situation, with comparison of the GFS and ECWMF runs at T96H EC: GFS: While posting this, the 12z run of the GFS came out. It appeared that it converged toward the ECWMF solution (00z run). Therefore, uncertanity seems to have decreased some, with both models now indicating the low pressure area to almost skirt Newfoundland on Friday. Sources: http://moe.met.fsu.edu/cyclonephase/gfs/fcst/index.html http://www.ral.ucar.edu/hurricanes/realtime/plots/northatlantic/2013/al982013/track_early/aal98_2013111812_track_early.png http://www.wetterzentrale.de/topkarten/fsfaxsem.html

After a lull of about a month in TC activity, a new subtropical storm has developed in the Central Atlantic, and it has been named Melissa. The system is quite large, and seems to have a quite large range of tropical storm winds, but in the last few hours, convection has also built at the center of Melissa, which is a characteristic of a (sub-)tropical cyclone. Current OSCAT data shows the large radius of tropical storm winds associated with the system (winds of at least three and a half flag suggest tropical storm force winds) Current water vapor imagery shows a tongue of dry air curving toward the center of Melissa, likely impeding in development. Shear analysis by CIMSS (not shown here) shows the system is currently in a sharp shear gradient, with values ranging from 20 kt to the east, to 50 kt to the west of the system, providing, along with the dry air, only marginal conditions for development. The NHC is currently forecasting Melissa to get close to hurricane strength, as shear values are expected to drop to values below 10 kt, and SSTS are about 27 degrees Celsius. Thereafter, extratropical transition is about to begin. The storm is forecast to move northward during most of its lifetime, with a recurve toward the northeast afterward. Behind that time, it is yet uncertain if the system will turn back toward Greenland, or continue its recurve toward Spain. The NHC is currently forecasting a backward curve toward Greenland, on which an increasing amount of models seem to agree upon. The track of Melissa as forecast by the NHC. Although the model spread has been reduced in the past 24 hours, there remains a considerable amount of uncertanity about the angle of the recurve. An image of the different forecasts of different models, showing the current spread at the medium to long range. It will be interesting to see how the models handle this system now it has been qualified as a subtropical storm, and especially the effects on the forecasted blockade west of Ireland. It is likely that there will be quite some model-hopping in the medium to long term time frame. It is also very nice to see how tropical cyclones could have a significant impact on the weather in Europe, directly or indirectly. To illustrate the model-hopping of the various models on the handling on the storm, some output of the GFS and ECMWF models at T96hr below: GFS: EC: While the GFS suggests a very pronounced southern part of the complex low pressure area (extreme left, remnants of Melissa), the ECMWF shows a much more pronounced northern part of the system (in this case, the remnants of Melissa would be absorbed). The different handle could easily result in very different outcomes at bigger timeframes. And finally (to get back to the storm itself), a visible image of the subtropical cyclone.

Currently, the undercutting of the low in Greenland is being discussed. The fate of the blockade over the Atlantic south of Iceland appears to be determined by the low. However, it seems to me like the the key feature lies much further south, in the tropical Atlantic. A non-tropical low pressure is currently developing to the east of the Lesser Antilles (which might become subtropical storm Melissa in the future). The forecast track shows the system recurving toward the central Atlantic (between Nova Scotia and Spain). In this GFS chart (T+66h), the system can be seen nearing in the extreme southeast corner of the map. At T+114h, the system is being absorbed by another low pressure area. Thereafter, at T150 (in FI), the coupled system can be seen moving toward Greenland. It must be emphasized that this is just a model run, so the outcome of the system could easily be much different than shown here. As tropical cyclones (or their remnants) usually complicate forecasts in the mid latitudes, models often have a hard time resolving such situations. It will be interesting to see how the models handle the remnants of the tropical cyclone in the future. Very interesting to watch. Sources: http://www.wetterzentrale.de/topkarten/fsavneur.html http://moe.met.fsu.edu/cyclonephase/ EDIT: What I would like to point out is that the energy associated with the tropical system is likely to interfere with the development of this low. Though I don't know what the outcome will be, it shows nicely how closely the tropics and the mid-latitudes can be related to each other.

The inactive 2013 hurricane season is up for a (potentially final) subtropical cyclone in the mid-Atlantic. A low pressure area is currently in the process of developing in the open tropics. NHC is currently giving it a 50% chance of developing in the next 5 days (10% in the next 48 hours), as it moves slowly northward. As the system hasn't been declared an invest yet, I'll be showing images of the Central Atlantic. Current visible imagery shows some weak convection associated with the low pressure area, with no real turning evident yet. The lack of convection might be becuase of the system having some problems with dry air currently to the west of the system. This can also be seen in the Water Vapor imagery below: Because the system is currently extratropical in nature, it first needs to acquire some subtropical characteristics in order to become a subtropical cyclone. The FSU Phase Diagram below, a method to assess and predict to wheather a cyclone is tropical or subtropical, shows the system acquiring an asymmetric warm core (characteristic for subtropical cyclones), before transitioning back into a cold core system (as form the GFS model): The image above shows the nature of the core of a low pressure area. Tropical cyclones usually have a symmetric warm core, while mid-latitude extratropical cyclones tend to have an asymmetric cold core. An asymmetric warm core is more a characteristic of a subtropical cyclone, as this cyclone is forecast to become. Note that the system isn't forecast to have a very pronounced warm core, which shows there is still some uncertanity as wheather this cyclone will actually become subtropical. The forecast track of the GFS shows the system moving westward, and then slowly recurving northeastward in the westerlies. The image below also shows the SSTS, which will drop below 26 degrees Celsius after two days. Note that many subtropical cyclones have actually developed on SSTS much below 26 degrees, so development is still possible after the cyclone crosses the 26*C isotherm Regardless of TC development, the GFS shows the system becoming a potent low pressure area with a minimum pressure below 995 hPa. Thereafter, the cyclone is forecast to become adsorbed by another low pressure area between Newfoundland and Spain, before moving as quite an intense cyclone toward Greenland (though this is in the less-reliable phase), as seen below in the forecast map below. The chart below shows the system getting adsorbed in the low-left corner of the map at T114. Summarizing, it would be very interesting to see what the long-term effects of this cyclone will be on the weather in Europe, as well as if this system could become a subtropical cyclone, or possibly even a hurricane. As models usually have difficulity resolving situations with TC's involved, it will take some time before the far future of this system becomes clear, as well as the implications on the weather in Europe and the forecasted blockade. Sources: http://www.wetterzentrale.de/topkarten/fsavneur.html http://www.nhc.noaa.gov/ http://moe.met.fsu.edu/cyclonephase/

I'm glad I could be of some help It's indeed a very good thing that the Philippines won't be terrorized by more TC's or heavy rain, so that the rebuild can begin. @ Vorticity. Thank you very much; good news if a respite can allow the relief effort to continue without more weather problems. I'll bookmark the links in my growing tropical file. Currently, discussions of wheather we (as humas) caused this cat.5 typhoon are starting to pile up. In my opinion, human-caused global warming won't have caused the cyclone, but it definitely could have helped bringing the cyclone to its extreme intensity. What could actually have caused the explosive intensification and monstrous intensity of Haiyan is very high SSTS, extending to a great depth. Though the surface waters near the Philippines seem to be near average, the waters just below this surface (up to 100 m depth) are up to 5 degrees above average. This map shows the anomalies of the SSTS at 100 meters below the surface. Note that the track of Haiyan passed directly over a large area with anomalies up to 3 degrees Celsius. The surface warming could have occured because of more intense trade winds toward the west, increasing the pile up of warm watersjust to the east of the Philippines. This phenomenon is not yet well understood, but such extensive heating has a very likely link to global warming, as the ocean takes heat up at a very slow pace. This in combination with altering climate patterns (the so called Walker circulation, an indicator of those trade winds, is anomalously strong since 1990). However, nothing is set in stone yet, so one should be cautious to point directly toward any reason. A link containing the full story about this warming can be found here: http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2579 Another theory is that a very strong jet stream may have contributed to the RI of Haiyan, providing lots of ventillation to the cyclone. The theory can be found at one of the bloggers at the link I posted above. This theory is a lot less likely, though. This chart shows the strength of the jet stream when Haiyan was to the east of the Philippines, about to begin its RI. And finally, a very interesting blog about the small swirls noted in Haiyan's eye (mesovortices). An interesting read. http://www.wunderground.com/blog/24hourprof/comment.html?entrynum=81

To give a more sophisticated answer, the analysis of the CPC (climate predicition center of NOAA) is out. It generally shows below average rainfall over the west Pacific, greatly diminishing the potential of TC development occuring in the next 2 weeks. But as always, there are some uncertanities in such forecast. But now, this is especially so. Quoting a part of the CPC anlysis: Concluding, even the experts are uncertain of the chances of a TC occuring in the WPAC, but the odds seem to be (luckily) against that. For the full article, see http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/ I hope your question is answered satisfactory.

The answer is: yes it could, but signals for an active final period of the typhoon season are -once again- quite mixed (taking the GFS MSLP maps into account). First, I think I made a mistake regarding Kelvin waves. Even in modern science, there is still a lot of uncertanity as wheather and how those Kelvin Waves interfere with TC development. There seem to be indications of enhanced TC activity because of those waves, but no firm evidence has yet showed up concerning these waves. There was also a scientific article, stating that: Source: Schreck, Carl J., John Molinari, 2011: Tropical Cyclogenesis Associated with Kelvin Waves and the Madden–Julian Oscillation. Mon. Wea. Rev.,139, 2723–2734. However, another article states that the Kelvin waves do enhance the chance on TC development (though only stated for the Atlantic). Source: http://www.atmos.albany.edu/student/ventrice/documents/publications/Dissertation.pdf Concluding: I think I was a little too quick stating the above. My excuses for that. A good site regarding the chances of TC formation up to 2 weeks out, is the one below: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/ (updated every week). An in-depth blog regarding Kelvin waves (without going too much into detail) can be found here: http://www.wunderground.com/blog/TomTaylor/largescale-atmospheric-equatorial-waves And finally for Kelvin waves, a link with some basic information about the different shallow wave structures and their properties: http://www.kylemacritchie.com/equatorial-wave-background/equatorial-wave-theory/ BTW: I'm sorry to go a little OT.

I completely agree. When seeing such horrible pictures of devastation, you really start to realize what impact such cyclone has. It makes one feel really humble. I think this is a question which can't be answered that easily. One indicator might be that there was an active phase of a Kelvin wave in the end of October in the West Pacific (around 120W). This picture shows the past and future Kelvin wave activity. An active phase of such Kelvin wave could enhance the threat of TC formation. The active phases are indicated with blue (negative). Note the large area of an active phase of a Kelvin wave over the western Pacific in the end of october. Some more search shows that the MJO would suggest a lack of TC activity in the WPAC. This chart shows the MJO anomalies expressed in Outgoing Longwave Radiation. The non-active phase is indicated in yellow (without going much in detail, as my knowledge is far from adequate about MJO). This phase is expressed in a lack of precipitation, and this would normally decrease the chance of development of a tropical cyclone. This yellow color was mostly present around the Philippines in October. However, this thinking goes completely against what we've seen so far. Strange, to say the least. The only thing I can say is that there are no firm signals which argued for a very busy October. So I fear I can't answer your question. More information about MJO expressed in OLR anomalies can be found here: http://www.bom.gov.au/climate/mjo/#tabs=Average-OLR Sources: http://mikeventrice.weebly.com/forecast.html http://www.bom.gov.au/climate/mjo/#tabs=Average-OLR http://monitor.cicsnc.org/mjo/archive/2013-10-21/ (more composites of different indices can be found here).

30W/Zoraida hasn't strengthened yet, fortunately. This means that strong winds and storm surge won't be an issue with this cyclone. Also, models have been trending south away from the areas hit the worst by Haiyan. Another TC would have been the last thing they needed. Unfortunately, rain bands of 30W are hitting the worst-hit areas, as seen in WV-imagery. As from PAGASA, the rain totals are expected to be up to 15mm/h within a radius of 300 km away from the invest. That would mean the worst-hit areas would suffer some rain, but the totals won't be devastating. http://www.pagasa.dost.gov.ph/wb/fcst/bulletin.pdf My heart goes out to the people hit by Haiyan and Zoraida. Sources: http://www.ral.ucar.edu/guidance/realtime/plots/northwestpacific/2013/wp902013/ http://www.nhc.noaa.gov/ http://www.pagasa.dost.gov.ph/

Yes, it was Tropical cyclone Vamei in 2001/2002 which hit Sumatra as a tropical storm (it hit Malaysia as a typhoon). The cyclone developed at 1.4N, about the lowest latitude a TC has ever formed. (according to Wikipedia). The track of Vamei, showing landfall in Malaysia and Indonesia. However, according to JMA, this record has almost been broken by 36W, which developed at 1.5N. The JTWC hasn't designated the invest as a TC yet. Very impressive to see TC formation at such low latitudes. The WPAC cyclone season has become a very interesting season at that, with a record-active October (regarding Typhoon formation), the most intense cyclone to make landfall, with the horrible consequences (unfortunately, death tolls still seem to be rising), and now a TC developing at 1.5N latitude. Finally, visible imagery of 90W/36W, showing some pretty intense convection occuring over a possible LLCC. More information about Haiyan and 90/36W can be found at http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2575&page=4#commenttop Sources: http://www.jma.go.jp/en/typh/ac.html http://en.wikipedia.org/wiki/Tropical_Storm_Vamei

As Sommerset Squall and others noted in the thread of Haiyan, another invest has developed in the West Pacific, which could strike the Philippines. The invest is currently rather disorganized, and only broad cyclonic rotation is noted in the IR loop below. http://www.ssd.noaa.gov/PS/TROP/floaters/90W/flash-vis-long.html As the system is not yet recognized on the CIMSS web site, the analysis will be done by charts of the complete West Pacific. Current shear levels are low around the system, as an anticyclone is directly overhead (or just to the west of the system). The system itself is currently located near 2.0N, 144.0E. The anticyclone can be found as the area where the wind vectors spiral out of that particular point. (around 2N, 142E) Shear tendency over the past 24 hours shows that the shear is decreasing to the west of the cyclone, but increasing to the east of the cyclone. (Cyclone Haiyan is the cyclone indicated with the red cyclonic shape, this is not the area I'm discussing right now). Concluding, shear levels are quite favorable around the cyclone, improving the chances on development. Next is the 850 hPa vorticity. The vorticity map shows that there is currently some pronounced vorticity at the area of the invest, though slightly west of the position the JTWC is indicating. An overview of the West Pacific in Water Vapor imagery does show high levels of dry air directly to the north of 90W, but because this system is at such low latitude, I don't think it will be a big impediment to development. Because the area hasn't been initialized as an invest yet, there are also no direct TC forecast tracks available. Because of that, the GFS full WPAC charts will be used to make a forecast. Below is a forecast of the MSLP (minimum surface level pressure) at T84, based on the GFS output. It shows a weak TC making landfall just to the south of the area Haiyan hit yesterday. This could lead to even more heavy rainfall and consequently flash floods to the already soaked middle and southern Philippines. It would be a very bad scenario if this pans out. And finally, the NAVGEM model (it doesn't seem to be very reliable). It also shows a weak cyclone making landfall right at the spot Haiyan made landfall (T96hr) Currently, the available models aren't showing a real monster to develop. As the system becomes more pronounced and gets initialized by the models, we'll get a better assessment and forecast of the system, and how much it could impact the Philippines. Let's hope a disaster like Haiyan won't repeat itself with this system. Sources: http://www.ssd.noaa.gov/PS/TROP/floaters/31W/31W_floater.html http://tropic.ssec.wisc.edu/ http://www.wetterzentrale.de/topkarten/fsfaxsem.html http://tc.met.psu.edu/wpac/indexwpac.html http://www.usno.navy.mil/JTWC/