thegreatdr Posted October 24, 2012 Share Posted October 24, 2012 You can have an extratropical cyclone with a shallow warm core near the center (warm occlusions/seclusions of the Shapiro-Keyser type). Some former tropicals have done so as they approach Europe/passed by Iceland. If the warm core is deep enough, there should be an eye feature. But would the convection be tall enough for anyone to categorize the mesoscale convective system as a tropical cyclone? We'll find out soon enough. It looks to me as if this storm will be warm core through landfall. WIth that in mind... even though it will have some extra tropical characteristics... and the potential for damage you have to keep it going as a hurricane. You could make an argument that if the 1938 storm passed HSE and was undergoing ET it was no longer a true hurricane but rather a warm seclusion. Link to comment Share on other sites More sharing options...
billgwx Posted October 24, 2012 Share Posted October 24, 2012 Yup, hopefully in coming days the media communicates that even though the pressure will be at cat 4 levels it will only have cat 1 winds if it made landfall in the northeast, and will not be a typical hurricane. I think it'll probably do more damage than a typical hurricane though if the current favored model scenario happened due to the potential for a huge wind radius. Could inner core winds end up stronger than expected due to warm core seclusion? It's going to be a very difficult call for the NHC if it happens, do they let the NWS handle it since it's gonna be mostly non-tropical or will they issue hurricane advisories anyways since it will be partially tropical and have major impacts? Absolutely. Both of the above have been big worries of mine for a long time, and fear one or both may come to pass. Link to comment Share on other sites More sharing options...
CT Rain Posted October 24, 2012 Share Posted October 24, 2012 I feel like I should know this, but what in particular about the transition to warm seclusion/asymmetric warm core (as opposed to a cold core) makes it so dangerous? Is it that since it's still technically warm core, it keeps its strong core of winds, but also since it's asymmetric, it has an expanding pressure field and thus an expanding wind field as well? And you're getting the benefits of baroclinic enhancement without the hindrances to the core of winds? You got it Link to comment Share on other sites More sharing options...
turtlehurricane Posted October 24, 2012 Share Posted October 24, 2012 It looks to me as if this storm will be warm core through landfall. WIth that in mind... even though it will have some extra tropical characteristics... and the potential for damage you have to keep it going as a hurricane. You could make an argument that if the 1938 storm passed HSE and was undergoing ET it was no longer a true hurricane but rather a warm seclusion. I agree with this line of thinking. If the NHC were to declassify Sandy a day or 2 before landfall the public perception would be that it's weaker and not as much of a threat, even if the media does their best to keep hyping it. Just not worth the potential trouble, especially when the post-season analysis can fix the error. Could inner core winds end up stronger than expected due to warm core seclusion? Absolutely. Both of the above have been big worries of mine for a long time, and fear one or both may come to pass. I could see this maintaining a tight wind field in the inner core if the warm seclusion is as persistent as modeled, kind of like a tropical cyclone within a larger mid-latitude cyclone. It's probably impossible at this point to tell how strong the winds will be in the inner core, could be anywhere from about the same as the rest of the outer core to much stronger if it maintains an eyewall structure, which is possible especially since the warm seclusion is usually a low vertical shear environment. Link to comment Share on other sites More sharing options...
phil882 Posted October 24, 2012 Share Posted October 24, 2012 In terms of societal impacts, if either the 12z GFS or ECMWF solutions verify, its obvious that the greatest impact from Sandy will be storm surge and inland flooding. In this way, the societal impact ultimately won't be that different from Irene last year, except that the incipient environment will be around 10-15 C colder. The angle of approach, however, is another key aspect and could substantially impact the amount of surge that impacts a region. We had a nice discussion today @ SUNY Albany referring to the tendency for models to over-forecast minimum central pressure on TCs that are undergoing extratropical transition. The main focus was on the model physics and especially on how the models handle cumulus parameterization. It turns out that both the GFS and ECMWF seem to have a bias with over-forecasting TCs in the mid-latitudes due in part to their cumulus schemes. We have seen this with a number of tropical cyclones recently, including Igor (2010), Irene (2011), Debby (2012), Isaac (2012), and Leslie (2012). This also seems to be a more common problem in very large TCs, like those that you tend to experience as a storm expands in the mid-latitudes due to EWRC or baroclinic influences. This over-forecasting error is not as much of a problem in the deep tropics (S of 20N). It also shows up more frequently in the ECMWF due to its higher resolution. The problem with the over forecasted intensity of Sandy is two fold. First, this obviously results in a weaker storm with lower winds and a higher central pressure. However, it also means that the downstream response to a weaker TC is also impacted. The anticyclonic flow associated with tropical cyclones can often lead to downstream Rossby wave trains as they interact with the polar jet, leading to downstream amplified ridges and troughs. If Sandy's intensity is over forecasted in the 96-120 hour period, it could mean less of a downstream ridge to turn it back towards the US. At this point though, it looks like the intensity forecast with Sandy has exceeded expectations, and the models adjusting westward might just be the correction, acknowledging that the downstream amplification of the ridge will in turn lead to more meridional flow, and less of a chance for Sandy to eject eastward (zonally) south of the polar jet. Link to comment Share on other sites More sharing options...
green tube Posted October 24, 2012 Share Posted October 24, 2012 For posterity a black hole. damn, that's an outcome i didnt even think of. Link to comment Share on other sites More sharing options...
Guest Imperator Posted October 24, 2012 Share Posted October 24, 2012 Help me understand...what is the difference between a 970mb Winter Noreaster vs. a 970mb Extratropical Storm we would be getting next week? Assume "landfall" of the low on Eastern LI. Link to comment Share on other sites More sharing options...
billgwx Posted October 24, 2012 Share Posted October 24, 2012 I agree with this line of thinking. If the NHC were to declassify Sandy a day or 2 before landfall the public perception would be that it's weaker and not as much of a threat, even if the media does their best to keep hyping it. Just not worth the potential trouble, especially when the post-season analysis can fix the error. Exactly. We are already talking internally about the public perception of this and how to handle it, even avoid it if possible. Luckily NYC's program covers non-tropical storms as well, so the City could ask for voluntary or mandatory evacuations no matter what the storm classification. Might be an insurance headache for many if carried as a tropical entity longer than scientifically accurate. Link to comment Share on other sites More sharing options...
billgwx Posted October 24, 2012 Share Posted October 24, 2012 a black hole. damn, that's an outcome i didnt even think of. Only if it gets close to the RHIC here at Upton (BNL): http://www.bnl.gov/rhic Link to comment Share on other sites More sharing options...
phil882 Posted October 24, 2012 Share Posted October 24, 2012 Help me understand...what is the difference between a 970mb Winter Noreaster vs. a 970mb Extratropical Storm we would be getting next week? Assume "landfall" of the low on Eastern LI. Precipitable Water is substantially higher than what you would normally experience during the middle of winter, plus tropical cyclones themselves have a huge positive perceptible water anomaly. The GFS is forecasting 2.00"+ in precipitable water associated with the storm as it makes landfall on the coast of Maine. This would be an all time record for the region for the month of October. Link to comment Share on other sites More sharing options...
turtlehurricane Posted October 24, 2012 Share Posted October 24, 2012 In terms of societal impacts, if either the 12z GFS or ECMWF solutions verify, its obvious that the greatest impact from Sandy will be storm surge and inland flooding. In this way, the societal impact ultimately won't be that different from Irene last year, except that the incipient environment will be around 10-15 C colder. The angle of approach, however, is another key aspect and could substantially impact the amount of surge that impacts a region. We had a nice discussion today @ SUNY Albany referring to the tendency for models to over-forecast minimum central pressure on TCs that are undergoing extratropical transition. The main focus was on the model physics and especially on how the models handle cumulus parameterization. It turns out that both the GFS and ECMWF seem to have a bias with over-forecasting TCs in the mid-latitudes due in part to their cumulus schemes. We have seen this with a number of tropical cyclones recently, including Igor (2010), Irene (2011), Debby (2012), Isaac (2012), and Leslie (2012). This also seems to be a more common problem in very large TCs, like those that you tend to experience as a storm expands in the mid-latitudes due to EWRC or baroclinic influences. This over-forecasting error is not as much of a problem in the deep tropics (S of 20N). It also shows up more frequently in the ECMWF due to its higher resolution. The problem with the over forecasted intensity of Sandy is two fold. First, this obviously results in a weaker storm with lower winds and a higher central pressure. However, it also means that the downstream response to a weaker TC is also impacted. The anticyclonic flow associated with tropical cyclones can often lead to downstream Rossby wave trains as they interact with the polar jet, leading to downstream amplified ridges and troughs. If Sandy's intensity is over forecasted in the 96-120 hour period, it could mean less of a downstream ridge to turn it back towards the US. At this point though, it looks like the intensity forecast with Sandy has exceeded expectations, and the models adjusting westward might just be the correction, acknowledging that the downstream amplification of the ridge will in turn lead to more meridional flow, and less of a chance for Sandy to eject eastward (zonally) south of the polar jet. Interesting stuff. What aspect of the cumulus parameterization scheme results in the positive intensity bias for storms poleward of the deep tropics? Also are there any other reasons? Now that I think about it the globals often seem to blowup transitioning storms into huge lows, but I've never checked the verification on that. Link to comment Share on other sites More sharing options...
thegreatdr Posted October 24, 2012 Share Posted October 24, 2012 +1. Sometimes I feel like one of the only people who has noticed this. It helps that HPC has such a large forecast area for Medium Range (40W to 140E). This just happens to be one of the only cases which have occurred so close to the East coast of the US. If this was seen with Irene as well, no wonder why the guidance had a high QPF bias during Irene. The HWRF and GFDL have shown this for years...though I'm not so sure this year's had been quite as bad. Overdeepening and high QPF bias go hand in hand. =) In terms of societal impacts, if either the 12z GFS or ECMWF solutions verify, its obvious that the greatest impact from Sandy will be storm surge and inland flooding. In this way, the societal impact ultimately won't be that different from Irene last year, except that the incipient environment will be around 10-15 C colder. The angle of approach, however, is another key aspect and could substantially impact the amount of surge that impacts a region. We had a nice discussion today @ SUNY Albany referring to the tendency for models to over-forecast minimum central pressure on TCs that are undergoing extratropical transition. The main focus was on the model physics and especially on how the models handle cumulus parameterization. It turns out that both the GFS and ECMWF seem to have a bias with over-forecasting TCs in the mid-latitudes due in part to their cumulus schemes. We have seen this with a number of tropical cyclones recently, including Igor (2010), Irene (2011), Debby (2012), Isaac (2012), and Leslie (2012). This also seems to be a more common problem in very large TCs, like those that you tend to experience as a storm expands in the mid-latitudes due to EWRC or baroclinic influences. This over-forecasting error is not as much of a problem in the deep tropics (S of 20N). It also shows up more frequently in the ECMWF due to its higher resolution. The problem with the over forecasted intensity of Sandy is two fold. First, this obviously results in a weaker storm with lower winds and a higher central pressure. However, it also means that the downstream response to a weaker TC is also impacted. The anticyclonic flow associated with tropical cyclones can often lead to downstream Rossby wave trains as they interact with the polar jet, leading to downstream amplified ridges and troughs. If Sandy's intensity is over forecasted in the 96-120 hour period, it could mean less of a downstream ridge to turn it back towards the US. At this point though, it looks like the intensity forecast with Sandy has exceeded expectations, and the models adjusting westward might just be the correction, acknowledging that the downstream amplification of the ridge will in turn lead to more meridional flow, and less of a chance for Sandy to eject eastward (zonally) south of the polar jet. Link to comment Share on other sites More sharing options...
billgwx Posted October 24, 2012 Share Posted October 24, 2012 24/18Z GFS = out to sea. Link to comment Share on other sites More sharing options...
thegreatdr Posted October 24, 2012 Share Posted October 24, 2012 If this is due to Sandy's current forward motion, we would see the other global guidance windshield wiper back to the east, including the hurricane guidance which follows the GFS like a tail on a dog. Life on the medium range can be difficult, but rewarding. =) 24/18Z GFS = out to sea. Link to comment Share on other sites More sharing options...
Dsnowx53 Posted October 24, 2012 Share Posted October 24, 2012 You got it Thanks! Link to comment Share on other sites More sharing options...
wxphanatic Posted October 24, 2012 Share Posted October 24, 2012 Precipitable Water is substantially higher than what you would normally experience during the middle of winter, plus tropical cyclones themselves have a huge positive perceptible water anomaly. The GFS is forecasting 2.00"+ in precipitable water associated with the storm as it makes landfall on the coast of Maine. This would be an all time record for the region for the month of October. Think there's a typo there. When I lived there got many October storms in excess of 2.00" -- here are a couple whoppers i rememeber specifically... http://www.erh.noaa.gov/gyx/pdf/ta2000-02.pdf http://en.wikipedia.org/wiki/Northeast_U.S._flooding_of_October_2005 Link to comment Share on other sites More sharing options...
Riptide Posted October 25, 2012 Share Posted October 25, 2012 24/18Z GFS = out to sea. The 18z GFS operational is a far eastern outlier compared to its ensemble group. Link to comment Share on other sites More sharing options...
phil882 Posted October 25, 2012 Share Posted October 25, 2012 Think there's a typo there. When I lived there got many October storms in excess of 2.00" -- here are a couple whoppers i rememeber specifically... http://www.erh.noaa....f/ta2000-02.pdf http://en.wikipedia....of_October_2005 I'm not talking about total rainfall... I'm talking about precipitable water which is the total column of moisture in atmosphere. In that respect it is a record total: Link to comment Share on other sites More sharing options...
CT Rain Posted October 25, 2012 Share Posted October 25, 2012 The 18z GFS operational is a far eastern outlier compared to its ensemble group. Hey... where's that from? My site seems to update awfully slow. Link to comment Share on other sites More sharing options...
Riptide Posted October 25, 2012 Share Posted October 25, 2012 Hey... where's that from? My site seems to update awfully slow. http://www.emc.ncep.noaa.gov/gmb/tpm/emchurr/tcgen/ Link to comment Share on other sites More sharing options...
turtlehurricane Posted October 25, 2012 Share Posted October 25, 2012 The GFS is windshield wiping, it obviously has a poor handle on the situation. It wasn't even in the east coast landfall camp until today. Link to comment Share on other sites More sharing options...
EasternUSWX Posted October 25, 2012 Share Posted October 25, 2012 18Z GFDL. That would be just deadly. Link to comment Share on other sites More sharing options...
Dosh Posted October 25, 2012 Share Posted October 25, 2012 18Z GFDL. That would be just deadly. Holy hell. One question: how well does this tropical model handle mid-latitude systems? I've only seen it used for hurricanes, and think the SLP may be a bit too bombed out. Then again the Euro is still cranking sub-950 so is it still anyone's guess? Link to comment Share on other sites More sharing options...
wxphanatic Posted October 25, 2012 Share Posted October 25, 2012 I'm not talking about total rainfall... I'm talking about precipitable water which is the total column of moisture in atmosphere. In that respect it is a record total: Ahhhh...thx for clarifying. That is worthy of note... Link to comment Share on other sites More sharing options...
Geos Posted October 25, 2012 Share Posted October 25, 2012 The GFS is windshield wiping, it obviously has a poor handle on the situation. It wasn't even in the east coast landfall camp until today. If I interpret all the track discussion on Sandy correctly... it is a combination of the digging trough and the North Atlantic Blocking that decides whether this system is a fish storm or a landfall hybrid storm? I take it that if the trough wasn't there then this storm would head due north or NNW. Since it is there, it starts to head out to sea, but recurves due to the trough digging in from behind to the SW? Then the blocking stops it from continuing to say... Nova Scotia or there abouts. Link to comment Share on other sites More sharing options...
thegreatdr Posted October 25, 2012 Share Posted October 25, 2012 You need either a progressive upper low moving through the Great Lakes into New England or a digging, negatively tilted trough to approach Sandy at the right time to bridge the northern and southern stream portions of the ridge to its east and shift Sandy's track to the left. A northern stream closed high/ridge has a weakness 20 degrees under the base of its respective positive anomaly, so without a strengthening shortwave/upper low upstream to help bridge the downstream ridging, or with a faster moving Sandy and/or slower moving shortwave, Sandy has an eastern escape route between Bermuda and the 40th parallel. A bridged ridge to its east would have a more southerly positive anomaly and force Sandy north to northwestward If I interpret all the track discussion on Sandy correctly... it is a combination of the digging trough and the North Atlantic Blocking that decides whether this system is a fish storm or a landfall hybrid storm? I take it that if the trough wasn't there then this storm would head due north or NNW. Since it is there, it starts to head out to sea, but recurves due to the trough digging in from behind to the SW? Then the blocking stops it from continuing to say... Nova Scotia or there abouts. Link to comment Share on other sites More sharing options...
HKY_WX Posted October 25, 2012 Share Posted October 25, 2012 18Z GFDL. That would be just deadly. lol look at the 5h heights. unreal. looks like a cat 5 SECS Link to comment Share on other sites More sharing options...
Geos Posted October 25, 2012 Share Posted October 25, 2012 You need either a progressive upper low moving through the Great Lakes into New England or a digging, negatively tilted trough to approach Sandy at the right time to bridge the northern and southern stream portions of the ridge to its east and shift Sandy's track to the left. A northern stream closed high/ridge has a weakness 20 degrees under the base of its respective positive anomaly, so without a strengthening shortwave/upper low upstream to help bridge the downstream ridging, or with a faster moving Sandy and/or slower moving shortwave, Sandy has an eastern escape route between Bermuda and the 40th parallel. A bridged ridge to its east would have a more southerly positive anomaly and force Sandy north to northwestward Thanks for that explanation! Link to comment Share on other sites More sharing options...
yoda Posted October 25, 2012 Share Posted October 25, 2012 NOGAPS refuses to go down with the ship and says bombs away for the MA Link to comment Share on other sites More sharing options...
Thunder Road Posted October 25, 2012 Share Posted October 25, 2012 00Z GFS.........out to sea, basically identical to the 06Z run. Doh! Curves back in to NS. Maybe it's not a US hit but it's not really out to sea either. Basically the same as 18z, on the eastern edge of the guidance ensemble (one would presume anyway, barring a dramatic shift in the 0z solutions). Link to comment Share on other sites More sharing options...
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