gkrangers Posted July 31, 2011 Share Posted July 31, 2011 It's going to be an interesting night tonight when the only GOES channel that is really critical to watching this wave develop is the the visible. Microwave from POES systems are going to be crucial tonight. There is nothing crucial about watching a broad gyre develop into a tropical depression. Link to comment Share on other sites More sharing options...
janetjanet998 Posted July 31, 2011 Share Posted July 31, 2011 notice the NHC now includes the western wave in the outlook area too(both blobs now under the same circle) Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 I know I'm late to the storm-relative shear/vertical wind shear party. I was confused myself a few years back, so I contacted someone at NHC that believes in expressing the mathematical representation (vertical wind shear) and someone at SPC who believes storm-relative shear is a more visual/conceptual way of looking at the idea. The two debated for a while, but there was no real consensus. The point is, the two are talking about the same concept, and one concept is used more within severe weather circles and one is used more within TC circles. You see this a lot within meteorology...the math-based versus conceptual model-based camps of thinking. Different people will pick different terms when discussing the same issue, normally based upon their process of learning. I don't see why there is a debate. Shear is a mathematical concept. Storm relative shear = absolute sheer, by definition. There should be no debate, if you (not specifically picking on you, just "you" in general) understand simple math. This applies to models as well. I think the issue here is people (including folks from NHC, it sounds like) confusing storm relative shear with storm relative flow (the orientation of which is often important with respect to convection). Again, in low-shear environments, there is little-to-no storm relative flow anyway. Link to comment Share on other sites More sharing options...
winter_warlock Posted July 31, 2011 Share Posted July 31, 2011 this is looking like it may have a shot at the southern to mid east coast, but still 7 to 10 days out... Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted July 31, 2011 Share Posted July 31, 2011 This is such a weird and awkward evolution for a developing tropical cyclone. I can definitely say now that I do not buy any model solution that shows an intense system heading north. I think we are moreso looking for a system struggling with organizational issues through at least 96 hours, possibly a little longer, with max possible intensity during that period being a moderate to strong tropical storm at best. Link to comment Share on other sites More sharing options...
Doorman Posted July 31, 2011 Share Posted July 31, 2011 Snapcast Link to comment Share on other sites More sharing options...
winter_warlock Posted July 31, 2011 Share Posted July 31, 2011 Snapcast its looking actually like two separate areas of storminess, they will probably join together as we go along. Link to comment Share on other sites More sharing options...
nycsnow Posted July 31, 2011 Share Posted July 31, 2011 Doorman haven't heard from ya since winter with your cool graphics lol Link to comment Share on other sites More sharing options...
Bostonseminole Posted July 31, 2011 Share Posted July 31, 2011 There is nothing crucial about watching a broad gyre develop into a tropical depression. lol Link to comment Share on other sites More sharing options...
k*** Posted July 31, 2011 Share Posted July 31, 2011 Doorman haven't heard from ya since winter with your cool graphics lol this isn't a snow thread Link to comment Share on other sites More sharing options...
OSUmetstud Posted July 31, 2011 Share Posted July 31, 2011 I don't see why there is a debate. Shear is a mathematical concept. Storm relative shear = absolute sheer, by definition. There should be no debate, if you (not specifically picking on you, just "you" in general) understand simple math. This applies to models as well. I think the issue here is people (including folks from NHC, it sounds like) confusing storm relative shear with storm relative flow (the orientation of which is often important with respect to convection). Again, in low-shear environments, there is little-to-no storm relative flow anyway. There is a such thing as storm-relative shear in the thunderstorm/severe world and it does not always equal the absolute environment shear. Thunderstorms propagate and don't translate...and will move at different speeds relative to the mean flow. MCSs and supercells will occasionally move faster and a slight right angle to the mean flow...meaning it can tap a greater amount of shear and helicity than is available by just looking solely at the environment. Link to comment Share on other sites More sharing options...
nycsnow Posted July 31, 2011 Share Posted July 31, 2011 So biggest impact along east coast will prob be high surf? Link to comment Share on other sites More sharing options...
Sickman Posted July 31, 2011 Share Posted July 31, 2011 So biggest impact along east coast will prob be high surf? Patience. Link to comment Share on other sites More sharing options...
Amped Posted July 31, 2011 Share Posted July 31, 2011 There is a such thing as storm-relative shear in the thunderstorm/severe world and it does not always equal the absolute environment shear. Thunderstorms propagate and don't translate...and will move at different speeds relative to the mean flow. MCSs and supercells will occasionally move faster and a slight right angle to the mean flow...meaning it can tap a greater amount of shear and helicity than is available by just looking solely at the environment. HECS also seem to have some propagation behavior, they move to the left of the flow closer to the ULL as they deepen and the surface high erodes over the gulf stream. But for hurricanes it's pretty much pure translation. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 There is a such thing as storm-relative shear in the thunderstorm/severe world and it does not always equal the absolute environment shear. Thunderstorms propagate and don't translate...and will move at different speeds relative to the mean flow. MCSs and supercells will occasionally move faster and a slight right angle to the mean flow...meaning it can tap a greater amount of shear and helicity than is available by just looking solely at the environment. This is a good point actually - a right moving supercell, in many cases, will ingest higher SRH values than a supercell moving along with the mean flow, or a left moving storm. Squall lines/bowing segments that tend to propagate along boundaries will also deviate from the mean flow. In TC world, i suspect that this does not frequently occur. Link to comment Share on other sites More sharing options...
snowNH Posted July 31, 2011 Share Posted July 31, 2011 Does anybody see any analogs to this storm, or is it still too early? I know David from 1979 was already brought up. Link to comment Share on other sites More sharing options...
Doorman Posted July 31, 2011 Share Posted July 31, 2011 http://www.esl.lsu.e...pics&channel=wv LSU enlarged enhanced Link to comment Share on other sites More sharing options...
k*** Posted July 31, 2011 Share Posted July 31, 2011 Does anybody see any analogs to this storm, or is it still too early? I know David from 1979 was already brought up. Hugo is my primary analog. Link to comment Share on other sites More sharing options...
Riptide Posted July 31, 2011 Share Posted July 31, 2011 Hugo is my primary analog. Hazel is your secondary analog. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted July 31, 2011 Share Posted July 31, 2011 Hugo is my primary analog. I was waiting for that. I also knew you'd be the one to do it. Link to comment Share on other sites More sharing options...
My Weather Today Posted July 31, 2011 Share Posted July 31, 2011 You're bringing up a good point. Actually, one week prior does appear to have a smaller partial correlation while two weeks prior appears to have little, if any, correlation. I count 26 (earlier I had 25 but I had missed one) nongrazing east coast hurricane hits from 1950-2010: 1) Avg. NAO day of hit: +0.3; 19 (73%) had +NAO and 7 (27%) had -NAO. 2) Avg. NAO seven days prior to hit: +0.2; 16 (62%) had +NAO and 10 (38%) had -NAO. 3) Avg. NAO 14 days prior to hit: 0.0 (right at neutral); 14 (54%) had +NAO and 12 (46%) had -NAO. Seven days earlier, there were actually three with an NAO of less than -1 with the lowest at -1.786 (Cleo of 1964). Regarding 14 days earlier, there was only one below -1 although it was at -2.001 (Cleo of 1964). So, yes, these stats tell me that on occasion the NAO has been solidly negative 7-14 days earlier (3 of the 26 hurricanes). However, the NAO did increase a lot by the day of the hit for these three storms to +0.324 (Carol of 1954), -.272 (Cleo of 1964), and -0.209 (Inez of 1966. With the GFS ensemble mean maintaining its NAO prediction near -2 for days 7-10 and considering their recent verifications (also the Euro ensemble has a similar -NAO), it is pretty likely going to verify as a strongly -NAO when 91L would likely be in its critical position north of the Greater Antilles (assuming it doesn't stay in the Caribbean). So, despite the good point you mentioned, this all still tells me the chances of a nongrazing east coast hit are very slim because the NAO is almost definitely still going to be quite negative. Had the NAO forecast for 7-10 days out been for a rise to only slightly negative or greater as opposed to sinking to strongly negative, I wouldn't be using the NAO to make these east coast avoiding predictions for 91L. So am I interpreting this data correctly...doesn't these results kinda support what am19psu said back on 07/30/11?: "NAO is kinda chicken and egg... the storm can have a definite effect in its status... I don't think you can just look at NAO progs and make a forecast off it because of the connection to the storm itself...Just that the future cyclone can have a direct effect on NAO state through latent heat release... not to mention other things like pacific convection and mountain torques that are not handled well by the models... I wouldn't use an NAO prog as a basis for my forecast verbatim." So others won't complain, maybe you (or I if necessary) need to create a separate thread for this research and we can continue this discussion over there, since I know everyone is skimming though here for the latest thoughts on Invest 91L. EDIT: I went ahead created a new thread for this discussion anyway...Atlantic Hurricane Tracks Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 18Z GFS, perhaps with some G-IV data (18Z NAM had some data ingested per a post a page or so back) and 12Z Euro are still fish storms, but close enough to the Carolinas to make it interesting. 18Z NAM and GFS and 12Z Euro spare Haiti the worst, I'm guessing this assumes fairly rapid organization of 91L. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted July 31, 2011 Share Posted July 31, 2011 Yo-- I've been roadtripping around Matagorda Bay the last 24 hr and I've essentially been offline. I see it's been a 100% cherry forever. lolz Is this a fish? A shredded island-hopper? Summary, plz. Link to comment Share on other sites More sharing options...
usedtobe Posted July 31, 2011 Share Posted July 31, 2011 This is a good point actually - a right moving supercell, in many cases, will ingest higher SRH values than a supercell moving along with the mean flow, or a left moving storm. Squall lines/bowing segments that tend to propagate along boundaries will also deviate from the mean flow. In TC world, i suspect that this does not frequently occur. MCSs and MCCs also can devaite quite a bit from the mean flow changing the relative shear. I suspect you are right about tropical systems and that they mostly move with the mean flow though I suspect that the depth of the flow steering the storm could impact it some. Still it's probably safe to assume that for most tropical systems the shear is the the shear. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 There is a such thing as storm-relative shear in the thunderstorm/severe world and it does not always equal the absolute environment shear. Thunderstorms propagate and don't translate...and will move at different speeds relative to the mean flow. MCSs and supercells will occasionally move faster and a slight right angle to the mean flow...meaning it can tap a greater amount of shear and helicity than is available by just looking solely at the environment. To elaborate further, Storm relative helicity can be different between propagating storms and translating storms; however, the sheer vector remains the same (see the mathematical argument in my previous post, which is valid regardless of the direction of storm motion (i.e. whether or not it is consistent with the mean flow). Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 I know I'm a weenie when I post stuff like this, but it help's me visualize the situation.. Data is from the G-IV. Green is 850 mb Blue is Surface (or closest to..) Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 MCSs and MCCs also can devaite quite a bit from the mean flow changing the relative shear. I suspect you are right about tropical systems and that they mostly move with the mean flow though I suspect that the depth of the flow steering the storm could impact it some. Still it's probably safe to assume that for most tropical systems the shear is the the shear. again, they may change the storm relative helicity, but the storm relative shear remains the same as the absolute wind shear - this is easily proven mathematically. generalized: C = storm motion, V1= absolute wind at low level V2= absolute wind at higher level Bulk "absolute" shear over layer between V2 and V1 = V2-V1 V1 - C = storm relative wind at low level V2 - C = storm relative wind at higher level Storm relative shear = (V2 - C) - (V1 - C) = V2-V1 C may be any arbitrary vector, aligned with or different than the mean flow. Edit: lol, i went back to spelling it "sheer" Link to comment Share on other sites More sharing options...
dan88 Posted July 31, 2011 Share Posted July 31, 2011 Yo-- I've been roadtripping around Matagorda Bay the last 24 hr and I've essentially been offline. I see it's been a 100% cherry forever. lolz Is this a fish? A shredded island-hopper? Summary, plz. Right now it is an impressive but elongated mess. For much of today, there have been two distinct complexes, one which was along the wave axis and appears to have included a low level circulation (which is now lagging behind this front complex, falling back just a bit and is moving relatively slowly compared to the wave axis), and a region to the East which has contained the mid/upper level vort maxes and has been the main region of the disturbance. Recon was going in to see what was up, but little data from the storm made it out because of large communication problems (the most recent data is from before 2pm), making it even harder to tell what has been going on. As to the future track, a Northward track from a strong system in the short term seems more unlikely because it is likely going to take some time to consolidate, keeping the system weaker for the short term. Link to comment Share on other sites More sharing options...
usedtobe Posted July 31, 2011 Share Posted July 31, 2011 To elaborate further, Storm relative helicity can be different between propagating storms and translating storms; however, the sheer vector remains the same (see the mathematical argument in my previous post, which is valid regardless of the direction of storm motion (i.e. whether or not it is consistent with the mean flow). BY definition that's correct. The storm relative winds differ due to the storm motion but the vector stays the same since all the winds are changed to the same degree. Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2011 Author Share Posted July 31, 2011 TROPICAL WEATHER OUTLOOK NWS NATIONAL HURRICANE CENTER MIAMI FL 800 PM EDT SUN JUL 31 2011 FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO... AN ELONGATED AREA OF LOW PRESSURE EXTENDING FROM THE LESSER ANTILLES EASTWARD SEVERAL HUNDRED MILES INTO THE TROPICAL ATLANTIC OCEAN IS PRODUCING A LARGE BUT DISORGANIZED AREA OF SHOWERS AND THUNDERSTORMS. CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE FOR A TROPICAL DEPRESSION OR TROPICAL STORM TO FORM...AND THIS SYSTEM HAS A HIGH CHANCE...90 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH. IF THE SYSTEM BECOMES A TROPICAL CYCLONE TONIGHT OR MONDAY... TROPICAL STORM WATCHES OR WARNINGS WOULD BE ISSUED FOR PORTIONS OF THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS ON VERY SHORT NOTICE...AND INTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM. A HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS SYSTEM MONDAY MORNING. REGARDLESS OF TROPICAL CYCLONE FORMATION...THIS SYSTEM WILL BRING LOCALLY HEAVY RAINFALL AND GUSTY WINDS TO PORTIONS OF THE LESSER ANTILLES TONIGHT AND MONDAY. ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS. $$ FORECASTER BRENNAN Link to comment Share on other sites More sharing options...
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