am19psu Posted July 31, 2011 Share Posted July 31, 2011 I wasn't necessarily just using the NAO value for the forecast anyway. I was looking at the height anomalies of both the GFS and the Euro and their ensembles which showed a -NAO type pattern (Davis Strait Blocking with low height anomalies over the US East Coast and into the Western Atlantic). That particular pattern does not look favorable for me to get a storm to the US East Coast if it's relatively strong north of the Antilles. Wouldn't the storm have more of an effect on the NAO during and after recurvature, not before? Yeah, sorry, like I said I was on my phone and meant my post to you as a general thing, not specific to the 91L forecast. But, yes, storms can affect the NAO prior to recurvature. All of that mass evacuated in the center of the storm has to go somewhere and it often leads to a stronger subtropical ridge. Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2011 Author Share Posted July 31, 2011 Link to comment Share on other sites More sharing options...
Floydbuster Posted July 31, 2011 Share Posted July 31, 2011 Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 Elaborate please... Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2011 Author Share Posted July 31, 2011 Until 91L slows its forward motion, development will remain rather slow, IMO. 15-20 WNW movement isn't going to allow for any rapid intensification. My hunch is RECON will confirm that dry air is still within the mid levels and therefore TD status will likely be the most we'll see until 91L slows down its forward motion. I also suspect that any future Emily would be a bigger concern once it enters the Caribbean Sea. The threat to PR and more so to Hispaniola, are the bigger concerns at the moment in the days ahead. We will see. Elaborate please... See above... Link to comment Share on other sites More sharing options...
battlebrick Posted July 31, 2011 Share Posted July 31, 2011 we went from a east coast recurver to a florida threat.. nice (or not). HWRF, GFDL, NOGAPS, and Euro head towards Florida. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 See above... i don't understand your reasoning. Simply "slowing down" won't make the difference between the system intensifying or not. Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 we went from a east coast recurver to a florida threat.. nice (or not). HWRF, GFDL, NOGAPS, and Euro head towards Florida. I learned this a long time ago from the wunderground tropic forums (yea, I know. Laugh all you want ) But it still holds true. "Don't try to predict more than 10° of latitude ahead of you!" Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 Now that we have another visible frames to look at, I see West winds to the South, but I'd have a hard time calling this a TD yet because it looks like the center is rather stretched in the E-W axis between the two distinct thunderstorm clusters. May even be elliptical around two smaller centers. NASA customized visible loop- I suspect the Eastern cluster of storms will become the dominant feature I don't dispute the near 100% 48 hour probs, and NHC may lean on the side of caution even with a broad/disorganized center to hoist watches and warnings, but I think recon will find a distorted center, or even two competing centers. Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2011 Author Share Posted July 31, 2011 i don't understand your reasoning. Simply "slowing down" won't make the difference between the system intensifying or not. Actually it can. Slowing down will allow the mixing out of the dry air ingested, therefore a consolidation, if you will of deeper moisture trailing the disturbance. The good news I see is the threat to the Windwards and Leewards is reduced this morning, but I am concerned for Hispaniola. Conditions look more conducive for development once 91L enters the Caribbean Sea. Link to comment Share on other sites More sharing options...
am19psu Posted July 31, 2011 Share Posted July 31, 2011 I learned this a long time ago from the wunderground tropic forums (yea, I know. Laugh all you want ) But it still holds true. "Don't try to predict more than 10° of latitude ahead of you!" That doesn't help much when clients expect seven day forecasts. Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 we went from a east coast recurver to a florida threat.. nice (or not). HWRF, GFDL, NOGAPS, and Euro head towards Florida. http://raleighwx.americanwx.com/models/euro/00zeurotropical850mbVortSLP_loop.html Link to comment Share on other sites More sharing options...
am19psu Posted July 31, 2011 Share Posted July 31, 2011 Actually it can. Slowing down will allow the mixing out of the dry air ingested, therefore a consolidation, if you will of deeper moisture trailing the disturbance. The good news I see is the threat to the Windwards and Leewards is reduced this morning, but I am concerned for Hispaniola. Conditions look more conducive for development once 91L enters the Caribbean Sea. Sorry, I've been out most of the weekend. Wasn't this always the CW concerning this storm? Link to comment Share on other sites More sharing options...
mappy Posted July 31, 2011 Share Posted July 31, 2011 That doesn't help much when clients expect seven day forecasts. Pfffft, who needs to give the clients what they want? Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 That doesn't help much when clients expect seven day forecasts. ... Well, that sounds like a public presumption problem. I mean NHC only goes out to five days and I'm sure everyone is aware of the average track errors on that range. Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 As mentioned/linked on previous page with visible loop, the lead blob is competing with 91L and is distorting the low level circulation. Link to comment Share on other sites More sharing options...
battlebrick Posted July 31, 2011 Share Posted July 31, 2011 http://raleighwx.ame...rtSLP_loop.html i said "heading towards" as in, the models are moving more west towards florida. Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 Now that we have another visible frames to look at, I see West winds to the South, but I'd have a hard time calling this a TD yet because it looks like the center is rather stretched in the E-W axis between the two distinct thunderstorm clusters. May even be elliptical around two smaller centers. Ed, I think know that the cluster to the west is just a set of small squall lines. If anything it like a bulldozer , mixing out the dry air ahead of it. I don't think its going to be a concern for the formation the LLC. You might find slower winds on the west side but I think that's it. Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 i said "heading towards" as in, the models are moving more west towards florida. If you insist. Link to comment Share on other sites More sharing options...
free_man Posted July 31, 2011 Share Posted July 31, 2011 wow...thanks...I've been looking for the daily data. The only research in papers I could find had to do with monthlies and TCs. The problem with that data is that it is using the NAO measurement on the day of the storm making a landfall. I would think the NAO phase either a week up to two weeks prior to landfall would be a more useful correlation, correct? Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 31, 2011 Share Posted July 31, 2011 Ed, I think know that the cluster to the west is just a set of small squall lines. If anything it like a bulldozer , mixing out the dry air ahead of it. I don't think its going to be a concern for the formation the LLC. You might find slower winds on the west side but I think that's it. Look at the vis, there isn't any (obvious) winds from the North around the Easternmost cluster. I think that cluster is dominant in the long term, but I don't think it is really a TD yet. Link to comment Share on other sites More sharing options...
wxmeddler Posted July 31, 2011 Share Posted July 31, 2011 Look at the vis, there isn't any (obvious) winds from the North around the Easternmost cluster. I think that cluster is dominant in the long term, but I don't think it is really a TD yet. I think you may be right, but I'm not going to go out on a limb and say that there is/isn't a closed circulation on the west side of the main cluster. There may be some north winds under the cirrus cover. RECON will be in this afternoon anyway and should answer all of our questions. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 Actually it can. Slowing down will allow the mixing out of the dry air ingested, therefore a consolidation, if you will of deeper moisture trailing the disturbance. The good news I see is the threat to the Windwards and Leewards is reduced this morning, but I am concerned for Hispaniola. Conditions look more conducive for development once 91L enters the Caribbean Sea. I confused as to the meteorological justification of this statement. How does forward speed have any effect on how "dry air ingested" is mixed out? Typically wind sheer is needed, to some extent, to introduce dry air into a system. Are you associating fast forward speed with wind sheer? They are not necessarily correlated. I don't follow what you are talking about with the whole "deeper moisture trailing the disturbance" bit either. Edit: I think maybe I understand what you are trying to say. Slow motion would allow dry air to mix out prior to arrival in Caribbean Sea, increasing the threat to the Windwards and Leewards. This will not, however, affect the rate of intensification of the system with all things being equal (i.e. same degree of wind sheer). Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted July 31, 2011 Share Posted July 31, 2011 http://www.ssd.noaa.gov/goes/flt/t2/flash-rgb.html Link to comment Share on other sites More sharing options...
nchighcountrywx Posted July 31, 2011 Share Posted July 31, 2011 Unlikely to get west of 74w before recurve. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 Unlikely to get west of 74w before recurve. Some support to your claim would certainly be useful. Though, based both ECMWF and GFS weakening the ridge along EUS, I would tend to agree with you at this point. Link to comment Share on other sites More sharing options...
usedtobe Posted July 31, 2011 Share Posted July 31, 2011 I confused as to the meteorological justification of this statement. How does forward speed have any effect on how "dry air ingested" is mixed out? Typically wind sheer is needed, to some extent, to introduce dry air into a system. Are you associating fast forward speed with wind sheer? They are not necessarily correlated. I don't follow what you are talking about with the whole "deeper moisture trailing the disturbance" bit either. Edit: I think maybe I understand what you are trying to say. Slow motion would allow dry air to mix out prior to arrival in Caribbean Sea, increasing the threat to the Windwards and Leewards. This will not, however, affect the rate of intensification of the system with all things being equal (i.e. same degree of wind sheer). But for a weak system the system relative shear might be stronger with a faster moving system if there is any hint of westerly flow aloft. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 But for a weak system the system relative shear might be stronger with a faster moving system if there is any hint of westerly flow aloft. There is likely a better chance for increased sheer with faster motion, yes; however, why implicitly suggest this by focusing on rate of storm motion, when the two are not necessarily correlated? There have been fast moving systems that became very intense through this region. Link to comment Share on other sites More sharing options...
usedtobe Posted July 31, 2011 Share Posted July 31, 2011 There is likely a better chance for increased sheer with faster motion, yes; however, why implicitly suggest this by focusing on rate of storm motion, when the two are not necessarily correlated? There have been fast moving systems that became very intense through this region. True, the relative shear is the important factor and there have been storms that moved fast that developed. I'd be interested in seeing research into system movement and rate of development if there are any articles. Link to comment Share on other sites More sharing options...
jpeters3 Posted July 31, 2011 Share Posted July 31, 2011 True, the relative shear is the important factor and there have been storms that moved fast that developed. I'd be interested in seeing research into system movement and rate of development if there are any articles. A fast mean storm motion combined with low wind sheer is essentially the same environment for a system as a slow mean storm motion and low wind sheer, since with the fast motion low sheer, the environment is essentially "moving with" the system. If anything, fast motion hinders upward mixing of cooler water due to less turbulent mixing of the oceanic surface layer, so I would suspect that, all else in the atmosphere being equal, faster storms may remain more intense over regions where the warm water layer is relatively shallow. I doubt there are any studies that directly compare storm motion to rate of intensification, since it is more useful to look at factors like sheer and SST/oceanic heat content. Link to comment Share on other sites More sharing options...
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