CUmet Posted August 27, 2012 Share Posted August 27, 2012 Isaac has a more sheared look than the satellite analysis is depicting. I have to imagine that's either because of a) shear is found at a level that is being missed by GOES (perhaps 300-500mb) or the combination of modest shear and dry air entrainment. Funny thing is, I was thinking the exact opposite. Most of the coldest cloud tops on IR/WV are left of shear, which is what you would expect from a sheared system. However, the radar returns from the Tampa radar are pretty symmetric about the center, and high-resolution visible imagery suggest this as well (although much tougher to tell). Something that does bode well for strengthening is the fact that recon had pretty substantial SFMR rain rates pretty close to the center, suggesting that there is quite a bit of diabatic heating in the inertially stable region inside the RMW. But as we all know, intensity forecasting is extremely difficult, so we'll have to wait and see how this plays out. Link to comment Share on other sites More sharing options...
Derecho! Posted August 27, 2012 Share Posted August 27, 2012 I don't think there's much of a chance for strengthening based on those TCHP plots. While people see slivers of warmer water, I see a real lack of TCHP that we usually see in this area of the Gulf and a large system that will be encouraging a large amount of upwelling. I think in the last couple of days there were some posts pointing out that the commonly posted TCHP plot was inaccurate, that the large "cold" areas in the GOM weren't "real" but were artifacts of missing data. Link to comment Share on other sites More sharing options...
OSUmetstud Posted August 27, 2012 Share Posted August 27, 2012 Funny thing is, I was thinking the exact opposite. Most of the coldest cloud tops on IR/WV are left of shear, which is what you would expect from a sheared system. However, the radar returns from the Tampa radar are pretty symmetric about the center, and high-resolution visible imagery suggest this as well (although much tougher to tell). Something that does bode well for strengthening is the fact that recon had pretty substantial SFMR rain rates pretty close to the center, suggesting that there is quite a bit of diabatic heating in the inertially stable region inside the RMW. But as we all know, intensity forecasting is extremely difficult, so we'll have to wait and see how this plays out. I was strictly looking at the IR with that classic downshear left convection...that's interesting the radar looks considerably more symmetric, though. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 27, 2012 Share Posted August 27, 2012 Latest update i would expect those areas haven't changed much since Fri. For whatever reason, the AOML SST/TCHP satellite page has been analyzing SSTs 28 to 30º, but a persistent area of sea level heights below normal resulting in no depth of water warmer than 26º. OHC calculation is an integration of some type involving SST and the depth of warm water. I looped the last few days before the 24th, it doesn't change much I have no idea why the satellite sees abnormally low sea level heights there, but I suspect it is a satellite error and that the warm water isn't paper thin there. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 Latest update i would expect those areas haven't changed much since Fri. It will have changed slowly which is important if you are basing predictions off of areas where small changes occur such as that corner of higher TCHP. This is in addition to the fact that we have to keep mentioning about how shallower, near-coastal waters with lower TCHP are fine for the intensification of tropical cyclones. Link to comment Share on other sites More sharing options...
Uncle Bobby Posted August 27, 2012 Share Posted August 27, 2012 I was strictly looking at the IR with that classic downshear left convection...that's interesting the radar looks considerably more symmetric, though. Maybe so, but the closest radar is Tampa, and even that radar is so far away that the slice is reaching Isaac at around 40,000 feet. Link to comment Share on other sites More sharing options...
turtlehurricane Posted August 27, 2012 Share Posted August 27, 2012 Winds sustained at 30+ mph are nearing the Mississippi Delta, gusts in the 20s across the Florida panhandle westwards to MS. Waters are already a foot above normal in eastern LA. Even a strong tropical storm can be very bad down in the Bayous, pretty similar to the Florida Keys vulnerability wise. Link to comment Share on other sites More sharing options...
Msalgado Posted August 27, 2012 Share Posted August 27, 2012 I think in the last couple of days there were some posts pointing out that the commonly posted TCHP plot was inaccurate, that the large "cold" areas in the GOM weren't "real" but were artifacts of missing data. Interesting. I'll do some reading up a bit later on how the data is gathered. Thanks for the info. Link to comment Share on other sites More sharing options...
airmarci Posted August 27, 2012 Share Posted August 27, 2012 Latest update i would expect those areas haven't changed much since Fri. Link to comment Share on other sites More sharing options...
heavy_wx Posted August 27, 2012 Share Posted August 27, 2012 Station 42003 NDBC Location: 26.044N 85.612W Date: Mon, 27 Aug 2012 15:50:00 UTC Winds: SE (140°) at 7.8 kt gusting to 13.6 kt Significant Wave Height: 15.4 ft Dominant Wave Period: 10 sec Mean Wave Direction: ENE (68°) Atmospheric Pressure: 29.17 in and falling rapidly Air Temperature: 82.8 F Water Temperature: 85.1 F Link to comment Share on other sites More sharing options...
DaculaWeather Posted August 27, 2012 Share Posted August 27, 2012 I hope the modes don't get mad at me for posting this link... just trying to help provide resources. I have an old discontinued page on my site that shows the buoys in the Gulf with a rotating display of the conditions, as well as the values in tabular format. Easy to read and use. http://www.daculaweather.com/buoy_new.php FWIW... if a mod wants to delete it, feel free. Link to comment Share on other sites More sharing options...
salbers Posted August 27, 2012 Share Posted August 27, 2012 Waters are already a foot above normal in eastern LA. Which station has a 1 foot rise in tides? This one is showing little rise so far... http://tidesandcurre...ot&plot_backup= Link to comment Share on other sites More sharing options...
CUmet Posted August 27, 2012 Share Posted August 27, 2012 Upon further analysis of the radar and visible imagery, it looks like the strongest convection has now shifted to the south quad. This distribution of convection is consistent with a more easterly shear vector. Now, the shear magnitude may have decreased, allowing for the convection to attempt to wrap completely around the center. However, if the convection continues to "stick" to the south quad, then it would indicate that the shear has not decreased, only the direction has changed. This is something to watch over the next few hours... Link to comment Share on other sites More sharing options...
turtlehurricane Posted August 27, 2012 Share Posted August 27, 2012 Which station has a 1 foot rise in tides? This one is showing little rise so far... http://tidesandcurre...ot&plot_backup= Link to comment Share on other sites More sharing options...
Derecho! Posted August 27, 2012 Share Posted August 27, 2012 VERY Interesting data from the buoy (Just updated): At 16:38 GMT had a pressure of 986.3 mb, but at 16:39 GMT 1-min wind was 37 kts. Suggests a 985 pressure at least. Link to comment Share on other sites More sharing options...
Max Posted August 27, 2012 Share Posted August 27, 2012 Upon further analysis of the radar and visible imagery, it looks like the strongest convection has now shifted to the south quad. This distribution of convection is consistent with a more easterly shear vector. Now, the shear magnitude may have decreased, allowing for the convection to attempt to wrap completely around the center. However, if the convection continues to "stick" to the south quad, then it would indicate that the shear has not decreased, only the direction has changed. This is something to watch over the next few hours... Does the convection being south and west quadrant dominant mean in the short term a more westerly heading for Isaac? Link to comment Share on other sites More sharing options...
jconsor Posted August 27, 2012 Share Posted August 27, 2012 Looks like at least part of the eye passed over that buoy: http://www.ndbc.noaa...p?station=42003 Note how the winds rapidly decreased to ~10 kt around 1545Z and stayed that low til around ~1620Z. VERY Interesting data from the buoy (Just updated): At 16:38 GMT had a pressure of 986.3 mb, but at 16:39 GMT 1-min wind was 37 kts. Suggests a 985 pressure at least. Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 The 12Z UKMET is entertaining: After going towards the MS gulf coast, it has Isaac slowing considerably, drifting NE into Mobile, then west to Biloxi, then NE to roughly north of Lucedale, MS. Link to comment Share on other sites More sharing options...
salbers Posted August 27, 2012 Share Posted August 27, 2012 Tide has been running high the past few days. Unsure how much is due to Isaac. We can see some uptick in the latest plot magnified more below (about 3-4 inches)... http://tidesandcurre...ot&plot_backup= Link to comment Share on other sites More sharing options...
CUmet Posted August 27, 2012 Share Posted August 27, 2012 Does the convection being south and west quadrant dominant mean in the short term a more westerly heading for Isaac? Maybe slightly if the convection sticks to those quads, but we'll have to see over the next few hours if the convection starts to swing around the east and north quads. Link to comment Share on other sites More sharing options...
N. OF PIKE Posted August 27, 2012 Share Posted August 27, 2012 visible looks best in a few days http://aviationweath...t_big&itype=vis not to mention gulf bouy at 1138 cdt read 986.3 Link to comment Share on other sites More sharing options...
David Reimer Posted August 27, 2012 Share Posted August 27, 2012 Several 55-59 knot SFMR values in the NW quadrant of the storm with the max FL wind around 53 knots. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 27, 2012 Share Posted August 27, 2012 visible looks best in a few days http://aviationweath...t_big&itype=vis not to mention gulf bouy at 1138 cdt read 986.3 looks pretty good to me and I think we will see the convection on the south succeed in wrapping around the N/E quads. Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted August 27, 2012 Share Posted August 27, 2012 2pm advisory has pressure down to 984. Link to comment Share on other sites More sharing options...
CUmet Posted August 27, 2012 Share Posted August 27, 2012 Funny thing is, I was thinking the exact opposite. Most of the coldest cloud tops on IR/WV are left of shear, which is what you would expect from a sheared system. However, the radar returns from the Tampa radar are pretty symmetric about the center, and high-resolution visible imagery suggest this as well (although much tougher to tell). Something that does bode well for strengthening is the fact that recon had pretty substantial SFMR rain rates pretty close to the center, suggesting that there is quite a bit of diabatic heating in the inertially stable region inside the RMW. But as we all know, intensity forecasting is extremely difficult, so we'll have to wait and see how this plays out. The recon pass through right now indicates that the wind field is responding to this. The RMW has now contracted to 20 km as a new inner wind maximum has sprouted up. We *could* be looking at the beginnings of an accelerated intensification, with the caveat that these things are always difficult to diagnose/predict. Edit: RMW in the SW quad is bit further out at 40-50 km, but the point still remains valid: an inner wind maximum has sprouted up when before it didn't exist. Link to comment Share on other sites More sharing options...
N. OF PIKE Posted August 27, 2012 Share Posted August 27, 2012 26.1 85.9 at 2pm seems center was tugg'd west bc 11 am was at 26.1 as well Link to comment Share on other sites More sharing options...
David Reimer Posted August 27, 2012 Share Posted August 27, 2012 63 Knot FL wind with SFMR values of 60-64 knots. 000 URNT15 KNHC 271803 AF306 2709A ISAAC HDOB 17 20120827 175500 2559N 08558W 8410 01394 //// +221 //// 298017 019 031 001 01 175530 2558N 08557W 8408 01400 //// +218 //// 269019 019 031 002 01 175600 2557N 08555W 8410 01400 //// +215 //// 265022 024 035 001 01 175630 2555N 08554W 8412 01400 //// +210 //// 261026 027 037 003 01 175700 2554N 08552W 8412 01403 //// +198 //// 259027 028 037 003 01 175730 2553N 08551W 8410 01406 //// +187 //// 262030 031 039 006 01 175800 2552N 08550W 8402 01415 //// +179 //// 270036 039 057 016 01 175830 2550N 08548W 8423 01398 //// +164 //// 258042 043 062 017 01 175900 2549N 08547W 8412 01415 //// +163 //// 253046 048 062 017 01 175930 2548N 08545W 8415 01420 //// +156 //// 244057 060 060 021 01 180000 2547N 08544W 8407 01433 //// +156 //// 240049 053 064 032 01 180030 2546N 08542W 8409 01435 //// +153 //// 242053 055 062 017 01 180100 2544N 08541W 8408 01443 //// +168 //// 240052 054 062 016 01 180130 2543N 08539W 8410 01443 //// +164 //// 241058 060 060 007 01 180200 2542N 08538W 8408 01450 //// +181 //// 239060 063 061 007 01 180230 2541N 08537W 8408 01455 //// +183 //// 243054 058 058 006 01 180300 2540N 08535W 8413 01453 //// +185 //// 244051 051 055 006 01 180330 2538N 08534W 8409 01461 //// +189 //// 243053 054 055 005 01 180400 2537N 08532W 8410 01464 //// +197 //// 241052 054 055 005 01 180430 2536N 08531W 8409 01466 //// +187 //// 242048 051 050 003 01 $$ Link to comment Share on other sites More sharing options...
PSUBlizzicane2007 Posted August 27, 2012 Share Posted August 27, 2012 12Z Euro has landfall just a smidge west near Bay St. Louis/Waveland, MS. Link to comment Share on other sites More sharing options...
wxmx Posted August 27, 2012 Share Posted August 27, 2012 A bit lopsided, but we have around 2/3s of an eyewall. Cat 2 is a high probability, IMO. Link to comment Share on other sites More sharing options...
Max Posted August 27, 2012 Share Posted August 27, 2012 Can that ULL over the Yucatan be helping to induce a more westerly motion at this time? Link to comment Share on other sites More sharing options...
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