IsentropicLift Posted September 4, 2011 Share Posted September 4, 2011 chill...it's common for the eye to wax and wane in size, shape, and clarity when a hurricane is starting to develop one. it was just a question in terms of what is going on structure wise with the core. It seems to early for an eyewall replacement cycle and it appears to be strengthening quickly Link to comment Share on other sites More sharing options...
OKpowdah Posted September 4, 2011 Share Posted September 4, 2011 Is that a true "pinhole" eye? There was a larger ragged eye on the last few frames before being replaced by this No, it's just thunderstorm growth in the eyewall with some of the outflow obscuring part of the eye. Btw, in the initial formation of the eye, look mainly at visible, because the eye is often less noticeable on IR if there is cold cirrus over it Link to comment Share on other sites More sharing options...
Eyewall2005 Posted September 4, 2011 Share Posted September 4, 2011 Pattern really hasn't really changed all that much since last year with a break in the ridge between bermuda and southeast U.S. allowing for CV storms to recurve. Link to comment Share on other sites More sharing options...
k*** Posted September 4, 2011 Share Posted September 4, 2011 it was just a question in terms of what is going on structure wise with the core. It seems to early for an eyewall replacement cycle and it appears to be strengthening quickly the point is that if you microanalyze every frame you'll drive yourself crazy and be called a weenie. Link to comment Share on other sites More sharing options...
Mallow Posted September 4, 2011 Share Posted September 4, 2011 it was just a question in terms of what is going on structure wise with the core. It seems to early for an eyewall replacement cycle and it appears to be strengthening quickly Not much is going on. Check out the visible, the eye's character hasn't changed much. It's just a thin layer of cirrus over the eye. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted September 4, 2011 Share Posted September 4, 2011 Pattern really hasn't really changed all that much since last year with a break in the ridge between bermuda and southeast U.S. allowing for CV storms to recurve. That's called climo. Irene, Hugo, Floyd, etc are the exception that prove the rule. Link to comment Share on other sites More sharing options...
OHweather Posted September 4, 2011 Share Posted September 4, 2011 Hurricane Katia Forecast/Discussion: Hurricane Katia has undergone rapid intensification today and is now a catagory two hurricane on the Saffir Simpson Hurricane Wind Scale. Katia had a very well defined eye on satellite imagery earlier this afternoon, but the eye has filled somewhat since. The hurricane is exhibiting an eyewall with cold cloud tops (-70C) especially in the western quadrants, with a possibly struggling eyewall especially in the eastern quadrants, perhaps suggesting some dry air entrainment. Based on this information, believe that Katia's intensification may have stopped for now. Over the past several hours Katia's motion has been a fairly steady 305/10kt*. The hurricane is being steered by the southwestern periphery of a rather small sub-tropical ridge located to the northeast of the hurricane, and because of this the general NW motion is expected to continue in the short term as the hurricane remains well south of the westerlies and as the pattern over the eastern US slows down as the remnants of tropical storm Lee interact with a mid level trough over the Ohio/Tennessee Valleys. This will occur due to the westerlies being much farther north than normal, due to a -PNA and +NAO, which is shown well on the 0z ECM Ensembles. Because of this, the track of Tropical Storm Lee's remnants will be very important to this track forecast, which will result in less than normal confidence in the track forecast days 4-5. However, given that a trough will be in place over the Eastern US in the short term and that given Lee and Katia will be both on the western side of ridging when the trough moves off to the northeast in the coming days, I believe it will be hard for ridging to build back in north of Katia to the east coast and force the hurricane westward. The 12z European Model showed this well compared to the model's 0z run, as the heart of the ridging is clearly east of the hurricane and the heart of the ridging and is already parallel to Katia, showing it will be hard for ridging to build back in to the north of the system. In fact, the majority of the 12z global models showed this and showed Katia remaining safely off the southeast US coastline. By the time Katia passes the latitude of Bermuda it should be well on the northwestern periphery of the subtropical Atlantic ridging and will begin to approach the westerlies. Given this, will forecast a continued NW motion in the first 72 hours as the hurricane remains on the southwestern edge of ridging to its east, and will then show a turn to the north by day 5, well off the southeastern US coastline, as the hurricane rounds the west side of the rather small area of high pressure. It appears as though Katia's explosive intensification from this morning is done as noted above, and the hurricane currently is experiencing 10-20 kts of southeasterly shear per current shear analysis. The hurricane currently appears to be on the edge of an upper level anti-cyclone, with an enhanced upper level flow near the hurricane due to a small upper low to its northeast. Over the next 48 hours this upper level low is prognosticated to weaken and the hurricane is expected to gradually move under the upper level anti-cyclone. In addition, the hurricane will remain over SSTs of 28-30C for the next 4-5 days. Although the depth of the warmth is not particuarly impressive in Katia's path, the fairly warm sea surface temperatures, normal forward speed and improving upper level environment should allow for further intensification, likely rather modest, over the next 48 hours followed by a gradual leveling off in intensity and weakening by day 5, as the hurricane approaches cooler waters and begins feeling increasing southwesterly shear in response to apporaching the westerlies. This forecast brings Katia up to a major hurricane which is in good agreement with the 12z global models, of which the CMC, GFS, and Euro all showed Katia deepening significantly over the coming days. Katia should weaken below major hurricane status by day 5, which is in fairly good agreement with the most recent ATCF intensity guidance. Forecast track: Intensity: Initial (15z Sunday): 85kt/Cat 2 12 hours (6z Monday): 85kt/Cat 2 24 hours (18z Monday): 90kt/Cat 2 36 hours (6z Tuesday): 95kt/Cat 2 48 hours (18z Tuesday): 100kt/Cat 3 72 hours (18z Wednesday): 100kt/Cat 3 96 hours (18z Thursday): 95kt/Cat 2 120 hours (18z Friday): 85kt/Cat 2 (Not spell checked, I'm sure there were some interesting spellings in there) Link to comment Share on other sites More sharing options...
phil882 Posted September 4, 2011 Share Posted September 4, 2011 The 12z ECWMF trended back to the east mainly because the upper level feature that is associated with Lee also trended stronger and further east. The ECWMF is now much more in line with the GFS. Again it seems that the strength of the cutoff low associated with Lee is going to affect how this plays out, and it seems that this run was a step towards the 12z GFS. Link to comment Share on other sites More sharing options...
bluewave Posted September 4, 2011 Share Posted September 4, 2011 The 12z ECWMF trended back to the east mainly because the upper level feature that is associated with Lee also trended stronger and further east. The ECWMF is now much more in line with the GFS. Again it seems that the strength of the cutoff low associated with Lee is going to affect how this plays out, and it seems that this run was a step towards the 12z GFS. Yeah,the GFS Ensembles timing and tracks are not that far off from the Euro today. Link to comment Share on other sites More sharing options...
dan88 Posted September 5, 2011 Share Posted September 5, 2011 Still lopsided with the convection, mid level center might be to the SE of the surface center looking at this. Link to comment Share on other sites More sharing options...
LovintheWhiteFluff Posted September 5, 2011 Share Posted September 5, 2011 00z GFS east and 00z CMC says very close to east coast landfall or at the very least and east coast threat... Indeed...The difference is the westerlies which is much further north allowing the ridge to setup further north. It forces Katia north instead of northeast. Link to comment Share on other sites More sharing options...
LovintheWhiteFluff Posted September 5, 2011 Share Posted September 5, 2011 One thing is suspect to me. The trough setup seems similar to the Eur and GFS. One would thing the motion would be at least NNE given the location of the trough and ridge. Link to comment Share on other sites More sharing options...
phil882 Posted September 5, 2011 Share Posted September 5, 2011 Currently, it looks like Katia is undergoing an eyewall replacement cycle. In the short term we might see a bit of weakening, but ultimately Katia will blossom again as the new eywall closes off fully and we see the diameter stabilize at around 30mi. As for the track guidance, it looks like the ECWMF is now in very good agreement with the GFS about a re-curving system well offshore the United States. It teased us for a few runs in the past 24 hours, but ultimately it looks like the mid-level cutoff low associated with the remnants of lee will be too strong and too far to the east to allow a further westward track. The +AO and +NAO will likely not allow too much ridging to build in northward as well, so I'm still confident in my sharp re-curvature scenario. Link to comment Share on other sites More sharing options...
dan88 Posted September 5, 2011 Share Posted September 5, 2011 Looks like that Eyewall Replacement Cycle is going well Link to comment Share on other sites More sharing options...
phil882 Posted September 5, 2011 Share Posted September 5, 2011 Looks like that Eyewall Replacement Cycle is going well Yep... From the looks of it this was underway this afternoon and is just now starting to complete. This term gets overused, but I think we are going to have a beautiful annular storm later today as the enhanced IR presentation improves. I still think my max intensity of 120 knots looks good, but may happen a little earlier than expected given how quickly the storm completed this EWRC. Link to comment Share on other sites More sharing options...
Bannor Posted September 5, 2011 Share Posted September 5, 2011 Link to comment Share on other sites More sharing options...
bluewave Posted September 5, 2011 Share Posted September 5, 2011 Katia will produce large swells as she recurves to our east. Link to comment Share on other sites More sharing options...
winterymix Posted September 5, 2011 Share Posted September 5, 2011 The +AO and +NAO will likely not allow too much ridging to build in northward as well, so I'm still confident in my sharp re-curvature scenario. It seems that the idea above is so very important. The Mid-hemispheric Atlantic Ridge is flattening like a souffle after the oven door was opened and then slammed. Poooof...Katia will more likely slide south of Greenland and Iceland than threaten Cape Cod. Link to comment Share on other sites More sharing options...
OSUmetstud Posted September 5, 2011 Share Posted September 5, 2011 SHIPS initialized at 95 kt at 12z. SATCON average is up to 101kt. Link to comment Share on other sites More sharing options...
donsutherland1 Posted September 5, 2011 Share Posted September 5, 2011 Yesterday, I had been leaning toward a somewhat more westward course for Katia, but the GFS's consistency farther east suggested caution and I held off making any adjustments to my estimated track. Overnight and through 6z, the guidance has moved toward consensus east of earlier Euro runs. At the same time, the GFS has persisted in a somewhat less dramatic turn to the right. Hence, I've left my track as it was: Estimated Track: 17.5N 52.8W; Actual: 17.5N 52.4; Error: 26 miles--1.5 hours in advance 20.0N 56.8W; Actual: 20.0N 57.0W; Error: 13 miles--33.0 hours in advance 25.0N 63.9W 30.0N 72.0W 35.0N 69.6W 40.0N 63.5W In terms of intensity, depending on which satellite guidance one uses, Katia is currently rated T5.0 or T5.5 on the Dvorak scale. A compromise would bring the storm's winds to about 95 knots/110 mph. So, at least according to the satellite data, Katia is nearing major hurricane status. I expect Katia to grow into a major hurricane later today en route to eventually peaking at perhaps Category 4. Finally, well behind Katia at around 9.5N 29.6W, there is a tropical wave with maximum sustained winds of nearly 30 mph. That system may bear watching down the road. Link to comment Share on other sites More sharing options...
gkrangers Posted September 5, 2011 Share Posted September 5, 2011 Yep... From the looks of it this was underway this afternoon and is just now starting to complete. This term gets overused, but I think we are going to have a beautiful annular storm later today as the enhanced IR presentation improves. I still think my max intensity of 120 knots looks good, but may happen a little earlier than expected given how quickly the storm completed this EWRC. The anti-Irene. Link to comment Share on other sites More sharing options...
OSUmetstud Posted September 5, 2011 Share Posted September 5, 2011 Katia's 91 color image as of 1014z. Link to comment Share on other sites More sharing options...
Srain Posted September 5, 2011 Share Posted September 5, 2011 Continue discussions here... http://www.americanwx.com/bb/index.php/topic/25335-hurricane-katia-part-2/ Link to comment Share on other sites More sharing options...
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