Isopycnic Posted November 8, 2011 Share Posted November 8, 2011 ...New subtropical storm develops midway between Bermuda and the Bahamas... summary of 400 am EST...0900 UTC...information ---------------------------------------------- location...27.2n 69.4w about 445 mi...720 km SW of Bermuda maximum sustained winds...45 mph...75 km/h present movement...stationary minimum central pressure...1002 mb...29.59 inches watches and warnings -------------------- there are no coastal watches or warnings in effect. Discussion and 48-hour outlook ------------------------------ at 400 am EST...0900 UTC...the center of subtropical storm Sean was located near latitude 27.2 north...longitude 69.4 west. The storm is nearly stationary...and little motion is expected today. A slow westward or northwestward motion is forecast to begin by tonight or Wednesday. Maximum sustained winds are near 45 mph...75 km/h...with higher gusts. Little change in strength is forecast during the next 48 hours. Winds of 40 mph extend outward up to 380 miles...610 km...primarily west through northeast of the center. The estimated minimum central pressure is 1002 mb...29.59 inches. Hazards affecting land ---------------------- none next advisory ------------- next complete advisory...1000 am EST. $$ Forecaster Stewart DISCUSSION: Statement as of 4:00 am EST on November 08, 2011 corrected time from EDT to EST Satellite information and surface observations indicate the large non-tropical low pressure system that has been meandering between Bermuda and the Bahamas the past few days has acquired enough organized convection to be classified as subtropical storm Sean. An 08/1021z ascat overpass indicated the entire low-level circulation had become better defined...especially the inner core wind field. A large field of 34-kt winds extends a few hundred miles west through north of the center...but the ascat overpass appears to have underestimated the actual strength of winds based on winds of 41 kt reported by NOAA buoys 41047 and 41048 at 08/0100z. Since the time of the ascat pass...thunderstorm activity has increased in all quadrants...and has become more concentrated near the low-level center. Furthermore...weak anticyclonic outflow has started to develop during the past few hours...and the 08/00z FSU phase evolution diagrams based off the GFS...UKMET...and Canadian models indicate this system has developed a shallow-moderate depth warm core. All of these data give credence that this system is at least a subtropical cyclone. The initial intensity of 40 kt is based on the NOAA buoy reports and satellite subtropical classifications of st2.5/35-40 kt from both TAFB and SAB. The initial motion is nearly stationary. Sean has been making a small cyclonic loop during the past several hours and little overall motion is expected today as the cyclone remains trapped in weak steering flow. By 12-24 hours...however...Sean is expected to move slowly northwestward as the subtropical ridge to the north begins to erode and retreat to the east as a strong frontal system and associated deep-layer trough move eastward across the eastern United States. By 48-60 hours...the aforementioned frontal system will be moving off the U.S. East Coast...and the strong southwesterly flow associated with the front should begin to accelerate Sean toward the northeast. In the 96-120 time frame... the cyclone is expected to merge with the frontal system...although dissipation of Sean due to strong vertical shear is a very distinct possibility. The official forecast track is to the right of the consensus models...and is a blend of the GFS and ECMWF models. Sean is expected to remain over 26c SSTs for at least the next 48 hours...which means the cyclone could possibly transition into a tropical storm as the vertical shear weakens. However...all this would likely do is contract the wind field. Overall...only a slight increase in strength is expected...assuming that an eye feature does not develop. I should be noted that Sean is a relatively shallow system whose vertical extent likely only extends up to the 300 mb level. As a result...the normal shear computations made by the SHIPS model are likely going to be too strong since that models uses winds at the 200 mb level. Forecast positions and Max winds init 08/0900z 27.2n 69.4w 40 kt 45 mph 12h 08/1800z 27.2n 69.7w 40 kt 45 mph 24h 09/0600z 27.4n 70.0w 45 kt 50 mph 36h 09/1800z 28.2n 70.5w 45 kt 50 mph 48h 10/0600z 29.2n 70.8w 45 kt 50 mph 72h 11/0600z 31.5n 68.8w 45 kt 50 mph 96h 12/0600z 37.5n 59.0w 40 kt 45 mph...Post-trop/extratrop 120h 13/0600z...dissipated $$ forecaster Stewart Link to comment Share on other sites More sharing options...
Scotty Lightning Posted November 8, 2011 Share Posted November 8, 2011 IR shot Link to comment Share on other sites More sharing options...
Isopycnic Posted November 8, 2011 Author Share Posted November 8, 2011 IR shot He's trying... Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 8, 2011 Share Posted November 8, 2011 He's trying... Congratulations. Link to comment Share on other sites More sharing options...
Scotty Lightning Posted November 8, 2011 Share Posted November 8, 2011 Is Josh going to fly to Bermuda to chase Sean? Getting windy there....http://weather.noaa.gov/weather/current/TXKF.html Link to comment Share on other sites More sharing options...
Amped Posted November 8, 2011 Share Posted November 8, 2011 Link to comment Share on other sites More sharing options...
free_man Posted November 8, 2011 Share Posted November 8, 2011 http://www.ssd.noaa.gov/goes/flt/t1/flash-wv.html Link to comment Share on other sites More sharing options...
wxmx Posted November 8, 2011 Share Posted November 8, 2011 Haven't checked phase diagrams, but it certainly looks more tropical this morning. Convection is wrapping around the center, and the convection itself is deeper.... there's a slim chance that it will become a hurricane in the next 36 hours, if enough deep convection can wrap all around the center and form an eyewall. I don't bet on it though, and my best guess is 50-55 kts at peak. Link to comment Share on other sites More sharing options...
CoastalWx Posted November 8, 2011 Share Posted November 8, 2011 Haven't checked phase diagrams, but it certainly looks more tropical this morning. Convection is wrapping around the center, and the convection itself is deeper.... there's a slim chance that it will become a hurricane in the next 36 hours, if enough deep convection can wrap all around the center and form an eyewall. I don't bet on it though, and my best guess is 50-55 kts at peak. I was just saying...convection trying to somewhat wrap around. Slowly moving a way from an ordinary frontal type low to something more tropical. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 8, 2011 Share Posted November 8, 2011 Congratulations!!!!! BULLETIN TROPICAL STORM SEAN INTERMEDIATE ADVISORY NUMBER 2A NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011 200 PM AST TUE NOV 08 2011 ...SEAN TRANSITIONS TO A TROPICAL STORM... SUMMARY OF 200 PM AST...1800 UTC...INFORMATION ---------------------------------------------- LOCATION...27.7N 69.5W ABOUT 425 MI...685 KM SW OF BERMUDA MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H PRESENT MOVEMENT...STATIONARY MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... NONE. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A TROPICAL STORM WATCH IS IN EFFECT FOR... * BERMUDA Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 8, 2011 Share Posted November 8, 2011 BULLETIN TROPICAL STORM SEAN ADVISORY NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011 500 PM AST TUE NOV 08 2011 ...SEAN A LITTLE STRONGER... SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...27.8N 69.8W ABOUT 430 MI...695 KM SW OF BERMUDA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...WNW OR 300 DEGREES AT 2 MPH...4 KM/H MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... NONE. Link to comment Share on other sites More sharing options...
tmagan Posted November 8, 2011 Share Posted November 8, 2011 Decent chance to make it to a hurricane. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 9, 2011 Share Posted November 9, 2011 Sean is pretty pathetic. TS warning still for Bermuda Link to comment Share on other sites More sharing options...
wxmx Posted November 9, 2011 Share Posted November 9, 2011 It actually looks better than it has ever looked in it's lifetime. Convection has increased after waning late yesterday and early today. The band of convection is actually wrapping most of the center, and it's probably around 50 kts now. It still has a slim chance to shot for hurricane in the next 18 hours before shear increases, but this window of opportunity is too short, and I doubt it will make it. My guess for peak has increased a little, but with the small window of opportunity there's some added uncertainty, so I'll increase the range to 50-60kts at peak. Link to comment Share on other sites More sharing options...
wxmx Posted November 9, 2011 Share Posted November 9, 2011 Interesting discussion in the last advisory, which has a bullish tone to it. The latest advisory confirmed my suspicions that it was a 50kt TS now, and they have increased the peak to 55kts, but that could be conservative if an inner core establishes... Hurricane probabilities have gone up, IMO, because the trends in sat imagery show continuous organization improvment this morning. Bermuda should watch it up, it might not be a direct hit, but Sean is big enough to induce some TS conditions while it approaches. Link to comment Share on other sites More sharing options...
wxmx Posted November 9, 2011 Share Posted November 9, 2011 Not bad for an extratropical->subtropical->tropical transformer in November... Link to comment Share on other sites More sharing options...
klw Posted November 9, 2011 Share Posted November 9, 2011 Doesn't look bad on the visible, all things considered. Edit: Sorry I thought that would be a movie and not just a still. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 9, 2011 Share Posted November 9, 2011 2 recons tomorrow. Link to comment Share on other sites More sharing options...
wxeyeNH Posted November 9, 2011 Share Posted November 9, 2011 I think Sean looks like he is really trying to rap the deep convection around the center and looks to be intensifying right now. Wonder if we can get an eye by late this afternoon. I think the next advisory will show an increase in wind. Link to comment Share on other sites More sharing options...
wxmx Posted November 9, 2011 Share Posted November 9, 2011 Almost there... this is probably a 60kt TS now. Deep convection is 90% wrapped around the eye feature Link to comment Share on other sites More sharing options...
wxmx Posted November 9, 2011 Share Posted November 9, 2011 Sean is a few hours away from becoming a hurricane, IMO Link to comment Share on other sites More sharing options...
wxeyeNH Posted November 9, 2011 Share Posted November 9, 2011 Came back to look after posting 2 hours ago. Yes, Sean is developing an eye and I would be very surprised if he doesn't become a cane. Maybe even on the next advisory? Link to comment Share on other sites More sharing options...
U_Thant Posted November 9, 2011 Share Posted November 9, 2011 This calls for a 3-day Calamityloop Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 9, 2011 Share Posted November 9, 2011 24H 10/1800Z 30.6N 69.5W 65 KT 75 MPH Link to comment Share on other sites More sharing options...
wxmx Posted November 10, 2011 Share Posted November 10, 2011 CDO has shrunk and is more symmetrical. There's almost nothing reminiscent of it's sordid past. Recon will be there in about 3 hours Link to comment Share on other sites More sharing options...
Sickman Posted November 10, 2011 Share Posted November 10, 2011 CDO has shrinked and is more symmetrical. There's almost nothing reminiscent of it's sordid past. Recon will be there in about 3 hours Classic case of a small TC embedded within a larger cyclonic envelope. Link to comment Share on other sites More sharing options...
am19psu Posted November 10, 2011 Share Posted November 10, 2011 If I had to wager, I'd bet the hurricane hunters find wind speeds less than the Dvorak estimates due to poor mixing in the boundary layer. Link to comment Share on other sites More sharing options...
am19psu Posted November 10, 2011 Share Posted November 10, 2011 If I had to wager, I'd bet the hurricane hunters find wind speeds less than the Dvorak estimates due to poor mixing in the boundary layer. Or not. Link to comment Share on other sites More sharing options...
wxmx Posted November 10, 2011 Share Posted November 10, 2011 63FL 52SFMR 983mb latest vortex Link to comment Share on other sites More sharing options...
Srain Posted November 10, 2011 Share Posted November 10, 2011 63FL 52SFMR 983mb latest vortex Not helping my November call at all... URNT12 KNHC 101743 VORTEX DATA MESSAGE AL192011 A. 10/17:21:30Z B. 30 deg 29 min N 070 deg 07 min W C. 850 mb 1267 m D. 52 kt E. 147 deg 28 nm F. 245 deg 63 kt G. 148 deg 27 nm H. 983 mb I. 13 C / 1824 m J. 16 C / 1832 m K. 11 C / NA L. NA M. NA N. 12345 / 8 O. 0.02 / 1 nm P. AF309 0119A SEAN OB 05 MAX FL WIND 63 KT SE QUAD 17:13:00Z MAX OUTBOUND FL WIND 63 KT E QUAD 17:31:30Z CLDS IN CTR BLO Link to comment Share on other sites More sharing options...
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