OKpowdah Posted December 30, 2012 Share Posted December 30, 2012 We are witnessing tonight the rapid intensification of a compact sub-synoptic low level vortex. Pretty impressive. Keep in mind the vorticity equation / basic dynamics of rotation ... convergence shrinking the area of rotation, conserving angular momentum, increasing angular velocity. Notice the sharp angle at which the wind is crossing the isobars, and how that angle increases toward the center of circulation. Consider a Rankine vortex, the critical radius of the edge of the inner solid body vortex is shrinking. Then consider the mechanisms for lift right over the low ... intensifying low level convergence ... very strong warm advection as seen through the 0-3km helicity. The temperature gradient that coincides with the low and the high magnitude velocity gradient tensor associated with the tight vortex also leads to strong frontogenesis, associated with enhanced lift. Link to comment Share on other sites More sharing options...
OKpowdah Posted December 30, 2012 Author Share Posted December 30, 2012 check out buoy 44008 for some cool looking pressure falls Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted December 30, 2012 Share Posted December 30, 2012 Good thread Sam. Not sure if you had seen but a lot of guidance had a very tight wind core around the center. not the typical mid-lat cyclone fields where your best low level jet structures are a good distance removed. Link to comment Share on other sites More sharing options...
dryslot Posted December 30, 2012 Share Posted December 30, 2012 BOMB Link to comment Share on other sites More sharing options...
OKpowdah Posted December 30, 2012 Author Share Posted December 30, 2012 Good thread Sam. Not sure if you had seen but a lot of guidance had a very tight wind core around the center. not the typical mid-lat cyclone fields where your best low level jet structures are a good distance removed. To be perfectly honest, I hadn't been paying close attention to the models over the last few days, so following this low as it developed was really cool for me. Definitely a very compact cyclone Link to comment Share on other sites More sharing options...
RCNYILWX Posted December 30, 2012 Share Posted December 30, 2012 I would imagine not unlike the Dec 9, 2005 storm. That's one of the more fascinating events in recent history. http://www.erh.noaa.gov/box/climate/pns/DEC9_2005.txt Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 30, 2012 Share Posted December 30, 2012 I would imagine not unlike the Dec 9, 2005 storm. That's one of the more fascinating events in recent history. http://www.erh.noaa....s/DEC9_2005.txt I called this storm Dec 9, 2005 light....not quite as ridiculous as that storm where ACK lost 16mb in 3 hours....but not too far off. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted December 30, 2012 Share Posted December 30, 2012 Yes ... and I further assert, this sort of meso-beta scaled "hyper low" will materialize whenever there is a collocation of the best (and sufficient) QG forcing (from mid levels) running over top of anomalously tilted frontal slopes between the ~850 and 600mb levels. Upward vertical motion gets very exotic where that intersect takes place, and of course ... all mass is conserved and not lost in the system, thus requires equally exotic pressure falls at low levels underneath - subsequent sub-geostrophic wind response at the surface can quite literally be cross-isobaric when that happens because it takes place faster than integrated f Will mentioned 9 Dec, 2005 - the day before that event, the NAM model was really arguing for some kind of exotic meso-beta scaled response along intense thickness packing just S of the S Coast of SNE. I recall posting about that... Anyway, one other aspect that is compelling (if determined to be different) about that 9 Dec ', it induced a tropospheric fold, ultimately contributing to excessive wind acceleration event on the Cape. Isallobaric wind pulse would have transpired in that anyway, but a huge mass of stratospheric air also wound up underneath the isentropic surfaces and freely accelerated via gravity to the surface - the combination of the two led to 110mph wind gusts! Not sure if last eve's nukey had that type of event - perhaps it did seaward. Link to comment Share on other sites More sharing options...
OKpowdah Posted December 30, 2012 Author Share Posted December 30, 2012 I called this storm Dec 9, 2005 light....not quite as ridiculous as that storm where ACK lost 16mb in 3 hours....but not too far off. Yeah, we can draw comparisons to two storms that pop out ... 12/9/05 and 1/27/11 One big difference with those two comparisons is that the upper level s/w was equally as small scale ... half-wavelength was also very sub-synoptic. Those storms were both potent as a result of the very intense mid level dynamics associated with such a tight system. We tracked a wicked vort max for a day or two with both of these before witnessing rapid surface cyclogenesis. In this case, the trough was pretty broad. Granted there was a decent vort max, but the mid level dynamics don't really get going until the vort max is offshore, when the surface low is taking off. Which makes me think this system started with the egg, and then we got a chicken ... opposite the two examples. Just based on the performance at the surface yesterday evening, I want to say that most of the bombogenesis we saw yesterday evening can be attributed solely to positive feedback from the low level circulation ... surface PV anomaly extends upward --> impinging on a temperature gradient --> warm advection --> lift above the surface low --> stretching the vortex --> convergence at the surface --> tightens the circulation --> increases vorticity --> strengthens warm advection --> strengthens lift --> strengthens the vortex, and so on. As this process happened, the PV anomaly extended further upward, warm advection increased heights aloft just downstream of the vort max aloft, and the whole mid level system tightened up, increasing those dynamics aloft. Link to comment Share on other sites More sharing options...
LocoAko Posted December 31, 2012 Share Posted December 31, 2012 Great stuff Sam. Link to comment Share on other sites More sharing options...
USCAPEWEATHERAF Posted January 1, 2013 Share Posted January 1, 2013 Great write up Sam. Link to comment Share on other sites More sharing options...
RCNYILWX Posted January 7, 2013 Share Posted January 7, 2013 Fantastic stuff. Just curious, have there been any journal articles written on the 12/9/05 bomb? Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.