Well the 530PM TWO is out, and it looks like we dont have Delta... just yet. I would guess that NHC are waiting for the system to generate persistent and deep convection. It has been generating convection during today, but most of this has been relatively shallow. Recent IR imagery would suggest that this may be changing though, with an area of intense cold topped convection having formed to the immediate west of the centre, and now wrapping around the southern and eastern quadrants. If this continues then it has a decent shot. I would also imagine that NHC are waiting for it to break free totally from the frontal system to its northeast. Given how it is moving away from the front, and the continually improving convective patterns, we could see this upgraded within the next 6 to 12 hours.
..Whether HPC has pulled the trigger on this at 5pm or not, I believe the after thought of most tropical Mets is that it has already acquired sub-tropical characteristics - check that, IS a nameable system at this time. Not sure with the overwhelming signal we are getting from heat channels what the hold up is, but I suspect it may have something to do with the actual meteorology of what is going on out there... I'll eat crow if wrong, but I suspect this is an internal policy decision because of certain meteorological observations that need to be atoned for; they will soon enough! (*I cast no aspersion at HPC for any policies they have and frankly believe they are completely necessary for a few reasons I won't broach here..)
For example, we do still see a tendency for a subtended baroclinic field between the remnant mid-lvl trough N, and the system its self, W of 30 longitude. However, there are no current large scale synoptic suggestions/reasonings that connote "Delta" will effectively be re-captured by the westerlies therein. Normally, when observing a tropical system so close to a baroclinically forced sfc trough you immediately think "..Oh, NNE motion along/ahead of that boundary.." - Nope, not this time.
I'm sure you are much agreed with this stuff already...But, in fact, quite the opposite as the continued separation from said attenuating trough is certain and already underway... This "monster" (for you HF ) is taking on more independent structure in tandem with that trough N losing its own present in the N Atlantic... It is filling and will be totally gone from the regions along 30W soon as the exertion of the -NA0 is coming into prominence. The -NAO will provide for a nice deep layer ridging there much sooner over later. This will effect/incur a S drift to "Delta", as HF has been intimating and follows quite logically...
Lastly, it is intriguing that in the -NAO phase we typically do see the amplification of the Azore's Low... I find it interesting that the counter part variant for this particular NAO seem to be an evolving tropical phenomenon... You have to find that awesome?
--...bold and or highlighted meteorology reference-able sections are for the general reader... I should also add a caveat that the SSTs are a slightly less that 26C....so we are certainly not talking explosive development!
Edited by typhoon_tip (Tue Nov 22 2005 06:33 PM)