Fri Oct 28 2005 03:41 PM
Re: Beta...


The big flare up of convection NE of Beta adds another fly in the ointment to the forecast. Since 91L is probably in there somewhere, there is a slight chance of something tropical developing out of that, but in any case it seems like the intense convection is causing enough outflow to disrupt Beta somewhat. The very cold convection with Beta right now is not a surprise, since systems undergoing some shear often produce colder (but asymmetric) convection. When a perfectly symmetrical system starts producing super-cold cloud tops (i.e. Wilma), then you know rapid intensification is occurring.

Normally, It would not surprise me if this fly in the ointment quelled just a tad during the day, for merely having taking advantage of the nocturnal cycle (where nighttime cloud-top radiative transfer augments instability in the area..etc.) However, I suspect there is a synoptic cause.

(As a side note: This presentation/looped satellite imagery almost looks like a Great Plains nocturnal MCC of all things...; also an event aided along by radiative properties of the mid/u troposphere. ...But, since this is a tropical sounding over hot water down there, whether this was aided along by radiative transfer or not would probably be a coincidence.. )

What I do find interesting is that vigorous tropical wave that entered the eastern Caribbean Sea yesterday. It has raced to approximatley 70W, while the circulation of Beta sits increasingly uncomfortably near. The llv structure of a t-wave usually bends the E/ENE background environmental flow somewhat more NE at the surface, as a given region is approached by the wave axis (for N-S oriented wave axis'), as well as accelerating the flow just tad. It may just be that the eastern semi-circular atmospheric motion of Beta, albeit weak at nearly 5 degrees separation, is interacting normally with these said NE vectors. This would induce a llv through perhaps h850 mb convergence axis - roughly colocated where we see cloud tops temperatures as cold as the Beta's core, near 75 longitude.

Unfortunately, that is a data sparse region so it is difficult to confirm this using obs to support a convergence field if one truly exists. ...So, I suppose I shall try to find other means to demonstrate this hypothesis..

In the meantime, agreed! This should be watched... The water is warm and there is a definitely anticyclonic outflow evidenced by sat, over the entire area. Favorably placing a convergence axis, incidental or not, is an intriguing proposition to say the least.

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