T S FELIX: *PRO MET* Discussion, Analysis, Questions

[hurricanefloyd5]

two things 1 the RainBands getting ready to move ashore do they have Gusts winds and two do anyone have a web cam live from the area???????

[Wthrman13]

Howdy,

can someone explain the increased outflow evident on the latest sat images?

http://www.ssd.noaa.gov/goes/flt/t1/loop-avn.html

If Felix was a thunderstorm I would call those outflow boundaries. Is this an indication of lost strength while the core re-organizes?

--Mark

What you are seeing (I think, if I'm understanding your observation correctly) is the expansion of upper-tropospheric outflow on the NW quadrant in particular. This is almost always a good thing for a hurricane, since it indicates good venting of air out of the top of the hurricane in the anticyclonic outflow, rather than shear, which restricts the outflow and also disrupts the vertical continuity of the warm core.

When you mention outflow boundaries, however, you are talking about something quite different. Outflow boundaries are low-level features which indicate strong, cool outflow coming out from the base of the convection, not the top.

I don't see any (low-level) outflow boundaries on this loop. However, I have seen them on the periphery of even strong hurricanes before, without any apparent detrimental effects to the inner core structure. Usually, the presence of outflow boundaries is a good indication that some relatively dry air is interacting with the convection, wherever they happen to show up. Rain evaporates into the dry air, producing cooler and denser downdrafts, which create the outflow boundaries. If lots of dry air is entrained into the inner core region, this can result in cooler downdrafts and outflow, which will interact with the overall inflow in possibly detrimental ways. However, if this is occurring on the periphery of the system, in the outer rainbands, I would say this is normal and would probably have a minimal effect on the intensity of the system.

[tolakram]

Thanks for the explanation Wthrman13, that's what I was seeing.

[Rod Hagen]

the TS wind field is maybe 6 times that of Tracy

In Tracy, the TS winds only extended out about 25NM form the center... that's where the cane force winds extend with this one

Many thanks, Derek.

Cheers

Rod

[wxmann_91]

Here's my (probably dumb) question:

Once a TC moves over land, and lets say the LLC is ripped apart and what's left are the mid level remnants (i.e. it doesn't become extratropical or anything), do the low-levels steer the cyclone or is it still steered by the deep layers? This scenario would apply to Felix.

BTW, I know this is a pro met thread, but if you're a knowledgable amateur and know the answer, feel free to PM me the answer.