Why such little, or no lightening in Hurricanes?

[paul e]

Can you guys clear something up for me? I was watching Anderson Cooper and his meterologist, Chad, last night as they were being blown around... Somebody asked about ligtening, and Chad said, you dont usually see much ligtening in a hurricane, and he gave a rather technical explanation about the splitting of the raindrops that usually comes from sheer in 'normal' thunderstorms, which is largely absent within hurricanes..

Well, heres my confusion. Ive always heard/read that its the grouping of the Thunderstorms around the center, which creates the Eye Wall.. Well, so far as I know, you cant have thunderstorms without Lightening.. So, if the eyewall comprises Thunderstorms, then Why so little lightening??

[PurdueWx80]

You can't have thunder without lightning. If there is no rapid expansion of that air, there will be no sound made, period. The no lightning thing near the center of hurricanes has to do with instability, and w/ the warm nature of the center of the storm. With all the heavy rain and cloud cover, the sun isn't able to warm the ground, so you have little difference in temperature between the surface and the upper levels, at least not as much as you do in more continental type storms. The atmosphere is also typically saturated from the ground to near the top of the troposphere near a TC, and w/out any very cold dry air, you don't get the necessary seperation of charge for lightning. Away from the center of the storm, perhaps in feeder bands and in the supercells w/ tornadoes, you probably will see lightning, because chances are, there is at least some solar insolation.

[PurdueWx80]

Here is another explanation I found from faq.org. Their sources came from NOAA and other gov't agencies so the info is correct.

Surprisingly, not much lightning occurs in the inner core (within
about 100 km or 60 mi) of the tropical cyclone center. Only around a
dozen or less cloud-to-ground strikes per hour occur around the eyewall
of the storm, in strong contrast to an overland mid-latitude mesoscale
convective complex which may be observed to have lightning flash rates
of greater than 1000 per hour (!) maintained for several hours.
Hurricane Andrew's eyewall had less than 10 strikes per hour from the
time it was over the Bahamas until after it made landfall along Louisiana,
with several hours with no cloud-to-ground lightning at all (Molinari et
al. 1994). However, lightning can be more common in the outer cores of
the storms (beyond around 100 km or 60 mi) with flash rates on the order
of 100s per hour.

This lack of inner core lightning is due to the relative weak nature
of the eyewall thunderstorms. Because of the lack of surface heating
over the ocean ocean and the "warm core" nature of the tropical cyclones,
there is less buoyancy available to support the updrafts. Weaker updrafts
lack the super-cooled water (e.g. water with a temperature less than 0 C
or 32 F) that is crucial in charging up a thunderstorm by the interaction
of ice crystals in the presence of liquid water (Black and Hallett 1986).
The more common outer core lightning occurs in conjunction with the
presence of convectively-active rainbands (Samsury and Orville 1994).

One of the exciting possibilities that recent lightning studies
have suggested is that changes in the inner core strikes - though the
number of strikes is usually quite low - may provide a useful forecast
tool for intensification of tropical cyclones. Black (1975) suggested
that bursts of inner core convection which are accompanied by increases
in electrical activity may indicate that the tropical cyclone will soon
commence a deepening in intensity. Analyses of Hurricanes Diana (1984),
Florence (1988) and Andrew (1992), as well as an unnamed tropical storm
in 1987 indicate that this is often true (Lyons and Keen 1994 and Molinari
et al. 1994).

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[paul e]

>>This lack of inner core lightning is due to the relative weak nature of the eyewall thunderstorms. Because of the lack of surface heating over the ocean ocean and the "warm core" nature of the tropical cyclones, there is less buoyancy available to support the updrafts...weaker updrafts lack the super-cooled water <<

Interesting.. Answer me this then.. if the thunderstorms in the eyewall are so weak, and up/down drafts relatively weak, then how come the thunderstorm tops are So High up in the atmosphere? Dont high thunderstorm tops usually equate with powerful thunderstorms, in the same way that increasing of the reds on the IR shots indicates a stronger storm?

I appreciate the explanations, but maybe it raises more questions than it answers?

[PurdueWx80]

They are so high in the atmosphere because the air is saturated up through these locales. Updrafts are just strong enough and shear is light enough to allow warming of the air up to the tropopause. High thunderstorm tops in continental regions (or even every day popcorn storms in the subtropics) experience enough cold/dry air and supercooled water/ice to get the necessary separation of charge. Lightning is very poorly understood, even moreso in tropical systems, if you couldn't tell. Here is the sounding from Tampa this morning - It shows relatively warm air (by relatively I mean -30 isn't as cold as -60...you can still have little to no ice at -30) all the way up. Notice also that the dewpoint and temperature are very close (saturation) through the top of the sounding.

[Anonymous]

Tornadoes come from thunderstorms as well as hail... So how can hurricanes have no thunderstorms yet have tornadoes and in rare cases hail? All other times, you would find tornadoes in thunderstorms but not with a hurricane.

[PurdueWx80]

Jekhye..look at this post:

http://www.storm2k.org/phpbb2/viewtopic.php?t=47987

Basically, there is a tremendous amount of shear very close to the ground. Any updraft will allow very short episodes where conditions are perfect for a tornado. The lack of instability, owing to no solar insolation, prevents these tornadoes from lasting very long. Still, in the short time they are on the ground (for the most part...there are always anomalies) they can be quite potent because of the high ambient wind field. The tornadoes associated with tropical systems usually form in convection that more than likely does have lightning since the cells are well removed from the thick cloud deck over the center of the storm. Hail is another story, I have no idea how hail can make it to the ground in such warm conditions. That is why it is so rare, but beyond that I have no idea. I'm guessing it is probably closer to rime (because of the excess of supercooled water above the freezing point) - if you could pick it up it would be very soft and crushable.