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Old 16-01-2017, 21:15   #1
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Explosive cyclogenesis?

I han't heard of it before either but it seems Unzud is about to cop some... unusual for summer.

Hadn't heard of a 'bomb low' either although I have had a tickle up from a few over the years.

What is a 'bomb low' and how did it get that name? | Stuff.co.nz
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Old 16-01-2017, 21:32   #2
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Re: Explosive cyclogenesis?

Its all about the upper level low and its relationship to the surface low, but that's too complicated for the TV news.
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Old 17-01-2017, 03:08   #3
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Re: Explosive cyclogenesis?

There's always the concept of how much energy such systems "release" over X time interval, & the inevitable comparison to Hiroshima.
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Old 17-01-2017, 03:30   #4
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Re: Explosive cyclogenesis?

We are on the hard in a yard in Wellington and they are so worried about the weather they parked the 50 ton lift over our boat and cradle with the strops holding the boat in addition to the cradle. The are predicting gusts to 100 mph!

We hope to get another coat of paint on the bottom before the weather worsens.
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Old 17-01-2017, 11:12   #5
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Re: Explosive cyclogenesis?

^^^^^
Thanks for that, Moondancer, the practical applications from the lessons of the Queen's Birthday storm.

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Old 17-01-2017, 11:51   #6
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Re: Explosive cyclogenesis?

Quote:
El Pinguino;2305193]I han't heard of it before either but it seems Unzud is about to cop some... unusual for summer.
Thanks for the read...interesting. Always something new.

Obviously my guess that it had something to do with the after effects of #2 Beef Vindaloo were incorrect.
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Old 17-01-2017, 11:53   #7
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Re: Explosive cyclogenesis?

The term Low Bomb has been largely retired in the Northern Hemisphere, as it was an unofficial meteorological term in the first place and there are so many media sorts that have taken the opportunity to make severe weather into a profit center using such terms as leading lines on newspapers and newscasts that frighten folks into terror, only to have the forecast bust or the storm to veer into another direction, thus diluting public concern and faith in the weather field in general, which in turn leads to people ignoring the warnings and dying in greater numbers than would have been necessary if even basic precautions had been taken by the dead (see Hurricane Katrina, New Orleans, Louisiana, USA). The surfers take to the ocean any time a hurricane screams toward the East coast of the US, especially if it parallels the shore at all. I am sure the same happens in Australia.

Essentially, when a trough at about the 500 MB chart level passes over and causes a rapidly deepening low pressure system the low can go from a mild circulation of a couple hundred miles across into a massive cyclone (or hurricane, typhoon, willy willy, etc.) in hours, and if it shores up against a high pressure ridge down stream relative to the directional overall track of the storm's center of rotation the result is a massive storm with intensive pressure gradient within the storm interior as well as especially the side closest to the high pressure ridge. This pressure gradient funnels wind flow along lines of equal pressure (aka "isobars") to even greater speed than exists elsewhere around, or even potentially within, the storm interior.

Yes, the Queen's Birthday event is a classic example, and your area was definitely experiencing severe events that day/night. If I recall, there were something like 7 lost recreational yachts, and I think some people died on one of the lost vessels or in combination, at sea. 3 or 4 people, something in that range?

Hurricanes that strike the United States have done this on occasion, and someplace here I have the satellite fax we received at NAS Jacksonville, Florida, that showed the timeframe of Hurricane Andrew exploding as it passed over the Gulf Stream current along Florida's coast. The damage to Florida was devastating, and while part was due to low geography along the state and into the interior, part was due to inferior construction methods (since then, these construction problems have largely been addressed in local building codes, but we shall see how successfully one day), and the rest was due to the severe nature of the winds and especially tornadic activity within the bands and the eye wall itself.

I also have the last teletype forecast that the USAF lead shift forecaster on duty sent out from the Homestead Air Force Base weather office. While his winds forecast was the stuff of meteorological legend in our military circles (200-250 knots on station is amazing for gust predictions for a shore station, but the base was in direct track with the actual storm center at landfall), it was the first and only time I have seen anyone forecast tornadoes in a specific location and time (he predicted "tornadoes all quads" in the immediate forecast, then "Closing and departing weather office, we're gone, Bourne out, see ya!").

When they returned from shelters, the weather office consisted only of a foundation; the structure itself, the air terminal, and nearby vehicles, along with the rest of the base, did not exist, other than a single hangar left with a massive destroyed Galaxy or Constellation transport aircraft caved on inside, I don't think anything else on the base remained at all in the structural sense. In fairness, many structures on that base were wood framed structures, and the base was older than many. Still, I don't think the concrete stuff survived the scouring tornadoes either, though. The base is now the oval Homestead-Miami NASCAR racetrack!

Yep, the 500 MB chart overlaid on a surface chart does not often lie. Stronger winds upstream means deepening low, stronger winds downstream means the low will fill (become less intense), and a trough closing on the low (moves about twice the speed of the surface wind field) leads to VERY intensive deepening (relative to strength of the trough itself and rapidity of approach makes the low blow up sooner or faster, and will be max effect when vertically stacked), or what the OP called the explosive cyclogenisis effect. Normally. Sometimes the winds can fool you, but it is damned unusual that the 500 MB chart lies...
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Old 17-01-2017, 12:13   #8
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Re: Explosive cyclogenesis?

Quote:
Originally Posted by Saleen411 View Post
Thanks for the read...interesting. Always something new.

Obviously my guess that it had something to do with the after effects of #2 Beef Vindaloo were incorrect.
HA HA HA!!! When I first heard the term (a LONG time ago, back in the 1990's), I had no idea what it was either, and I cannot tell you the number of times that Bob Sheets at the NHC (National Hurricane Center) or Tex (the regional forecaster for tropical development relative to effects on naval assets in the Southeastern US, we knew him as Tex, I don't remember his Christian name (was it "something" Anderson?? Don't remember...), however. It was too long ago, and I only ever saw it rarely on paperwork) had to go through the actual physics computations of this simple thing with me before my barely of age brain figured it out. Once I did get it down, though, it stuck, and I remember the content of those discussions now like we had conducted them yesterday. For those interested, look up "air entrainment" and "conservation of angular momentum" and you will gain a great deal more info on the "why" of this situation. Maybe more than you wanted to!

Evan Rosenthal (RIP) was also a formative mentor for me, he was one of the climatologists at NAS Jacksonville who actually wrote the test questions for all the examinations for the Aerographer's Mate occupational rating in the US Navy, and due in part to my studies under his tutelage and guidance, I did danged well every time I tested on those measurements. I never missed an advancement cycle, and my work showed his influence daily. I sure miss that guy (unlike Tex, who was a bit of a butthead to me most of the time simply because he seemed to be pretty self-assured and treated everyone that asked what he considered a simple question as if they were too far below his level to be there in the first place; but hey, you gotta learn someplace, right?).

Diabetes and Parkinson's Disease blinded, then finally took Mr. Rosenthal, a literal climatology genius, away from us WAY too soon. Ev, here is a shout out to you, Sir! I am using your tutelage in real life yet again!
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Old 12-02-2017, 11:17   #9
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Re: Explosive cyclogenesis?

Another New Zealand weather system...We are in a marina near Wellington F9 gusting F12...Saw 73 knots...

Caused by a massive low off Antarctica between two strong highs.

https://www.windytv.com/?pressure,-51.998,-172.090,3
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Old 12-02-2017, 11:31   #10
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Re: Explosive cyclogenesis?

The gods are angry.
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