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Moderately Unstable

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    Philadelphia, PA

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  1. It would be quite surprising, and unprecedented, to see an EF5, given their rarity here--iirc the strongest Philly area tornado was an EF4 that hit the north broad part of town coming down from Norristown over a century ago. But that radar signature was definitely something else. I stopped what I was doing at work and remarked to a coworker, "this is the strongest tornadic signature I may have ever seen around here"--I am not at all shocked by your report. Certainly seemed EF3+ based on the debris sig and definitely based on the videos. Not something you expect to see in the Philly area. Last year we had a couple strong ish ones from Isias EF2 level...but tonight was just shocking. I will add with that line earlier tonight it felt like everything was rotating to some extent at some point. I went outside a couple of times and in addition to the ground scraping LCLs there was just so much non linear motion on everything. It seems rather clear that there must have been some local enhancement of the low level wind field to cause this degree of widespread and significant damage. It will be interesting to read the storm reports when they come out....honestly I just hope no one died. When I saw that sig earlier that was my first thought. Not something something I'd want to be in.
  2. U.S. Watch/Warning Local Products UPDATE 000 WTNT64 KNHC 300356 TCUAT4 Hurricane Ida Tropical Cyclone Update NWS National Hurricane Center Miami FL AL092021 1100 PM CDT Sun Aug 29 2021 ...HURRICANE CONDITIONS SPREADING FURTHER INLAND... ...CATASTROPHIC STORM SURGE, HURRICANE-FORCE WINDS, AND FLASH FLOODING CONTINUE IN PORTIONS OF SOUTHEASTERN LOUISIANA... During the past couple of hours, a sustained wind of 66 mph (106 km/h) gusting to 111 mph (179 km/h) were measured by a Weatherflow station in Mandeville, Louisiana. SUMMARY OF 1100 PM CDT...0400 UTC...INFORMATION ---------------------------------------------- LOCATION...30.4N 90.7W ABOUT 5 MI...10 KM W OF KILLIAN LOUISIANA ABOUT 30 MI...50 KM ESE OF BATON ROUGE LOUISIANA ABOUT 45 MI...70 KM NW OF NEW ORLEANS LOUISIANA MAXIMUM SUSTAINED WINDS...95 MPH...155 KM/H PRESENT MOVEMENT...NW OR 340 DEGREES AT 9 MPH...15 KM/H MINIMUM CENTRAL PRESSURE...960 MB...28.35 INCHES $$ Forecaster Stewart/Papin // The Lafitte situation is gut wrenching. That is the type of report that can indicate a possible mass casualty event--I hope that doesn't occur. And, let's be clear, being trapped in your attic and drowning is not a peaceful way to go. It's one of the most traumatic and painful ways a person can die. When you actually think about what some people are going through *right now* as you read this.. it's tragic. And that situation is occurring in several areas.
  3. I would frankly be surprised if he's even hit 100. Lots of stuff starts flying once you hit triple digit winds. It's very much "obvious". One easy way to tell--the deciduous trees he's been filming are not toppling over, or even swaying wildly. Those tree types don't handle wind well--palm trees evolved the way they did specifically to handle wind. He's barely seen hurricane strength yet. He will, and he will quickly learn what real strong winds actually look like. His poor estimates are concerning because as a chaser, you need to know what different strength stuff looks like. Also, he should be monitoring the nearby observation sites, have reliable in-situ equipment, and be monitoring radar. If you don't--and I say this having chased before-- you can put yourself into harms way and this isn't a situation where someone can rescue him if he gets into trouble.
  4. Well, it isn't fully over land yet. It brushed the coastline and is now back over water--albeit shallow. Separately, research has indicated that the low-level mesocale environment near the coast in situations like this can be extremely moist and end up largely mirroring the oceanic environment. Another thing to consider is that the part of the circulation that remains over water (including the replacement eyewall), is still able to tap into the oceanic energy. Once the eye firmly crosses land and begins trekking inland, weakening will begin in earnest.
  5. That camera is very impressive. Hats off to John and co. Definitely could offer insights for future ways to construct in situ mesonets for strong future landfalling storms were it needed for a research purpose.
  6. VDM 907 URNT12 KNHC 291626 VORTEX DATA MESSAGE AL092021 A. 29/16:01:50Z B. 28.94 deg N 090.07 deg W C. 700 mb 2517 m D. 931 mb E. 235 deg 10 kt F. CLOSED G. C14 H. 101 kt I. 286 deg 8 nm 15:50:30Z J. 025 deg 111 kt K. 286 deg 8 nm 15:50:30Z L. 114 kt M. 155 deg 5 nm 16:06:00Z N. 228 deg 127 kt O. 146 deg 7 nm 16:06:30Z P. 16 C / 3041 m Q. 20 C / 3014 m R. 3 C / NA S. 12345 / 07 T. 0.02 / 1.5 nm U. AF303 1509A IDA OB 03 MAX FL WIND 127 KT 146 / 7 NM 16:06:30Z ; Quick Links and
  7. Lightning can indicate RI, it is not necessary though conceptually. Also, just to play devils advocate (looking at you Iota and Eta), the plane isn't actually in the eyewall yet (edit: now it is). The forum is convinced due to the sat presentation that it is bombing out--and, yes, anyone looking at that imagery will come to that conclusion. But, the reason we fly into storms is because sometimes the satellite is wrong in either direction--the storm might NOT be bombing as quickly as it looks, or, a seemingly poorly organized storm may in fact have a solid circular closed eye that's just not well discerned on sat imagery. Point is: let's wait for lé plane. That being said if it doesn't find a substantial uptick that accounts both for the current period of intensification and the lack of wind-response to the pressure drops earlier in the day, I would be quite surprised. I was a little surprised that they didn't upgrade to 115 at 10PM frankly but I think the idea was to wait for recon which does seem prudent given earlier sat presentations didn't end up matching the winds that were found. It appears that, yeah, it caught up.
  8. It's actually the same aircraft, 303. Let's hope they fixed the issue--it helps that the base is not a long flight from the storm.
  9. A lot of factors. Various teleconnections feed into the Atlantic basin, and thus their phase and orientation can affect the synoptic environment. Hurricanes are heat and momentum transporters. There is more of both at the equator, and less at the poles. Hurricanes do well as I'm sure you know in barotropic environments. Due to (possibly/probably/degrees-of-relativity), climate change, fundamentally two things are happening: 1) There is more heat in the ocean, and that heat penetrates to a greater depth, on average. 2) The temperature gradient between the equator and poles is weakening. Point 2 has a BUNCH of MAJOR consequences, but, one simple one is, baroclinicity (aka zones of frontal development and the opposite of a barotropic environment), decreases. In simple terms: the temperature difference between the poles, and equator, is decreasing. This reduces frontal strength and makes the environment more homogenous--barotropic--and thus, conducive to hurricane development. It goes without saying that there's more to the story than that, but just taking a big step back, you can certainly note a pattern of destructive, high intensity, rapidly strengthening, water-laden hurricanes hitting the gulf....and everywhere else... over the past few decades. That's not in itself atypical in a vacuum, rather, the consistently increased number of strong storms is the red flag...e.g., the frequency. Another thing that happens with reduced latitudinal temperature gradients is that the steering winds are more prone to break down. Wind--> balance of PGF & Coriolis (assuming you also know this). Less temperature contrast--> less pressure contrast--> less PGF--> less wind--> storms tend to slow down and can "linger" over cities which causes the Harvey-type situation where you get 40" of rain in Houston. With respect to my original point, beyond the physics fundamentals that are responsible for changes to overall hurricane formation patterns, whose trends are beginning to become more evident now, we are in relatively good phases of several teleconnections at the moment. That helps things along. But at the end of the day, this is quite literally the same thing as boiling a pot of water on the stove. Turn up the energy supplied, you will get more steam.
  10. Unwarned couplet approaching Calhoun on the Huntsville radar.
  11. So, it's difficult to tell, but what you can see on the radar is the *orientation* of the couplet changes. In a handoff, you see two distinct mesos, one weakens, the other strengthens. Here, we have the same meso which was "oriented" "up down" and after passing the radar is now "left right". That's the same circulation. The doppler effect only shows motion towards and away from the radar. Ergo, as you translate around a radar site, the orientation of the couplet can shift as the storm motion is captured in the non-storm-relative base reflectivity with a different relative motion (given a different angle of incidence to the site). Same tornado folks. In fairness, there was one single scan that looked "confusing", so if you just looked then you could go "hm what's going on", but subsequent scans, and playing them back with the prior ones, tell us the whole story.
  12. There's no specific requirement not to discuss ratings--I think it's reasonable to expect somewhere along path you'll see EF4+ reports...but remember that radars, unless they're DOWs are not measuring the wind AT THE GROUND. That's super critical and why you can't take "wow look at this gate to gate shear" stuff verbatim--that's what's happening a few k feet up. Friction is real, yo. El Reno was an EF5 according to DOW...it's rated EF3. Why? No structures were hit that verified EF5. Same for the Bassfield tornado. Had an EF5 signature at times and would be super easy to believe a monster that big, on the ground that long, produced EF5 winds in a sub vortex somewhere...but clearly didn't do so over a place for which EF5 criteria could be applied. This long track, fatality producing tornado...seems rather clearly destined for EF4+ status with a special wikipedia subsection dedicated to it within the discussion about the overall event. EF5 could have verified if the tornado had gone straight through Brent...looked particularly nasty around then. It may still verify...that's what damage surveys are for. In general though..remember that velocities do not tell you what's happening at the ground unless you're right next to the radar site like now, or using a DOW. It's useful to know what the G2G is, but really the better measure is how high up debris gets lofted. There's a somewhat direct correlation btwn debris height and strength of the tornado.
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