Regional and Mesoscale Meteorology Branch

00:00:00:00 – 00:00:04:21
Speaker 1
Your screen. Okay, I can see your screen. Mark.

00:00:04:24 – 00:00:34:10
Speaker 2
Okay. Just go ahead. Yeah. Yes. Okay. We are going to talk a little bit about rapid intensification of tropical cyclones, on the chart. But I couldn’t resist starting off a little bit about today’s weather. So I’ve got the, NHC web page up here, and we’ve got a Hurricane Edward, which was the first major hurricane, I believe if you look at the headline down here, the first major hurricane in the Atlantic since 2012, and that is intense, as I found this morning.

00:00:34:13 – 00:00:56:03
Speaker 2
It’s specific so far this year has been very active, and I believe we had maybe six major hurricanes in the East Pacific, which is just getting close to a record. And, right now we’ve got a remnants, Tropical Storm Odile, which actually hit Cabo San Lucas had a major hurricane earlier this week and newly formed Tropical Storm Polo.

00:00:56:05 – 00:01:24:27
Speaker 2
So that’s what we’re working with right now. Just a quick satellite images of the two systems. Here’s Danielle up here, heading, along the divide and possibly will be a rainfall threat to the U.S.. I think the forecast track is just the remnants that go up here across Mexico and maybe into, Arizona. And then, although is just kind of getting formed out here on the edge of this diagram.

00:01:24:29 – 00:01:52:01
Speaker 2
Switching over to the Atlantic side, here, you see the, major Hurricane Edward, and it’s very curving tracks. No, no threat to the U.S.. You can see it’s going to interact with this upper level trough and probably recurve out to see. But again, it’s a fairly impressive looking, tropical cyclone right now. So I’m going to switch over to some slides I prepared on, rapid intensification.

00:01:52:01 – 00:02:00:21
Speaker 2
And then I’ll end up with some, so that’s again, going back to real time data. If I put that in full screen mode, that show up. Okay.

00:02:00:27 – 00:02:02:14
Speaker 1
Yeah, that looks good.

00:02:02:16 – 00:02:26:16
Speaker 2
Okay. So some talk a little bit about that. Just the definition of rapid intensification. And so I’m going to stick with the the definition that John Cowpland and I came up with about ten years ago, defining it as a 39 increase or greater in 24 hours in the max wind. And that corresponds to the 94th percentile of Atlantic intensity change.

00:02:26:19 – 00:02:47:20
Speaker 2
And with East Pacific tending to be a little more active, the Atlantic. So only the 92nd percentile of East Pacific tropical cyclone intensity changes in 24 hours. And and sometimes there’s other thresholds and other time periods that are considered, and I’ll show a little bit later some examples of sometimes we’ll use a 30 to O’Hara 35, not threshold 49.

00:02:47:21 – 00:03:16:16
Speaker 2
Threshold. Just a little bit about climatology. Again, this is from a John Kaplan 2010 paper that shows the 24 hour periods where rapid intensification actually occurred for about, roughly a 20 year period. And you can see planning here tends to be the Cape Verde type systems for the most part, although sometimes the really happens, after curvature, in the higher latitudes.

00:03:16:16 – 00:03:50:27
Speaker 2
And it’s also pretty common in the Gulf of Mexico, East Pacific is, the storms tend to have a west northwest track anyway, but you can see that pretty much they occur south of 20. Okay. The distribution in terms of, the time of year and, this person shows, both a 25, not a 30 and a 35, not, definition of all right, with different color bars, but that and the distributions are pretty similar that September’s a big not for I or I in the Atlantic.

00:03:51:00 – 00:04:15:16
Speaker 2
With the with August 2nd, each Pacific season occurs start a little earlier and the distribution is a little bit more spread out than in the Atlantic. But again, with September being the dominant but with, some activity in July and August and then, even to even into October, the specifics sometimes can have all right and tails off after that.

00:04:15:18 – 00:04:41:12
Speaker 2
First stage. Looking at this, when our rapid intensification actually starts to happen in terms of the current intensity and, it’s a little bit different depending on what threshold you use for these smaller changes. 25, 30 knots. It’s kind of right after the onset of, trouble storm formation. But the really big changes have happened more at 65 knots.

00:04:41:12 – 00:05:06:12
Speaker 2
And those are often associated with information. So you get a different type of behavior, depending on your definition. And I think these are really associated with different physical processes. The lower thresholds there are so tend to be associated more with the initial formation or organization. Or is that, as I said before, that, that the big changes, happen when you get to an AI forms and things happen quickly.

00:05:06:15 – 00:05:20:19
Speaker 2
Similar situation is specific, but the distribution is not quite as peaked in terms of the 35 knots. But is that, the same basic idea?

00:05:20:21 – 00:05:43:07
Speaker 2
So again, the, the study that, John Kaplan I did back in 2010, we looked at what factors are important for rapid intensification, looking at GFS model information as well as those satellite imagery. But it came up with seven different factors. The first one maybe is obvious. And this is it kind of application in the previous 12 hours.

00:05:43:09 – 00:06:20:06
Speaker 2
So if the storm is already intensifying, I mean, it’s organized and it’s, it’s, ready to go. 200 Millibar, divergence was a factor for vertical wind shear in terms of the Goes imagery. When you have cool cloud tops that tend to be symmetric. That favors intensification. Rapid intensification. Of course, in terms of, being able to intensify, you need to have a system that’s not too strong already that if Peterson can’t support, say, a major hurricane, and you’re already close to make it hurricane intensity, it means there’s really no room for the room to intensify.

00:06:20:09 – 00:06:47:22
Speaker 2
So that’s a factor. High humidity and low levels. And also the amount of area that’s covered by coal cloud tops. These factors are a little bit different in the Atlantic and Pacific, but they’re roughly it’s listed here in order of importance. What about, the first four being of roughly equal importance, and then the last three tend to be a, a slightly lesser importance.

00:06:47:24 – 00:07:18:07
Speaker 2
And another factor that’s been used recently is, for microwave imagery is the identification of, ring formation that you can see in the 37GHz, imagery. And this is from the work of Margie Kiefer and I engineering from few. And this is her schematic. When you start to see, the signature up here or, or sort of the the early semblance of an eye formation.

00:07:18:09 – 00:07:43:23
Speaker 2
But you can see that actually much earlier in the microwave imagery a lot of times. So typically have, central vents, overcast and the infrared. So you can’t see this in the entire data, but you can see it in the microwave. And this has been shown to be, precursor to, rapid intensification. So kind of moving on to forecasting a, dynamical models that are used at the hurricane center.

00:07:43:29 – 00:08:10:03
Speaker 2
There’s others, besides these, but I think these are the primary ones, the two dynamical models, h work and you have the L, two statistical models, the ships model, and then its counterpart, LGM, which also uses the same kind of information, some consensus model which used averages of these for icon and iBeacon. The difference between these is, I cannot requires all the models to be there at work.

00:08:10:06 – 00:08:35:01
Speaker 2
I kind of wanted to say you can still make a forecast. And then for, there’s a probabilistic forecasting, there’s a rapid intensification index, which, just provides, the probability of rapid intensification and the motivation for that is that these other deterministic methods and I really don’t work that well for prediction of rapid intensification. It’s still is a very difficult forecast.

00:08:35:08 – 00:09:06:03
Speaker 2
Problem. This is just a verification of, how how well, dynamical models you have to model, the physical shapes model, did with being able to forecast rapid intensification. These statistics are kind of old from 2006 and 2007, but I don’t believe they’ve really gotten that much better since that time period. There may be there may be a little bit of improvement, but, nothing major, that this diagram here shows the probability of detection.

00:09:06:06 – 00:09:49:02
Speaker 2
And you can see that except for this, probabilistic or I, none of the models really even had a detection percentage. It’s greater than 20%, in the Atlantic. And even for the lower thresholds, ni even in the Pacific, the threshold for a probability detection is really pretty low. And, corresponding with that, sometimes the models do forecast for a rapid intensification, but they usually are wrong when they do it that that false alarm ratio is actually very, very high for really for all the techniques of the, rapid of statistical rapid intensification, it has at least it has a probability of detection, comparable to its, false alarm ratio.

00:09:49:05 – 00:10:21:23
Speaker 2
So, it may have a little bit of skill in that regard. But the human performance is, at this time, it’s still pretty lacking. So I’m going to just give you an example of a recent, the rapid intensification, again, for Hurricane Odile. And, this shows the track of the system up to the point where it, has hit by a major hurricane and eventually formed and had looked initially here for a while, but it ended up in a pretty good environment.

00:10:21:26 – 00:10:47:13
Speaker 2
The last day or two before landfall. And, this diagram shows two examples of deterministic model forecasts. These endgames are kind of rough, but the the dark blue line here shows the working best. Right? So the system intensified slowly for the first, three days, underwent the, rapid intensification period, leveled off and then the decayed after hit land.

00:10:47:15 – 00:11:15:02
Speaker 2
And you can see the H4 model really did a pretty good. The red lines are just every forecast, every six hours, up to five days. And you see the first part of the forecast was pretty good. But the H4 just totally missed the the rapid intensification period. And again, this is it’s fairly common. One of the statistical models, the LDA model, did a little better with capturing the peak intensity, but it really didn’t get the timing very well.

00:11:15:04 – 00:11:38:24
Speaker 2
It it didn’t really capture this, delayed intensification. And then during the entire period, the rapid intensification was, underestimated by the model. There’s some over, over intensification afterwards. And that that was primarily due to the fact that the the forecast track didn’t hit land when the real storm hit. Again, that, that that’s a separate problem.

00:11:38:24 – 00:12:06:06
Speaker 2
But again, when you’re close to land, the timing at landfall is pretty important for your density forecast. Looking at the rapid intensification index, again, this black line is just a repeat of the, working best track for oatmeal. And you can see that the, the probability of rapid intensification was hovering around 25 to 30% of a dense rate before the after a period of just jump up to almost 50%.

00:12:06:09 – 00:12:30:21
Speaker 2
So despite the fact that the deterministic models were not accurately predicting that there’s a ramp up, at least the rapid intensification index is giving a hint that something was going to happen, at least at the 50 5050 chance. This is a little bit hard to read, but this is the the output that the forecasters here see from the Rapid Intensification Index.

00:12:30:24 – 00:12:55:04
Speaker 2
And this was the values right before, rapid intensification occurred for a deal. And if you look at the at the bottom here, for the 25 month threshold, the probability was up to 60%. Again, a tip off that something might happen. These were five times the sample. Be pretty specific. So the conditions is, really pretty good.

00:12:55:07 – 00:13:16:06
Speaker 2
And, what was the most favorable? Yes. Again, this is difficult to read, but, this is good pain because the storm is already intensifying. It was only five knots. The vertical shear, at least in the GFS analysis. And again, that’s, well within the range of what’s happened for AI in the past. That’s a very low value.

00:13:16:08 – 00:13:41:19
Speaker 2
The storm is way below its potential intensity at this time, so there’s plenty of room to intensify further. The infrared brightness, temperature or standard deviation, that’s a measure of the cemetery star is extremely symmetric, since the standard deviation with low, oceanic heat content was not super high, but but enough for intensification. Divergence was good for plenty of cold cloud tops, and then the relative humidity was maybe an average range.

00:13:41:21 – 00:14:08:08
Speaker 2
So all the factors were really, signaling that the conditions were right for rapid intensification. And just to go through what some of the imagery looked like, this was a right before the right period. And you can see it’s called cloud tops covering a big area. And then you start to see some symmetry near the center, but sort of a hint of and I formation in this picture, this was the 37GHz.

00:14:08:11 – 00:14:39:03
Speaker 2
And again, you see evidence of this, a cold ring again, another tip off that. I would right. Which is in the, just show the, discussion for Hurricane Odile. And I believe this was, Richard Parsons forecast a cut off the end there. But if you go through this, some of the, the discussion here is that he says, despite the seemingly favorable environment, it’s peculiar that none of the deterministic guidance breaks a deal to a major hurricane.

00:14:39:06 – 00:15:02:09
Speaker 2
And then he talks about, I guess he was actually looking at the Rapid intensification index, and he’s quoting this, 5050 value, which, which he believed actually more than deterministic guidance in this case. And what he ended up doing is, is that, he actually forecast, that intensification is greater than all his objective guidance.

00:15:02:12 – 00:15:34:18
Speaker 2
And again, that was using the satellite information in the one favored way, as well as some of the environmental conditions. Okay. Just to end on, something new that we’re working through, the those are proving ground that, using lightning data that also seems to provide a, some new information for forecasting rapid intensification. And what we found using that ground based on data that when you get you tend to get a flare up of lightning in the rain bands of the storm.

00:15:34:21 – 00:15:55:24
Speaker 2
That tends to be a step on a very high. And or rather the his vacation. It was true in this case as well. We got this, and the blue line here shows the, the, the rain band lightning, which is defined as one 200km from the storm center. And just before the hour for the rapid distribution period, we’ve got this big ramp up of the, the rain band.

00:15:55:24 – 00:16:20:11
Speaker 2
Lightning had a decrease in the inner core lightning again. That’s, that’s a signal we we’ve seen many times for a off for, rapid intensification. And just, I want to end on, going back to the, a web, going back to, her hurricane and warning, here’s what the Rapid Intensification Index is looking like for that.

00:16:20:13 – 00:16:48:21
Speaker 2
And you can see here that the, the probability for rapid intensification is only a couple of percent. And the primary reason for that, we look at the factors that we saw that recent intensification. And the shear is reasonably low in about ten knots. Storm is plenty symmetric. But that really the limiting factor is that, the hurricane is already, a it’s already a major hurricane.

00:16:48:23 – 00:17:10:03
Speaker 2
And that with the sea surface temperatures forecasted, decrease, this is a case where it doesn’t really have a room to intensify too much further. And I believe the official forecast reflects that. So I’ll I’ll stop there and see if there’s any questions.

00:17:10:06 – 00:17:30:19
Speaker 2
Hi. This is Mark from DSP in Tampa. I had a quick question regarding the overshooting tops and how that might lead to some hints for our, you talked about the lightning, which was very interesting, a decrease in the inner core. And and did you say that, lightning in the rain bands more than 200 miles out are somewhat of a precursor to.

00:17:30:19 – 00:17:52:15
Speaker 2
All right. Yeah, it’s more likely maybe in the range of 100 to 300km, from the center. It’s kind of it kind of seems to be a sweet spot for a tip off for rapid intensification. We looked at the, four shooting tops using some data that, the, the University of Wisconsin service people, gave us.

00:17:52:15 – 00:18:11:13
Speaker 2
And we did a, was an objective study to look at the information content of those. And the if you use them by themselves that they seem to have, there seems to be some information as well when you have overshooting tops. Not so much near the center, but again, in the, in the outer portions of the storm.

00:18:11:15 – 00:18:35:09
Speaker 2
But the, that same information seems to be captured just in the imagery itself. So, for example, we use the storm cemetery and the cold coal cloud amount and that, the overshooting tops information doesn’t seem to provide any quantitative information that’s not captured with the ghost data. But the lightning data for some reason, seems to be providing independent information.

00:18:35:12 – 00:18:57:12
Speaker 2
When we put the lightning data in, that goes information, we get additional predictive skill. So I guess the short answer is that the overshooting top is telling you something, but you should really use it in conjunction with the ghost data itself. Or the lightning data is really telling you something independent. Thank you.

00:18:57:14 – 00:19:33:11
Speaker 2
I, I this is Scott and I just have a question about the super rapid scans. Have you had enough cases, with the one minute imagery to be able to determine whether that’s giving you information you don’t have otherwise? But I would say that the, maybe we haven’t looked at quite enough cases, but the the time scale of the super grab a scan data seems to be a little bit too fast for, you know, identifying something for rapid intensification.

00:19:33:14 – 00:19:51:02
Speaker 2
The one case where I think that would be different is where you have kind of a rapid change in the convective structure, where you get a sudden eruption of convection that didn’t exist before. And so I think that there are going to be cases where there’s at least the rapid scan, and maybe the super rapid scan are going to be a tip up.

00:19:51:02 – 00:20:05:15
Speaker 2
But, I don’t think we have enough, just yet to make a definitive statement on that.

00:20:05:18 – 00:20:13:18
Speaker 1
So.

00:20:13:20 – 00:20:24:17
Speaker 1
Okay. Any other questions from Mark?

00:20:24:19 – 00:20:55:09
Speaker 1
Okay. I guess I’ll open it up to any more general questions either maybe a question on real time weather or just, some general discussion we still have about, several more minutes here, so I’ll just one more time. Any other, discussion points or questions?

00:20:55:11 – 00:21:09:21
Speaker 1
Okay. Well, I guess we’ll wrap it up here. And, Well, I want to thank, Mark for, taking the time to deliver this, satellite chat. So we thank him very much for that. Everybody, have a great day.

00:21:09:24 – 00:21:11:00
Speaker 2
Okay, I think that. Thanks.