The dangers of a tropical rainstorm

AccuWeather

AccuWeather's Jon Porter explains why despite losing wind intensity as hurricanes, tropical rainstorms remain a threat.  Tropical rainstorms often produce life-threatening flooding and tornadoes.

Transcript

00:00John, you may hear the term, you're going to be hearing the term, certainly, here on

00:04the AccuWeather network, AccuWeather.com and the AccuWeather app, which by the way is a

00:07free download, tropical rainstorm.

00:11We're the ones that invented it.

00:12We're the only ones to use it.

00:14Let's explain why we, you know, the hurricane center, we'll call it a post-tropical storm

00:21and then the name gets lost and thrown in the air and forgotten forever.

00:25We don't do that here until the system leaves the United States or totally dissipates.

00:31Explain why.

00:32That's right.

00:33Good morning.

00:34The tropical rainstorm designation, which was first implemented by AccuWeather decades

00:38ago is to emphasize that the storm, though it has lost wind intensity, still has major

00:45dangers associated with it, especially related to that flooding concern.

00:49So that's why AccuWeather meteorologists always refer to these types of systems as tropical

00:54rainstorms.

00:55Many times, those dangerous impacts, including flooding and isolated tornadoes, can occur

01:00well inland days after a storm makes landfall.

01:03We don't want people to let their guard down.

01:06All this in an effort, once again, here at AccuWeather to help you stay best prepared

01:10and keep you and your family safer.

01:12I want to go back to one of the storms I think that, along with Debbie, was one of the poster

01:18for tropical rainstorms, and we're bringing it up, Ida, which came onshore in 2021 and

01:25has attracted the Northeast, John.

01:28We saw heavy impacts all the way toward the Mid-Atlantic and Northeast that included life-threatening

01:34flash flooding around the New York City area, and we had actually tornadoes east of Philadelphia.

01:39That's right.

01:40That was another one of these very dangerous situations.

01:43Before the storm even made landfall in Louisiana, AccuWeather meteorologists had first warned

01:48that that rain was going to come into New York City and Philadelphia and surrounding

01:51areas fast and furious, and that there would be a dangerous, life-threatening flooding

01:55situation with four to eight inches of rain falling in a matter of a few hours.

02:00That, of course, is exactly what happened.

02:01The storm then moved up across the eastern part of the United States and merged with

02:05another storm coming across from the Great Lakes.

02:08That's usually a recipe for big trouble.

02:11That's the recipe today.

02:12In fact, you talked about this.

02:13You get the center of circulation from the rainstorm, and then what happens is you get

02:17a dip in the jet stream, the northern branch of the jet stream that kind of feeds in, and

02:23actually what we're going to be looking at this afternoon, as you can see that tropical

02:27rainstorm symbol across south-central Pennsylvania, it moves northeast.

02:32Actually pressures are going to lower within this system, and that means the systems, it

02:38may not have a lot of wind intensity, but in a sense the overall structure of the storm

02:42gets better organized, and we think that's going to happen.

02:44Yeah, you got it.

02:45You see all these greens and blues.

02:47This is that tropical moisture surging northward, and then that dip in the jet stream is providing

02:52extra lift in the atmosphere.

02:54So when you're lifting this moisture-laden air, you can wring that out, especially when

02:58that air is ascending the mountains, and that's why we have such a concern about flash flooding

03:03today.

03:04And, you know, the concern is now with Ida, the heaviest rain was I-95 corridor.

03:10With Debbie, it's going to be north and west, and that provides a different set of problems.

03:15Yes, it does.

03:16See how that moisture is aimed right in the higher terrain from portions of western Maryland

03:22through Pennsylvania, upstate New York, into northern New England, so it's aimed in this

03:26direction with this storm as opposed to Ida, which was closer to the I-95 corridor.

03:30So the problem here is this is where the most significant flash flooding risk is going to

03:34occur here in the interior with a widespread four to eight inches of rain, and AccuWeather

03:39local storm max of a foot.

03:41But more importantly than those significant totals is how quick the rain will be falling.

03:46One to three inches per hour, Bernie, that's coming too fast, too furious, and especially

03:50in mountainous terrain where that water can run off very quickly.

03:54That's why we're very concerned about significant flooding, and there can even be rock slides

03:58and mud slides in some of the higher elevations.

04:01And you know, we don't want to forget, and this is another reason why we keep that tropical

04:04rainstorm definition tornadoes.

04:07Not that we're going to be looking at dozens of them, but there's going to be, I think,

04:11a handful within that red area, John.

04:14We are very concerned about this whole corridor later, especially through the day today.

04:19And I want to point out along the I-95 corridor, I was just talking with AccuWeather regional

04:22expert Bob Larson, and we think in New York City and Philadelphia up into parts of Connecticut,

04:28look out later this afternoon, poorly timed with the evening commute.

04:32That's when the heaviest rain risk may exist, localized flash flooding, isolated tornado

04:37risk, and some gusty winds.

04:39So this is a dangerous day today across the mid-Atlantic and northeast.

04:43Stay tuned to us here at AccuWeather, download the AccuWeather app and turn on push notifications

04:47so everybody can stay safer through the day today.

04:50Big airport delays, too, by the way, at the major airports in the mid-Atlantic and northeast.

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