Multiple storm systems to soak the East Coast and steer the future path of Hurricane Melissa

AccuWeather

AccuWeather's Geoff Cornish explains the multiple storm systems targeting the East Coast in the final week of October and how they could determine the path Melissa takes after it leaves the Caribbean.

Transcript

00:00In tonight's forecast feed, we have a lot to talk about.

00:05We want to take a quick look at the latest with Melissa's steering influences for the longer term,

00:11as, again, after crossing Jamaica and Cuba, probably clipping the western end of Jamaica

00:16with a fierce Category 5 impact across the entire landmass, and then Cuba,

00:22it's going to get scooped up by some upper-level winds,

00:24and it may still potentially directly impact the Canadian Maritimes,

00:28but we want to also bring it closer to home for many of us here in the U.S.

00:31with our forecast feed looking at two storms along the coast this week,

00:35one moving offshore, another one's going to come in through the interior, both with significant impact.

00:40So as we take a look at the current setup here through this evening and tonight,

00:43we're saying goodbye to the one storm that's now moving out to sea,

00:46and now the center of low pressure is making pretty good progress.

00:49So this is storm system number one, but there's another one behind it,

00:52and before we get too far down the line, you can see this dip in the jet stream here

00:57It's a small one, and it's beginning, that's the one following the coastal storm.

01:03This is the main one driving it.

01:05The surface low is just east of it.

01:07That is an influence in driving the offshore steering influences,

01:13and as low pressure begins to fall, pressure begins to deepen off the east coast of the U.S.

01:19with this trough.

01:20And another one following, we're going to see a little bit more of a vacuum drawing our storm, Melissa northward.

01:28So you can see this trough is just broad enough.

01:32The initial jet stream dip is going to be followed by a more pronounced one for our second storm of the week.

01:38But that is just far enough east, just broad enough that it's kind of creating this large vacuum

01:43with, again, a lot of steering flow out over the far west Atlantic.

01:48That is going to draw Melissa northward.

01:50Now, some of the mechanics and the details are up in the air still.

01:53Will this clip the Canadian Maritimes?

01:56Could it be absorbed by the second trough?

01:58Well, that may still happen.

02:00The GFS model would say no.

02:03With our second trough, this is the stronger one, negatively tilted northwest to southeast.

02:08It becomes a big problem for the east coast with soaking rain, and it impacts some of those

02:12Halloween plans up in New England.

02:14Strong onshore winds leading to problems.

02:16You'll notice that this one within the GFS model, it's still just far enough west that

02:22it never fully absorbs Melissa.

02:24There's Melissa going out to sea there with this bit of energy here, while the trough is still

02:29kind of anchored over the Canadian Maritimes and the New England states.

02:33That's the GFS.

02:34The European model has, again, a little bit more in the way of a separation between the

02:41second trough.

02:42I'm going to press pause on things Thursday night, Thursday evening.

02:47Here's Melissa pooling north.

02:49Here's that pretty amplified trough that's becoming more negatively tilted over the eastern

02:54U.S., but they're just separate enough that in this case, the European model, again,

03:00Melissa outruns the trough, and it never really gets absorbed by it until it's way, way up

03:06there somewhere closer to Greenland or Iceland.

03:08Now, if we look at the Canadian model, it's a little bit different looking at Melissa.

03:11It's just a little farther west, and this trough that moves through is just a little bit

03:17closer to Melissa.

03:19And as we go forward into Friday morning, again, less of a separation in the Canadian

03:25model.

03:26Our storm, Melissa, is closer to the trough and actually gets absorbed, and it slings some

03:31of Melissa's wind and rain into eastern Nova Scotia and the Canadian Maritimes.

03:35So it won't be a direct U.S. impact, but again, this would be absorbed by that system, that

03:40east coast trough in the Canadian.

03:41Now, looking more specifically at the sequence of one storm exits, another enters the east

03:47coast, kind of dialing the conversation away from Melissa back into the eastern U.S., you

03:52can see that our first trough is moving offshore here.

03:56Here we are Tuesday afternoon.

03:58Here's the surface low is actually going to be way out this way, and that system moves

04:02out to sea.

04:03But a stronger trough really digs in here.

04:06Look at this surface low pressure system under this upper level pattern here.

04:10We're looking at about 20,000 feet up into the sky.

04:13But this is going to be kind of given a shot in the arm here by some jet stream energy kind

04:18of wrapping around from the plains and from ultimately its tracks across the Canadian Rockies.

04:25So that bit of jet stream energy wraps into the bottom of the storm, amplifies it, and

04:30then it takes on more of a negative tilt on Friday morning.

04:34So there's Thursday night to early Friday morning.

04:36We say negative tilt, we're talking about sloped from northwest to southeast.

04:42That's the way this is kind of shaped, egg-shaped if you will, but pointed toward the southeast.

04:47And these storms are stronger.

04:48They have more lift in them.

04:50There's more of a proclivity for that colder air to begin to spill out over the relatively

04:54warm water of the Atlantic.

04:56And that's going to drive a pretty intense little storm late this week.

05:00A couple of factors tied to this that we'll be tracking.

05:03One of them, as this storm begins to dip down through the southern plains into the Gulf Coast

05:10states, there's a narrow window of opportunity for severe weather.

05:14You can see our instability, those shaded colors, basically lifting the atmosphere.

05:18Warm air near the ground, colder air aloft.

05:21There's a period of time Tuesday afternoon into the evening where there's some instability

05:24with this one from east Texas into Louisiana.

05:27It's not terribly significant, but it's something to track.

05:30And we can show you our forecast that aligns with that.

05:33So that's why we're looking at some potential for severe thunderstorms with this.

05:36But also, one thing to watch, overall, day after day, storm one moves out to sea.

05:43This is the storm that's already moving offshore.

05:45Look at these isobars.

05:46We've got high pressure to the north.

05:47We've got low pressure to the south.

05:49There's your low.

05:50Here's your high.

05:51These are working in tandem with one another to drive a pretty strong onshore wind.

05:55So the onshore wind blows Tuesday and still Wednesday.

05:59And then Thursday, as that second storm ramps up, that prolongs the onshore wind up into

06:04the New England and northeastern states.

06:06So that becomes a bit of a strong onshore wind driver.

06:10Look at the hint of snow up there in the high elevations, by the way.

06:13So because of this, one of the more significant things that we're interested in, bridging the

06:16gap between one storm system and another, an increasing risk for coastal flooding along

06:22the east coast, those dunes have been compromised, and that is your forecast feed.

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