eye on the storm

Thursday Tropical Update

Weather

6:00PM UPDATE: The forecast data for Barry’s future path is still a dog’s breakfast — the range of possibilities still includes a wide stretch of the Gulf Coast:I still wouldn’t bet against the European forecast model, whose ensemble shows a landfall just south of Lafayette, Louisiana — but even it’s output encompasses possibilities all across the Louisiana coastline:The official forecast from the National Hurricane Center jogged east at 11:00am, but now they’ve pushed it back to the west, close to where it was early this morning. Also, the NHC is now predicting that Barry will remain just below hurricane strength (something I discussed in this morning’s original post below):That path is just the center of circulation, thought…this is a large and messy storm whose impact will stretch hundreds of miles away from the center. Locations east of the forecast path will bear the brunt of the flooding threat, and that region still includes Baton Rouge and New Orleans. The bullseye of 20″+ rainfall is just west of New Orleans, but the 10″-15″ forecast for the city would still be catastrophic (also discussed below):Unsurprisingly, the Weather Prediction Center and NHC continue to highlight that portion of the Gulf Coast in a High Risk of excessive rainfall:

That’s it for the updates from me this evening. I’ll be on the air at 4:30am with the latest on Barry, and of course on our local storm chances too!

———————–
11:30AM UPDATE: The National Hurricane Center has now officially classified the disturbance in the Gulf of Mexico as Tropical Storm Barry. They’ve also adjusted the forecast path of the storm — still a Category One hurricane at landfall, but that point of landfall is now farther east on the Louisiana coast, and earlier in the day Saturday:I discussed that possible shift in this morning’s original post below — such a shift is especially bad news for New Orleans, and leaves Baton Rouge in a bad spot as well. Both cities are likely to experience major flooding if this forecast track holds.

I’ll post another quick update this afternoon, once some additional model data comes in and we get another update from the NHC.

——————————–
POSTED 8:00AM: We’ve been tracking this developing tropical system for several days, but as of 8:00am it’s STILL not even a tropical depression. It’s likely to reach that status later today and become Tropical Storm Barry by tomorrow. The National Hurricane Center’s latest forecast shows soon-to-be-Barry reaching Category One hurricane status before making landfall on Saturday:

I looked at the flooding potential associated with Barry in the video above, but this is a space where we can really get into the details of this intensifying storm. To begin with, it’s precise path and intensity are both still really up in the air. The latest forecast model output on the “spaghetti plot” is starting to shift a bit farther east of the NHC’s official forecast:And most of the forecast models’ intensity estimates keep it below hurricane strength:But remember, forecast models are used for guidance, not gospel…and trying to predict tropical storm intensity is the most difficult part of this process! There are plenty of factors that would favor rapid intensification over the next 24-48 hours, especially the bathtub-warm water temperatures and very low wind shear:The whole Gulf of Mexico has above-average sea-surface temperatures, but this system is about to move over some of the very warmest water. The green lines in the image above highlight an area of very low wind shear, where the upper-level winds won’t be able to tear the system apart as it gets organized. Even with those favorable factors, the European ensemble model only estimates a 15-20% chance it reaches hurricane strength before landfall:

But storm intensity (depression, storm, or hurricane) is only determined by the storm’s maximum sustained winds. And regardless of soon-to-be-Barry’s wind intensity, it’s still going to bring devastating flooding somewhere along the Gulf Coast. The European model’s ensemble roughly agrees with the National Hurricane Center’s forecast path (as opposed to the eastward shift in the other model data), but the whole Louisiana coast is still well within the range of possibilities for landfall:The heaviest rain will fall near and east of the storm’s center of circulation…the Weather Prediction Center’s “Excessive Rain Outlook” shows a High Risk of flash flooding Saturday and Sunday:Specifically, we’re looking at a stripe of rainfall totals approaching 20″ somewhere in Louisiana — right now that stripe is forecast to be just west of New Orleans, and right over Baton Rouge:That area of heaviest rain will wiggle around with any future adjustments to the forecast path. Even the 5″-10″ currently forecast for New Orleans would be devastating for the city, because the Mississippi River is already so high (thanks to floodwaters in the Midwest this spring traveling downstream). The river forecast chart shows the Mississippi hitting 20 feet by Saturday night:Many of the city’s levees aren’t even 20 feet tall (red dots on this map):The situation could get even worse, as the storm’s southerly winds push a storm surge up the Mississippi River channel, raising river levels even higher.

In terms of the storm’s eventual impact on our weather in central North Carolina, that’s still highly speculative. The European forecast model thinks the remnants will eventually get caught up in the large-scale atmospheric flow, and affect our weather by Wednesday of next week:The American GFS model kinda-sorta agrees:That doesn’t mean it’s etched in stone — far from it! Right now we’re leaving Wednesday’s storm chances at 40%, because so much can change between now and then:We’ll keep a close eye on it, of course!

Okay, that’s a LOT of information. Just to summarize:

  • The system is likely to become Tropical Storm Barry over the next 24-36 hours, and will move into an environment that could easily allow it to become Hurricane Barry.
  • Regardless of storm intensity (wind speeds), it will bring catastrophic flooding to parts of Louisiana, along with some wind damage.
  • There will still be adjustments to the forecast as the entire system evolves. I’ll keep this post updated today (new info will be right at the top), and I’ll have a whole new write-up tomorrow.

Copyright 2019 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

Don't Miss