Tropical Storm Barry Strengthens, Heavy Rainfall remains the Primary Concern

Tropical Storm Barry was designated yesterday in the northern Gulf of Mexico, and has since been moving gradually and erratically westward with time. As of now, Barry has maximum sustained winds of 65mph and a minimum central pressure of 998mb, despite its atypical structure for a storm of its caliber. It is moving generally towards the west at 5mph and is centered about 100mi SW of the Mississippi River Delta. Barry is expected to impact Louisiana tomorrow, possibly as a weak hurricane, and produce extreme rains over a wide area.

Visible imagery of Tropical Storm Barry south of Louisiana with its asymmetric structure. (SSEC)

Barry, while better organized than it was yesterday, is still not a normal-looking tropical cyclone. Most of the convection is still sheared off towards the south of the surface center due to northerly upper and mid-level shear and dry air, leaving the northern half of the circulation relatively bare. Despite this, Aircraft Reconnaissance has been able to detect steadily dropping surface pressures, flight level winds above hurricane force, and surface winds near 65mph or greater within the primary area of convection. In addition, the wind field has become much better symmetrized despite the convective asymmetry. Due to the continued convective initiation in the southern quadrants and frequency and tugging of eddies visible within the broader circulation, the surface center has been jogging around rather than maintaining a purely westward movement. Rather, the mean motion of the storm is towards the west.

AF302 data from their mission into Barry, revealing the strongest winds in the southeastern quadrant and the variable center fixes. (Tropical Tidbits)

The forecast is much more certain now than it has been, and there are two crucial things that are expected to occur within the next 12-24 hours. First of all, Barry is forecast to take a turn towards the north. This is in response to a weak cold front that has dropped into the southeastern U.S., causing a break in the ridge that was initially steering the cyclone westward. The second thing is that the main area of convection is forecast to shift from the southern quadrants to the eastern quadrants. As the storm does its northward turn, the strongest winds will shift towards the eastern quadrants, a process currently ongoing, and the increased convergence on that side with the frontal flow will allow more convection to fire towards the east. This will be crucial in forecasting the anticipated heavy rainfall event, the primary threat with Barry discussed in detail below.

12z HWRF run of Barry, depicting the northward turn and the shifting of convection into the eastern quadrants. (Weathernerds)

The storm still has about 24 hours left over water before it makes landfall tomorrow morning somewhere in St. Mary Parish in Louisiana. If these strengthening trends continue up until landfall, then it’s possible that Barry could become a hurricane before it moves onshore despite its non-classical appearance. This is currently depicted in the National Hurricane Center forecast track, although the difference between a strong tropical storm and a weak hurricane is purely academic at this point. Tropical Storm Warnings are in effect throughout almost all of the Louisiana coastline, including Lake Pontchartrain, and Hurricane Warnings are in effect from Intracoastal City to Grand Isle, Louisiana. Storm Surge Watches and Warnings are also in place from Vermilion Bay to the Mississippi/Alabama border, as storm surge could approach 3-6′ feet in some marshlands of Louisiana. While landfall is expected on the western edge of these warnings, the lopsided structure based towards the east, as mentioned previously, will bring the worst of the impacts near and to the right of where Barry makes landfall, including the highest winds, highest storm surge, highest tornado potential, and most importantly, the heaviest rainfall.

NHC 5-day forecast cone for Barry, showing the storm’s wind field, forecast track/intensity, and issued warnings. (NHC)

Undoubtedly the biggest threat from Barry is the rainfall. Due to the slow movement and large size of the system, rainfall totals are likely to be prolific across southeastern Louisiana and up the Mississippi River Valley, where rainfall is anything but wished upon. Rainfall totals near and east of the landfall zone will certainly approach double digits, with some isolated totals potentially exceeding 20 inches depending on where exactly the primary feeder band is located. This will be falling on top of an area that already saw flash flooding on Wednesday in association with a mesoscale convective feature that developed on the northwestern side of Barry’s precursor low. Places such as Baton Rouge, Morgan City, Houma, and even portions of New Orleans may see up to or over a foot of rainfall. To the west of the landfall point, the gradience of the rainfall totals will be much steeper than that seen on the eastern side, so Lake Charles may see just as much rain as Panama City despite Lake Charles being much closer to the storm’s core. Heavy rainfall of up to 6 inches is expected northward as well into Mississippi and portions of western Tennessee and extreme western Arkansas. Outside of that, over 2 inches of rain is expected from the Ohio River Valley southwards as Barry moves inland and weakens. If there is any good news, the bullseye of rainfall appears to have shrunk and shifted west of New Orleans, but still, extremely heavy rains are surely coming to a part of the country that does not need it.

[Image of WPC QPF U.S. rainfall potential]
WPC forecast rainfall from Barry, indicating a wide swath of heavy flooding rains across portions of eastern Louisiana, western Mississippi, and surrounding areas. (WPC)

Aircraft Reconnaissance planes will continue to fly through the storm until it moves onshore tomorrow. Until then, if you are in the path of Barry, then finalize your preparations now so that you do not have to leave during the storm. Flooding from rainfall is often an underrated but enormous threat with landfalling tropical systems, so don’t be caught off guard by flash flooding. Listen to the advice from your local National Weather Service Office, other local authorities, and news stations for the latest information specific to your location. If an evacuation order is issued, leave. Don’t think that because “it’s only a tropical storm or category 1” that it won’t be a big deal, because it certainly can or will be. That’s it for me on Barry; I will continue to post updates on Twitter as needed, as I myself am actually flying to the western Florida Panhandle tonight for reasons unrelated to the storm. Please stay safe, everyone.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s