Category: Posts EN

 

The first major heat wave of the summer is affecting the Plains and Midwest. By late this week into the weekend, the scorching hot air mass will spread east. Cities in the Urban Corridor will see heat index values well above 100 deg F!

 

 

A dome of strong high pressure has helped push air temperatures well above normal over much of the U.S. Meanwhile, a surge of tropical moisture originally tapped by now-extinct Hurricane Barry has encompassed much of the central and eastern states. This combination of hot temperatures and high humidity results in dangerous heat index values. Studies have shown that heat index values above 105 deg F greatly increase the risk of serious health impacts (see chart above). These include heat stroke, which can be fatal especially in the population of elderly and infirm. As you can see from the map below, this threshold will be passed over a large area of the central and eastern U.S. from Thursday through Sunday. Some areas will see peak heat index values of 115 deg F or higher! In urban areas like New York City, heat retained by the vast amount of asphalt and concrete will mean overnight temperatures staying warm. This is critically important as the human body requires recovery time between hot spells, especially those in vulnerable populations like the elderly. Indeed, extreme heat events are the deadliest among all weather events, killing more people annually than floods, tornadoes, or hurricanes.

 

 

Many areas have seen excessive heat warnings and advisories issued by the National Weather Service. More will be needed for the Thu-Sun time frame. Officials in some communities are going door-to-door to make sure vulnerable residents have supplies and shelter options as needed. Saturday looks to be the hottest day from the Mid-Atlantic to southern New England with some cooling likely beyond Sunday.

 

Hurricane Barry made landfall near Intracoastal City in south-central Louisiana around midday Saturday. Barry has continued to struggle with dry air intruding on the northern side. However, surface and reconnaissance plan data indicate the storm may have been producing hurricane-force conditions at landfall. As the storm moves further inland, heavy rain and flash flooding will become the predominant threat!

 

 

#Barry started the day not looking like a typical tropical cyclone.. now it does, ironically after moving inland pic.twitter.com/vde53o9FYv

— Stu Ostro (@StuOstro) July 13, 2019

Numerous reports of damaging winds and significant storm surge have been received from across southern Louisiana. Gusts of 40-70 mph (60-110 kph) have knocked down numerous trees and power lines, leading to thousands of power outages. A storm surge measured as high as 5-7 feet (2 m) has flooded coastal communities from the LA-MS state line to near the landfall point. Some levees protecting low-lying areas have been overtopped and damaged. Fortunately, as the center moves further inland, winds and surge flooding will continue to slowly subside, although localized flooding will still be likely around the astronomical high tide.

 

Terrebonne Parish in #Louisiana was hard-hit with storm surge inundation on Saturday. Here’s a few scenes from the area. #LAwx #Barry pic.twitter.com/a3Zrd8jThu

— WeatherNation (@WeatherNation) July 13, 2019

The heaviest rains so far have been falling to the south and east of the storm center. For much of the day, the heaviest rains were falling with a stationary band way east of the center, in Mobile, Alabama. Rainfall amounts up to 5-6 inches (125-150 mm) there lead to localized flooding. A new band of rain has set up over southeast Louisiana. This tropical moisture tap will be persistent through the next 24+ hours, eventually expanding further north into portions of Mississippi and Arkansas. Within this band, rainfall amounts of 3-6 inches (75-150 mm) will be common. Much heavier amounts of 6-12 inches (150-300 mm) or more are likely for central LA and southwest MS, where some serious flooding will occur.

 

Tropical Storm Barry remains somewhat organized with dry air disrupting the northern half of the circulation. Nevertheless, aircraft reconnaissance planes continue to find stronger and stronger winds in the core. Damaging winds, a significant storm surge, and especially torrential, flooding rainfall will accompany this dangerous storm!

 

 

The storm has been moving mainly to the west today, skirting just south of the coast (see satellite animation above). The track has shifted somewhat to the west in model guidance. Landfall is now expected to be closer to Vermillion Bay or Pecan Island. This is a fairly sparsely populated region, and the danger appears to be somewhat less in the New Orleans metro.

 

 

 

Barry remains a strong tropical storm as of Friday afternoon. However, it still has time to achieve hurricane status before landfall on Saturday. Regardless of whether it does or not, areas along the coast can expect to see high winds downing trees and power lines. The map above shows gusts already exceeding tropical storm force over southern Louisiana. A storm surge up to 5-6 feet in spots will also cause major problems along the central coast of Louisiana.

 

 

However, the most widespread danger will be from flooding rainfall. Although southern Louisiana has seen a relative break in the past 24 hours, a band of heavy rain is expected to become established over the southeast, especially west of New Orleans. This band will develop on Saturday and persist through Sunday and possibly into Monday. Within the band, totals exceeding a foot will be common, with some spots seeing closer to 24 inches! This copious rainfall will cause already-high rivers to rise even more, including the Mississippi, which is expected to reach the highest levels in nearly 70 years.

 

The tropical low that moved into the northern Gulf earlier this week strengthened Thursday to become Tropical Storm Barry. The second named storm of a fairly quiet 2019 season thus far, Barry is taking aim at coastal Louisiana. Further strengthening is expected and Barry could be a hurricane as it approaches landfall!

 

 

Louisiana is no stranger to hurricanes, but this would be the first to strike since Hurricane Isaac in 2012. Barry will bring a risk for damaging winds exceeding 40 mph and a significant storm surge locally up to five feet. However, the most widespread and dangerous threat could be flooding rainfall. The storm is in no hurry, crawling westward at about 5 mph. This slow forward movement combined with rich tropical moisture being wrapped in to the storm’s center will mean days of torrential rain. Totals of 12-18 inches (300-450 mm) will be common across southeastern Louisiana. Localized totals up to of 24 inches (600 mm) are likely! Serious flooding has already been occurring in the New Orleans area (see tweets below). The Mississippi River is expected to rise to levels not seen since 1950 in the New Orleans area.

 

Flooding on canal street in #NewOrleans #weather #storm #floods cc:@NBCNews pic.twitter.com/SL3KpNCDJt

— xuan thai (@Xuan_Thai) July 10, 2019

 

#TropicalStormBarry is slowly moving westward across the northern Gulf of Mexico, as seen here by NOAA’s #GOESEast. @NHC_Atlantic warns that Barry could produce dangerous storm surge, heavy rains and high winds along the Gulf Coast. More imagery: https://t.co/gnoNmVgqS3 pic.twitter.com/lje4WNKnGh

— NOAA Satellites (@NOAASatellites) July 11, 2019

 

A state of emergency has been declared for parts of Louisiana, and mandatory evacuations are in effect for some coastal communities. However, neighboring states will see significant wind and especially rain impacts as well. The worst impacts from wind and storm surge will be felt along coastal Louisiana from late Friday into Saturday. However, the freshwater flooding threat will stretch well into early next week for the entire Lower Mississippi Valley.