Hurricane Threat Louisiana coast

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Key Messages:

1. A tropical depression is expected to form on Thursday over the
northern Gulf of Mexico. Conditions appear favorable for this system
to strengthen to a hurricane that will bring storm surge, rainfall,
and wind hazards to the central Gulf Coast.

2. A dangerous storm surge is possible in portions of southern and
southeastern Louisiana where a Storm Surge Watch is in effect.
Additional storm surge watches may be needed on Thursday. Residents
in these areas should monitor the progress of this system and listen
to any advice given by local officials.

3. A Hurricane Watch is in effect for much of the Louisiana coast
and additional tropical storm or hurricane watches and warnings
could be needed on Thursday. Residents in the watch area should
ensure they have their hurricane plan in place.

4. The slow movement of this system will result in a long duration
heavy rainfall threat along the central Gulf Coast and inland
through the lower Mississippi Valley through the weekend and
potentially into early next week. Flash flooding and river flooding
will become increasingly likely, some of which may be significant,
especially along and east of the track of the system.

Key Messages:

1. There is a danger of life-threatening storm surge inundation
along the coast of southern and southeastern Louisiana where a Storm
Surge Warning is in effect. The highest storm surge inundation is
expected between the Mouth of the Atchafalaya River and Shell Beach.
Residents in these areas should listen to any advice given by local
officials.

2. The slow movement of Barry will result in a long duration heavy
rainfall and flood threat along the central Gulf Coast and inland
through the lower Mississippi Valley through the weekend into early
next week. Flash flooding and river flooding will become
increasingly likely, some of which may be significant, especially
along and east of the track of the system.

3. Hurricane conditions are expected along a portion of the coast of
Louisiana, where a Hurricane Warning has been issued. Residents in
these areas should rush their preparations to completion, as
tropical storm conditions are expected to arrive in the warning area
by Friday morning.

TROPICAL UPDATE: THURSDAY, JULY 11, 2019

TROPICAL STORM BARRY IS STILL DISORGANIZED, BUT ITS HEADING TOWARD LOUISIANA WITH A TREMENDOUS AMOUNT OF MOISTURE. IT’S EXPECTED TO MAKE LANDFALL LATE TONIGHT OR IN THE MORNING, WITH THE MOISTURE REACHING NEW ORLEANS SATURDAY INTO NEXT WEEK. ELSEWHERE IN THE TROPICS, A STRONG TROPICAL DISTURBANCE MIDWAY BETWEEN THE ISLANDS AND AFRICA HAS A CHANCE OF DEVELOPING, BUT IS NOT EXPECTED TO BE A THREAT.

Tropical Storm Barry is in the Gulf of Mexico well south of New Orleans. It is slowly turning toward a landfall on the Louisiana coast overnight tonight or early tomorrow – according to most of the best computer models. Hurricane Warnings are in effect for the eastern half the Louisiana coast, and wind over 40 mph are expected to affect inland areas including New Orleans.

The biggest threat for the most people, however, is not from the wind, but from water. Two bad things are expected to happen. The question is, how bad?

If Barry tracks to the west of New Orleans, and most forecasts indicate that’s most likely, the onshore wind will push the Gulf water up the Mississippi River. That will, in effect, slow the river’s flow and back the water up upriver. That will make the river water rise in New Orleans and other upriver communities. In a normal July, this wouldn’t be a problem, but the river is already much higher than normal due to the extreme rainfall farther north this spring, and only about four feet of rise will top the lowest levees, which protect neighborhoods.

Separately, the dry upper winds which are currently pushing the strong thunderstorms and heavy rain south of the center of Barry are forecast to shift as the center moves into Louisiana. The expectation is that the very heavy rain will be on the right side, the east side, of the center, and that likely means over the New Orleans area and the State of Mississippi. As Barry moves slowly north, that corridor of rain may continue over the same areas for two days or more.

The forecast is for 10 to 20 inches of rain, with some location getting 25 inches.

We can hope that some different scenario plays out, of course. Any areas in Louisiana or Mississippi or surrounding states that get one or two feet of rain will suffer major flooding, and the best evidence says, that’s what people have to be prepared for. Saturday and Sunday appear to be the days with the highest chance of rain, but it’s not inconceivable that the rain continues to be heavy at times in some areas into next week.

Elsewhere in the tropics, a well-developed tropical wave is tracking west in the Atlantic midway between the islands and Africa. It has a slight chance to develop in the short run, but as it gets closer to the Caribbean, the upper winds are forecast to be very unfavorable, and it does not appear to be a threat at this time.

Key Messages:

1. Life-threatening storm surge inundation is ongoing along the
coast of southern and southeastern Louisiana, portions of Lake
Pontchartrain, and portions of coastal Mississippi where a Storm
Surge Warning is in effect.

2. Life-threatening, significant flash flooding and river flooding
will become increasingly likely later today and tonight as Barry
moves inland, especially across portions of south-central and
southeast Louisiana into Mississippi. The slow movement of Barry
will result in a long duration heavy rainfall and flood threat from
Sunday into next week, extending from the central Gulf Coast north
across the Lower to Mid Mississippi Valley and portions of the
Tennessee Valley.

3. Hurricane conditions are occurring within portions of the
Hurricane Warning area along the Louisiana coast. Tropical storm
conditions will continue along much of the Louisiana coast and
spread inland across portions of the lower Mississippi Valley where
tropical storm warnings are in effect