Flooding Likely Along Gulf Coast And Miss. Valley As Cristobal Strengthens This Weekend

Tropical Storm Cristobal made landfall near Ciudad del Carmen in southern Mexico on Wednesday after several days of meandering and strengthening in the Bay of Campeche. The system will remain inland until Friday evening, when forecasters expect it to reemerge over the Gulf of Mexico and slowly strengthen as it heads for the northern Gulf Coast. The system will bring heavy rain, gusty winds, and a risk for tornadoes to portions of the Southeast and Midwest early next week.

The center of what's now Tropical Depression Cristobal spent Thursday moving along the Mexico/Guatemala border at walking speed. The storm is quite ragged looking now, having lingered over land for about a day now. The system will begin lifting north toward the Yucatan Peninsula and the Gulf of Mexico on Friday, reemerging over open waters by Friday night.

The latest forecast from the National Hurricane Center shows the system regaining some of its strength and making landfall along the northern Gulf Coast as a tropical storm on Sunday or Monday. While folks near the point of landfall will likely see the strongest winds and greatest potential for storm surge flooding, this will be a large system and the potential for flooding will extend many hundreds of miles from the center of the storm.

Rain

It's been raining for days in some parts of Central America and southern Mexico—remember, this system originally made landfall on Sunday as Tropical Storm Amanda over in the eastern Pacific—and some communities have measured several feet of rain as a result. Widespread flooding and mudslides will continue until the system lifts away this weekend.

We won't see that kind of intense rainfall in the United States, but this is a juicy storm and it's going to rain quite a bit across areas affected by Cristobal. The Weather Prediction Center's latest forecast calls for up to half a foot of rain along the Gulf Coast. It's easy to trace the predicted path of the storm by following the swath of heavy rain from the Gulf to the Midwest through the first half of next week.

Heavy rain that falls too quickly will lead to flooding issues in vulnerable areas. Flooding accounts for most deaths in a landfalling tropical storm. We've been through this time and time again in the last couple of years. The messaging should be driven home by now: the wind gets all the headlines, but it's the water that causes most of the problems.

Wind

While it's the water that causes the most problems, we can't completely ignore the threat for wind. Meteorologists warn severe thunderstorms for wind gusts of 60 MPH. A tropical storm with sustained winds of 60 MPH at landfall will certainly do some damage to trees and power lines, as well as blowing around objects outside that could cause injury or damage. The rain-soaked soil will make it easier for trees to come down in gusty winds.

Tornadoes

Tornadoes are a threat with any landfalling tropical system. The greatest threat for tornadoes lies in the right-front quadrant of a tropical system—in this case, to the east of the center of circulation. If the storm follows its projected path, a threat for tornadoes will exist on Monday and Tuesday in eastern Louisiana, Mississippi, Alabama, and possibly the Florida Panhandle.

Rough Seas

Rough seas across the Gulf of Mexico will lead to an increased threat of rip currents from Texas to Florida. A rip current is a swift channel of water that moves from the shore to the sea, induced by waves that hit the coast head-on.

Rip currents don't suck you under like you see in movies—they pull you out away from land. Folks susceptible to drowning include inexperienced swimmers or folks who quickly get exhausted from trying to fight against the pull. If you're ever caught in a rip current, it's wise to do one of two things:

1) swim parallel to the shore until you've left the current, then swim back toward shore, or;

2) calmly signal for help.

Rip currents often look appealing to swimmers since they look like oddly calm sections of the beach amidst otherwise raucous waves, but the calm you're seeing is the channel of water retreating out to sea.

It's always a good idea to check the rip current forecast and make sure it's safe to swim. The National Weather Service offers regular rip current forecast for shores in their service areas, and most public beaches post warnings when dangerous rip currents are possible.

[Satellite Image: NOAA]

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Heavy Rain Likely Along Gulf Coast This Week As A Tropical Disturbance Enters Gulf

The National Hurricane Center gives a tropical disturbance over Central America a 60 percent chance of developing into a tropical depression over the Gulf of Mexico later this week. Regardless of development, the system is going to be a heavy rain threat to much of the Gulf Coast. This is going to be a slow-burn event and we have several days to watch and wait for what happens next.

Heavy rain and widespread flooding are ongoing across much of Central America as the remnants of the eastern Pacific's first tropical storm of the year linger over Guatemala. The system, former Tropical Storm Amanda, has produced more than a foot of rain at higher elevations, bringing flash flooding and mudslides to vulnerable areas.

A large-scale circulation known as a "Central American Gyre" will foster unsettled conditions over the region throughout the week. The remnants of Amanda will continue to bubble over the next couple of days in that favorable environment, slowly drifting toward the Gulf of Mexico by midweek. It's in the Bay of Campeche that the National Hurricane Center sees a 60 percent chance for tropical development by the middle of the week.

Source: WPC

Regardless of tropical development, this is a rainmaker if there ever was one. The latest precipitation forecast from the Weather Prediction Center shows an enormous amount of rain falling over the Gulf of Mexico over the next seven days. The outer extent of the rain touches coastal areas from southern Florida to eastern Louisiana, potentially leading to flooding issues if too much heavy rain falls all at once.

The closer the system gets to the United States, the greater the potential for heavy rain over land. Everyone from Texas to Florida needs to keep an eye on the forecasts to see how this system develops and prepare now for potential flooding or wind-damage issues. Map out alternate routes to get to work, home, or to run errands. Areas that don't normally flood can wind up covered in water during exceptionally heavy rain events. It may be difficult to stock up on emergency supplies given the pandemic, but it never hurts to have a few extra non-perishables and batteries on hand in case the power goes out.

This is going to be a watch-and-wait situation. I know we hate those when it comes to the weather, but it's both a curse and a benefit of modern weather forecasting. It seems like a headache to watch something for a week to see if you'll be fine or if you need to invest in a pontoon boat, but hey, that's an improvement over the old way of finding out you'd get hit with a windswept flood once the waters started rising.

The Atlantic hurricane season officially begins on June 1, but we already saw two tropical storms during the month of May. The next name on the list is Cristobal.

Correction: I put the wrong date on the NHC outlook map above. The outlook was issued on May 31, not May 30 like I had in the original. Fixed. Sorry.

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Life-Threatening Flooding Likely As Tropical Storm Barry Crawls Toward Louisiana

Extremely heavy rain associated with Tropical Storm Barry will lead to life-threatening flooding across southern Louisiana and the lower Mississippi River Valley over the next couple of days. The slow-moving storm could reach hurricane strength before it makes landfall on the Louisiana coast on Saturday. Latest forecasts show double-digit rainfall totals across the eastern part of the state, compounding ongoing flooding issues across the region.

NHC Forecast

The disturbance we've been watching for the last couple of days developed a closed surface circulation on Thursday morning, allowing the National Hurricane Center to upgrade the system to Tropical Storm Barry. The NHC's 7:00 PM CDT advisory shows the storm slowly organizing over the next two days, possibly strengthening into a hurricane before making landfall in southern Louisiana on Saturday morning.

Conditions across the northern Gulf of Mexico are conducive to strengthening if the storm can get its act together fast enough to take advantage of its environment. Barry's structure on Thursday afternoon was...lacking...with an exposed low-level circulation south of the mouth of the Mississippi River, and almost all clouds and convection fanned-out on the southern side of the system.

The window for strengthening will begin to close the longer the storm remains disorganized. That's great news in terms of wind and storm surge, but Barry is set to bring flooding rains to the northern Gulf Coast regardless of its strength at landfall.

Rainfall Forecast

While wind speeds and the phrase "hurricane warning" will get the most attention, the real story of this storm is the water. Barry threatens to wring out a tremendous amount of tropical moisture over the northern Gulf Coast through this weekend.

The latest rainfall prediction from NOAA's Weather Prediction Center shows the potential for 20" or more—yes, that's twenty inches or more—of rain across southern Louisiana. A wider swath of half a foot or more of rain spreads up the Mississippi River toward the Memphis area.

Not everyone will see all of the rain in the forecast. But the storm will move slow enough that rain bands and thunderstorms will be able to tap into a deep reserve of tropical moisture and produce copious amounts of rain in a short period of time.

It's important to note that these predicted rainfall amounts will change as the storm gets closer to land and forecasters get a better handle on the structure and future track of the storm. Small changes in intensity, organization, and track will shift the bullseye for heavy rain with time. The overall point is that everyone in Louisiana should prepare for a potentially significant flooding event.

Flooding Potential

NOAA/NWS

The combination of accumulated water from heavy rain, the Mississippi River rising from excess upstream runoff, and a potential storm surge could severely strain the ability of New Orleans and surrounding areas to stave off floodwaters.

The Mississippi River is already in flood from months of heavy rain across the central United States. Add that on to the flash flood emergency that played out across New Orleans on Wednesday—dropping more than half a foot of rain in a couple of hours—and it won't take much heavy rain to cause major flooding along the area's already-strained waterways.

River flooding forecasts from the National Weather Service show the Mississippi River in New Orleans cresting at 19 feet if current precipitation forecasts hold up, which would be the highest crest recorded there since February 1950. The levees along the Mississippi in New Orleans are only 20 feet tall, so the water would only be about a foot away from the top.

The entire city of New Orleans sits below sea level. Not only does it face a threat from the bodies of water that surround the city, but rainwater has to be pumped out of the city because it can't seep into the ground. The pumps can handle rainfall rates of 1.00" in the first hour and 0.50" in every subsequent hour after the rain stops. Rain that falls faster than that will cause flooding in spots around the city until the pumps can catch up with the excess water.

It's not just New Orleans, either. The excessive rainfall amounts forecast across Louisiana and throughout the lower Mississippi River Valley will cause extensive and life-threatening flash flooding across the region.

A scenario like this played out not too long ago. A disturbance over the northern Gulf of Mexico brought a widespread swath of 10"-20" of rain to central and eastern Louisiana back in the summer of 2016. The resulting flooding was some of the worst in Louisiana's modern history, killing more than a dozen people and causing more than $10 billion in damage. Many homes destroyed by the floods in 2016 didn't have flood insurance, as the owners thought they were safe from flooding.

Winds

Flooding is the greatest threat, but we can't ignore the winds. Hurricane warnings are in effect for the central Louisiana coast for the potential that Barry could strengthen into a hurricane before reaching land. In practical terms, though, the difference between a 70 MPH tropical storm and a 75 MPH hurricane is negligible.

Wind gusts above 70 MPH and soggy ground will allow trees and power lines to fall with relative ease. Widespread power outages are likely where the strongest part of the storm makes landfall. Strong winds will easily snap tree limbs and blow around small debris—stuff like trash cans and yard decorations.

Tornadoes

Tornadoes are always a threat in the right-front quadrant of any landfalling tropical system. Folks along and to the east of Tropical Storm Barry's track will stand the greatest threat for tornadoes. Tropical tornadoes are different from tornadoes you'd see in a "regular" thunderstorm. They can happen so quickly that forecasters can miss them between radar sweeps. Eastern Louisiana, Mississippi, and Alabama will have to be on the lookout for tornadoes as the storm makes its way inland.

[Satellite Image: NOAA]

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Tropical System In Gulf Likely To Strengthen; Greatest Threat Is Flooding From Heavy Rain

A tropical disturbance entering the Gulf of Mexico has a high chance of growing into a named storm by the end of the week. Some models have the system intensifying before it makes landfall on the northern Gulf Coast this weekend. Flash flooding from heavy rain is far and away the greatest threat with this system, no matter what it's called at landfall.

Tuesday afternoon's update from the National Hurricane Center gave the disturbance, dubbed "Invest 92L" for now, an 80 percent chance of developing into a tropical depression by Thursday morning. We've been watching this trough of low pressure mosey southward across the southeastern United States for a couple of days. The disturbance emerged in the northeastern Gulf of Mexico on Tuesday morning, opening the window for potential development over the next day or two.

Conditions over the Gulf of Mexico are capable of supporting a tropical system. Sea surface temperatures in the northern Gulf are in the mid- to upper-80s, which is plenty warm enough to support tropical development. Low wind shear will allow thunderstorms to develop without getting ripped apart, and ample moisture should stave off intrusions of dry air from suffocating the storm.

The major complication here is the structure of the disturbance itself. It's pretty disorganized at the moment. Assuming the system develops, exactly where it takes root and how strong it gets will ultimately determine how far west it travels across the northern Gulf. A stronger storm may be able to tap into winds that could steer the storm farther west across the Gulf.

Water is the greatest threat with this system no matter what it does. The best case scenario right now is that this system remains disorganized and weak. The worst case scenario is that the system gets its act together in a hurry, posing a threat for wind damage and power outages in addition to lots of heavy rain.

Either scenario would bring heavy rain to the Gulf Coast. The latest forecast from the Weather Prediction Center shows more than five inches of rain falling across a wide swath of the southern United States, with a maximum near the coast where the system ultimately makes landfall. This swath of heavy rain will shift in location and intensity as forecasters get a better handle on exactly what will happen. Everyone along and inland of the Gulf Coast is at risk of seeing flooding rains through next weekend.

We've seen so many storms in recent years—from tropical storms to major hurricanes—leave behind horrendous flooding in their wake. Folks in Texas and North Carolina are intimately aware of the threat for flooding in a landfalling tropical system. Even so, it's still a major battle to get folks in harm's way to appreciate the threat of water over the threat of wind.

The threat of winds can't be completely ignored, of course. Strong winds could cause damage if this system reaches shore as a tropical storm or hurricane. Tree damage, power outages, and some structural damage would be possible in that scenario. Those are significant hazards, made even worse by the potential for flooding from heavy rains.

Forecasters (and weather models!) will have a better idea of what's going to happen over the next couple of days once—and if—the system develops and there's actually something there to analyze. It's a good idea to prepare for an extended period of heavy rain if you live in any of the southern states. Good questions to ask yourself right now include "do I have multiple routes to get around if roads are flooded out?" and "do I have food and supplies to get through a couple of days without power?"

The National Hurricane Center will begin issuing advisories on this system every 3-6 hours if/once it develops into a tropical depression. In the meantime, they issue tropical weather outlooks every six hours at 2:00 and 8:00 AM/PM Eastern Time.

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A Trough Over Georgia Could Become A Tropical System In The Gulf—And It's Not As Weird As It Sounds!

The National Hurricane Center is monitoring a trough of low pressure over the southeastern U.S. for signs of tropical development once it reaches the Gulf of Mexico in a couple of days. A disturbance turning into a tropical cyclone once it moves from land to sea isn't as weird as folks are making it sound on Facebook and Twitter—after all, where do you think Cape Verde hurricanes come from? (It ain't the stork!)

Sunday's 8:00 PM EDT update from the NHC gives the disturbance over northern Georgia a 60 percent chance of developing into a tropical system once it reaches the northern Gulf of Mexico later this week. Conditions are favorable for the system to slowly organize by late next week as it meanders in the northern Gulf.

Even if the storm doesn't develop, it looks like a good bit of rain will fall along the northern Gulf Coast and points inland once this whatever-it-is starts moving inland next weekend. The latest rainfall forecast from the Weather Prediction Center shows a boatload of rain (technical term!) falling across parts of Florida, Alabama, and Georgia, through next Sunday, and these totals could easily tick higher if the system organizes and grows stronger once it reaches the Gulf. Flash flooding is likely in areas that see too much rain too quickly.

Everything I've seen about this system on social media so far makes a hullabaloo about the National Hurricane Center mentioning it in their outlooks while the trough was still over Tennessee. If that seems weird, it shouldn't. Lots of tropical systems begin as clusters of storms that form over land and move over the ocean.

You know how we talk about Cape Verde hurricanes and "tropical waves" moving off of Africa in August and September? Those are disturbances that begin over western Africa and move over Atlantic Ocean. Most of the big hurricanes we remember—Katrina! Andrew! Rita! Charley!—started as troughs or thunderstorms over the African continent.

Most folks just aren't used to hearing about this process occurring over the United States. Well, that, and the fact that it's a little unsettling to see a giant X over Tennessee on a map produced by the National Hurricane Center. But this is certainly one method of tropical development this early in the season, and the Gulf of Mexico is a prime location for storms to develop in July.

Oh, and if you're wondering..."Barry" is the next name on this year's list of tropical cyclone names for the Atlantic Ocean. (We used the name Andrea back in May.)

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