One had a name, the other did not. Both brought flooding but had different outcomes
By Jennifer Gray, CNN meteorologist
If you woke up this morning feeling like the last two days lasted for two weeks, you’re not alone.
Tens of thousands of our friends woke up with no power, trees down surrounding their homes, and, in Tennessee, there’s heartbreaking devastation.
We are with you. Weather is our passion, but destruction is not. We’re mourning along with everyone else.
One of the storms was a tropical system, a hurricane, which eventually made landfall as a tropical storm.
Henri was widely forecast, talked about and analyzed. But the storm without a name made the biggest impact.
It was a cluster of thunderstorms that did not move. They sat over one area for hours on end and left destruction you have to see to believe.
Henri is winding down, but not over
Henri is now a tropical depression STILL sitting over New England and STILL producing torrential downpours from the mid-Atlantic to New England.
The rain is going to linger much of Monday because, well… I could easily outrun the storm — and I’m not a fast runner.
The depression is only moving at 1 mph, so there is still the threat of more flooding Monday. In fact, 33 million are still under some sort of flood alert, from eastern Pennsylvania to New Hampshire.
We could see an additional 1 to 3 inches.
More than 50,000 customers are without power across New England, and I’m worried that number could grow even more.
Yes, the winds have weakened with this storm, but the rain is still coming down. So be on the lookout for more trees to come down through Monday.
Henri’s heaviest rainbands seemed to set up right over New York and New Jersey, producing some of the heaviest rains.
The rain flooded subways, stranded motorists, and forced rescues amid the rising water.
In fact, people were sent home early from the star-studded concert in Central Park on Saturday night, after inclement weather from Henri moved into the area.
Most of the rain has pushed out of New York City and New Jersey, but there is still plenty of moisture with Henri to produce heavy rain from Long Island to New Hampshire on Monday.
What’s left of Henri should pick up some steam later Monday and move out of New England Tuesday.
Travel should get back to normal by Tuesday, and The Northern Trust golf tournament in Jersey City, New Jersey, should be able to resume, after being postponed due to Henri.
MORE ON HENRI
How did the flooding in Tennessee even happen?
As we see more pictures of destruction, devastation and sadness come out of the flooding event in middle Tennessee, we see how sometimes those storms without a name will be the storms we will never forget.
We have gotten so many questions about how this could have happened.
The first strike was a wet July. According to the National Weather Service (NWS) in Nashville, more rainfall than normal fell across central Tennessee in July. Nashville had up to 8.74 inches of rain in July, “which was more than double the normal value of 4.16 inches,” said the NWS in Nashville. This made the ground incredibly saturated, and left little room for any additional rain to be absorbed by the soil.
Of course, to be fair, with more than a foot of rain in 24 hours, flash flooding would have been the outcome even if the ground was dry. However, the wet soil most likely made the flooding even worse.
The flooding on Saturday was caused by several storms training over the same area.
“We had a stationary boundary set up over western part of middle Tennessee that provided the perfect set up conditions, a constant training of [storms] over that one area for several hours right along that boundary,” said meteorologist Mark Rose from NWS Nashville.
The rainfall totals were jaw dropping. The town of McEwen received 17.02″ of rain, which likely broke the all-time 24-hour rainfall record for the state.
This is more than four months’ worth of rain in a 24-hour period. The rain caused rivers to rise at tremendous speeds, carrying away cars and even homes.
These images show just how devastating the flooding was across Middle Tennessee.
The floods have killed at least 21 people and left dozens more missing.
These storms are so hard to forecast, because it’s nearly impossible to pinpoint where training storms will set up.
This area will get a break from the rain for the next week. “The rainfall forecast for this upcoming 7-days shows almost nothing [for the area that flooded over the weekend]. It’s going to be a relatively dry week ahead,” said Rose.
This type of extreme rainfall rates are fueled by warmer temperatures, which can hold more water vapor in the atmosphere — about 7% more per 1 degree Celsius. More water vapor in the atmosphere makes more moisture available to fall as rain, thus increasing the rainfall rates.
Extreme rainfall rates such as this one, and the deadly flash flooding event in Tennessee Saturday, are becoming more common because of human-caused global warming, scientists say.
A recent UN climate report stated, “the frequency and intensity of heavy precipitation events have increased since the 1950s over most land area.”
Saharan dust will give us a short term breather from hurricanes
As we say good riddance to Henri, we might actually get a breather in the tropics for the short term.
“Tropical activity across the Atlantic certainly looks much quieter this week than last,” said CNN meteorologist Taylor Ward. “While there are a few areas we are monitoring, it will be tough for them to develop as another expansive area of Saharan dust has moved off of Africa and will be heading across the Atlantic this week.”
Last week I spoke with Dr. Bowen Pan, who’s with the atmospheric sciences department at Colorado State University about this week’s Saharan dust event, and she told me, “There still could be something pop up during the Saharan dust event, but it’s more likely that it will suppress hurricane development.”
This is very typical during the summer months to have Saharan dust events. It will have positive and negative impacts, but for the development of hurricanes, the dust tends to win majority of the time.
“Hurricanes need relatively moist conditions and an unstable atmosphere,” said Pan.
“The Saharan Air Layer is a warm and dry layer that located about 15,000 feet high so basically that will introduce very dry and warm conditions in the north Atlantic, so that will create very stable and unfavorable conditions to hurricanes.”
She does say that the one area to watch is right on the southern edge of the Saharan dust layer because of the contrast of conditions.
“The southern edge of the Saharan dust outbreak is associated with the Intertropical Convergence Zone (ITCZ), where 70% of the hurricanes are generated from that region. So if there’s a Saharan dust outbreak, there’s more likely going to be a greater temperature contrast between the Saharan desert and the Sahel region that will increase the convection activity in the ITCZ,” said Pan.
Right now, models are showing a brief pause for the very short term, only a few days, before things begin to churn once again.
I (we) will be back in your inbox for the next MAJOR storm as well… and the next… and the next.
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This autumn could ‘feel’ much different
If you are like me and count down the days until Starbucks has the red cups and you are ready to get your hands on anything tasting like pumpkin spice, this might have you spitting out your coffee.
According to the Climate Prediction Center, this autumn’s temperatures are expected to be above-normal for most of the country.
That not only keeps our fleece hoodies on the hanger, it also impacts the beautiful fall foliage. That’s because perfect foliage conditions rely on a good combination of temperature and moisture.
With drought conditions expected to continue in the West, the fall foliage will struggle to display those red and golden leaves.
Read more about why autumn won’t be the same this year.
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CNN meteorologists Brandon Miller, Haley Brink and Judson Jones contributed to this newsletter
