CLIMATE CRISIS COMMUNICATOR

Yes, it CAN happen here!

Helene is the type of multi-state catastrophe that we will unfortunately see more of in the future. And not just in the Florida to Carolinas area. Using the term “disaster” doesn’t capture the devastation over such a huge area. Major or total damages stretched across at least 5 states: Florida, Georgia, South Carolina, North Carolina, and Tennessee. Millions of homes lost power. Damages will surely be in the tens of billions of dollars. Fatalities are over 100 and continuing to be counted.

WHY WAS HELENE SO POWERFUL? WHY WAS THERE SO MUCH INLAND FLOODING?

Helene intensified rapidly (35+ mph increase over 24 hours) over the record-warm waters of the Gulf of Mexico. This is nothing new. And it was no surprise. Look at how many major (Category 3+) hurricanes have hit the Gulf States recently:

SEVEN of those hurricanes were Category 4 or 5. Since 1850 there was only one decade that even had THREE. 

Some of them produced unbelievable rainfall (Harvey, with up to 50”), and some produced unbelievable storm surges (Ian, Michael, Helene). Only Helene fit both catastrophic categories.

IT STARTED WITH THE CLIMATE-AIDED RECORD WARM GULF WATERS.

September is the historical peak of the Atlantic hurricane season, so we expect the Gulf of Mexico waters to be warm. But the past two years have seen record warmth. The strength of a hurricane is directly related to the warm surface and near-surface waters once other conditions are favorable. 

Water temperatures at 80°F or higher are considered “favorable” for hurricane development and/or intensification. Water temps in Helene’s path were up to nearly 90°F. 

Between 1982 and 2016 (a 34 year period) there were SIX major Gulf hurricanes that intensified all the way to landfall. There now have been EIGHT since 2017.

So, it’s simple: unprecedented water warmth leads to unprecedented odds of rapid intensification. This has happened so frequently in recent years that it is virtually indisputable.

It's not just the average Gulf temperature reached record levels. Look at this:

Notice the reddish band in the eastern Gulf in the picture in the upper left. That’s known as the “Loop Current,” an extra warm zone that Helene (and others) have tracked over. Water temperatures were close to 90°F. It’s “the warmest of the warm.” Here is an illustration of how it happens:

RECORD MOISTURE = RECORD RAIN & RECORD FLOODING

The amount of total moisture in the atmosphere can be estimated accurately and then compared to previous storms. The Helene pattern didn’t just set a record - it smashed the record.

Moisture from the ground through the whole atmosphere can be measured in different ways. The one meteorologists use the most is called “Precipitable Water,” which is sometimes called “Total Column Water”. Below is a graphic I found from weathermodels.com – a site known for it’s unique and spectacular graphics:

(courtesy weathermodels.com)

A precipitable water of even ONE inch is a lot. TWO inches gets forecasters attention (and often Flood Watches). But THREE+ inches is the most forecasters have seen away from the tropics. By Friday the 27th, the area being flooded the worst in Western North Carolina, reached near 3.5.” Simply unheard of.

(The zone of high precipitable water extends from the Caribbean to North Carolina, and even to the Ohio Valley. This is known as an “Atmospheric River,” which is more common near the U.S. West Coast)

A PRE: WHY DID SO MUCH RAIN FALL IN A FAST-MOVING HURRICANE?

Typically, it is slow-moving hurricanes that lead to record rainfall. Harvey (2017) and Florence (2018) are perfect examples. But Helene was moving at an unusually fast pace, especially for a storm in the Gulf of Mexico. So, how did so much rain and flooding happen, especially far away from where Helene made landfall?

THE PRE: PREDECESSOR RAINFALL EVENT

It’s not a common term, even in meteorology. And the term hasn’t been around long - less than 20 years. That doesn’t mean it’s a new thing. But it’s a dangerous thing, made even more dangerous by extra moisture due to ocean and atmospheric warming.

Helena was a perfect example of a PRE, and it was correctly predicted to be one. The moisture plume extended more than 600 miles from the eye. In this case, it combined with a stalled front to keep that plume in the same area. 

So, Atlanta actually got most of its record rainfall AHEAD of the core of Helene. It was even worse near the Southern Appalachians, from Northeast Georgia through western North Carolina and eastern Tennessee, where strong winds raced UPWARD in elevation. Upward motion intensifies rainfall rates. That’s why some spots got close to 30”. You can almost see where the eastern part of the mountains are just by looking at the zone of maximum rainfall.

(map courtesy of weathermodels.com)

A wider rainfall map shows how big an area the downpours covered. The 3”+ zone stretched over 1200 miles:

(map courtesy weathermodels.com)

AGNES WAS A PRE ALSO - BUT….

Now, look at the rainfall map from Tropical Storm Agnes in 1972. This produced rainfall and flood records that, in some places, still stand. A large area of 10-16” covered Central Pennsylvania, with most of it falling BEFORE the core of Agnes moved in and stalled right over the state.

A repeat of the Agnes size and track would produce much more rain and flooding in Pennsylvania and surrounding states. The reasons:

*Warmer water (in the Gulf and Atlantic, which aided the Agnes rain).  *Warmer air (holding more moisture). 

*Stronger re-intensification as Agnes curved out into the Atlantic before the left turn into PA. All the factors would be magnified.

It’s not a question of IF; the questions are WHEN and just how much worse it will be than Agnes.

Glenn "Hurricane" Schwartz

Climate Crisis Communicator

50+ Years as Meteorologist

www.thehurricaneschwartz.com

thehurricaneschwartz@gmail.com