The Changing Climate of Atlantic Storms and How The Are Reported

Hurricanes are well defined systems with characteristics that quite literally set them apart from other storms. Large storms such as Nor'Easters are sometimes less well defined and interact more with major troughs, the jet streams, etc. We have come to understand Hurricanes as the worst case scenario, while other storms are less dangerous.

But sometimes, and I suspect more recently lately, these non-tropical storms become quite dangerous. The Great Storm of '78 killed hundreds in New England and made us suddenly realize that coastal property was a temporary thing. But we sense the danger of recent storms less acutely because for all storms we have better warning systems, and most storms don't kill that many people these days, like they used to. So worse storms seem less bad.

And sometimes, it turns out that these large powerful and dangerous extratropical systems and the tropical hurricanes or their remnants merge and interact, creating what sometimes emerges as a "superstorm" or at least, a "really inconvenient storm."

Sandy is an example of the former. Perhaps Hermine is an example of the latter. Hopefully not the former as well!

The focus on hurricanes as the dangerous big brother of temperate storms (including Nor'Easters) has unintentionally shaped our storm warning system to downplay by default non-hurricane storms, including the hurricanes themselves when they become extratropical. But the "remnants" of hurricanes over land are usually very dangerous because of the flooding they cause, and late in life former hurricanes are capable of ganging up with temperate systems to become very dangerous.

In the case of Superstorm Sandy, owing to global warming driven warm waters, the storm remained as a hurricane at the time it started to interact with temperate storm systems, and the result was one of the worst storms to hit the US East Coast. Yet, it was technically not a hurricane at landfall. Rather, it was a hurricane that ate another storm on its way to Ohio, and got too big, too powerful, too messy, and too dangerous to maintain use of the term (hurricane) normally reserved for better organized, more predictable, and better behaved dangerous storms.

Maybe we are seeing a shift in where the danger lies in Atlantic storms. There will never be a storm as dangerous as a Major Hurricane moving just the right way at just the right time against just the right piece of coastline. Ivan, Andrew, Katrina, like that. But the typical Category I hurricanes and the seemingly new phenomenon of more frequent post-tropical hybrids, and more frequent certain supercharged Nor'Easters seem all in about the same category of overall badness.

We are certainly seeing some self reflection on the part of meteorologists, who are always faced with the very difficult task of properly informing and educating the public, properly modulating alarm over a given storm system, always trying to not cause problems for the next storm by overstating or understating expectations. Some of this self reflection, as well as the gory details of how these different kinds of storms (Nor'Easter or Hurricane-Extratropical hybrid) develop is demonstrated in the following passages taken from various Hurricane Center discussions or Wikipedia, pertaining to the storms as indicated. I put them here for your enjoyment and/or horror.

1991 Perfect Storm

The 1991 Perfect Storm, also known as the The No-Name Storm (especially in the years immediately after it took place) and the Halloween Gale, was a nor'easter that absorbed Hurricane Grace and ultimately evolved back into a small unnamed hurricane late in its life cycle. The initial area of low pressure developed off Atlantic Canada on October 29. Forced southward by a ridge to its north, it reached its peak intensity as a large and powerful cyclone. The storm lashed the east coast of the United States with high waves and coastal flooding before turning to the southwest and weakening. Moving over warmer waters, the system transitioned into a subtropical cyclone before becoming a tropical storm. It executed a loop off the Mid-Atlantic states and turned toward the northeast. On November 1 the system evolved into a full-fledged hurricane with peak winds of 75 miles per hour (120 km/h), although the National Hurricane Center left it unnamed to avoid confusion amid media interest in the predecessor extratropical storm. It later received the name "the Perfect Storm" (playing off the common expression) after a conversation between Boston National Weather Service forecaster Robert Case and author Sebastian Junger. The system was the fourth hurricane and final tropical cyclone in the 1991 Atlantic hurricane season.

Hurricane and Superstorm Sandy

FIRST A NOTE ON THE NWS WARNING STRATEGY FOR SANDY. IN ORDER TO
AVOID THE RISK OF A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO
NON-TROPICAL WARNINGS WHEN SANDY BECOMES POST-TROPICAL...THE WIND
HAZARD NORTH OF THE TROPICAL STORM WARNING AREA WILL CONTINUE TO BE
CONVEYED THROUGH HIGH WIND WATCHES AND WARNINGS WARNINGS ISSUED BY
LOCAL NATIONAL WEATHER SERVICE OFFICES.

SANDY CONTINUES TO MAINTAIN AN AREA OF DEEP CONVECTION NEAR THE
CENTER...WITH AN EYE OCCASIONALLY VISIBLE ON SATELLITE IMAGERY.
ALTHOUGH THE SATELLITE PRESENTATION OF THE SYSTEM IS NOT VERY
IMPRESSIVE...SFMR MEASUREMENTS...FLIGHT-LEVEL WINDS...AND DROPSONDE
DATA FROM THE AIR FORCE HURRICANE HUNTERS INDICATE THAT THE WINDS
HAVE INCREASED TO NEAR 75 KT. SINCE THE HURRICANE WILL TRAVERSE
THE GULF STREAM THIS MORNING...AND THE SHEAR IS NOT TOO STRONG AT
THIS TIME...SOME MORE STRENGTHENING AS A TROPICAL CYCLONE IS
POSSIBLE IN THE NEXT FEW HOURS. HOWEVER...THE MAIN MECHANISM
FOR INTENSIFICATION LATER TODAY SHOULD BE BAROCLINIC FORCING. THE
OFFICIAL WIND SPEED FORECAST IS CLOSE TO THE LATEST GFS PREDICTION
AS THAT MODEL SHOULD BE ABLE TO HANDLE THE EVOLUTION OF THIS TYPE
OF SYSTEM FAIRLY WELL.

THE CONVECTIVE STRUCTURE OF SANDY HAS DETERIORATED TODAY...EVEN AS
THE CENTRAL PRESSURE HAS CONTINUED TO SLOWLY FALL...SUGGESTING THAT
THE CONVECTION IS NO LONGER DRIVING THE BUS. THE INTENSIFICATION
OBSERVED THIS MORNING WAS ASSOCIATED WITH STRONG WINDS OCCURRING TO
THE SOUTHWEST OF THE CENTER...OUTSIDE OF THE CENTRAL CORE...AND WAS
ALMOST CERTAINLY DUE TO BAROCLINIC FORCING.

SATELLITE...RADAR...SURFACE...AND RECONNAISSANCE AIRCRAFT DATA
INDICATE THAT SANDY MADE LANDFALL NEAR ATLANTIC CITY NEW JERSEY
AROUND 0000 UTC. THE INTENSITY OF THE POST-TROPICAL CYCLONE WAS
ESTIMATED TO BE NEAR 80 KT AT LANDFALL WITH A MINIMUM PRESSURE OF
946 MB. AT LANDFALL...THE STRONGEST WINDS WERE OCCURRING OVER
WATER TO THE EAST AND SOUTHEAST OF THE CENTER. HURRICANE-FORCE
WINDS GUSTS HAVE BEEN REPORTED ACROSS LONG ISLAND AND THE NEW YORK
METROPOLITAN AREA THIS EVENING. IN ADDITION...A SIGNIFICANT STORM
SURGE HAS OCCURRED ALONG A LONG STRETCH OF THE MID-ATLANTIC AND
SOUTHERN NEW ENGLAND COAST.

2016 Hermine

Satellite imagery indicates that Hermine has become a post-tropical
cyclone, with the coldest convective tops now located more than 200
n mi northeast of the exposed center. Despite this change in
structure, surface data from the Outer Banks indicate that some
strong winds persist near the center, and the initial intensity is
set to 55 kt for this advisory. During the next 48 to 72 hours,
Hermine will interact with a strong mid-latitude shortwave trough
and all of the global models show the system re-intensifying during
that time and a redevelopment of a stronger inner core, albeit one
situated underneath an upper-level low. Regardless of its final
structure, Hermine is expected to remain a dangerous cyclone through
the 5 day period.

More like this

Atlantic Hurricane Gonzalo is a Major Hurricane, Category 3 at the moment, and it is heading towards Bermuda. The storm will weaken a little bit before getting there but it will still be major. This is a significant event. It is possible that a storm surge of about 10 feet could occur there.…
For the latest post on Hermine GO HERE. Update Thursday PM Hermine has grown in strength, and may even make landfall as a Category 2 storm. At least a strong Category 1. The right front quadrant of the storm is where the main "punch" (of winds) is located. If the storm winds come into an…
Update (Sunday PM): Hermine is still a big storm and will affect eastern regions to some degree, but the storm never reformed as a hurricane, and is not not expected to do so. Also, the storm has jinked out to the east more than expected and will likely move farther east. So, there will be some…
If you are in the path...the thousand mile wide path...of Hurricane Sandy, a.k.a. Frankenstorm, then you should make sure you know what the storm could do in relationship to where you are. If you are in or near an area with mountains, look for very serious flash flooding. The winds will be strong…

I came across work by Schmitz and Pujalte years ago, when started reading after I first learned (from some Spanish forestry scientists, on sci.environment I think) about planning ahead for managing wildland differently to take into account the changes coming with climate change.

The sudden change in rainfall that led to a large sedimentary outflow due to greatly increased inland erosion has worried me ever since.

One such paper:
https://www.researchgate.net/publication/240669718_Sea-level_humidity_a…
Sea-level, humidity, and land-erosion records across the initial Eocene thermal maximum from a continental-marine transect in northern Spain
Article in Geology 31(8) · August 2003 
DOI: 10.1130/G19527.1

Then someone pointed out that the currently dry southwest US also had huge erosion fans below most of the mountains, which hadn't carried water for centuries and which have been built up in the cheerful expectation that whatever caused all that sediment to flow out of the mountains can't happen again.

Rates of change .... if more intense precipitation is expected, what's to be done?

By Hank Roberts (not verified) on 03 Sep 2016 #permalink

Thinking how hurricanes are reported this is a classic if now relatively old proposal which actually makes a lot of sense :

https://www.youtube.com/watch?v=Xua78w7e4DA

(Starts @ the 20 second mark into the clip. With petition.)

Naming hurricanes after Climate Deniers? I reckon they sure should.

The NWS has changed its policy so that the National Hurricane Center continues to issue forecasts on post-tropical cyclones that are still a potential threat to land, such as Hermine. This change is intended to prevent much of the confusion from Sandy making its extratropical transition so close to landfall: many people in New Jersey and New York didn't get the warnings because the warnings were issued by a different NWS agency.

By Eric Lund (not verified) on 06 Sep 2016 #permalink

Naming hurricanes after Climate Deniers? I reckon they sure should.

Only the big ones, the ones that make landfall and do a lot of expensive damage. And kill people.

Such as: "Hurricane Katrina" would have been renamed "Hurricane Anthony Watts" as it made landfall. That sort of thing.

By Brainstorms (not verified) on 06 Sep 2016 #permalink