Meteorological perfection

INFRARED SATELLITE IMAGE - OCTOBER 30, 1991

Hard to believe it's been 20 years since the Perfect Storm. And, just as it represented a meteorological event unique up until that point in the historical record, there has been nothing like it since.

[UPDATE FRI AM: Though amazingly, on the 20th anniversary, even though it'll be of a different nature it looks like there's going to be another wild and highly unusual (for October) storm in the northeast U.S.!]

[ADDENDUM FRI NOV 4: For in-depth scientific analyses of the weather situation in late October and early November 1991, see these papers by Jason Cordeira and Lance Bosart of SUNY Albany, one on the development of the storms and one on the large-scale pattern associated with their formation, which includes not only the two I highlight in my blog, but also one over the northeast Atlantic near Europe.]

This is a repost and update of previous blogs I've written about the 1991 Perfect Storm.

Tropical cyclones have official numbers and names, but not other kinds of weather systems. Sometimes, though, one will be exceptional enough to come to be known informally by name, such as the "Blizzard of 1888" or 1962's "Ash Wednesday Storm" in the Mid-Atlantic and "Big Blow" in the Pacific Northwest.

Until today when TWC severe weather expert Dr. Greg Forbes and I unofficially categorized what happened in late April 2011 as a tornado "superoutbreak," there had only been one outbreak known as that, in April 1974. There still is only one storm that has gained acceptance as a "superstorm," in March 1993. And there is still only one known as the "Perfect Storm." There have been other contendas, but none ended up rivaling the atmospheric process which unfolded this final week of October in 1991.

For a while it was known as the "Halloween Storm" (even though it was past its peak by October 31), until Bob Case of the National Weather Service coined it "The Perfect Storm," and then came the book & movie which chronicled the plight of the Andrea Gail and escalated this weather event's legacy into popular culture.

Mr. Case was not engaging in hyperbole. This was a truly extraordinary confluence of atmospheric ingredients. Although other East Coast cyclones (e.g. hurricanes and snowstorms) have been "worse" in terms of severity of wind and precipitation, and overall impact to people and/or property, this one was unique in its evolution, and per these NCDC and NWS reports it was no slouch in its atmospheric and oceanic statistics either. And of course there were the tragedies at sea for which the storm is [in]famous.

For all of these reasons, the event is more well-known than many of those in recent decades which have made the official billion dollar disaster list (this one's cost was in the hundreds of millions of dollars).

This is a great sequence of satellite images showing the life cycle of the storm; this is an animation of the evolution at the surface and aloft.

And here are a meteorological analysis; a video clip of me on The Weather Channel during the Perfect Storm, showing a rare satellite loop of it; and a look at another lesser known but also whopper storm walloping North America at the same time.

IT ALL BEGAN ...

... on the 28th and 29th of October 1991 with a cold front and burgeoning non-tropical storm over the northwest Atlantic eating Hurricane Grace for breakfast. We'll never know exactly what the outcome would have been without Grace; the situation was already potent, but the hurricane did play a key role by providing extra moisture & energy and influencing the overall configuration of weather systems.

Meanwhile, there was also a strong high pressure system over eastern Canada to the northwest of the developing storm which helped develop a steep "pressure gradient" and long fetch of wind. This already caused waves to build, and it was during this phase that the Andrea Gail met its fate. (The exact time of the vessel's and its crew's loss is unknown but the final reported contact was on the 28th).

Ultimately the developing storm became quite a formidable one in strength and a behemoth in size, and it backed toward the U.S. coast rather than move away as most storms which are already at sea do.

The most significant impacts on land were felt in the northeast U.S. where damage was widespread, including, as you might recall, to then-President George H. W. Bush's house in Kennebunkport, Maine, but effects in the form of high waves were felt all the way from Newfoundland to Florida and Puerto Rico.

Although the storm was officially "extratropical" at its peak and it certainly did have non-tropical aspects, near its center the cyclone also had some characteristics of a tropical or at least subtropical cyclone.

It's not easy to find radar imagery of the Perfect Storm, but I have this screen shot from TWC's coverage, as the cyclone moved westward near southeast New England. Sure looks like an eyewall on the north side of the center, doesn't it? (The south "eyewall" may have been too far away from the radar to show up, or the rain might have not completely surrounded the center.)

After whacking the coast on October 30 -- its estimated lowest pressure of 972 millibars was that day and its closest approach to land was that night -- the storm rapidly wound down on Halloween itself.

However, in a bizarre (yet fitting) final chapter ...

Within the weakening larger overall circulation, a small circulation (see below) that was decidedly "warm-core," indicative of a tropical cyclone, spun up on November 1 and became an unnamed hurricane!

Thus, the "unnamed hurricane" wasn't The Perfect Storm per se, but it was a component of the evolution of the system, one which ironically did not produce the significant damage.

[Click on image for close-up of the unnamed hurricane.]

VISIBLE SATELLITE IMAGE - NOVEMBER 1, 1991

The hurricane was not named because it was feared that would confuse people. Given how bad the original storm was, there was the potential for undue alarm if residents along the coast heard a hurricane with a traditional "name" had now developed. But ironically the hurricane was so tiny that it was relatively harmless, especially given that it was heading away from the U.S. coast, not toward it like the parent storm a couple days prior. Landfall was eventually made, but as a rapidly waning tropical storm in Nova Scotia on November 2 with little impact.

A non-tropical system absorbing a tropical one is not unprecedented, nor is a tropical cyclone developing from a non-tropical system. But for both processes to occur with the same system, not to mention one of this magnitude, is what made the cyclone so amazing. In fact, Grace even started as a subtropical storm. This weather system was an ultimate hybrid!

MEMORIES ...

I have vivid memories of that whole situation as it unfolded. I had been at The Weather Channel for only a couple of years, and was in the midst of a few days off. Upon briefly stopping by the office to attend a meeting, my colleague Tony Fulkerson, who was working the shift on the other side of the week, popped his head in the room and said, "Stu, have you looked at the weather situation?"

Upon doing so shortly thereafter, I thought, "Oh, my!"

Next thing I knew, I found myself on the air the following evening, with Jeff Morrow, whom I've known for -- gasp! we're not as young as we once were! -- 35 years now since our first math class together in our freshman year in college.

This was the second weather event during which I made cameo on-camera appearances. The first was Hurricane Bob a couple months prior. The next ones after The Perfect Storm included Hurricane Andrew and the severe nor'easter in December 1992, then the Superstorm in March 1993 [video clip of that is here]. Ahh, those were the days ...

And, as much as it makes me wince to go back and look (for example, my not-ready-for-primetime eyeglasses!), here is a video of one of my Perfect Storm segments.

I can't definitively lay claim to that being the first time water vapor imagery was ever shown on television because I don't know for sure what else might have taken place before that, but at least to the best of my knowledge it was the first time on TWC and elsewhere. In any event, I couldn't resist displaying and talking about that water vapor loop, as it seemed if ever there was a time to spring it on the masses, this was it -- what a sight! And now that clip is the only easily accessible satellite loop that I know of which shows the development of the storm including the ingestion of Grace.

THE OTHER STORM

Not having received the worldwide notoriety that its cousin to the east did but remembered vividly by those who were in Minnesota and thereabouts at the time was another extreme storm concurrent with the latter part of the Perfect Storm.

Portions of the Upper Midwest were being affected by another powerful cyclone and an unusually cold arctic outbreak for so early in the season, the combination of which resulted in a record early-season snowstorm. It was dubbed by some the "Great Halloween Megastorm" and set the record for the largest single-storm snowfall (28.4") in Minneapolis history for any month of the year! Likewise, the 37.9" snowfall in Duluth was the largest on record at that time for the state of Minnesota, beating any storm in the middle of winter. (It was exceeded in January 1994.) On the southern fringe of the wintry precipitation was a severe ice storm in Iowa.

And the two atmospheric explosions were connected, as can be seen by the pattern aloft (first map below), in an exceptionally "high-amplitude" pattern: a big-time trough over all of western North America with a strong disturbance about to swing from the southwest U.S. toward the Great Lakes, which led to the intense cyclone centered near Lake Superior a few days later (second map below, and note the relatively benign unnamed tropical storm in Nova Scotia); a mammoth cutoff low in the western Atlantic, associated with the Perfect Storm which was blocked from a rapid exit out to sea; and a ridge in between waaay up across eastern Canada.

If you remember either one of these storms, submit a comment!

View the original article here

Meteorological images of 2011

Previous editions:
2006
2007
2008
2009
2010

So I guess that makes this the 6th annual!

As I've noted in the introduction the past few years, the content is not meant to represent a complete list of every significant weather event everywhere or images thereof, but there's a lot of stuff which will bring back memories.

This time, in addition to the blog entry, I've also put a selection of a dozen other images into a slide show on weather.com.

In 2011 there were photographs that were so dramatic and widely seen, such as of cars stranded on Lake Shore Drive in Chicago in the February blizzard, and the haboob in Phoenix in July, and the devastation and tragedies caused by the tornadoes and hurricanes and wildfires and drought (and tsunami/earthquakes), and that have been part of other year-in-review features, that I'm not including any photographs here, other than a couple not-so-noteworthy, low-resolution ones that I took myself with a cellphone camera. Instead, I'm going to focus mainly on meteorological imagery and charts; thus this year's title instead of "weather images."

There were plenty of them, as what a year it was. A record number of billion-dollar disasters in the United States, and a lot of meteorological extremes contributing to that. Let's hope for a much less dramatic 2012!

====================

Okay, so I took a photo of a snowy motel parking lot in January. What's the big deal? Well, it not only had personal significance (a harrowing drive to get there that night, and that was to be able to be within walking distance of TWC the following morning), but that relatively little bit of snow compared to what areas farther north experienced last winter was enough to essentially shut down the whole metro Atlanta area for days.

Stu Ostro

Like has been the case so many other times in recent years with precipitation and temperature extremes, the key to the colossal storm in early February which brought a severe blizzard to Chicago was a strong ridge of high pressure aloft (red/orange/yellow shades on the map below, which technically represent above average "500 millibar heights").

NOAA

At the same time of that storm, on the other side of the world was Severe Tropical Cyclone Yasi. In the slide show, I included the image of the "E" in the eye. Here I'm adding another freaky feature in a tropical cyclone eye that it was reminiscent of, a "2" in Hurricane Wilma in 2005.

Naval Research Laboratory; NOAA

Vortices over the Great Lakes in lake-effect snowbands are not rare; TWC severe weather expert Dr. Greg Forbes blogged about them a few years ago and authored a scientific paper on them nearly 30 years ago. However, this, approximately a week after the Groundhog Day blizzard, was a particularly vivid example and included a combo of two.

Gibson Ridge / GRLevel2

A very cold low pressure system aloft, represented by the bright colors on this map depicting temperatures a few miles up, brought snow to parts of the Tucson area in late February after doing so to the higher elevations of San Francisco.

wright-weather.com

This is not meteorological, but it has something in common with weather, as both earthquakes and wind produce waves which can be destructive. This image, which looks like a gigantic bloodshot eyeball, represents a computer model simulation of tsunami waves that were catastrophic in Japan and propagated to other locations all the way across the Pacific.

NOAA

On April 4, a potent weather system brought an astonishing number of severe weather reports (most of them straight-line wind damage). That was a bad omen for the rest of that month ...

NOAA

The next day that system ran out of steam, but as a squall line came through the Miami metro area, a webcam operated by Bryan Norcross, hurricane specialist at TWC, captured this:

Bryan Norcross

A few days later, atmospheric instability represented in the fiery model forecast image below surged way up into Wisconsin, fueling a record-setting tornado outbreak there.

WSI

This was a classic dryline-triggered eruption of thunderstorms that produced tornadoes, including a deadly one in Tushka, Oklahoma the evening of April 14. There were additional casualties in Arkansas as the system moved east overnight.

NASA/GSFC, MODIS Rapid Response (satellite); Gibson Ridge / GRLevel2 (radar)

Then a very energetic stream of wind aloft associated with that system sliced east a couple days later and led to the largest North Carolina tornado outbreak on record.

wright-weather.com

The following Friday, on a flight from Atlanta to Oklahoma City, I observed the atmospheric "cap" breaking. A few hours later a tornado hit Lambert-St. Louis International Airport.

Stu Ostro

The cap broke again on April 27. Dry air aloft as shown in the "water vapor" image on the left can, along with relatively warm air upstairs, put a lid on thunderstorm development. If the lid holds, that's good news. But the energy can build to the point that it explodes sky-high if it can break through the cap/lid. Not only did that happen as shown in the image on the right side, but there was a textbook and extreme set of other ingredients. The outcome: a tornado superoutbreak.

UCAR

I was so stunned to see this extraordinary number and concentration of supercells, many of which had "ground truth" of tornadoes, not just a radar indication of rotation aloft, that I suggested to Dr. Forbes that we should go with a "TOR:CON" index of 10 in northern Alabama, meaning a 100% chance of a tornado within a given spot, and he agreed.

Gibson Ridge / GRLevel2

The Weather Channel

A particularly vivid "debris ball" signature on radar, between Tuscaloosa and Birmingham. Yes, that's not precipitation, it's debris blown by the tornado.

Gibson Ridge / GRLevel2

A swirl of a tropical cyclone wannabe makes landfall on the Mexico coast. What's remarkable about this is that the spin originated from a thunderstorm complex in the Great Lakes during Memorial Day weekend, swung out over the Atlantic Ocean, and then ended up here on the west coast of the Gulf of Mexico a week later!

NASA/GSFC, MODIS Rapid Response

A few days after that, a smoke plume from an Arizona wildfire inferno gets blown by strong winds at sunset.

WeatherTAP (all WeatherTap images used with permission)

Quite a bow echo on radar, and this one was interesting in the way it was moving due north (in southeastern South Dakota).

Gibson Ridge / GRLevel2

During the peak of the summer heat, a meteorological milestone was reached: the big six-oh-oh. 600 decameters is a benchmark value for "500 millibar heights," representative of an extremely strong ridge of high pressure aloft, and the measurement above Omaha the evening of July 17 was close to being a record for that part of the country. The colorful image shows a model forecast for the ridge a few days in advance, and the verification of 600 decameters (6000 meters) was even a bit higher than what was predicted.

wright-weather.com (color map); NOAA via Colorado State University archive (B&W inset)

A few days later, on the northern periphery of the heat ridge, a particularly interesting thunderstorm outflow boundary signature on radar in Minnesota, extending like a long tail well away from the storm cell.

Gibson Ridge / GRLevel2

Tropical Storm Don and its convection croak remarkably rapidly between mid-afternoon and midnight upon arrival in extreme south Texas. Our luck would run out later in the 2011 Atlantic hurricane season ...

Naval Research Laboratory

Although Irene's inner core weakened, sparing places such as the Jersey Shore and New York City from the kind of wind and surge that otherwise would have been experienced, strong upper-level outflow to the northeast helped maintain Irene's low central pressure and overall strength, and that and the cyclone's massive size resulted in widespread wind damage and power outages from North Carolina to New England and contributed to the amount of rainfall which fell.

NOAA

Lee soon followed, and took on an odd appearance on water vapor satellite imagery along the Gulf Coast as dry air wrapped all the way in around the center but then moisture swirled in too.

NOAA

At one point Lee very closely resembled Cindy when it was in a similar position, and both went on to be prolific tornado producers.

Naval Research Laboratory

Lee's remnants and tropical moisture flowed north, and unleashed torrents of rain in the northeastern U.S., much of it occurring in association with long north-south bands of "training," in which individual showers and thunderstorms keep going over the same spot like railroad cars on train tracks. This band persisted all night.

Gibson Ridge / GRLevel2

A map of two-week rainfall which includes what fell from Irene and Lee.

NOAA

In the slide show, I featured a striking satellite image of a swirling "cutoff low," so named because they are completely cut off from the main jet stream. This one persisted in nearly the same place for many days.

NOAA via CSU

And here's another wild-looking water vapor satellite image of it along with another large swirl over the Atlantic Ocean.

WeatherTap

Within an overall large "pressure gradient" and wind field south of a high pressure system in early October, a low pressure system spun up rapidly just offshore of the east coast of central Florida and took on characteristics of a tropical storm.

Gibson Ridge / GRLevel2

That system was part of a repetitive pattern in October that featured low pressure and moisture from the western Caribbean to the subtropical Atlantic, during which, on October 18, there was this cluster of thunderstorms near the Keys, and three days later an exceptionally sharp contrast between dry and moist air aloft.

Both images above: Cooperative Institute for Meteorological Satellite Studies (CIMSS)

A critical factor in causing "Snowtober" to have the impact it did in the Northeast was so much heavy wet snow falling so early in the season, onto trees which still had leaves. Meteorologically the ingredients which came together were just enough cold air from the north meeting up with lots of tropical moisture surging up from the south, all the way from the Caribbean ...

NOAA

... and the interaction of those along with jet stream energy led to a meteorological "bomb," in which there's a drop of at least 24 millibars in 24 hours of central pressure of a cyclone. As this one passed over a buoy east of New England and south of Nova Scotia, the barometer measurement plummeted.

NOAA

Satellite imagery showing the transformation of a disorganized mass of clouds into the cyclonic bomb.

NASA Earth Science Office

This is a common sight in western Oklahoma in spring, not so common in November. This supercell on November 7 produced an EF4 tornado near Tipton, the first tornado on record to get such a high rating in Oklahoma in November.

Gibson Ridge / GRLevel2

At the same time, what was described by the National Weather Service in Alaska as the strongest storm to reach the Bering Sea so far north since 1974 was developing, and during the night of November 8 it resembled a giant ? on satellite imagery.

NOAA

A high-resolution shot of the cyclone's core.

NASA/GSFC, MODIS Rapid Response

Look at the whirlpool that formed in the storm surge in Nome!

KNOM Radio Mission, photographer Matthew Smith; embedded with permission; full-sized image is here

A long nose of cold air dips down at the end of November ...

wright-weather.com

.. as another cutoff low develops, the result being up to 8" of snow reported in Arkansas to the northwest of Memphis, unusually so far south for so early in the season. That November event and Snowtober are quite ironic given the lack of snow in the central and eastern U.S. since then.

UCAR

Yet another cutoff develops, this one with quite a wind flow aloft ...

wright-weather.com

... as well as an exceptionally large (both in magnitude and geographical extent) pressure gradient at the surface, the upshot being a western windstorm which is not only no ordinary Santa Ana, with its effects so widespread in SoCal, but extreme wind gusts occur in spots all the way from there to Steamboat Springs, Colorado.

NOAA

A storm headed for Europe taps moisture from the tropics, resembling a Pacific "Pineapple Express," in this case over the Atlantic ...

NOAA

... but precipitation is not the main impact of this quickly-moving storm, it's wind. A "low-level jet" upwards of 100 mph a few thousand feet up sweeps into France and thereabouts on December 16, with powerful wind gusts blasting down to the Earth's surface.

Plymouth State University Weather Center

Much of the rest of the country was wondering in December, "Where's winter?" Well, it was certainly present in New Mexico. Surreal desolation on a closed I-40 at night was captured by this traffic webcam.

advanced.nmroads.com

What a difference a year makes for what percentage of the country experienced a white Christmas, and where.

NOAA

The turnaround from the past two winters to this one so far was primarily due to the opposite extremity of phenomena known as the AO (Artic Oscillation, shown in this set of graphs) and NAO (North Atlantic Oscillation).

NOAA

That manifested itself in a flip from anomalously strong and persistent ridges of high pressure over and near Greenland during late November and December 2010 (top map) with low pressure aloft to the south, to the reverse in late 2011. The former, an extreme "blocking pattern," led to major snowstorms and persistent cold weather in the central and eastern U.S. and in Europe.

NOAA

Something which is likely a factor contributing to the atmospheric extremity in/near the Arctic in recent years is the precipitous drop in the amount of sea ice there. The black line on this graph plots the volume, which takes into account both the area and thickness of the ice, at the time of the annual minimum each September.

The colored lines represent different mathematical slopes, and what each would do in the future if it were to follow the respective rates of decrease. Although representing different methods and phenomena compared to computer model forecasts of hurricane tracks, this range of projected potential outcomes could be thought of as analogous to the "spaghetti model" plots that have become commonly used.

Hopefully over the coming years and decades the rate of decline showed by the black line will slow down and follow a path toward zero (no ice left in late summer) more like the purple line than the green one. But the recent and current rate is troubling, given the important role that the Arctic and its ice play in the Earth's climate system, and given that this is happening faster than the climate models predicted.

Source and full-sized image: https://sites.google.com/site/arctischepinguin/home/piomas/

On the final day of 2011, Tropical Cyclone Benilde looked scary, but was safely out at sea in the southern Indian Ocean.

Naval Research Laboratory

IMAGES OF THE YEAR

These are my choices for images that were most memorable (other than the indelible photographic ones noted in the introduction) -- not the images themselves, which are simply screen captures of The Weather Channel broadcast and are small in size and not of particularly high resolution, but what they represent in terms of what happened meteorologically and the effects upon those in the storms' paths. In each case it was hard to believe what I was seeing.

Thundersnow experienced live on television by Jim Cantore in Pennsylvania in October?? Yep.

Is that whole seething black mass of cloud extending to the ground a gigantic rotating tornado, live on TV?? Yes, the power flash (bright spot) indicated that it was.

And did a supercell thunderstorm actually spew out debris -- which Jeff Morrow is holding (pieces of shingles and plexiglass) after it fell from the sky -- many miles away from the tornado??

Yes, it did.

Mike Bettes was overcome with emotion upon arriving on the scene in Joplin moments after the EF5 tornado hit.

This high a death toll from a single tornado (and from the April 2011 superoutbreak and other events last year), in the 21st century?? Yes, just as Katrina and the 2004-05 hurricane seasons could be thought of as a wake-up call for our vulnerability to weather even with today's modern forecasting and communication technology, so can 2011 with its tornadoes.

View the original article here