Extraordinary storm, extremely serious threat
A special edition of the trosum (tropical summary) ...
Image credit: NOAA
- History is being written as an extreme weather event continues to unfold, one which will occupy a place in the annals of weather history as one of the most extraordinary to have affected the United States.
- REGARDLESS OF WHAT THE OFFICIAL DESIGNATION IS NOW OR AT/AFTER LANDFALL -- HURRICANE (INCLUDING IF "ONLY" A CATEGORY ONE), TROPICAL STORM, POST-TROPICAL, EXTRATROPICAL, WHATEVER -- OR WHAT TYPE OF WARNINGS ARE ISSUED BY THE NATIONAL WEATHER SERVICE AND NATIONAL HURRICANE CENTER -- PEOPLE IN THE PATH OF THIS STORM NEED TO HEED THE THREAT IT POSES WITH UTMOST URGENCY.
- TAKE COASTAL FLOODING EVACUATION ORDERS SERIOUSLY; PREPARE FOR DOWNED TREES AND STRUCTURAL DAMAGE BY OBSERVING TORNADO SAFETY GUIDELINES, I.E. STAYING INSIDE AND GETTING INTO THE LOWEST, MOST-INTERIOR PORTION OF THE BUILDING OR ANOTHER DESIGNATED SAFE PLACE; BE KEENLY AWARE OF YOUR LOCATION'S SUSCEPTIBILITY TO FLASH FLOODING (URBAN AND SMALL STREAM) FROM RAINFALL AND RIVER RISES; KNOW THAT YOU COULD BE WITHOUT POWER FOR A LONG TIME BUT ALSO UNDERSTAND THE DANGERS OF CARBON MONOXIDE POISONING FROM IMPROPER USE OF GENERATORS.
- With Sandy having already brought severe impacts to the Caribbean Islands and a portion of the Bahamas, and severe erosion to some beaches on the east coast of Florida, it is now poised to strike the northeast United States with a combination of track, size, structure and strength that is unprecedented in the known historical record there.
- Already, there are ominous signs: trees down in eastern North Carolina, the first of countless that will be blown over or uprooted along the storm's path; and coastal flooding in Florida, North Carolina and Virginia, these impacts occurring despite the center of circulation being so far offshore, an indication of Sandy's exceptional size and potency.
- A meteorologically mind-boggling combination of ingredients is coming together: one of the largest expanses of tropical storm (gale) force winds on record with a tropical or subtropical cyclone in the Atlantic or for that matter anywhere else in the world; a track of the center making a sharp left turn in direction of movement toward New Jersey in a way that is unprecedented in the historical database, as it gets blocked from moving out to sea by a pattern that includes an exceptionally strong ridge of high pressure aloft near Greenland; a "warm-core" tropical cyclone embedded within a larger, nor'easter-like circulation; and eventually tropical moisture and arctic air combining to produce heavy snow in interior high elevations. This is an extraordinary situation, and I am not prone to hyperbole.
- That gigantic size is a crucially important aspect of this storm. The massive breadth of its strong winds will produce a much wider scope of impacts than if it were a tiny system, and some of them will extend very far inland. A cyclone with the same maximum sustained velocities (borderline tropical storm / hurricane) but with a very small diameter of tropical storm / gale force winds would not present nearly the same level of threat or expected effects. Unfortunately, that's not the case. This one's size, threat, and expected impacts are immense.
- Those continue to be: very powerful, gusty winds with widespread tree damage and an extreme amount and duration of power outages; major coastal flooding from storm surge along with large battering waves on top of that and severe beach erosion; flooding from heavy rainfall; and heavy snow accumulations in the central Appalachians.
- Sandy is so large that there is even a tropical storm warning in effect in Bermuda, and the Bermuda Weather Service is forecasting wave heights outside the reef as high as 30'.
- There is a serious danger to mariners from a humongous area of high seas which in some areas will include waves of colossal height. Wave forecast models are predicting significant wave heights up to 50+ feet, and that is the average of the top 1/3, meaning that there will be individual waves that are even higher. The Perfect Storm, originally known as the Halloween Storm because of the time of year when it occurred, peaking in 1991 on the same dates (October 28-30) as Sandy, became a part of popular culture because of the tragedy at sea. This one has some of the same meteorological characteristics and ingredients coming together, but in an even more extreme way, and slamming more directly onshore and then much farther inland and thus having a far greater scope and variety of impacts.
- On the other side of the world, after bringing to the Philippines its own share of severe impacts, Typhoon Son-tinh is headed into northern Vietnam and then the nearby part of China.
A high-amplitude, high-energy, highly interesting pattern
[Have added an update at the end with info on Tropical Storm Sandy.]
There’s not been anything (at least not yet!) of the extremity of what I wrote about in a recent blog entry describing October’s meteorological split personality, but in 2012 the month is again showing its wild side!
This past week, a deep, large, strong trough over the central-eastern U.S. was reminiscent of the one which begat the April 2011 tornado superoutbreak.
The maps below show 500 millibar heights and wind speeds on April 27, 2011 (top) and October 18, 2012 (bottom):
Image credit: Plymouth State University.
Fortunately this time the atmosphere wasn’t nearly as hot, moist and unstable – on 4/27/2011 temperatures in Alabama were as high as 91 with a dewpoint of 70 – but even so, tornadoes of rare intensity for Mississippi in October were spawned.
Base reflectivity and velocity radar images of the Conehatta, Mississippi EF3 tornado early in the morning of Thursday, October 18, 2012. Image credit: Gibson Ridge
And here on a satellite image from Friday is something you don’t see every day: a cloud of dust which got kicked up by powerful winds in the Plains blowing over extremely dry soil and carried all the way almost to Atlanta!
Image credit: NASA/GSFC MODIS Rapid Response
Now, this coming week, a vivid signal is showing up in model forecasts for the pattern aloft: strong ridging (indicated by the band of bright red colors on the map below) all the way from west of Alaska to east of Greenland.
ECMWF model ensemble mean 500 millibar heights and departures from average for this coming Wednesday. Image credit: Allan Huffman's Model and Weather Data Page
South of that, the remnant of Rafael, which combined with a system from the Labrador Sea, is being forced south back toward the Azores, and it looks like what’s left of it will head into Portugal and then maybe bring stormy weather eastward across southern Europe.
In the U.S., a deep trough is setting up over the West with inclement weather there, and models indicating it will progress to the central and eastern U.S. by next weekend, with a big temperature swing from balmy to chilly.
And over the Caribbean is Invest 99L, almost certain to become a tropical depression and likely then Sandy.
Exactly where it ultimately goes as it heads north into the Atlantic later this week will depend on how it interacts with that trough expected to be over the Southeast and the ridge out ahead of it. Most model forecasts have portrayed just a brush of Florida and then staying out at sea, though recent runs of one model (the GFS) have shown it eventually hooking back to New England or the Mid-Atlantic. While that looks goofy, patterns such as this can sometimes lead to goofy outcomes. [Update mid-afternoon Sunday: Now the ECMWF model shows it doing that even more sharply and quickly.]
Regardless of that or how strong 99L gets wind-wise, it poses a serious threat of heavy rain, flash flooding and mudslides in the Greater Antilles.
GFS model forecast of precipitable water amounts for this coming Wednesday, showing deep tropical moisture flowing squarely into the Greater Antilles. Image credit: Wright-Weather
UPDATE MONDAY EVENING OCTOBER 22
The low pressure system in the Caribbean formed on schedule and is just insulated enough from atmospheric conditions not far to the northwest which are hostile to it (wind shear, dry air), that it quickly organized and was upgraded from Invest 99L to Tropical Depression Eighteen and then Tropical Storm Sandy, and it is expected to further strengthen. No matter how much the winds are able to increase, the serious rainfall threat noted in the original entry above continues to be present.
As the storm heads north, models are consistent in predicting it to get energy from the jet stream and remain solid rather than getting sheared by those strong upper-level winds and falling apart, suggesting that it becomes somewhat of a hybrid with some characteristics of a non-tropical cyclone while retaining at least some of its tropical nature.
Models have shown critical and at times extreme differences in their track forecasts, however. Some runs have depicted a wild scenario with the storm getting sucked up into the mid-Atlantic and northeast U.S. and producing everything from torrential rain, strong winds, and coastal flooding/erosion to heavy interior high-elevation snow. That has created a buzz; it's important to both take such a threat seriously, while not overreacting to particular model runs and prematurely making pronouncements. Other model runs have swerved it far out to sea. Most recently, there is less model guidance that portrays the worst-case scenario; it's still too early to declare a verdict, as subtle differences in the atmospheric jigsaw puzzle upstream/downstream can mean the difference in outcomes between a historic weather event and a near-miss. There's plenty of time for advance warning and preparation if necessary.
Tropical Storm Sandy. Image credit: UW-Madison SSEC/CIMSS
Updated: 2:36 AM GMT on October 23, 2012
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October's Wild Side
October has a split personality. On one side is its reputation of being an exceptionally quiet month weatherwise, but when I hear that, I wince! I understand why it is thought of in that way, as when October is quiet, it can be really quiet, when there are no late season tropical cyclone landfalls or early season snowstorms and the atmosphere is not as unstable as in spring for severe convection.
But October also has a wild side! When the weather in this month is wild, it can be really wild, in fact some of the wildest weather events in U.S. history have occurred during October.
One of those occurred 50 years ago, on Columbus Day 1962. Here is more on that storm as well as a selection of other extreme ones in Octobers past.
THE BIG BLOW
The definitive meteorological analyses on this storm are this one from Wolf Read’s fantastic website on Pacific Northwest storms, and this Monthly Weather Review paper by Lynott and Cramer.
About that storm log above included in his analysis on his site -- note the inscription in larger letters in the middle of it -- Wolf writes, "This is the only time in the history of the Pacific Northwest that an officially supervised weather station had to be abandoned due to high winds."
And here’s Wolf’s summary graphic:
THE PERFECT STORM
One of the most unusual storms on the opposite coast of the country also occurred in October.
Who’s that dude in this video (from which is the screen capture below) with the not-ready-for-primetime eyeglasses?
I posted a full analysis of what was originally known as the Halloween Storm a few years ago on weather.com.
Another one of the wildest East Coast weather events in recorded history occurred in October: Hurricane Hazel in 1954, which remarkably so late in the season set the record for the farthest-north Category 4 U.S. landfall, near the SC/NC border.
Not only did Hazel cause coastal devastation where it made landfall, it produced extreme wind gusts up across the Mid-Atlantic/Northeast urban corridor and then tragic flash flooding in Toronto.
Image credit: NOAA, Paul Kocin
WINDSOR LOCKS TORNADO
Another October extremity in the Northeast involved a tornado. F/EF4s are uncommon in October anywhere, much less in Connecticut, but in 1979 one hit Windsor Locks.
The type of radar map that existed in 1979, shortly before the time of the tornado, from an in-depth analysis of the meteorological situation by Riley and Bosart.
(That was the name given by the Buffalo office of the National Weather Service, which has been naming weather events long before The Weather Channel!)
Another extreme convective event, this one involving snow!
Very cold air aloft in October 2006 associated with an exceptionally big and intense mid-upper level low (map below shows departure from average 500 millibar heights), occurring so early in the season on top of warm water, produced a lake-effect snow blitz which was extraordinary even by Buffalo standards. At the time, Tom Niziol, now TWC's winter weather expert, was meteorologist-in-charge of the Buffalo office of the National Weather Service.
From the NWS analysis:
"Words cannot do justice to the astounding event which opened the 2006-07 season. Not only was it the earliest named event by far (two weeks) of the over 120 in the 13 year record of our lake effect archive, but it was the most unique in regards to destruction of trees and power outages, directly because of its out of season factor. Almost a million residents of the Niagara Frontier lost power, some for as long as a week, and tree damage was the worst in memory, especially to the lush vegetation in the many historic parkways and parks in the Buffalo area."
Another exceptionally early snowstorm in the Northeast in which huge amounts of heavy wet snow fell on still-leaved trees.
The cyclone last year which produced it was also a meteorological bomb, the criterion being the central pressure dropping at least 24 millibars in 24 hours. Here's how that process looked on satellite imagery:
Image credit: NASA Earth Science Office
And, speaking of weather bombs, TWC on-camera meteorologist Mike Seidel dropped one on me a couple of years ago when I was at dinner in Moab, Utah, where I was hiking. He called me on my cellphone and said, "Have you seen what the models are showing?"
"No," I responded. "Do I want to know? I’m in Utah trying to get away from everything!"
Of course, being the weather geek I am, I couldn’t help but at least briefly look at what the models were forecasting. I was able to not further engage much with it, but then, upon departing a couple of days later and after a flight cancellation from Grand Junction which led to a 3-leg, all-night journey back to Atlanta via SLC and LAX, and wanting to just go home and sleep, I instead went into TWC and encountered this (about which shortly thereafter I posted a blog on weather.com with commentary on the event and the title, "Historic hype. Historic storm?") …
October 26, 2010 surface pressure chart from an in-depth analysis by the NWS in Duluth of the cyclone bomb and its record-setting pressures
Updated: 3:31 PM GMT on October 13, 2012
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Trosum (tropical summary) -- Wednesday October 10, 2012
Been a while since I have posted anything -- was traveling in the weather (flying, and drove through a healthy MCS) and also for a while was under the weather -- but hope to start blogging more regularly. Also, there hasn't been as much to talk about in the tropics, but there's a lotta stuff going on at the moment (I've bolded in the entry below the elements most interesting to me), so I thought I'd post this version of the weather.com trosum.
[Source of all images in this entry is NOAA]
- There have been a number of tropical cyclones and wannabes with interesting and/or long histories this season, including Debby, whose potential for development models predicted weeks in advance, and whose track forecast entailed extreme differences between models; Isaac, whose remnants circled all the way back to the Gulf Coast and tried to redevelop; Nadine, which was one of the longest-lived tropical storms on record; and now Invest 97L.
- 97L's spin and moisture can be traced all the way back to the disturbance in the Caribbean which brought flash flooding to Jamaica at the end of September. It got sucked up to the north ahead of the system that produced flash flooding in Midland, Texas, to a position just off the Delmarva coast, then rotated clockwise around a ridge of high pressure to near the Bahamas, when it started trying to take on characteristics of a tropical cyclone.
- A part of it got strung out (and this system wasn't officially still designated as Invest 97L after yesterday morning until it was again this afternoon), but a portion continues to be quite resilient. In fact, it arguably has enough characteristics of a tropical cyclone to be designated as one. It'd be interesting to see what aircraft recon would find if there was one investigating. The only thing missing is that there are have been multiple centers of circulation at multiple levels, though the most recent satellite imagery suggests that even they seem to be consolidating.
- Strong upper-level winds, hostile to tropical cyclone development, continue to be strong just to the northwest, but are lighter overhead, which has enabled its survival, and given this system's resiliency, it is likely to hang on into tomorrow. Then models are suggesting a scenario in which the upper-level winds will become stronger across the whole system, finally discombobulating it Friday and Saturday, its top getting blown to the northeast while its lower portion detaches to the southwest toward Cuba. And in the meantime, its rain and wind are offshore, with its history and today's goings-on being a meteorological curiosity rather than this being a system which is having a significant impact.
- Invest 98L still does not possess enough organization to be close to tropical depression status, but it still has many days left to continue to try. As Dr. Masters noted in his blog today, the most likely time for that to happen is late in the weekend or early next week just north of the Caribbean islands. Regardless of the extent to which 98L takes on more characteristics of a tropical cyclone, as we head toward and into the weekend it'll bring gusty showers to the Leeward Islands. Looking ahead to next week, models have been consistent in showing a steering flow pattern that'll turn the system to the north and northeast, and keep it away from the U.S.
- A disorganized area of thunderstorms extending west from Central America within the "monsoon trough" of low pressure has been designated Invest 97E. Slow development into a tropical cyclone is possible as the system moves farther out to sea.
- Typhoon Prapiroon is drifting slowly, in an area of the ocean far from the Philippines, Okinawa and Iwo To (Iwo Jima), and is not in a hurry to travel very far anytime soon. In the longer range, i.e. early next week, Prapiroon is likely to accelerate toward the north and northeast, the question being whether it reaches or stays east of Japan.
- As indicated by the model forecast below for Sunday afternoon which shows a green plume of high "precipitable water," some of the typhoon's moisture will get carried by winds aloft all the way to the Pacific Northwest of the United States and contribute to heavy rainfall that will be ending the dry pattern there.
BAY OF BENGAL
- An area of convection and spin -- associated with the remnants of Tropical Storm Gaemi, which made landfall in Vietnam a few days ago -- moved off the coast of Myanmar and entered the Bay of Bengal from the east, regenerated into Invest 94B (and arguably is a tropical cyclone), and is now making landfall on the coast of Bangladesh with heavy rain and onshore winds which are likely near tropical storm force.
Updated: 8:37 PM GMT on October 10, 2012
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