Dr. Jeff Masters' WunderBlog

Blizzicanes

Posted by: Dr. Jeff Masters, 3:24 PM GMT on February 14, 2006

Did the Blizzard of 2006 have hurricane-like characteristics? Yes, it did. To explore this more fully, let's look at the two basic types of large scale (synoptic-scale) storms that meteorologists define:

1) Tropical cyclones (hurricanes), which have a warm core, and derive their energy from the latent heat of condensation. When water vapor condenses into rain, the phase change from gas to liquid liberates some extra heat energy--the latent heat--that was used to evaporate the water in the first place. Since maximum evaporation in the atmosphere occurs over the warmest ocean waters, tropical cyclones thrive in the late summer when ocean temperatures are at their peak.

2) Extratropical cyclones (mid-latitude cyclones), which have a cold core, and derive their energy from the potential energy released when cold air aloft sinks and is replaced by warmer, less dense air. Extratropical cyclones develop where two air masses of sharply different densities (and thus, temperatures) intersect. Extratropical cyclones exist only outside of the tropics (thus are "extra"-tropical), where there is some cold air to be found. The ordinary low pressure systems that bring rain and snow to residents of the mid-latitudes are examples of extratropical cyclones.

In recent years, meteorologists have begun to discover that many extratropical cyclones--including Nor'easters, which are strong wintertime extratropical cyclones that affect the Northeast U.S.--can make a partial transition to a warm-core system once they move out over the warm waters of the Gulf Stream. Like a hurricane, deep convection will appear near the center of the storm, and the hybrid system will begin to draw energy from the latent heat of condensation. These storms can "bomb" and deepen at rates of 10 mb/hour, and reach central pressures normally associated only with major hurricanes.

Figure 1. The Blizzard of 2006, visible satellite image from NOAA for Sunday February 12 2006. Note the eye-like feature south of Rhode Island. The "eye" was near the edge of the Gulf Stream, where water temperatures increased sharply from 6 degrees to 12 degrees C.

According to Louis Uccellini and Mel Shapiro, extratropical cyclone experts with NOAA, these storms may be undergoing a "seclusion" process that creates an semi-isolated tropical system in the midst of an extratropical cyclone. In the seclusion process, a strong extratropical cyclone draws in warm air from the south, and latent heat of condensation from the cyclone's intense precipitation makes this air even warmer. This extra-warm air spirals into the center of the low and wraps around to the west side, where it is pinched off. As result, one has an isolated "warm core" center where deep convection builds and spiral banding can occur. However, unlike a hurricane, there is no eyewall, and no cloud-free eye created by sinking air (subsidence) in the center. The eye-like feature in an extratropical cyclone has upward moving air, and is merely the center where the surface winds spiral into. Spiral bands of convection can develop in the warm air near the center, mimicking the spiral bands of a hurricane. If these convective bands become intense, subsiding air on the flanks of the bands may create subsidence that warms and dries out the surrounding air, creating cloud-free regions near the center that may give it a more eye-like appearance. Another difference with hurricanes is that the upper-level high pressure system (anticyclone) over the extratropical cyclone is displaced to the northeast (downwind) of the center. In a hurricane, the anticyclone is directly over the eye.

The Blizzard of 2006 developed a distinct eye-like feature when it moved offshore over the warm Gulf Stream waters. The storm was undoubtedly tapping the hurricane's source of energy--latent heat of condensation--at the time the photo in Figure 1 was taken, since we can see evidence of spiral banding occurring neat the center of the storm. As seen in Figure 2, the Sea Surface Temperatures increased sharply from 6 to 12 degrees C (43 to 54 degrees F) near where this eye-like feature developed, right along the edge of the Gulf Stream current. There was plenty of water warm water for the storm to tap into for an extra energy source.

However, the storm missed the warmest waters of the Gulf Stream to its south, and did not intensify much compared to other historic blizzards--the storm's central pressure only dropped to about 980 mb, and a pressure of 960 mb is more typical of a classic Nor'easter "bomb". Also, note that the band of heavy snow that extends from Long Island through Connecticut northeastwards is well away from the center of the cyclone. This band is what gave the Blizzard of 2006 its prodigious snow amounts, and the band developed just as the storm moved off the coast--well before the warm ocean waters had time to create a warm-core seclusion in the storm and enhance the storm's snowfall. This band of heavy snow was created by processes unrelated to the formation of a warm core in the cyclone. The band had some similarities to the intense bands of lake-effect snow one finds in the lee of the Great Lakes--drier, fluffier snow than one usually finds in a Nor'easter, and very high snowfall rates of up to four inches per hour. Lake effect snow bands, and the extreme snow band of the Blizzard of 2006, are examples of developments on the "mesoscale"--the scale of a few tens of kilometers--and are not well handled by computer forecast models. These models typically chop the atmosphere into grid cells between 20 km and 40 km square, and thus were not able to resolve features like the extreme snow band of the Blizzard of 2006, which concentrated its heavy snow into a band just 10 or 20 kilometers wide.

Figure 2. Sea Surface Temperatures at the time of the Blizzard of 2006.

From the Sea Surface Temperature plot in Figure 2, we can see that much warmer water lies further south, along the North Carolina coast. The Gulf Stream moves parallel to the coast here. The Blizzard of 2006 missed tracking over this warmer water, since the storm popped off the coast near New Jersey then tracked due east. Thus if a winter storm crossing the U.S. can take a track so that it moves offshore near the Carolinas, then move northeastwards along the axis of the Gulf Steam, it will spend a longer time over much warmer waters than the Blizzard of 2006 did, and have chance to really tap into that latent heat of condensation energy that powers hurricanes. This is what happened to a January 1989 cyclone I flew into as part of a field project the Hurricane Hunters were participating in, called the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA). This storm "bombed" while we flew through it, the pressure dropping an astounding 60 mb in 24 hours, bottoming out at 938 mb. I'll have the tale of the rough ride through that storm later this week.

Jeff Masters

Categories: Winter Weather

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51. oriondarkwood 1:46 PM GMT on February 15, 2006
Just a quick FYI I posted some more pics today.. http://tinyurl.com/dget7 Member Since: July 5, 2004 Posts: 51 Comments: 41

52. FUBFEE 2:09 PM GMT on February 15, 2006
Some more Satellite images of "The Great Blizzard of 2006" what NOAA is now calling it:Link Link

53. FUBFEE 2:17 PM GMT on February 15, 2006
Here is the Blizzard of 2005:Link Looks similar as was the dumping.

54. Snowfire 2:53 PM GMT on February 15, 2006
Tropical cyclones are not the only warm-core systems! Why must we speak of any warm-core system as 'tropical'? Polar lows are also warm-core (and they often have eyes, too) Member Since: June 29, 2005 Posts: 24 Comments: 300

55. CrazyC83 4:08 PM GMT on February 15, 2006
Delta should have been upgraded to a hurricane IMO...I guess they were being conservative based on the lack of land data until it hit the Canary Islands (although the damage there was definitely consistent with a Category 1 hurricane, not a tropical storm). The pressure of 980 mb is also too low for its intensity - more in line with an 85-90 mph storm. Member Since: September 19, 2005 Posts: 0 Comments: 142

56. VentusMaximus 4:35 PM GMT on February 15, 2006
Dr. Masters, [sarcasm follows] I regret to inform you that you are fired. It is now 8:30AM on the Pacific Coast and today's blog has yet to be published. This is totally unacceptable. You obviously don't realize that my mornings revolve around reading your blog. Please pack your personal belongings. Building security will be there shortly to escort you out. By the way, even if you are sick I still expect you to post a blog regarding how your cold could have been caused by global warming - charts and spreadsheets are optional. Thank you, Vent.

57. theboldman 5:30 PM GMT on February 15, 2006
LOL come on hes got a family which is more inportant Member Since: September 8, 2005 Posts: 24 Comments: 0

58. jeffB 6:19 PM GMT on February 15, 2006
More important to us? :-) Member Since: July 8, 2005 Posts: 0 Comments: 40

59. Skyepony (Mod) 6:26 PM GMT on February 15, 2006
FtWaltonBch~ Thanks for the correction, if you could throw me a link. The i one posted on here earlier, i'd googled in lastnight, seemed slightly different (thing on bottom saying it was to be inacted OCT 1, 2005). I've had a link in my blog to GovTrack, it has 11 members instead of 9 too. & everything (what little there is said it wasn't changed at all except for the title~ Amend the title so as to read: ``To establish a coordinated national weather modification research and development program, and for other purposes''. Member Since: August 10, 2005 Posts: 144 Comments: 29266

60. rwdobson 6:39 PM GMT on February 15, 2006
colby wrote: Just a thought - isn't less government oversight a good thing? :P Not when we're talking about a government weather-modification program. And really, the discussion is about non-government oversight (i.e. from scientists and others outside of the gov't) of a government program. Member Since: June 12, 2002 Posts: 0 Comments: 1574

61. FtWaltonBch2Tucson 6:43 PM GMT on February 15, 2006
I cheated and followed Colby's link...... Member Since: January 9, 2006 Posts: 0 Comments: 21

62. FtWaltonBch2Tucson 6:59 PM GMT on February 15, 2006
Skyepony, I just did some digging. If you read the text file on govtrack.us the first seven and change pages are the /old/ bill. Near the top of page 8 you can see that the section numbers start over. /That's/ the current bill. The PDF makes that clear by having the first part typed in struck-out text. Member Since: January 9, 2006 Posts: 0 Comments: 21

63. Skyepony (Mod) 7:18 PM GMT on February 15, 2006
On Thomas's it was a little clearer~ there are now 2 versions of the bill~Link. The 2nd one part of which you posted said it had been reported in senate, so perhaps the hearings have begun? Besides the bill being pretty well changed this was added~ The heads of the departments and agencies of the United States and the heads of any other public or private agencies and institutions that receive research funds from the United States related to weather modification shall, to the extent possible, give full support and cooperation to the Weather Modification Subcommittee. One of the only things unchanged was the title amendment~ other puposes? What's that about? Member Since: August 10, 2005 Posts: 144 Comments: 29266

64. ForecasterColby 7:29 PM GMT on February 15, 2006
While it is true that not all warm-core systems are tropical, all warm-core systems that the U.S. is going to deal much with are.

65. TampaSteve 8:12 PM GMT on February 15, 2006
ProgressivePulse wrote: "You can have your sub zero temps, looks like the mid 70's are back to Florida and 80's and Sunny Sat and Sun. Great thing about Florida weather is you know great weather is always right around the corner." Yup...we may get a chiller from time to time here in Tampa, but we bounce back quickly...looks like it's gonna be sunny with highs around 80 and lows around 60 for at least the next week or so...not bad for February...ahhhhh...gotta love Florida!

66. Skyepony (Mod) 8:16 PM GMT on February 15, 2006
Dr Master's ~I'd love to hear your take on the subject...anything brought up at the WMS meeting? I dug around for articles on th weather modification bill~ to be fair one from each side of the fence~ FOX NEWS & News With Views. Also how it's related to the chemtrails, since i brought that up the otherside of weather modification & chemtrails would be weather wars. While there ran across this about the recent blizzard being arranged by homeland security, to add urgency to the matter!lol My blog made the 2nd page of google on the matter, guess i got too update it with the 2nd version of the bill. Thanks for helping me keep up to date info out there ya'll. Member Since: August 10, 2005 Posts: 144 Comments: 29266

67. wxforecaster 4:56 AM GMT on February 19, 2006
This couldn't be anything farther from the truth. I can't believe a PhD would post such incorrect meteorology, and 50 suckers bought off on it. How one can mistake a dryslotted extra-tropical cyclone that BARELY met blizzard criteria for a warm core system is beyond me. This system didn't have ANY hurricane-like characteristics: 1.) Wind maxima around the center. NO. Wind maxima were WELL displaced to the NW of the cyclone, as is the expected behavior with the gradient maximized between the cyclone and polar/arctic high pressure to the north. Nevermind the fact that hurricane force winds weren't observed anywhere (even remotely close) -- again this system BARELY met blizzard criteria as it was. 2.) Deep convection around the center. NO. The satellite image Jeff uses as his own example clearly shows nothing more than low level stratus/strato-cumulus around the exposed low level center. Towering Cu, cumulonimbus non-existant. Cirrus anvils? Nada. 3.) Eye like feature around the center? NO! This is anything but an eye. It's is the expected representation of an extratropical cyclone with pressures below ~990mb. The same mid-upper level dry slotting that completely eroded this system from the SW leads to large scale subsidence as the system occludes. If a hurricane entrained this much dry air, it wouldn't be a hurricane! These systems don't deepen from massive latent heat release from 50 degree water!! LOL!!! The process here is simple with the strong thermal gradient along the edge gulf stream instead offering a perfect baroclinic zone for systems to deepen. This system did not deepen like other Nor'easters because it moved over "cooler" water slightly NW of the gulf stream. Those systems intensify more quickly only fractionally because of warmer water, but of MUCH greater reason, the increased low level thermal gradient and strongly cyclonic curved upper jet streaks that accompany a southeast coastal low. This system was dry slotted with a very STRAIGHT jet sreak. Dr. Masters, please try to use a bit more basic thermodynamics and dynamics in your blogs. Overall they're very good, but in this case you blew even the most basic understanding of our science.

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