THE RECORD SNOWSTORM AT NEW YORK CITY 02-12-2006
COMPARISON TO THE STORMS OF 1983 AND 1996
In an attempt to place the "blizzard of 2006" in perspective, here is a comparison of its key surface and upper air atmospheric characteristics to those of two past winter storms that were very severe at New York City. I chose the storms of 1983 and 1996 because they also produced record amounts of snow in the NYC metro area and were classic examples of explosive cyclogenesis with thundersnow. I did not include the "Superstorm" of 1993 because the snowfall totals at Central Park and surrounding areas were much lower than in other storms due to warm air ingested into the storm, causing rain, sleet, and wet snow at the coast, which lowered the total accumulations.
The times chosen are from the peak of the storms' effect on southeastern New York, and all data shown are from the same time unless otherwise noted. Column 1 data are from the "Blizzard of '83", column 2 covers the "Blizzard of '96", and column 3 covers the "Blizzard of 2006". Under the "Primary Statistics" section, along with the dates, I have added the official snowfall total from Central Park, New York, the lowest recorded pressure noted in the storm, and the ratings from the new scale, NESIS, used by the National Weather Service to rate snow storms by their total impact on the heavy population corridor from Washington, DC to Boston, MA.
Table 1. Storm statistics fro the blizzards of 1983, 1996, and 2006.
* The 1983 storm pressure was estimated from surface charts.
The 1996 storm pressure is from this NWS storm analysis.
The 2006 storm pressure was estimated from surface charts.
The above charts clearly show the difference between these storms. The 1996 storm had a walloping amount of snow compared to the other 2 storms. Most importantly, the area of coverage of 20" plus snow in the 2006 storm is minuscule compared to the other two.
The above charts also tell us a lot about these storms. All 3 of these charts are from the time when the low pressure was beginning to rapidly gain strength. I noted the air temperature over the water east of South Carolina and at New York City in the captions so that we can see the temperature differences available to each of the storms. The 1983 storm had a difference of 52 degrees F (70-18), the 1996 storm had the same, 52F (67-15), and the 2006 storm had a 36F difference (67-31). Because no buoy reading east of South Carolina was available for the 2006 storm, I used the reading east of Jacksonville, FL. Since this station is even further south, it doesn't skew the difference in favor of the '06 storm. Clearly, more energy was available at the surface to the '83 and '96 storms. Also notice the size and strength of the cold high pressure area north of the developing low. The 1983 storm had a frigid 1036 millibar high positioned north of the storm, with a reading of -3F at Montreal. The 1996 storm had an even colder 1032 mb high, with a reading of -17 at Montreal. The 2006 storm had a less intense, but decidedly cold 1024 mb high, with a reading of 9 at Montreal. Also, the 1983 and 1996 storms had a clearly visible "wedge ridge" established over the eastern Appalachians (note the south and southwestward "sagging" of the isobars (solid black lines) from Pennsylvania to South Carolina on both maps.) This feature is caused by "cold air damming", and basically is the result of cold air moving down the eastern seaboard and then "damming" backward up against the Appalachian mountains. What's noticeable about the 2006 storm is the absence of this feature. This partially explains the lesser potency of the 2006 storm on its southern extent. There was no wedge ridge of very cold air dammed up against the mountains of Virginia and southern Pennsylvania, so that the precipitation in these areas started and often continued as rain, sleet or heavy wet snow, keeping the snowfall totals down.
These 500mb heights readings are quite interesting. The 1983 storm shows a less vigorous 500mb trough than the other two storms, but it is very wide, and extends way down into the tropics. Also, while the shortwave is open in the 1983 storm, the other two show a closed 500mb low at the bottom of the trough. The 1983 storm had less snowfall totals at New York City than the 1996 and 2006 storms, but was much windier and had more widespread heavy snow, in toto, than the 2006 storm.
WINDS FROM THE SURFACE TO 30,000 FEET - KEY LEVELS
These surface wind charts show how the two earlier storms produced blizzard conditions at most of the New York City metro area while the 2006 storm did not. An interesting feature on all three maps is the split or almost split nature of the 35 knot winds, with one large area to the northeast of the low, and another located southeast of it.
In severe winter storms such as these, the 850mb winds are of significant interest, because they can bring in a strong influx of warm air from the south and east into the center of the storm, providing tremendous amounts of energy. These winds are also referred to as a low-level jet. All three of these storms show a very strong 850mb low-level jet pulling in very warm, moist air from as far south as the Bahamas and Cuba. Another interesting note is the presence of a fairly symmetric area of almost calm winds in all three storms near their center at this level. Notice how the 2006 storm has the lightest winds at its center, which is offshore, and this is the storm that exhibited an "eye" on the visible satellite photograph displayed earlier.
These maps show the all important 500mb level. Notice that all three exhibit very powerful winds racing up the eastern seaboard on the right side of a strong 500mb trough. What stands out here is the configuration of the 500mb trough in figure 6a for the 1983 storm. There are two troughs visible. The weaker one extends through the center of the country with almost no tilt, and the second, much more powerful one is very negatively tilted, but half as deep. It also has a large feed of air coming into it from the deep tropics.
Here at the jet stream level, we have three different cases. In the 1983 storm, there is not only the left exit region of a jet streak over the strengthening low, but a right entrance region of another jet streak is also close by to the north, giving this storm extra energy. In addition we have the coincidence of the northern and southern jet streams, which had split over the Pacific coast, with the southern jet coming from deep within the tropics. (These observations courtesy Professor Lee Grenci of Penn State University.) In the 1996 storm, a fairly strong left exit region and a very powerful right entrance region are providing the energy. Lastly, the 2006 storm also shows the southern branch of the jet stream merging with the northern branch to supply large amounts of energy, and a resultant very powerful left exit region of a jet streak supplies tremendous lift to the air in the intensifying low.