Hurricane Sandy Pounding Jamaica, May Hit U.S. This Weekend

Figure 3. The Wednesday morning 06Z (2 am EDT) run of the GFS model was done 20 times at lower resolution with slightly varying initial conditions of temperature, pressure, and moisture to generate an ensemble of forecast tracks for Sandy (pink lines). These forecasts show substantial uncertainty in Sandy’s path after Friday, with a minority of the forecasts taking Sandy to the northeast, out to sea, and the majority now predicting a landfall in the Northeast or mid-Atlantic states of the U.S. The white line shows the official GFS forecast, run at higher resolution.

by Jeff Masters, via Wunderblog

Sandy: a potential billion-dollar storm for the mid-Atlantic and New England

Hurricane warnings are flying for Jamaica and Eastern Cuba, as an intensifying Hurricane Sandy plows north-northeast at 13 mph towards landfall.

On Friday, a very complicated meteorological situation unfolds, as Sandy interacts with a trough of low pressure approaching the U.S. East Coast and trough of low pressure over the Central Atlantic. The Central Atlantic trough may be strong enough to pull Sandy northeastwards, out to sea, as predicted by the official NHC forecast, and the 06Z GFS, 00Z UKMET, 00Z Canadian, and 06Z HWRF models (00Z is 8 pm EDT, and 06Z is 2 am EDT.) However, an alternative solution, shown by the 00Z ECMWF, 06Z GFDL, and 06Z NOGAPS models, is for Sandy to get caught up by the trough approaching the Eastern U.S., which will inject a large amount of energy into Sandy, converting it to a powerful subtropical storm that hits the mid-Atlantic or New England early next week with a central pressure below 960 mb and sustained winds of 60 – 70 mph. Such a storm would likely cause massive power outages and over a billion dollars in damage, as trees still in leaf take out power grids, and heavy rains and coastal storm surges create damaging flooding. The full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding. A similar meteorological situation occurred in October 1991, when Hurricane Grace became absorbed by a Nor’easter, becoming the so-called “Perfect Storm” that killed 13 people and did over $200 million in damage in the Northeast U.S.

When might Sandy arrive in the mid-Atlantic and New England?

The models vary significantly in their predictions of when Sandy might arrive along the U.S. coast. The 06Z NOGAPS model predicts Sandy’s heavy rains will arrive on North Carolina’s Outer Banks on Saturday, then spread into the mid-Atlantic and New England on Sunday. The 00Z ECMWF model predicts that Sandy’s rains won’t affect North Carolina until Sunday, with the storm making landfall in New Jersey on Monday night. The GFDL model is in-between these extremes, taking Sandy ashore in Delaware on Monday morning. The trough of low pressure that Sandy will be interacting with just moved ashore over the Western U.S. this morning, and got sampled by the 12Z (8 am EDT) set of land-based balloon-borne radiosondes for the first time. One of the reasons the models have been in such poor agreement on the long-term fate of Sandy is that the strength of this trough has not been very well known, since it has been over the ocean where we have limited data. Now that the trough is over land, it will be better sampled, and the next set of 12Z model runs, due out this afternoon between 2 pm – 4pm EDT, will hopefully begin to converge on a common solution. I’ll have an update this afternoon once the 12Z model runs are in.

Figure 4. Morning satellite image of Tropical Storm Tony.

Tropical Storm Tony forms in the middle Atlantic

Tropical Storm Tony formed Tuesday night in the middle Atlantic, becoming the nineteenth named storm of this very busy 2012 Atlantic hurricane season. Tony has a modest area of heavy thunderstorms, as seen on visible satellite images, but is battling dry air , wind shear, and ocean temperatures that have fallen below 26°C. Tony will not threaten any land areas, and will likely be dead by Thursday night.

Tony’s place in history

Tony is the Nineteenth named storm of the 2012 Atlantic hurricane season, tying this year with 1887, 1995, 2010, and 2011 for third busiest Atlantic season since the HURDAT historical data base began in 1851. With five more weeks left before the November 30 end of hurricane season, 2012 is likely to move into second place for most named storms before the year is out, as all six prior Atlantic hurricane seasons with nineteen or more named storms have had at least one named storm form after October 24. Here, then, is a list of the seven busiest Atlantic hurricane seasons on record:

2005 (28 named storms)
1933 (20 named storms, according to a new re-analysis)
2012 (19 named storms)
1887 (19 named storms)
2010 (19 named storms)
2011 (19 named storms)
1995 (19 named storms)

It’s pretty remarkable that we’ve now had three straight years with nineteen named storms in the Atlantic. But how many of these storms might not have been counted in the pre-satellite era (before 1960)? Here’s a list of weak and short-lived storms from 2010 – 2012 that stayed far out sea, and would likely have gone unnoticed in the pre-satellite era:

2012:
Tropical Storm Joyce
Tropical Storm Oscar
Tropical Storm Tony

2011:
Tropical Storm Jose
Tropical Storm Franklin

2010:
Tropical Storm Gaston

Even if we correct for the possible over-count of approximately two named storms per year during the 2010, 2011, and 2012 hurricane seasons, compared to the pre-satellite era, there is nothing in the HURDAT data base that compares to the type of activity we’ve seen the past three years. One likely contributor to the unusual string of active years is the fact hurricane season has gotten longer, perhaps due to warming ocean temperatures. I discussed in a 2008 blog post that Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters titled, “Is the North Atlantic hurricane season getting longer?” He concluded that yes, there is a “apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high.”

Jeff Masters is co-founder of the Weather Underground. This piece was originally published at the Wunderblog and was reprinted with permission.