It is natural for scientists and nonscientists to ponder whether the virtually unprecedented hybrid superstorm is still another sign of the climate models’ predicted more frequent extremes? Short answer: Quite possibly. Sea surface temperature anomalies off the eastern U.S. are positive. Can it be PROVEN this is due to overall warming? No, but the trend of this happening in more years in recent decades is clear. The rarity of the evolution of this hurricane into a hybrid hurricane with a wind field greater than 1000 miles in diameter cannot be overstated. That broadening of the wind field was modeled despite increasing wind shear, and continental influences. By any and all measures, this was an extreme event.
I can’t really answer my own question conclusively. I know it and you know it. But the water levels in NY harbor have risen 15 inches in the past 150 years, and 4 to 6 inches of that–providing uncountable (to me, anyway) millions of tons of extra water– has occurred in just the last 15 years. At the very least, any hydrologist, storm surge specialist or storm surge modeler can safely postulate that extreme coastal storms will have greater effects than they would have had just 15 years ago. They will have greater destructive potential. Even less powerful storms will be able to produce more damage along the coasts and in harbors–including the financial and cultural capital of our nation, New York City.
As I’ve said before, I don’t know how much can be done to mitigate the effects of these new risks and, if global warming is the cause, the warming itself. But in the massive rebuilding of the infrastructure which is required, along with recreational and vacation communities, this new Probability will have to be factored into the costs, design and engineering of the new infrastructure. How we afford all that is a question for others to answer. That’s out of my field. But what I’ve said here is that even if we don’t see another storm like Sandy for a long time, other powerful storms will be able to cause more and more damage with the passage of time.
Okay…the Big News is the radical departure in the 12z operational GFS. The GFS now keeps this storm closer to the middle Atlantic seaboard and has it fully captured by the inland 500mb trough, bringing it onshore near Maine as a monster Atlantic storm Tue-Wed, on the scale of what we’ve been seeing in the Euro. It stacks it up vertically near the Adirondacks by Wed night-Thur.
While the synoptic scale of the model doesn’t lend itself to close scrutiny as to where the best dynamical cooling will occur, this solution would make a period of at least mountain snow more likely. The storm would bring destructive tidal flooding to eastern New England, especially Maine, and the potential for high winds well into the interior back to WNY and PA. The modeled 850 temp doesn’t really get quite cold enough for snow, but strong vertical velocity might overcome this. With even the out-to-sea Canadian GEM showing a second strong low reforming near New England, the majority of operational models are on board for an immense Atlantic storm to move to the coast and inland.
I have not yet seen ensemble members in the GFS run…and this could still be an all rain event, especially at the lower elevations.
We are, frankly, in scientific nowheresville when it comes to the predictability of the upcoming winter. NOAA/CPC issued their new Winter Outlook this afternoon (October 18th), and we have seen quite a change from previous CPC outlooks for the eastern U.S. from modest anomalies projecting a warmer than average winter to what most our bloggers have seen before–”EC”. That’s Equal Chances. It could go either way, temperatures and precipitation. That’s tied to what I’ve been posting about for some weeks now. In layman’s terms, it’s the lack of anything upon which to hang a hat. We’ve gone from modeled projections of a weak to moderate el nino which was supposed to have set up by late summer to a currently nonexistent el nino (neutral ENSO). Many models are still projecting a limited chance for a weak el nino to develop this autumn and then fade away in the winter. But there is no sign of that happening at this time.
IMPO, the CPC had no choice but to broaden the EC coverage because of the neutral ENSO, and because other models they use show only a modestly better than even chance for milder than average conditions in parts of the central and western US, with a stronger chance of warmer than average temperatures in northern Alaska in November, and in the Alaska panhandle in Dec-January. With the unpredictability of the NAO, AO, PNA, and MJO beyond a couple of weeks, the uncertainties in the east central and much of the eastern US have increased. CPC was hoping for a better el nino signal so they could at least tie into el nino climatology. Without even that weak signal, EC was definitely the way to go. It probably won’t be until we get very close to the cold weather season when we can even venture a guess as to whether or not a prevalent trend may begin to show for the AO and/or the NAO.
As I’ve posted several times, research done by Bob Hamilton of the NWS Buffalo Office shows that weak el ninos tend to be associated with normal to below normal temperatures in WNY winters, with no correlation shown for snow. However, the original date of his research was in 2004, when Judah Cohen’s work was in its infancy, and even less was known about the MJO than is known now–which isn’t that much. The other variables being unknowns at this point reinforces the need for EC locally as well, even if that’s not what most of the public wants to hear. WE. DON’T. KNOW.
As forecasted last week, a couple more shots of chilly air will reinforce the cool pattern in place since this past weekend. But a fairly abrupt turnaround will begin to take shape on Saturday, after a potentially widespread frost and freeze before dawn. During the weekend, an area of low pressure moving north of our region will provide a gusty warmup, accompanied by some showers–mainly on Sunday. After that, the details grow somewhat hazier.
It does appear unlikely that the lower 48 will be visited by any true arctic airmasses for some time, with a more zonal/west-to-east flow showing up in the mean. That’s the big, fuzzy picture. However, short wave low pressure systems are still likely to traverse this flow, producing ups and downs not yet discernible in this mean flow. Some ensembles and models have a trough trying to establish itself over the central U.S., while others keep that trough more to the west, which would allow a warm ridge to build up over the east. There is a great deal of “spread” between models and some ensembles, leading to a great deal of uncertainty in the details after Sunday. Confidence levels at CPC are only 2 out of 5 and 1 out of 5 respectively for the 6-10 & 8-14 day outlook periods. Although the “indices”, the AO, NAO, and PNA do not initially match up with the zonal flow all that well, other inputs keep models and ensembles in rough agreement that there will be no lasting western ridge/eastern trough pattern in that time period. That does not preclude a couple of those “ups and downs” amplifying within that moderate mean pattern, as I’d posted in the last thread.
Temperatures will be running above average Tuesday through Thursday of this week, with a fairly sharp cold front arriving by around Friday (some uncertainty in the timing). Fairly abundant Gulf moisture will be streaming overhead by Tuesday, but the triggering mechanism doesn’t look strong enough to deliver coverage or amounts suggested by the amount of precipitable water which would be available. Temps will peak on Wednesday–probably the warmest day in some time, heading toward the mid 70s in many lower elevation locations, with residual warmth on Thursday. There could be a few Tshwrs Wednesday, mainly late, though much of the day will prove to be rainfree.
The long-advertised pattern change to cool, then Chilly, temperatures is still coming. While nothing looks extreme, the ensemble mean 500 mb products suggest persistence from the weekend through about Thursday of next week. However, the reality will probably be some embedded short waves traversing the longer wave trough, producing some ups and downs through the chilly pattern. Some limited lake shower response will show up along the way–timing still to be worked out.