The Northeast Weather Blog...

Significant Impacts to the East Coast; October 29-31, 2012

By: Blizzard92, 1:39 PM GMT on October 26, 2012

Hurricane Sandy (Nor'easter/Hybrid Tropical Event; October 29-31, 2012

Satellite Picture...

(Courtesy of Penn State EWall)

Early Thoughts...
The upcoming storm event holds many unique characteristics that not only make the forecast difficult, but also will prove challenges for impacts along the entire eastern seaboard. Hurricane Sandy is beginning to charge due north and will continue on a similar trajectory until it begins to hook northwest. This is a very rare and perhaps unprecedented track, which will make any comparison to previous storm systems quite difficult. Given the unique jet stream structure, Sandy is actually expected to strengthen despite encountering land and losing warm core tropical characteristics. This again is very unusual; a few ensemble guidance models depict a nearly 20mb+ drop in surface pressure during this period. The track remains highly uncertain, but we can begin to narrow down the width of the cone to a narrower 200-300mi or so.

While Sandy remains several days away before making landfall, this blog will highlight general threat areas and precautions that need to be taken at this point in time. Given my upcoming schedule, I was only able to put out a full blog this Friday morning. But you can expect me to be actively posting in comments below through Wednesday.

It is important to understand that the location of the landfall will be critical particularly for coastal flooding and storm surge. Certain locations are much worse off for this threat depending on the track of the center of circulation. For the time being, it looks like a track will lead itself somewhere between Ocean City, MD and Sandy Hook, NJ. A few ensembles are farther north towards Long Island and New York City, but given the strength of the block, I am leaning towards a landfall very close to Atlantic City, New Jersey (ACY). The area currently under the highest threat for the combination of wind, heavy rain, and coastal flooding is the region from central New Jersey to northern New Jersey. This area may likely be just northeast of the center of circulation and therefore will be the strongest quadrant of the storm. Given the slow movement, the strong easterly flow will pool water up and along the coast with devasting effects from beach erosion. More on threats and the synoptic setup can be found below.

Remember, the unique setup brings in itself a load of additional problems for areas in the Middle Atlantic and Northeast. The forecast remains uncertain, although the track cone will begin to be narrowed down by Saturday. Stay tuned to the latest updates and for areas along the coast, be sure to heed to local authorities and be prepared to evacuate low lying areas. While Sandy may loose her tropical status, the combination of an anomalous jet structure and bizarre track will be almost as if a stronger and larger hurricane were actually making landfall on the coast. I have seen a great deal of hype by not only the media, but also other meteorological authorities. These statements must be taken with a grain of salt. This is not a worst case scenario and likely not a crippling event. Bottom line is that impacts will be felt over a large region and impact one of the largest concentrations of metropolis in the United States. But conditions are not expected to be any worse than previous destructive nor'easters such as the storm of December of 1992 and Hurricane Hazel. This storm is not going to feature the same variables as the deepening hurricane of 1938 in New England, so impacts will be lessened. All in all though I would not be surprised to hear this is a 1-2 billion dollar disaster with impacts worse than that of last year's Hurricane Irene.

Current Advisories...

(Courtesy of NOAA)

Daily impacts...
Keep in mind this is not a tightly wound hurricane. Given the hybrid structure of the storm, impacts will be large and felt over a wide region of the Northeast. In fact tropical storm force sustained winds will be felt possibly from Massachusetts to as far south as North Carolina. Even hurricane force wind gusts may stretch a bit inland. The precipitation shield and associated spiral bands will stretch all the way as far west as Michigan and Ohio. Impacts will be greatly magnified as depending on the exact angle of landfall. Should Sandy make landfall coming from the due west, impacts would be lessened for coastal flooding due to the trajectory of the winds and pooling of water. But under a northwest angle (more likely scenario) water will flood many of the bays and sounds along the Middle Atlantic courtesy of a substantial and consistent easterly and northeasterly flow.

Heavy rain- Flash flood guidance (FFG) is relatively high over the entire Northeast. Despite consistent rain chances each week over the region, rainfall has been relatively near normal. The wettest areas are across the Middle Atlantic, particularly in Pennsylvania. But even in this region, FFG is pretty high. Nevertheless some areas will receive over 6in+ of rain and that will certainly cause at least urban flooding. Sandy will not be one consistent rain shield that is common in nor'easters. It will likely take a structure of a hybrid storm with multiple wide bands that will contain the strongest winds and heaviest rain. The heaviest bands will be to the west of the center of circulation. Currently the heavy rain axis looks to position itself from the Delmarva stretching northeast to northern Maryland and southern Pennsylvania. Highest QPF totals will likely reach 10in+ especially in parts of Delaware, Maryland, and southern New Jersey. Keep in mind the tropical origins of the system despite the time of year being late October. Elsewhere over the Northeast a widespread 2-4in of rain can be expected. The highest threat of flooding will exist as flash flooding and urban areas along with creeks and streams. Major river flooding is not expected at this time given the relatively low levels present. Should QPF increase in the northern tributaries of major rivers such as the Susquehanna, Schuykill, Juniata, and Delaware Rivers, then this threat may increase.

Winds- A tight pressure gradient exists and is highly evident on all upper air and surface maps. A 1035mb high pressure sits to the north near the Gulf of Maine and an anomalous block of upper level heights exists near Greenland. This gradient will enhance the winds over the region from Sunday. Also noticeable on upper level maps is an impressive jet structure on the synoptic scale. A screaming 120knot jet streak near the right front entrance quadrant along with a tight area of divergence aloft will allow for an expanding wind shield that will stretch several hundred miles. Tropical storm force sustained winds can be expected well away from the center of circulation. The strong winds can be be expected just northwest of the center, where gusts may exceed 70mph. Given the time of year, many leaves are off the trees, so wind damage will be less for foliage than if had this had occured earlier in the season. Nonetheless, widespread power outages (millions of people possible) may be expected stretching from New England to the Delmarva. Major cities including Philadelphia, New York City, and the Baltimore to Washington DC corridor can expect maximum gusts upwards of 60-70mph. Sustained winds though will only around 40mph during their height. Along the coast hurricane force gusts may occur.

Severe Weather- Given the time of year, there is significantly less instability both at the surface and aloft. But there remains a great deal of lift and shear, that may allow for a few quick spin-up tornadoes to occur. The area that may under the gun for this threat will stretch from Norfolk, VA north through southern New Jersey. It will be difficult to pick up these areas of rotation using our current NEXRAD radar system, but these possible weak tornadoes will be most likely in the spiral bands as they make landfall on the coast. Farther inland, the threat will decrease due to colder air aloft and less elevated instability.

Storm Surge/Coastal Flooding- I would be getting very concerned if I were living anywhere along the coast from Virginia to Connecticut. This long-duration event in combination with full moon high tides will plague the region with significant coastal flooding and storm surge. It is expected that water levels will exceed Irene values by several feet. I think the highest threat for flooding will be along the Long Island Sound especially in the northwest corner. There water may rise upwards of 8-10 feet and be more representative of a category 2 hurricane than an extratropical cyclone. Also significant flooding can be expected along the barrier islands of New Jersey where many of the sounds and bays will flood as east and northeast winds pool water into the narrow features. This will also be a long duration event given the slow movement as Sandy begins its phase with the trough and hooks west and northwest. Impressive seas and wave heights can be expected, and I am definitely interested in seeing some buoy heights for areas just off the coast. Locations from the Long Island Sound down through low-lying areas in Delaware need to be prepared for evacuations. Farther south into the northern Outerbanks, water levels will only rise 1-3 feet. Major beach erosion can be expected and may cost several million dollars to repair after the event.

Snow- I will admit I have not been following the snowfall forecast as closely as other factors for this event. But it is likely the some peaks along the Appalachians receive a healthy 12-18in of wet snow. Elevations above 3500ft will have the highest threat. Latest models have been consistent in indicating H85 thermals to fall below 0C in association with a cold pocket and Sandy becomes entrapped in the trough. Heavy snow will fall possibly even into a few valley locations into West Virginia and maybe Ohio. Western Maryland is also under the threat zone in Garret County, and perhaps into the southern Laurel Highlands in southwestern Pennsylvania. Most of these locations have already had the leaves fall off the trees, so damage to foliage will be less than the October Nor'easter of 2011. Power outages though can be expected given snow ratios will be at 10:1 or slightly less. Once Sandy begins to pull to the northeast by mid to late week and the trough becomes situated over the area, a northwest flow will allow for widespread lake effect snow showers and flurries over the Northeast especially in the favored snow belts. Many areas will see their first flakes of snow in the November 1-3 time frame from just east of the Appalachians on westward.

"Radar for Central Pennsylvania"

"Radar for Eastern Pennsylvania"

Current Surface Map...

(Courtesy of Penn State EWall)

Synoptic Discussion...
A sharp cold front is plowing through the midwest and noticed on surface maps by a clear 40F temperature drop. It will continue to march east in association with a steep trough that will begin to become negatively tilted. Anomalous upper level heights near Greenland will act as a block in correspondance with a deep negative NAO to slow down the long waves and general flow. A 1035mb high pressure near Nova Scotia will remain generally stationary over the next few days. Meanwhile a hurricane near the Bahamas, Sandy, will continue track at near 5 degrees north through the day on Friday and Saturday. Increasing vertical shear will begin to tear Sandy apart. This is already noticeable on the first look at this morning's visible satellite given a relatively ragid looking cirrus deck with two concentrated areas of convection. The latest hurricane hunter reports indicate max sustained winds may have dropped to 80 knots aloft with surface winds at sub 60 knots. This is slightly weaker than most operational models have it at this point.

As Sandy continues to move north, she will begin to take on extratropical characteristics and form a hybrid storm. An fast jet streak near 120 knots in association with a vibrant low level jet will help to capture and phase Sandy as she reaches above 30N. Noticeable and impressive divergence aloft in combination with an area of baroclinicity will actually help to strengthen Sandy despite losing its tropical features. This hybrid system is forecasted to drop surface pressure to as low as 960mb as it makes landfall and moves inland. The timing of the phase is critical to the landfall location. Sandy does have an easterly component given the natural forcing of the prevailing westerlies and coriolis, but given the synoptic setup, she will eventually turn to the northwest. I am favoring a landfall just north of Atlantic City, but it is possible for a Long Island hit given this easterly component.

Rising PWATs at near +3SD, given climatology, will allow tropical moisture to flood the region. Meanwhile to the west, continental polar air will leak into the area turning some precipitation into snow across the higher elevations of the western Appalachians.

Sandy will feature a large wind shield and will be a long duration event therefore giving way to high storm surge. Peak height may be over 10ft in a few isolated locations, which may cause major problems given the geographic structure of the Middle Atlantic coastline. This threat is highest from New Jersey up to the Long Island Sound.

As she begins to become captured by the trough, she will slowly begin to move west then north and northeast under a retrograding motion. Therefore wind, surge, and precipitation will plague the northeast for multiple days before coming to an end by mid week.

Current Water Vapor Loop...

(Courtesy of Penn State EWall)

Operational and Ensemble Forecast...
We still have a relatively large spread in the operational and ensemble models. The cone of landfall for guidance is as far south as Norfolk, VA to Long Island, with most models in between favoring the Delmarva up through central New Jersey. Models are having a difficulty in pinpointing the exact timing of the phase with the trough and the strength of the upstream blocking. I am presently favoring a track just in between the ECMWF and GFS. Given the highly parameterized ECMWF and its higher resolution, it lends me to believe that it is overestimating the actual phase (occuring to early) and therefore a bit too south in its track. I also believe the angle of the trajectory on the ECMWF is slightly too westerly and that Sandy will track a tad farther east before eventually turning northwest. The GFS on the other hand is farther north with its expected landfall, but has the tendency to underestimate the blocking to the north which acts like a well and will prevent Sandy from escaping to the east.

The tropical models such as the HWRF and GFDL will have a difficult time in forecasting Sandy given the similarities to a middle latitude cyclone and the complex jet dynamics. They can pretty much be discarded for this event. Ensembles will be very helpful in the forecast for Sandy and both the ECMWF and GFS's associated ensemble means are both just north of their operational partner's forecast.

Trends I would look for on Friday and Saturday include the strength of the block and the timing of the trough as it becomes negatively tilted. I am predicting we see the ECMWF shift a bit to the north in its forecast track as it may be underestimating the easterly component for Sandy. While I am presently favoring a landfall near Atlantic City, NJ or a tad north, I cannot rule out a landfall along Long Island. I do not expect the landfall to occur any further south than Delaware.

Forecast Model Links
-NAM model 12z...Link
-GFS model 12z...Link
-NMM model 12z...Link
-SREF model 9z...Link

Severe Weather Links
-Atmospheric Soundings Skewt T charts...Link
-SPC Mesoscale Analysis Pages...Link
-Public Spotter Reports for State College NWS...Link
-Severe Weather Model Forecast indices...Link
-Severe Weather Parameter Definitions...Link

Flooding Links
-Automated Pennsylvania Rainfall Recording Stations...Link
-Flash Flooding Guidance...Link
-HPC Forecasts for Excessive Rainfall...Link
-Hydrology Predictions for Lakes, Rivers, and Streams...Link

***Stay tuned and discuss below! Please... when reporting observations, include your exact location in every comment. It makes it very helpful for others to prepare for what they can expect in a later time.

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"Lower Susquehanna Valley Doppler"

(Courtesy of WGAL)

Tropics Storm Analysis Blog

Updated: 12:33 PM GMT on October 29, 2012


Hurricane Sandy/Nor'easter?

By: Blizzard92, 2:18 PM GMT on October 23, 2012

And so it begins. Yet again we are kicking off the end of October tracking another potential Nor'easter. Similar to last October, the threat of high winds, heavy rain, and heavy snow are a possibility. The synoptic setup is very different though in this instance and many different outcomes are possible.

Presently tropical storm Sandy is located in the central Caribbean tracking 0 degrees north.

It is encountering very little vertical shear (sub 10-15 knots) and slightly above normal SST's (80F+). Sandy will begin to increase in speed as it tracks north towards Cuba. A bit of drier air and increased shear along with the high mountain interactions with the tropical core, will weaken Sandy and prevent further strengthening. Intensity forecasts through Friday are only expected to peak at a minimal hurricane. As Sandy tracks north of the Bahamas encountering a more hostile environment, she will begin to take on extratropical characteristics. This time frame is around Saturday/Sunday. The track and intensity after this period is a bit more in question and will be detailed further below:

A deep negatively tilted trough will be swinging south through the central part of the nation by the end of the week. This feature is key in predicting the eventual path and impacts of Sandy. Located to the north is a very impressive blocking setup with an amplified ridge over Greenland and a steep west based negative NAO. The North Atlantic Oscillaion will be approaching the lowest value in several months during this time frame.

The blocking setup will allow for a very amplified jet stream pattern that is also slow moving. Three major scenarios are possible for the impacts of Sandy on the east coast.

1) Currently the 10/23/2012 runs of the GGEM and ECMWF are the most amplified and feature a tightly wrapped extratropical Sandy tracking up the eastern seaboard with a slightly northwest motion. They are also supported by this morning's 0z runs which have impressive consistency in allowing the negatively tilted upper level trough to capture and phase Sandy.

A broad precipitation deck forms while the surface low undergoes rapid bombogenesis courtesy of impressive baroclinic forcing. In some recent foreign model runs, the surface low has dropped sub 950hPa. A tight pressure gradient and raging low level jet sends strong winds to the surface in excess of 50mph up and down the Northeast. Meanwhile the cold air behind the front catches up to Sandy in a pocket of sub 0C H85 thermals located west of the center of circulation. Surface temperatures also fall due to dynamic cooling with heavy snow breaking out across western Maryland through all of central Pennsylvania. In fact the 0z 10/23/2012 ECMWF shows snow accumulations in excess of 12-24in from Reading west to the Laurel Highlands south to Hagerstown, MD and north to Elmira, NY.

Knowing a bit about 500mb maps shows that this solution requires many features to time perfectly to be able to capture Sandy and track with a slight northwest component. It is a dynamic setup and the anomalous blocking to the north makes this particularily more interesting than normally. This is also impressive and consistent support from both operation and individual ensemble guidance especially from the GGEM and ECWMF. A few ECWMF ensembles even show the surface low tracking right through southern New England with a landfall coming from the northeast near Cape Cod, Massachusetts. This setup would cause major problems up and down the eastern seaboard with heavy rain, high winds, coastal storm surge, and possibly heavy snow. Looking back at other analogs, Hurricane Wilma is a quick reminder how a system with tropical origins can quickly resemble a nor'easter with winter-like characteristics.

Key players to watch for the scenario require analysis of the 300mb and 500mb trough axis and tilt including time of these features for the upper level trough. Also the evolution will be highly dependent on the upstream position of the upper level heights near Greenland (blocking).

2) Another scenario is supported by the OP GFS and GEFS. In this evolution the overall jet stream is flatter and the trough lags behind a bit allowing Sandy to not phase and instead swing out to sea.

Therefore any precipitation in the Northeast is a direct result of the cold front and a small inverted trough feature in New England. A recent update in the GFS enembles this morning (6z run) show a clear west shift in about half of the models. This is a critical note to make especially when looking at future run times. Presently this evolution has support from the HPC and other NWS offices, although given recent developments for the ensembles and forecasts for blocking, it is starting to lose gravity.

3) For the time being, the following option has the most support looking at the overall orientation of the jet stream and synoptic setup. While this is a middle ground approach, it offers the most logical evolution given past analogs and our recent weather pattern over the last few months. Model support is lacking as most guidance is in the camps of the two extremes listed above. Nevertheless this possiblity allows Sandy to begin to rapidly take on extratropical characteristics and begin to wash out over the Atlantic as power vertical shear takes hold. A negatively titled -2SD trough will move east from the Ohio Valley and the interaction between the two features allows Sandy to track out to sea. But an inverted trough feature forms along the eastern periphery of the trough particularily towards New England. In almost a similar PRE (predecessor rain event) manner, an axis of +2SD PWATs would pool across New England as heavy rain streams through the region. QPF probably would be in excess of 1-2in given the inverted trough has tropical origins from post-Sandy. A screaming low level jet would also allow for gale force winds along the immediate coastline. Farther west and south impacts would rapidly diminish and mainly allow for a small corridor of rain showers along the immediate front. Both the GGEM and GFS show slight hints of this inverted trough feature.

Conclusion) It is a complex setup given both tropical and non-tropical features that need to interact to produce a solution with a surface low undergoing rapid cyclogenesis and pinwheels northwest sub 940hPa. Therefore given that Sandy just developed and is still located in the central to southern Caribbean, forecasts at this point can be taken with a grain of salt. It is important to note at this point the overall orientation of the jet stream and past analogs given the setup. Also the continuous support for dense upstream blocking is beginning to make odds of some sort of impact on the Northeast particularily higher than just a day or two ago. A few forecasts are already rotating about the cyber world concerning a grim storm tracking towards the east coast. These have little to no support and should be thrown out. The time frame for impact is early next week in the 144-174 hour time frame according to 0z 10/23/2012 model runs. Keep an eye the next few days on ensemble shifts and trends particularily in the timing of any possible phase of Sandy with the upper level trough.

As a final note as of 10/23/2012 at 10am, latest upper level air reports out of Sandy indicate the presssure dropping to 996mb with winds aloft up to 60 knots. Impressive strengthening and it is all courtesy of the warm bath water in the Caribbean.

Stay tuned and discuss below!

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"Lower Susquehanna Valley Doppler"

(Courtesy of WGAL)

Winter Storm Analysis Blog

Updated: 9:51 PM GMT on October 23, 2012


Next two weeks...

By: Blizzard92, 1:05 PM GMT on October 19, 2012

Good morning! It is almost the end of October and days are rapidly becoming shorter. Global wavelengths in the northern hemisphere are beginning to shortern in correspondance with a strengthening polar jet that continues to drop more south with each passing trough. These are sure signs that winter is fast approaching and actual snow chances are a little more than two to three weeks away for parts of the Northeast. The upcoming week looks relatively benign weatherwise, with the biggest story in the east being some abnormally warm temperatures. Highs will shoot into the 70s as far north as southern new England for several days with daily means nearly +10F.. This will likely solidify October as another abnormal month for mean temperatures continuing the two year trend. Below, this blog will take a look at the longer range forecast highlighting the possible first winter blast.

The Madden-Julian Oscillation is a measure of the position of convection and monsoonal patterns across the Indian Ocean. Several ensembles are operation models forecast the position of the convection, which then helps to give an idea of a general phase. This phase indicates the position of rossby waves across the Northern hemisphere, and therefore we can attempt to predict where troughs and ridges will be located. The current GEFS mean indicates a general shift through phase 8 into 1 through the end of October. The analogs for mean temperature composites for phases 8 and 1 are located below.

This would signal cooler air funneling south from Canada into the inner mountain west and northern Plains. The trough axis will likely center west of the central Plains. Therefore any cold-air intrusion will likely remain west of the Appalachians. It is expected through the end of October that warmer than normal temperatures will prevail across the Northeast.

The ensemble forecast for the AO and NAO teleconnections are listed below. During the transition seasons, the NAO and AO have less impact on the weather patterns across the Northeast than winter due to the larger wavelengths currently present. Although this correlation is still relatively misunderstood. The present NAO, while negative on CPC composites, is generally east-based and therefore the impacts on the Northeast are meager at best. A west-based positioning to the pressure differences is correlated to the significant troughing and storminess that is very common in winter forecast discussions for east coast snowfall.

As we continue edge closer to the months of November and December, these indices will have a larger impact on the short and long term weather.

Long range models are beginning to hint at another pattern swing by early November.

GFS ensembles are highlighting the development of a more west-based negative NAO as heights begin to increase towards Iceland and Greenland. Wavelengths are showing favorable trends for a winter storm possibility around the beginning of the second week of November. Composites for MJO phases begin to modify after October with phases 6,7,8,1 becoming the most favorable for east coast storminess and troughing. This allows convection to focus along the 180 degree longitude with troughing near Japan, the Aleutian Islands, and the east coast.

The OP ECMWF brings about this slight pattern change a bit later with warmer conditions prevailing through at least Halloween. But the most recent ECMWF weeklies indicate that cooler weather will reappear by November.

The GGEM ensembles are a bit constrasting at this point in the longe range, but still note cooler weather slowly spreading east over time from the west.

I am expecting that October will finish out above normal in all climatological reporting stations at or around a mean of (+)1.5F for the month. As the -NAO becomes more situated favorably, colder air over the western plains will begin to slowly spew east in a step-down pattern. Each cold front will allow the colder air to reach further and further east with each subsequent passing. This regime will allow for the development of several Great Lakes cutters. By the first week in November, near normal temperatures will begin to filter back into Northeast and by the second week cooler weather is possible. Given current wavelengths and equitorial convective patterns, it is likely the development of a storm system in the eastern half of the country will bring some areas this first bought of wintry precipitation.

I am relatively confident that there will be no snowfall through the end of the October across the Northeast. Precipitation means will range near normal also for this time period. My winter outlook will hopefully be posted by Halloween. Stay tuned!

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"Lower Susquehanna Valley Doppler"

(Courtesy of WGAL)

Weekly Forecast

Updated: 7:54 PM GMT on October 22, 2012


A taste of winter...

By: Blizzard92, 1:06 PM GMT on October 12, 2012

Good morning and happy Friday! It is another terribly dreary day here across the Finger Lakes as some light CAA rain showers move across New England ahead of an approaching cold front. Frost and freeze products have been issued for the entire Northeast and as far south as northern Virginia. A ridge of a high pressure behind the trough will create ideal radiational cooling conditions Friday night as temperatures drop at or below 32F for most climatological reporting stations. This will bring an official end of the growing season to the viewing area.

Looking at the climatological first frost dates, this year's freeze conditions are right around normal for areas along and north of I-80, but running even a few weeks early for areas to the south. Interestingly enough, last year's first 32F weather corresponded with the anomalous snowstorm around Halloween. This year is a bit different.

A lot of people have begun to ask me about the forecast for the coming winter. After last year's record warmth and low snow levels, many are left wondering how this winter will compare. With great certainty I can conclude that this winter will be colder and snowier than last year, but in reality that is not very to do. While I am waiting another two weeks or so for my official winter forecast, I will take a quick look today at some of the features in question.

The major player in forecasting long term weather during the winter months generally revolves around the condition of the ENSO. CFS prognostics for Nino region 3.4 SSTs continue to indicate weak to moderate El Nino conditions forming by early to mid winter, but taking a look at the actual pressure and SST anomalies in the equitorial Pacific show a different story.

The latest SOI numbers coming in indicate a bit of cooling for September and October supporting the idea of neutral to weak El Nino conditions this winter. Current GOA SST anomalies are more indicative of the previous La Nina with cooler water temperatures and a stubborn -PDO. There has been a bit of improvement in this region over the last few days and weeks, but concerns over the formation of the Alaskan vortex are beginning to grow.

None the less as rossby wavelengths become shorter, teleconnections will play a larger impact on the synoptic weather patterns across the CONUS. Nearly 12+ months have been dominated by anomalous warmth across the Northeast, but we are beginning to see the pattern break down. A strong -EPO is responsible for this recent surge in cold weather across the Midwest and East. As noted in the SST's above, this animation Link shows great improvement in the breaking down of the bold -PDO across the north Pacific.

The El Nino is also not dead. Long range ensembles indicate weakening easterly winds at 10mb in response to a westerly wind burst that is in the forecast grids during the next few weeks. This may help to restore weak El Nino conditions to Nino region 3.4.

The MJO is beginning to yield outside of the 'circle of death' as we begin to see an increase in monsoonal rain patterns over the Indian Ocean. This will impact long waves and the current ENSO.

Outside the equitorial Pacific, other factors including Siberian snowfall departures indicate a pretty substantial snow cover thus far this year. While still below climatological norms, snow cover is at or slightly more widespread than the past few Octobers. Snow cover though is lacking in Canada, but the correlation is much weaker between Canadian snow cover and weather patterns over the Northeast.

Above is a brief look at the status of the major indices critical to forecasting long term weather patterns. But what does it mean for us? I think we can expect a general weak El Nino presense, although its impact will be even more subdued due to the Nina-like -PDO. There are signs of a stratospheric warming event as we enter November and December, therefore possibly signaling colder and snowier weather in this time frame. In fact long term wavelengths are supporting some type of winter storm around this time next month. This could time nicely with an influx of colder air that is currently being sniffed out by long range guidance in early November. It is likely early November will feature a higher than normal chance of a widespread snow over the Northeast. Given the current state of the stratosphere, there are also higher odds that winter will start off colder in December. Based on current teleconnections and analogs, I am leaning towards a near normal temperature winter with slightly above normal snowfall for most areas. The major concern in the coming weeks will be the status of any formation of the Alaskan Vortex. This feature killed off most all snow chances last winter. While it does not mean anything at this point, the entire synoptic flow over the globe is entirely different than last year at this time.

This blog will hopefully kick off my once-a-week blogs starting from now through winter. I will have my official winter forecast posted around Halloween.

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"Lower Susquehanna Valley Doppler"

(Courtesy of WGAL)

Weekly Forecast

Updated: 1:08 PM GMT on October 12, 2012


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)

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