Wasatch Weather Weenies

Snow in the central and southern Appalachians is beginning to wind down as the remnants of the SuperFrankenStorm lift northward. Some nice photos from the LeConte Lodge, which is located at 6,593 feet in Great Smoky Mountains National Park and accessible only by trail, are available here  and here .  They report 34" of snow. Source: http://www.highonleconte.com More than 20 inches of snow fell at some locations during the 24-hour period ending at midnight last night.  Snow depths on the ground across a wide portion of the mountains of West Virginia exceed 20 inches in the latest analyses from the National Operational Hydrologic Remote Sensing Center. Source: NOHRSC As of Tuesday afternoon, 19" had fallen at Snowshoe Mountain Resort, and it looks like it was the really thick, creamy stuff. Source: http://myfox8.com This could be their deepest natural snowpack of the entire winter.  A real risk now will be flooding if they get a warm spell with rai...

Unfortunately, it was a worst-case scenario in upper and lower New York Bay last night with regards to storm surge.  As can be seen in the time trace of water levels at The Battery, the peak storm surge (indicated by green line) coincided with high tide, yielding an all time record water level of 13.88 ft above mean lower low water (roughly mean low tide) at 9:24 PM EDT, greatly eclipsing the former record, which is reported to be 10.5 feet during Hurricane Donna in 1960. Source: National Data Buoy Center Contributing to this surge was a veering of the wind during and following the landfall of the low center over southern New Jersey.  The time series below, which ends at 900 PM EDT, shows how the wind veered from NNE to ESE at Newark Airport in the five hours preceding peak water levels. Source: MesoWest The surface plot for 900 PM EDT shows strong ESE to SE flow streaming toward the New York Bight and adjoining bays and waterways of northern New Jersey and NYC. ...

Source: http://canaanresort.com Source: NWS

Sea level pressure at Atlantic City is now below 960 mb and still dropping like a rock (see middle frame below) as the low center approaches.  Note the dramatic warming (blue trace, middle frame) which is indicative of the system's warm core.  Water levels are now on the increase with high tide approaching. Source: NDBC The influence of the storm surge is clearly evident in at The Battery.  It appears we will exceed the peak water levels that were obtained this morning and unfortunately see a peak near or above the record of 10.5 feet. Source: NDBC La Guardia airport is now reporting wind gusts to 60 miles per hour, with sustained winds of over 45 miles per hour. I wonder how hard it is blowing on the top of skyscrapers and near the top of the Freedom Tower.  There is very strong vertical wind shear over the area, with the flow aloft much stronger than that observed at the surface.

Sandy is now off the Jersey shore, as indicated above.  Amongst the amazing observations is a the rapid increase in significant wave height to more than 30 feet at buoy 4408, which is located about 200 km east of Long Island.   Source: National Data Buoy Center The Battery in NYC peaked at about 9 feet above Mean Lower Low Water (MLLW) during the morning high tide, but the next high tide is expected to be worse. Source: NOAA/NWS/MDL Jeff Master's Blog  suggests that the peak during Hurricane Irene last year was 9.5 feet and that the record is 10.5 feet.  Thus, the next several hours are the most critical with regards to the storm surge.  Let's hope the forecast is overdone.

It remains to be seen how good and useful forecasts of Sandy and her impacts will be as she comes ashore, but for anyone who is old enough to recall how difficult it was during the youthful days of numerical weather prediction to even predict the formation of an east coast cyclone, let alone the track in a complex situation like this one, the forecasts thus far have been quite remarkable. Imagine if you will a situation where we have all of today's forecast tools, including satellites, but no numerical weather prediction systems produce a forecast.  My guess is that very few people would have anticipated several days in advance that Sandy would make a quick left turn and head to New Jersey, as she is presently doing. Note in particular in the loop below the amplification of the upper-level ridge south of Greenland, which is playing a critical role in steering Sandy to the west.  Such an amplification, which is likely related to a predecessor cyclogenesis event over central...

Hurricane Sandy, a.k.a. The Frankenstorm, remains a serious threat to the eastern United States.  I'm going to leave the wind, flood, and surge discussion to others (official forecasts at weather.gov ) and instead talk in this post about some interesting and likely influences of topography on the event. Current forecast models have Sandy making landfall somewhere between the Delmarva Peninsula and New York City.  For example, the NAM initialized this morning (1200 UTC 28 Oct) has Sandy making landfall in central New Jersey. 1200 UTC 28 Oct 2012 initialized NAM forecast of 12-h accumulated precipitation (inches color filled), 925 mb streamlines, and 850-mb 0ºC isotherm (red) valid 0000 UTC 30 Oct 2012. During landfall, precipitation is heaviest over the mid-Atlantic states.  To the north, where the flow at 925 mb (roughly mid-mountain level for the higher eastern ranges) is southeasterly to northeasterly, one can clearly see the influence of the terrain on precipit...

Source: http://www.barefootbenny.com By now you've heard of the Frankenstorm, the unoffical name given for Hurricane Sandy as it moves northward, undergoes extratropical transition (i.e., the conversion from a tropical to midlatitude cyclone), and impacts eastern United States. For a few days now it has been clear that Sandy would evolve into an exceptional cyclone as it moved into the mid latitudes.  The track forecast has proven more difficult. Below are track forecasts produced by the NCEP Global Ensemble Forecast System over the past four days.  Note the wide range of possible tracks in the older forecasts (top figures), including some that took Sandy eastward and well away from the US.  Over time, with decreasing forecast lead time, the GEFS ensemble converges toward a solution where Sandy curves westward and makes landfall somewhere between Maryland and southern New England.   Forecasts initialized 0000 UTC 24 Oct. Source: NOAA/ESRL Foreca...

Like a vampire, the Great Salt Lake Effect does not like the sun.  Yesterday's event provided a marvelous example of how lake effect tends to weaken during the day.  Note in the loop below how the lake effect is well organized during the morning, but falls apart and is replaced by scattered snow showers that form all over northern Utah during the afternoon. Just to drive that point home, the images below show the transition from coherent, organized lake effect in the morning [1600 UTC (10 AM MDT)] to scattered snow showers in the afternoon [2100 UTC (3 PM MDT)]. This daily modulation shows up very well in the Great Salt Lake effect climatology.  As shown by Alcott et al. (2012) , the Great Salt Lake effect is far more common from sunset to just after sunrise than it is during the afternoon.  This effect is strongest during the spring, when the days are long and the sun angle high, than during the winter, when the days are short and the sun angle low. ...

Lake-effect developed around 9 am this morning. Playing a critical role in the initiation of the event is a convergence zone that separates strong westerly flow over the western Great Salt Lake from weak or easterly flow over Antelope Island and the northern Wasatch Front. This convergence zone shows up very well in the surface plot below and extends from just southwest of Promontory Point into the Salt Lake Valley.   I'm still thinking the lake effect will weaken and become more widely scattered with time (see previous post), but if I'm wrong, I won't complain.

The northern mountains continue to be the big winners in this storm.  Another 1.43 inches of SWE fell in the past 24 hours at Snowbasin-Middle Bowl, bringing their storm total to just over 3.5 inches.  It looks downright wintery on the Needles Lodge web cam. Source: Snowbasin The snow depth at the Ben Lomond Peak SNOTEL hit 18 inches this morning, not bad considering the early snowfall has probably settled out some.  The Monte Cristo SNOTEL is down to 28", but again, given the ongoing settlement, that's a pretty healthy number.  I suspect the early season turns are quite good in the upper elevations of the northern Wasatch and Powder Mountain area, especially at or above 8000 feet. Snowfall in the Cottonwoods has been more limited, but they did pick up some this morning.  Alta-Collins had a 8" snowdepth at 8 am MDT, roughly consistent with the Snowbird web cam. Source: Snowbird We have about a 12-hour window left for snow, but much depends on that ...

The Ogden-area mountains remain the big winners from this latest storm cycle.  Snow depth at the Ben Lomond SNOTEL (8000 ft) peaked at 15 inches this morning. The storm-total snow-water equivalent was about 2.2 inches. As of yesterday afternoon @ 2 pm, Snowbasin reported 12 inches at their Middle Bowl observing site.  Accumulations might be greater at higher altitudes where the precipitation likely changed to snow earlier in the storm. If it can be trusted, the Monte Cristo SNOTEL reports a snow depth of 30 inches!  Perhaps it higher altitude (almost 9000 ft) enabled some of the precipitation early in the storm to fall as snow.  Storm-total SWE was 2.9 inches. Wondering where Monte Christo is?  It's along UT-39 between Huntsville and Woodruff. UT-39 usually closed during the winter, but UDOT presently lists it as open until Nov 3.  There's not much good ski terrain up there, and you have to go down from the SNOTEL to altitudes that likely...

With a narrow band of precipitation over northern Utah, it was all about location, location, location last night.  There was a remarkable contrast between the southern Wasatch Front, which got very little precipitation, and the northern Wasatch Front, which got pounded.  This shows up well in the radar loop below. It is also apparent when looking at the radar-derived and gauge-measured storm-total precipitation analyses, which show nearly 2 inches of total precipitation in the Ogden-area mountains, but less than a half inch in the Cottonwoods. I might add it was also colder to the north overnight.  Even at 0800 MDT this morning, it was 21ºF at Powder Mountain (8897 ft) compared with 30ºF at Alta-Collins (9662 ft).  The net result is that overnight the Cottonwoods saw very little snow, whereas the goods fell in the mountains to the north, as illustrated by the morning web cams. Source: alta.com Source: Powder Mountain As we discussed yesterday , t...

12:54 PM MDT 22 Oct 2012 I love the orographic clouds that form over Lone Peak in southwesterly flow.  Check out the orographically forced cumulus and capping lenticular in the image above.  Gorgeous stuff! Update @1:10 PM MDT: And now there's dust in the Salt Lake Valley.  Oh Yeah!

Winter arrives in northern Utah this week.  Whether or not it is here to stay is debatable, but the next few days look quite active.  As I write this on Monday morning, the snow level is sitting around 9500 feet.  As impressive as the Dodge Ram appears in TV commercials, I think this guy ought to get his pickup off of Hidden Peak really fast. Source: Snowbird.com Although snow levels are currently high, they will be dropping tonight.  Through noon tomorrow, however, the short-term precipitation forecast is remarkably difficult.  For example, this morning's 1200 UTC NAM calls for only 0.31 inches of SWE to fall at Alta through tomorrow (Tuesday) at noon.  Contrast that to the 0600 UTC GFS, which is going berserk with 1.10" of SWE.  That is a huge differential, especially when one considers the poor terrain resolution of the GFS, which usually underpredicts mountain precipitation.   Part of the reason for the difference is that we are right ...

To help stimulate your enthusiasm as ski season approaches, take a few moments to follow the footsteps of Alta's avalanche pioneers by reading The Avalanche Studies (available here as a 63 Mb pdf), which was written by Monty Atwater and Felix Koziol in 1949.  You won't be disappointed. It summarizes the incredible early avalanche history of Alta, including the activities during the late 1930s and 1940s to tame the white death.  Here are some of the historical gold nuggets. An early avalanche map of Alta, including current and proposed facilities Annotated avalanches photos that include some great historical shots of early Alta ski area Evidence that Mother Nature had as little sympathy for cars then as she does today Beautiful weather and avalanche charts that became the template for what is done today Discussions of avalanche control techniques And then there is the text itself.  Many people believe that the snow at Alta is unusually dry, ...