The hype of Sandy--

In the era of easy access computer models, about everyone heard of the "possible" mega event In short, a tropical system has formed well south of Jamaica and will move north towards the Bahamas. At the same time, a STRONG STRONG arctic front approaches from the west and a block forms to the north in NE Canada. As a result, the upper energy grabs the tropical system and quickly transfers it to a non tropical storm and as the cold air undercuts and HEAVY snow falls over much of WV, VA, MD and PA. Pretty wild stuff on the modes and about 99.8 % unlikely. It would be a once in 500 year even if anything remotely close happened. 

My long time reads now I love eye candy-- and here is the snowfall map based on 10-1 ratio over the area.

Pretty extreme map-- year, that is 48 inches over that inner circle and the 1-6 inch line is south fo 460. Because of the dynamics of the system, it was near Virginia Beach and ends up near Lake Erie per this model run. Amazing thing is as the storm moves NW our cold air is riding in on south and southwest winds. 

I'd say the odds of a BIG event is likely, but nothing remotely close to this. It's rare, but snow on the backside of Hurricanes does happen as moisture over runs or lingers behind as colder air comes in. There was an event in fall 2005 that had backside snow over central PA from a hurricane and I can recall another storm in the 80's. 

In summary, Sandy will interact with the arctic front and I imagine there will be snow and snow showers on the backside, but nothing remotely close to this extreme run. I think we will miss the bulk of the rain, have some colder temps and Mountain Snow showers after the cold front passes. (In Central and Western VA)

Take out the tropical part and the November 1950 is the closest event to what was modeled last night. NWS Blacksburg did a nice write up on this event in a newsletter last fall. There was a very tight gradient of snow to no snow where Roanoke and Martinsville had 5-6 inches and Danville and Lynchburg had a coating to an inch. 

http://www.erh.noaa.gov/er/rnk/Newsletter/Fall_2011/Fall_2011_Newsletter.pdf

Winter Outlooks are on the way..

I'm holding off a little more on my personal because there are many variables that have not resolved itself yet.
Many outlooks I have read are promising if you are a snow lover, and I read a TON of them. However, it's early in the fall to be convinced and the "signals" we look for are not as strong as other years. However, the fall pattern is much different than this time last year.

One key point- snowcover in Eurasia/Siberia has grown rapidly and that's a good harbinger going into winter. It ultimately helps displace the arctic jet AND weaken the polar vortex. With that, I'm not sold on the SUPER snow winter at this point.

Here's a link to an outlook from a Virginia forecaster. DT is a longtime friend of mine and a mix of a mad scientist and Trump the insult dog of forecasting. It's pretty technical but the bottom line is he's leaning colder and snowy, but not 100% sold yet. Enjoy-- DT is on FB as well, he's a good follow.

http://www.wxrisk.com/category/seasonal-forecasts/

October 10, 1979 SNOWSTORM + a little winter talk

September was a very benign month with it being a little on the dry side and temps averaged to VERY close to normal. Lynchburg, VA was .1 degrees warmer than normal and Roanoke, VA was .2 degrees warmer than normal. 

October is a BIG month when making a winter forecasts. Many venues have already released their outlooks and many are leaning near normal to below normal with normal to above normal snowfall in our region. Many of these were made when the El Nino looked to peak maybe close to +1c in regions 3/4 and this is NOT the case as of now. The El Nino has weakened and we could/should end up ENSO neutral going into the winter. (No El Nino or La Nina)

A west based El Nino that peaks as moderate late fall/early winter is our BEST chance of seeing an above normal snowfall winter. I've cited this over and over, but had we reached that point I'd be looking at predicting 150-200% of our normal snowfall. In our region, it tends to trump any other factors in the winter months. With this NOT being the case, we have to weight each global scale and I'm not ready to commit yet. With that, I'm not hedging cold and snowy at this point. One key factor will be Eurasian snow cover-- based on research by JL Cohen states that rapid snow cover increase in Eurasia in October is harbinger of a colder winter in the USA. In simple terms, the snow cover impacts the arctic jet, which weakens the polar vortex. This sounds backwards, but a weaker polar vortex allows for cold air to drift away from the pole while a stronger polar vortex tends to keep it bottled up. 

So, I'm going to monitor the snow cover, keep reading processing data and punt until late month. 

October 10 will be the 33 year annivesary of an amazing early season snowfall in the Lynchburg and Roanoke region. 

In Roanoke, almost a half inch of snow fell with the mounts to the north getting upwards of 6-10 inches. I've read a report of 10 inches up in Covington/Hot Springs area. Lynchburg, VA was hit even harder with 2.4 inches of snow falling. Some places along and near Skyline drive had 12-17 inches. 

What happened?

A slow moving cold front moved across the state while a low pressure formed along the front. The air was VERY cold for the time of year and the combination of a slow moving front along with the "upper air energy" creating strong lift pulled the cold air ALL the way down to the surface. Temps on the 9th had a high in the mid to upper 70's and the temp had cooled to only 53 degrees at midnight as the cold front approached the area. Moderate to almost heavy rain continued to near sunrise (While the higher elevations to our north had mainly snow) and as the upper air approach (with VERY cold air) Thunder and lightning was VERY common as heavy rain switched to heavy snow. VERY impressive for October 1979. 

Rain in Lynchburg with thunder and some gusty winds, changes to snow around 8:30. Heavy snow continued till about 11 am with maximum depth of 2.4 inches. 

Another link to some photos from the snow on the east coast. 

http://wintercenter.homestead.com/photooct1979.html

Expecting Isaac to be upgraded to a cane--

Isaac has been the SLOWEST developing storm I've even watched- like paint drying. Giving the NHC full credit, they said it would be a slow process and they were correct. Next update should have it at 75 MPH, maybe 80. It may get close to 100 MPH, but not much more. The official forecast is for it to remain a Cat 1 storm.

Note this image where the convection is finally wrapped around the eye. As this builds, the storm should get stronger.

The bigger problem will end up being rain and flooding. 90-100 MPH winds are dangerous, but they will be confined to the most outlying and coastal areas. There will be widespread power outages, but it should not be total devastation.

NHC preferred track.

Rainfall will be the biggest issue. Strongest winds and rains are always to the center (eye) and east of the system. Note the rain is forecast to be heaviest to the east of the landfall spot. New Orleans gets off with only 8-12 inches of rain while Southern Mississippi gets 15-18 inches.

Isaac very close to hurricane status..

If we are splitting hairs and making an argument for people to remain vigilant in the path of a storm, I'd have upgraded Issac to Hurricane Status at the 4PM advisory. The ability of modern science to see a storm from SO many angles-- satellite, radar, microwave, Hurricane Hunters and the advancement of computer modeling has made data overwhelming. With that, I trust their judgement and in it's proper time it will be Hurricane Issac.

Isaac has been SLOW in developing because of various patches of dry air along its path. There has also been a couple synoptic features along the path that has slowed the process. Ironically, if we are looking at things from a risk perspective, it would be better to have a storm peak over the mid gulf and be on the down side of it's top strength than peak or gaining strength at landfall. 

I've attached a recent enhanced sat pic of Issac-- there is plenty of colder cloud tops to the S and W of the center/eye. If those colder cold tops wrap around the center, we could get a period of rapid intensification. 

Isaac the enigma!

My apologies to those who read and expect updates from me. My Father's house has an older computer and between the computer freezing up every 10 minutes or so keeping track of my three kids, updates were not just in the card. The lack of cell service at his house sealed the deal.

Isaac the enigma has done everything in it's power to avoid land, not strengthen and be a difficult storm to track via both landfall location and intensity. It missed MOST of Hispaniola and clipped Cuba where it barely was over land BUT never really gained much intensity. Now it's in the Gulf  and as of this current update STILL has not reached Hurricane status. 

Where is it going?

Well, LAND! My thoughts last week near Pensacola were not bad but it looks to be a tad west of that, likely near New Orleans. And, the angle it is taking looks to be a "worst case" for the city built under sea level. I'm not sold on the current NHC track or timing because it has struggled to be stronger. YES, it could blow up soon-- but there are some synoptic features that could inhibit this. In a worst case, it COULD blow up to a Cat 3, in a best case it's a disorganized mess and is barely a Cat 1. It's going to CRAWL for the Wednesday to Friday time period- moving maybe 100 miles those total days. Flooding will be a HUGE issue to the near and to the EAST of the center. 

More updates later today. 

Check out http://icyclone.com/  or find him on FB under the same name for updates from his chase. 

Friday Afternoon

Model data still indicates that Isaac scrapes part of Cuba-- passes the FL Keys and goes into the Gulf of Mexico. Could end up at Major Hurricane in a worse case that currently seems to be 100 miles either side of Pensacola. FL

On the road and will be at my Dad's over the weekend. More limited access to computer data, but will update when I can.