Friday, September 21, 2012

Here we go again, a look at the severe setup for Saturday

The severe setup for tomorrow is marginal. The CAPE values look to be a bit higher than we saw the other day. SRH values look interesting, as do shear values. Lapse rates look about the same as Tuesday’s severe event. Like I said the indexes are marginal. But, they are such that they generate interest. We will have a strong cold front moving out of the Great lakes. this will likely produce showers and thunderstorms. Rainfall will be heavy at times.  At least a few of the storms should become strong / severe. The greatest danger will be strong damaging winds, small hail, and heavy downpours. We will have to be on the watch out for any bowing segments in the line that will develop in the afternoon. But with that said, the severe wind threat should be fairly limited

Here’s a look at the severe index parameters.

Convective available potential energy (CAPE)

CAPE is a measure of how instable the air overhead is, and the potential for thunderstorms.
normally, CAPE values of 1000 J/Kg are usually adequate enough to produce strong to severe storms. CAPE of 3,000+ shows the atmosphere is very unstable and could produce severe storms if other severe parameters are in place.

Around 5 pm SBCAPE looks to be 500-1000 J/Kg along the Hudson Valley; SB CAPE values of 1000-1500 J/Kg to the Southwest of the CD and south of the Mohawk Valley. MLCAPE looks to be in the 500 – 1000 J/Kg range.

Surface based CAPE at 5:00 pm


Mixed Level CAPE at 5:00 pm

CAPE < 1000 shows weak convection CAPE 1000-2500 moderate convection CAPE >2500 Strong Convection.

Lifted Index (LI)
During the early afternoon around the Hudson Valley and down into the Catskills, LI is going to start increasing. Around 1 pm it will be 0 to –2….then by 5 pm the LI will be –2 to –4. By 8 pm these LI values will be starting to shift to the west of the Hudson Valley.

LI at 2:00 pm


LI at 5:00 pm

When the LI is negative it means that the low level air from the surface up to around 500 mb is unstable, and suggests the possibility of convection.
LI of 0 to –1 is somewhat unstable, LI of –1 to –2 is moderately unstable, –3 to –4 is largely unstable, and LI below –4 is very unstable.

Storm Relative Helicity (SRH)

This is a measure of the rotational updraft potential…it can be useful for forecasting severe weather and the likelihood of of supercells. There are two levels that get looked at…the 0-1 Km and the 0-3 Km level.

Values of 0-3 Km SRH of 250 or greater and 0-1 Km values greater than 100 can suggest an increased threat of supercells and  tornadoes

The 0-1 Km SRH is going to be 150 – 200 Km

0-3 Km values will be 250-300 Km.

Lapse rates look to be 5-6 around the Mohawk and Upper Hudson Valleys. with values of 6-7 over extreme southeast NYS and most of New England. This should help keep the wind theat from become widespread. But localized damaging winds are possible

Bulk Shear, values look to be 40 - 70 KTs when the Bulk Shear is  30-40 KTs+ it shows severe storms are possible…maybe even supercells…the question is will we have enough instability to transport this to the surface?

Right now, we should see something similar to what we saw the other day. During the afternoon we will see a thin line of low topped convection (QLCS) develop to the west that will move east.

QLCS is normally a thin intense squall line, usually this type of line doesn’t have a lot of thunder and lightning with it. This is because the strong shear overhead keeps the cloud tops low, generally they stay under 15,000 feet. That may seem tall, but, a summertime thunderstorm can have tops of 30,000 feet or higher. A QLCS line can often have strong gusty winds accompanying the frontal passage. As we saw on Tuesday, this type of line can produce wind gust of over 40 mph.

Timing looks to be more or less like this.

By midday the line looks to be impacting Central NYS and the western Mohawk Valley.Then moving into the Hudson Valley around 5 or 7 pm. This would coincide with the increasing severe indexes, I mentioned above. By 2 am the line should be clear of the eastern NYS and western New England. Rainfall amounts look to be a widespread, 1-2 inches with perhaps more in spots. Right now those with the best shot at severe weather would be south of Albany and the Mohawk Valley into the Catskills and Poconos, but severe weather could popup anywhere along the line.

Well that about it.....just remember to heed all warning given. There could be flooding in poor drainage areas and ponding on roadways. So if your out and about, drive will caution. Also never drive over or approach downed power lines.


Monday, September 17, 2012

The Sept 18th weather threat.

The weather tomorrow is going to look a lot like what we saw on the 8th, only a bit more to the south. We will have a strong cold front that will be intensifying as it moves out of the Great Lakes, there will be several short-waves moving along it. A surface low will develop in the Tennessee and Ohio valley and move north. The low will pulling a lot of southern moisture into the Northeast. The cold front and the low will interact with each other. We will have marginal instability, with ML CAPE values of 200 to 750 J/Kg. Overhead the upper and lower jets will be very potent in the afternoon and evening; the lower jet will be in the neighborhood of 60 to 70 knots, with a upper level Jet parked just to the west of around 140 knots. However, the mid level lapse rates look very unimpressive at this time, around 5.5 C/Km. The shear profiles are such that CAPE values of 500 J/Kg would be more than enough to create a squall line.

In the animation you can see a very dynamic squall line quite clearly on the simulated radar. The line will stretch from NYS to North Carolina. The line will be thin but it will be very intense with extremely heavy rains and strong gusty winds. When the line goes through the winds will whip-up to over 40mph.

The timeline will be something like this. We run the risk for a few scattered showers after midnight, this threat will last until the early morning hours of tomorrow. As the morning progresses we will see more in the way of steady rain from west to east. The heavy rain will be falling in western NYS and Finger lakes in the morning; moving into areas east of Lake Ontario in the afternoon.I think the squall line will be approaching the Tug Hill around 4:00 pm and should be impacting the western Mohawk Valley around 5:00 pm. It should start to move into the Capital District after 8:00 pm Rainfall totals for the event will be 1-3 inches. But in spite of the heavy rain, I don’t think flooding will be a huge issue, do to it being so dry. However, there could be some small stream flooding in poorly drained areas.

As for winds, boundary-layer instability looks to be just enough to allow some of the wind energy overhead to mix down to ground level, especially for those at or above 1800 feet.
The thunderstorm threat is low, but those south of Albany have the greatest chance of seeing any storms that do develop, it looks like the greatest instability will be over Ulster, Dutchess, and Litchfield Counties. Any storms that do develop will carry an additional wind threat.
The lack of instability will be caused by pre frontal clouds and rain and weak lapse rates. But as we’ve seen in the past, that the models tend to under-forecast instability in this type of setup. We will be dealing with a chance for low topped convection, this can lead to significant convective weather, if things come together just right, so the instability will have to be closely monitored tomorrow in order to assess the tornado potential. The main threat will be the southern Mid Atlantic during the afternoon, with a much lesser threat in southern New England during the overnight as the squall line moves eastward. The greatest tornado threat will be from southeastern Pennsylvania into North Carolina during the afternoon and evening. CAPE values look to be 750 to 1200 J/Kg in Pennsylvania, and 1500 - 2000+  in the Southeast. 

Friday, September 14, 2012

A Winter Outlook Update

Hi it’s Rebecca again, I thought I would give a quick update on how the oscillation’s and Teleconnections are shaping up.

As I pointed out in my preliminary 2012-2013 winter outlook, it looks like this will be an El Nino winter. The data coming in for September is still showing that a weak to moderate El Nino is quite likely.The El Nino would kick in during the October – January timeframe.

As you can see in the Graphic on the left. there is warming going on in the equatorial Pacific. There are indications that warming is starting to occur in the central and western Pacific. If the El Nino does indeed become west based, it would have major implications for our winter weather in the Northeast.

East based vs.. West based:

Believe it or not, a west or east based El Nino makes a huge difference in weather on the East Coast. During an east based El Nino the wintertime temps are normally warmer. Whereas, a west based El Nino normally has much colder temperatures, especially in the Northeast.

Here are a few years that we had an east based El Nino

1951-52, 1972-73,  1991-92, 1997-98, and 1986-87

Here are a few years that we had an west based El Nino

1957-58, 1965-66, 1982-83, and 2002-03

The Strength:

The strength of an El Nino makes a world of difference. Weak to moderate El Nino’s pose a greater threat for a heavier winter, in the Northeast; this is because the setup allows storms to dive into the Southeast, where they pickup a lot of moisture, then move into the Northeast drawing in cold air as they move north….However, normally a strong El Nino will cause the temps to be warmer.
A weak El Nino generally means a snowy winter for the East Coast.
A moderate El Nino leans toward a average wither on the East Coast.
A strong El Nino typically brings less snow to the East Coast.

Years that featured weak to moderate El Nino conditions

1977-78, 1992-93, 2002-2003, and 2009-10

Of course the NAO and AO would have to play along. The vast majority of the models are showing a negative NAO. However, as I said in my preliminary outlook….this might not be the case…..But I’m starting to lean in the negative NAO direction.

The PDO will be positive this year. During the positive phase of the PDO, the Northeast sees a decent winter.

Here is a look at the current sea ice conditions. There has been a large increase in the amount of ice over what we saw last month. I will have a better Idea what the snow and ice looks like as we get closer to winter.

Right now, I think we will see slightly cooler than average temperatures with at least an average snowfall. The setup does favor more Nor’ Easters. Therefore southeast NYS and southern New England could do well. I still have a few things I’m trying to get a handle on. But, I’m confident we won’t see a snowless winter like we had last season.

If you want to see a cold and snowy winter; hope for a negative NAO to go along with the positive PDO, and west based weak El Nino.

I should have my final 2012-2013 winter outlook posted in three or four weeks.


Tuesday, September 11, 2012

The Long Hot Summer

Hi it’s Rebecca again. This post will be on the long hot summer. I’m not talking about the 1958 movie staring Paul Newman and Joanne Woodward. I’m going to talk about the hot summer of 2012.

It’s been warm:

There is no doubt it’s been warm. Last year we had a very mild and snowless winter. In fact the winter of 2011-2012 was the fourth warmest on record. Following right on its heels, The contiguous US saw the warmest spring on record. During the March, April, and May time period 31 states had their warmest spring on record. Record and near record warmth dominated the eastern two thirds of the country. The Northeast saw temperatures that the region hadn’t seen in over 117 years. In fact, the spring of 2012 averaged temperatures 5.2 degrees F above long term average, and surpassing the previous warmest spring 1910 by 2 degrees. 

untitledtemps For those of you who thought it was hot this summer, you were right. The National Climatic Data Center (NCDC) has listed the Summer of 2012 as the third warmest on record for the continental US. The hottest summer on record was in 1936 with a seasonal average of 74.6 degrees F. The summer of 2011 averaged 74.5 degrees F, for the season. This year had a nationally averaged temperature of 74.4 degrees F, 2.3 degrees F above the 20th century average. Across the Northeast seven states had an extremely warm summer.


The Northeast Regional Climate Center at Cornell University stated, this is the hottest year on record for all 9 states in the Northeast. The entire Northeast saw a January through July temperature average of 49.9 degrees; this far surpasses the second warmest seven month period in 1921, which averaged 49.2 degrees.

August was the the 15th consecutive month of above average temperatures across the country. The summer of 2012 would most likely have gone down as the hottest on record if not for August. The warm temps weren’t quite as extreme as we saw back in July. But still August was ranked 16th warmest since 1895. 

Stats for Albany, NY:

There have been 17 straight months where Albany has seen above average monthly temps compared to the 30 year mean. The Monthly mean is the average of a months daily high and low temperatures.

During  June, July, and August of this year, Albany recorded 11 days where the daily high was 90 or higher, and 7 days where the daily high was 89. Here is a table that shows how 2012 has stacked up to the average mean. The mean average came from the Northeast Regional Climate Center.

Month Average Mean This Years Mean Departure
January 22.2 28.6 +6.4
February 25.0 32.1 +7.1
March 35.0 45.9 +10.9
April 46.6 48.1 +1.8
May 58.1 63.1 +5
June 66.3 67.5 +1.2
July 71.1 74.8 +3.7
August 69.0 72.2 +3.2


January thru August time-frame was the 14th driest such period on record for the contiguous US. As of the end of August 63% of of the lower 48 continue to experience drought conditions.The national precipitation mean shows this summer was the 18th driest on record.

According to the Palmer Drought Index, 55.1 % of the Contiguous US is in moderate to extreme drought. The 2012 drought is exceeded only by the droughts of the 1930’s and 1950’s. Now while the northeast hasn’t seen drought conditions like the Midwest; The entire Northeast has seen year to date mean precipitation totals among their ten driest.

untitled Here is how the June through August precipitation worked out across the lower 48. But this only shows part of the story. If you take into account the snowless winter of 2011-2012. it’s easy to see why over 60% of the country is in dry or drought conditions. As of September 4th, most of New York State was abnormally dry or under moderate drought conditions.  Even though dryness is fairly rare in New England, northern Vermont and all of Massachusetts and Connecticut  are in abnormally dry conditions. 

Looking ahead into the Fall and Winter:

Droughts are slow to start and slow to depart. With this in mind, I don’t think we will get out of our precipitation deficit any time soon. As I’ve said, in past blogs and on my weather page, we’re going into a weak El Nino. During a normal El Nino, the jet stream often goes into a split pattern. The southern track becomes very active, while the northern jet stays rather weak. This kind of pattern is often good for the Northeast precipitation wise. That is as long was we can get some kind of Greenland block to set-up……As I said in the last blog…I’m not 100% sure we will see a long lasting block this year …The block will depend on what the NAO does.…But other than my thoughts on the NAO,  the other indexes are showing we will see a decent winter. So we should see at least an average winter for 2012-2013. Lets hope this is the case, because if we see another winter anywhere close to the one we saw last year, we will be in trouble.

Well that’s it for this blog installment. I will be happy to answer any questions you might have.