Wednesday, April 29, 2015

Tale of Two Different Aprils

Cedar Point in late April
It's hard to believe but temperatures for the first 3 weeks of April were well above normal. I've mentioned this fact to many people and they don't believe me.  Of course since then, the average temperatures have been anything but warm. The recency effect, as I've written, has certainly played a part in most people's perceptions of the April temperatures as a whole. Here are the numbers and handy pictures:

The first 20 days of April were above normal for not only Ohio but much of the US.
It was the 4th warmest first 20 days of April in Cleveland since 1871! The only years warmer were 1945, 1955 and 2010.

 Then the bottom fell out since then...

The temperatures across not only Cleveland but the Great Lakes, Ohio Valley and portions of the Deep South were well below normal. The period from April 21 through April 28 was the 7th coldest on record. The last year which featured a colder late April was 1940!

Luckily, the forecast for the beginning of May is showing a nice warm up. Expect temperatures in May to average above normal.

Monday, April 27, 2015

How Does Day-to-Day Weather Effect Spring Pollen Levels?

Flowing Pear Tree
Tree pollen is starting to read its ugly head.

Levels are running a bit behind last year as of April 27th. Pretty soon, a blanket of yellow or orange will cover everything.

Last Friday (24th), the level was between 1 and 9 grains per cubic meter. Last spring, after the cold and snowy winter of 2013-14, I charted the tree pollen count from early May through early June to see the seasonal trend. Notice how the numbers rose exponentially by the second week of May. The May 14th level of 2310 seems a bit high (it also occurred on a day with little wind) considering the overall levels. It might be a bogus reading.

The levels stayed fairly high with some variation through the end of the month. By early June, tree pollen was on the decline. Grass would replace it.

Did the tree pollen levels fluctuate day-to-day as the average wind speed changed?  The overall pollen count trend seems to stay in lock-step with the winds. As the winds increase, so does the pollen count.

How about temperature versus tree pollen levels AND wind speed?

Keep and eye on the tree pollen count as the winds increase with higher temperatures over the next 2-3 weeks. A few warm and breezy days will drive the tree pollen counts through the roof.

Get ready. Have your antihistamine handy!

Thursday, April 23, 2015

10 Year Anniversary of BIGGEST Late Season Snow Ever

I remember it well.

After the 10pm news on the evening of the 24th, I started my trek home along I-90 in Cleveland then south on I-71. The snow depth was approaching a foot.  It was a heavy, wet snow.  I hit something buried in the snow on the interstate which flattened my right front tire. I literally drove on the rim the entire way home because I didn't want to risk stopping on the side of the road assuming I could find it. Countless cars and trucks trying to find the easiest path to take without losing control. Our top speed was 25 mph for 40 miles.  After about 20 miles on the interstate, I decided to take a state route home.  If I needed to stop, I'd rather do it on a road that had strip malls and small businesses.  If I needed to call a family member to pick me up, better to do it from a parking lot than on the side of a major interstate with Tractor Trailers bearing down on you.

The temperatures at 850 mB (5000 feet) were very cold across the Great Lakes.  Notice how the core of the cold evolved and tracked west to east from early on the 23rd shortly before the snow began.

The 850 mB temperatures today are similar to the late April 24th reading:  -7 to -9. 

The difference is we don't have a major synoptic storm system today to produce widespread heavy snow this time around.

Radar image from 7:45am on April 23, 2015 for northern Ohio

The 2005 event developed as a east coast low which retrograded west continued to expand both at the surface and in the upper levels. By the 26th, it was absorbed into the mid-latitude trough in the middle of the US. 

The last 12 days of April ranged from lower 80s on the 19th to snow by the 23rd. By the 26th, daytime temperatures rose into the 60s with the majority of the snowfall melted away.

I wish we had photos of the May 10th snow back in 1907..the latest snow on record in Cleveland.

Tuesday, April 21, 2015

HUGE Winter 2014-15 Recap: Reasons for Arctic Cold, Snow, Records

I hesitated to post the final details on this past winter until I was pretty darn certain we were finished with snow. Historically, we have always used April 15th (Tax Day) as this magical, non-scientific date that signifies the demarcation between snow and spring.  If you can make it to the 15th, 99 times out of 100 you're good to go.  This winter worked out great in this regard.

Here are the final winter numbers. See my early March post on the metrics we typically use and why we used them.  Many of these graphics compare this winter to last winter and the COLDEST winter ever (1976-77) in northern Ohio.


Our winter outlook was created by analyzing the global sea surface temperatures in these regions.

Pacific warm and cool pools have shifted since last winter (2013-14). Yet the result was the same:  COLD EAST, MILDER WEST.

The pressure pattern over the Pacific Ocean and North American continent reflected the sea surface temperature pattern:  This pressure configuration was a strong -EPO, -WPO, +PNA set up. It stood firm all winter which locked in the ridge west and trough east for the most part.

Image courtesy: Larry Cosgrove

Negative EPO favors eastern cold. Eastern US Cold periods circled in red
Positive PNA favors eastern cold. Cold periods circled in blue
-WPO favors eastern cold. Cold periods circled in red

Last summer (2014), talk of a strong El Nino faded as a central based El Nino developed called a "Modoki". These central based weak El Nino come in many different flavors. The current El Nino is circled at the top of the graphic below.

These favor below normal temperatures across the eastern US and above normal temperatures across the west.  Ridge west, trough east. 

Our winter forecast was created with weighting certain years in our analog set. Our forecast matched up very close to the overall average temperatures across the US from December through February.

We started off very cold in November partially driven by the Typhoon in the Pacific. It boosted the Gulf of Alaska low which boosted the ridge of warmth in the west which in turn drove cold south across the eastern US.  I wrote about the Typhoon Rule back in November and how we uses that to forecast the November cold.

Overall temperatures across the continental US on November 18th were the coldest since 1976!

The high of 18 degrees on the 18th was the coldest November day since 1958; 4th coldest high temperature in November since the 1870s.  
US temperatures rebounded in December after the cold November. We had one SNOWFALL in December which was under an inch. The 3rd lowest total since 1893; lowest since 1931.

By New Year Day, people were wondering where this cold winter was we had outlined in our outlook back in late October. I kept telling people on Facebook and Twitter to be patient. The cold is coming and when it does, it will harsh and similar to the year before.  Guess what happened in January?  The slow turnaround toward ARCTIC COLD began across the eastern US.

By February, the arctic floodgates had opened across the eastern 1/2 of North America. It was ALL-TIME COLDEST February in Cleveland since weather records began in 1871.

Rome, Ohio in the heart of Ashtabula County, due to cold air drainage down the surrounding terrain had a low of -39 degrees!

As the winds dropped, so did the temperatures. The next day, temperatures jumped 65 degrees in 30 hours!

February 14th through the 20th was 5th coldest 7 day stretch in 145 years in Cleveland coming close to matching the arctic cold of 1994.

Remember back a few winter ago when the ski resorts were having a tough time staying open because of the lack of snow and cold? Look at the winter 2012-13 temperature ranks vs the last two winters.

Add caption
Coldest winter since 1977-78
Less days above 40...
More days below freezing

Arctic cold and clear/calm skies produced huge ranges of temperature.

 Very cold late season morning lows we haven't seen since the early 1960s!


 We had much more snow in 2013-14 vs this past winter...hard to believe.  If December snowfall would have been closer to average, the last two winter snow totals would have very close.
Days with snow cover of at least ONE INCH. Last winter we had more.

 Peak Lake Erie Ice Cover and Dates.