It's not all that unusual to see large temperature changes driven by strong cold fronts this time of year. Even though it is technically still summer, the sun isn't as strong as it was in early August. The early pushes of cooler air are becoming stronger and larger in extent. The polar jet stream is starting to become a more dominating force driving mid latitude systems the US and Canada much faster and with more punch. The front forecast to push through the Great Lakes late Wednesday/early Thursday is a prime example.
HUGE temperature contrast along the front.
Incidentally, last year almost to the day, we had a similar cold front and huge temperature contrast. We went from 96 and 95 to 62 in under 48 hours!
Atmosphere is very buoyant.
Precipitable water values are well over 2 inches!
Jet stream winds are very strong. Right-rear quadrant of the jet streak (diverging air aloft) over the mid-west will enhance the severe storms as they pass over Indiana and western Ohio.
Storm Prediction Center continues to show a slight risk for severe storms into northwestern Ohio for late Wednesday and early Thursday.
At this writing, line of storms should pass through northern Ohio between midnight Thursday and Thursday at 6am.
Temperatures will fall into the upper 50s and lower 60s Saturday.
The cool push of air is very strong and will envelop the northern 2/3rds of the US.
Good day everyone. Now that the meteorological summer period is behind us, let's recap the weather in Cleveland from June through August. A twitter follower reminded me that you can make numbers say what you want them to say. I responded to him saying that I always aim to paint a broad statistical picture with any weather recap to eliminate any biases and preconceived notions. Prior to the end of August, most of us had already involuntarily created our own narrative about summer before it had ended! So I try to combat the psychology with objective analysis while being cognizant of how people will perceive the numbers I present.
Enough of that, here is what I found. Remember, the time period is from June 1st through August 31st. Here is a quick look at the temperatures versus average across the US and North America. Much of the US especially the interior had temperatures around 1 to 3 degrees below average.
For Cleveland, the average temperature over the 3 months was the coolest in 10 years!
We forget about the summers in the early 2000s and a few in the 1990s.
2004 and 2000 were far cooler than 2014.
The real temperature story was the number of days below 80 degrees.This summer ranked 5th highest of any summer since 1935.
Summer rainfall was especially high as it was last summer and in 2011.
14.84" was 5th highest in the last 30 years.
The number of days with more than ONE INCH of rainfall was not impressive...
...yet the frequency of 1/4 inch rain events was the 2nd highest (one shy of the record--21--set in 1902) since record keeping began in Cleveland in 1871!
Prior to the late 1920s, the official measurements were taken in downtown Cleveland. Since then, Hopkins Airport is the official location.
* In summary, the summer was the COOLEST since 2004
* The number of days below 80 degrees was the highest since
* Most don't remember that 2004, 2000 and 1992 had more
* Rainfall was almost 5 inches ABOVE AVERAGE, 5th
highest in 30 years
* The number of 1/4" rain events was 2nd all-time. Only 1975
Over the last week, I've read several articles on the increase in extreme rain events as a contributor to the increase in Lake Erie algae bloom frequency. Here is some rainfall data I compiled for Toledo Metcalf Field. The data goes back to the late 1890s. Instead of using the entire year, I focused on the growing season period from April 1st through September 30th.
A steady increase in one inch rain events since the 1970s. The 1970s and 80s are comparable to earlier decades
The period from 2000 to 2009 wasn't off-the-charts when compared to the 1900s, 1910s or the 1940s. Yet an increase since the 1980s is evident. In the first 4 years (through August 20, 2014) already 17 one inch rainfall events; 3 in 2014 alone.
Several questions come to mind:
1) Are these rainfall numbers correct?
2) Is there any record of significant algae blooms in the early 20th century?
If anyone can shed light on any of this, please let me know.
In my last post, several drivers of this summer pattern were described in detail. Some of these carried over from the winter while the building somewhat weak El Nino (though not officially) has been a more recent factor. Some of these will no doubt carry over into the fall.
Rainfall since June 13th (last 60 days as of this update) is running 8-12" above average across a few counties. More than 90% of northern Ohio is running 1-2" above average rainfall.
Let recap: Where does this summer rank through August 2nd? 24th "coolest" in the last 60 years. We're only talking a few tenth of a degree from year-to-year in some instances.
In those summer that were "cooler" than 2014, the September 1st through October 31st period in Cleveland, HALF WERE SLIGHTLY ABOVE NORMAL AND HALF WERE BELOW NORMAL.
After taking into account the summer drivers (slightly warm water across the
tropical Pacific--not quite El Nino--and warm northeast Pacific Ocean), along with the weighted years from Dr. Joe B and Joe D, here is the analog for September and October combined.
This shows that northern Ohio in fall, in those years that closely match with 2014, is normal to slightly above normal.
This unseasonably cool pattern across the Great Lakes and upper mid-west hasn't been completely unexpected. Back in April and early May, we talked about how this summer would feature periods where temperatures would drop below normal. Take a look at the 12 day stretch from July 15th to July 26th. The area of the US that experienced below normal temperatures this year is exactly the same as 2009.
2009 was one of our years we used as a guide in formulating our summer outlook. Remember, this does not include this week's cool-down. I'll redraw this anomaly map at the end of this week.
The upper level (18,000 foot) trough is a bit stronger this year but in the same location as 2009.
Notice where the ridge (high pressure) is located: The western US where the present drought is the most extreme. Drought drives temperatures higher due to the dry ground. The dry ground and heat creates a high pressure ridge. This ridge keeps the dry conditions going further which drives the temperatures higher....and on and on.
Water temperatures in the Gulf of Alaska are off-the-charts above average this summer (as it was last winter).
The above normal Gulf of Alaska water temperatures have enhanced the western high pressure ridge by pushing the jet stream further north. The movement of the jet stream is indicated with the red arrow. The strongest portion of the jet stream (highest winds) is shown with the warmer colors over Alaska. The jet on the east side of the ridge dives southeast in the center of the country and bottoms out over the Ohio Valley where the trough is located.
The PNA index is used to measure these pressure patterns across the
Northern Hemisphere. When the PNA is positive, the ridge is very strong
out west and the trough/low pressure is strong east as it has been since
last winter. You can read about it more HERE.
The southeasterly jet becomes the conveyor belt for frequent rain and thunder events leading to above normal rainfall across much of the Great Lakes, Midwest and Ohio Valley. This also leads to more frequent periods of below normal temperatures.
For perspective, July in Cleveland, Ohio finished the 6th coolest since 1900.
The average high temperature in Cleveland from July 15th to July 31st was the the second coolest on record!
So the warmer Gulf of Alaska water and the drought out west have significantly boosted the high pressure ridge out west which is reinforcing the trough/cool pattern further east across the midwest and Ohio Valley. This is not a complete list of the drivers of this summer pattern. The weak El Nino, which garnered a lot of attention during the spring, has had an influence too but not to a major degree. The weak El Nino will factor into our winter outlook which I'll talk about in the fall. Let me know of any other major contributors that I've missed.
Bottom line, it doesn't look like this pattern is going to change anytime soon!
This picture of Cedar Point in winter might be overdoing it a bit. If you are heading there next Wednesday, I would suggest bring a sweatshirt.
While I was skeptical on biting to quick on this solution late last week, I quickly made adjustments Monday to reflect the huge changes for next week for two reasons:
1) The recurving typhoon. Typhoon Neoguri began a trek northwest then recurved toward Japan. When Typhoons recurve like this, it is a reflection of the overall hemispheric pattern which if followed "downstream" over North America typically means a major cool down across the eastern half of the US. This idea is called "The Typhoon Rule".
A ridge of high pressure in the western Pacific deflects the typhoon. This boosts the trough over the Gulf of Alaska which keeps the western US ridge going which in turn drives the trough/cool across the eastern US. While this "rule" shouldn't be used to determine specific day-to-day forecast details for any location, it gives us a very good indication of the overall jet stream pattern. Based on that, we can get a general idea of what to expect 6-10 days in the future.
2) Model performance: I didn't bite on the cool down was simply the models kept showing the trough/cool pocket over the east flattening which was suggesting a warming trend back into the mid 80s. A quick look at the model performance showed that they were having a tough time beyond 5 days probably due to the erratic behavior of the developing El Nino and the atmosphere's response to it. (Note the up and down SOI numbers--South Oscillation Index).
However, the models started to trend "not-so-warm"again (I like that wording versus "cool" since 70-75 degrees isn't really cool) where they have stayed all week.
The probability of temperatures above 90 degrees might not make it north of Dallas or central Florida according to the CIPS site.
Remember July of 2009? A major cool down occurred that month between 7/17 and 7/20 which mirrors what is coming next week.
Aside from Monday, get ready for a week that is about 8-10 degrees below average. Very comfortable but probably not pool weather.
Hurricane Arthur was upgraded from a tropical storm at 5AM EDT on Thursday. Hurricane warnings are up for the entire North Carolina coastline north to the Virginia border. Max winds are 90 mph; should reach Category 2 intensity early 4th of July morning with winds of 105 mph. Arthur is still 200 mph SW of Cape Hatteras moving NNE at 10-15 mph.
Its interesting to see how Arthur evolved from a disturbance over South Carolina, sliding southeast over the ocean then doubling back north off the coast of Florida over the last 5 days.
Most models take the center of Arthur over the Outer Banks. The HRRR shows it shifting track to the northeast hugging the coast later today.
The National Weather Service office in Morehead, North Carolina has an excellent discussion on the hurricane with wind and wave forecasts. Winds will increase rapidly Thursday evening with max gusts approaching 100 in local areas along the Outer Banks. The window for 80-100 mph will be around 12 hours.
Total rainfall could exceed 7 inches in many areas.
Wave forecast calls for 10-18 foot waves early Friday morning.