Thursday, June 01, 2017

Which Counties See the Most Spring Tornadoes in Northern Ohio?

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 The tracks of each tornado in each month




Thursday, May 04, 2017

Why The Abrupt Cooler Pattern in the Northeast?

After the warmest April on record in places like Cleveland, Ohio and across much of the Ohio Valley and much of the eastern US, the pattern has not only reverted back to spring, it took several steps back resembling elements of winter. Throughout April, this high pressure ridge stayed east which allowed the ridge across the eastern US to build allowing above normal temperatures. Many were fooled into thinking that summer was here and we were in the clear to plant gardens. Not so fast!

Look at April temperatures versus the 30 year average:

Now look at the first week or so of May per the American model (GFS).

Why the sudden flip?  In this case, we have to look over Greenland for the answer.

Remember that across the mid-latitudes, troughs and ridges (valleys and peaks in the upper levels of the atmosphere) travel like a fluid through the atmosphere. When one location is lucky enough to be blanketed by a ridge, fair weather typically is the result. Once the succession of trough and ridges is changed by an interruption in the wave pattern, the weather will change at the surface. These changes (too much to go into here. See Southern Oscillation Index) often originate over the Pacific Ocean and propagate east. Currently, these changes are reflected over the northern Atlantic and Greenland.

Notice the red (high pressure) at the top inching west blocking/stalling the blue (low pressure systems) over the NE
We can quantify the strength of this ridge using the NAO of the North Atlantic Oscillation.  The more negative the index goes, the stronger the Greenland ridge. The NAO has been forecasted to drop close to -300. Historically this has only happened once in the month of May since record keeping began.  That was back in 1993.

NAO drops to -300 soon


But be warned, historically, this pattern over Greenland in May doesn't always produce a cold and rainy May. Look at the high temperatures in Cleveland during these years of record low May NAO:


Look at the resultant upper level pattern across the US in each of these years. All but 1948 and 2008 show dominant warmth.

May 1948 - DOMINANT COLD OVER GREAT LAKES/NEW ENGLAND

MAY 1951 - WIDESPREAD WARMTH ACROSS US. COLDER SOUTHWEST

MAY 1962 -  WIDESPREAD WARMTH ACROSS US

MAY 1980 - WIDESPREAD WARMTH ACROSS US

MAY 1993 - MORE US WARMTH. COLDER DEEP SOUTH


MAY 2008 - MUCH OF US BELOW NORMAL

The NAO this low (or any other index) isn't always a great predictor of temperature and the overall pattern. 

Unfortunately, unlike any of the previous instances of strongly negative NAO in May, this cold is locked in for at least another week.  So get ready for rain, scattered frost and perhaps some light snow!




Friday, April 21, 2017

Don't Plant Tomato Plants Just Yet



This happens every year we enjoy a very warm period in early spring.  People prematurely want to plant their garden. Don't do it...at least not now. (as of this writing April 21)

Below are the top 15 warmest April years in Cleveland.  Interestingly, the majority of these years featured overnight lows in the lower 30s in May.


Thursday, March 16, 2017

Do The Defensive Trends Shed Light on NBA Offensive Increase?

The previous post looked at the dramatic increase in 3-point field goals and other offensive statistics over the last 30 seasons. Do the rate of steals, turnovers and personal fouls per game shed any light on this?

* Turnovers per game started dropping from 1989 through 2000 with a leveling off over the last 10 seasons.

* Steals per game started dropping in the late 1990s with some leveling off for brief period over the last 15 seasons.

* Personal fouls feature some ups and downs with a steady decline since 2006





Monday, March 06, 2017

Morning Severe Storm Event of March 1st

Lightning damage in Dorset, Ohio

We just experienced our first severe weather event during the morning show in almost 3 years.  Given the volatile history of the storm system which was responsible for baseball size hail and one fatality from a tornado in central Illinois, we knew this event had pretty high potential for severe storms and a tornado warning or two.  We mentioned the increased likelihood of strong/severe storms more than 24 hours before the event.

If you familiar with my weather casts, you know that I rarely use the word "severe" to describe storms unless the situation warrants it.  The reason why is simple: When most people hear the word "severe" when describing storms, they immediately think "tornadoes".  The last thing I want to do is invoke the idea of tornadoes when in most severe storm cases (less than 10%) the chances of a tornado occurring are small.

Tuesday morning--24 hours before--was one of those instances where I used the word "severe" multiple times to describe the next day's outbreak. The possibility of northern Ohio going under a severe thunderstorm watch was high enough to be included in the forecast. All high resolution projections showed two distinct severe storm clusters tracking across Ohio between 12am and 8am. It was the second one that had us concerned not only because of it's elevated severe weather potential but because it was developing overnight when most people are sleeping. This animation below was generated at 1am Tuesday more than 24 hours before the event:


The two severe storm clusters projected location at 1am Wednesday.


By Wednesday morning, the second storm line above had already produced a strong tornado in central Illinois and one fatality.  That same storm produced baseball size hail.

Ottawa, Illinois

The Storm Prediction Center had issued this discussion specifically for the second line of storms BEFORE the severe thunderstorm watch was issued at 3:25am. See the strong wording below.

Mesoscale Discussion 0233
   NWS Storm Prediction Center Norman OK
   1244 AM CST Wed Mar 01 2017

   Areas affected...Portions of southern Lower
   Michigan...northeastern/central Indiana...and northwestern Ohio

   Concerning...Severe Thunderstorm Watch 45...49...

   Valid 010644Z - 010745Z

   The severe weather threat for Severe Thunderstorm Watch 45, 49
   continues.

   SUMMARY...A squall line will continue advancing east across the
   discussion area early this morning. An attendant threat for damaging
   winds will persist as these storms track east.

   DISCUSSION...With broader large-scale ascent (e.g., coupled upper
   jet structure) spreading across the Great Lakes region, rejuvenation
   of an ongoing squall line over southern Lower Michigan/northern
   Indiana has occurred. Despite some surface-based convective
   inhibition/weak low-level stability, the upscale organization of the
   line, combined with 1-km flow around 50 kts, will maintain a threat
   for occasional damaging wind gusts, especially in any bowing
   segments. Additionally, considering the magnitude of the low-level
   shear, a brief tornado remains possible.

The severe thunderstorm watch was issued a few hours later for ALL of northern Ohio. Remember, on FOX8News This Morning the day before, we mentioned the strong possibility of a watch being issued.



Several tornado warnings were issued for portions of CUYAHOGA, GEAUGA, SUMMIT. MEDINA AND PORTAGE counties between 6 and 6:30am Wednesday morning by the National Weather Service due to rotation being detected by Doppler Radar. By 7am, the line was east of northern Ohio. The Severe Thunderstorm watch was discontinued from west to east.

========================

Yet even after a potentially dangerous situation like this, there continues to be individuals especially on social media who question how we covered the event. For the record, I always grade myself after events like this. Did I do everything right?  Did I convey the seriousness of the event without blowing it out of proportion?  I can honestly can that I wouldn't have done anything different.

In the weeks ahead, we'll talk about the advancements of severe weather prediction and communication.

Tuesday, February 21, 2017

Will Cold Air Return After the Late February Warmth?

The stubborn southeast ridge threw a wrench in our winter temperature and snow outlook for Cleveland and the Ohio Valley (more on that next week). We anticipated it to stay further east It has remained very strong throughout winter driving many panhandle low type storms along with temperatures recently to levels only reached a few times since record keeping began in 1871.




The stretch of warmth in Cleveland will more than likely end up being the warmest 11 day winter stretch ever!  This February stretch is similar to a warm February stretch back in 1976 and 2000. Notice the widespread nature of the warmth back in those years.

Looks similar to this stretch...

Yet California keeps getting pounded with heavy rain/snow as the very strong Pacific jet stream continues. Reanalysis of vector wind anomalies at 300 mB since December 1st (3 day running average). Pacific jet is through the roof strong. No sign of the ominous western ridge which was dominant over the last several winters.

The MJO strength increased significantly since early February to very high amplitudes into Phase 6,7 and 8 territory.


Phase 7 and phase 8 in February with high amplitudes tend to favor warmth east. Yet look at Phase 8. It tends to favor cooler temperatures east (middle chart below). So even with a very strong MJO the temperatures can be highly variable. What I find interesting is that the Phase 1 temperature composite (far right map below) looks very similar to the overall pattern since this current warm up began.
The chances of this February finishing out as the warmest ever in Cleveland is climbing fast.


Will colder air return?  If so, how strong?

To answer this we look at the Pacific teleconnections to start March. I reference my quick cheat sheet so that I can visualize the pressure regions in question.

PNA is heading sharply negative
EPO is heading positive/neutral
WPO is heading negative (strongly negative)



Strongly negative WPO during the first week of March
What do these teleconnection levels mean for our sensible weather?  Historic temperature composites for each of these indices (PNA,WPO,EPO) in March mean below normal temperatures across the northern states centered over the Corn Belt and High Plains. The Computer models are also depicting colder air (see graphic below, lower left) centered across the upper midwest/west to start March with above normal temperatures across the eastern US and deep south.

While we should anticipate short-lived cool intrusions across the Great Lakes, temperatures overall will average out near the 30 year average (see lower right graphic) for the first week of March.  For Cleveland, daytime average high temperatures for March are in the lower 40s. 


Long range teleconnections for the middle of March show some colder signs centered central US and west. Something to watch over the next week.


The South Oscillation Index (SOI)--changes in the pressure patterns in the tropical Pacific Ocean (click here for more on the SOI and here)--shows rising pressure in the central US March 10-13th after the central US trough slides east March 7-9th.


Will the weak trough be a more permanent feature over the Great Lakes or will a warmer ridge develop by the 3rd week of March?  The answer will be apparent in both the SOI changes. The teleconnections will reflect the changes by the end of next week.