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 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

   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.

Wednesday, February 08, 2017

Does A Warm or Cold Winter Mean More Late Season Snow?

We hear it every winter after a period of extremes:

"This cold means a rough start to spring".

or..."These warm temperatures mean were going to get a big snow in March".

Is there any truth to this historically?

The first chart below shows some of the coldest winters (December through February) on record in Cleveland and each daily snowfall occurrence regardless of the amount from the 3rd week of February to roughly the Vernal Equinox (March 20th). I didn't use years prior to 1900 as snowfall data is frequently incomplete. The second chart shows the same daily snowfall but for some of the warmest winters on record.

Light blue days indicate snowfall under ONE INCH
Dark blue days indicated snowfall greater than TWO INCHES
Red days indicate snowfall greater than FOUR INCHES

25 days with at least one inch of snow
3 days with at least four inches of snow

26 days with at least one inch of snow
3 days with at least four inches of snow

Bottom line: A very warm or cold winter overall seems to have little bearing on late winter snowfall

Outlook For The Rest Of Winter? Written January 19th/Updated Feb 9th

Yes. It's a catchy title that probably evokes many suspect responses.  Let me explain my self:

Big cool down late this month/first week of February followed by a warm up by mid month February per the Bering Sea Rule which dictates ridge over the Bering Sea correlates well to eastern US ridge roughly 16-18 days in the future.

The GFS shows this ridge evolution quite well.

February 9th Update:

BSR verification (forecast left panel with actual heights right) for the period above looks pretty good.

This warm up may be the final nail in the coffin shutting down arctic cold for good this winter. Why? Check this much snowfall did we get from 3rd week of February to start of spring in 10 historically cold winters in Cleveland? Not much...

Wednesday, January 04, 2017

Possible EPO/NAO Connection in January, Cold Implications

The EPO was forecast to drop significantly negative around New Years.

Today, the EPO has probably bottomed out with a slow increase over the next week or so.

The EPO derived by finding the pressure changes between these locations in the northern/eastern Pacific Ocean.

Notice how the Northern Pacific ridge evolved since Christmas to what it was on New Years Day. The SE ridge began to break down as the trough progressed east as the Greenland high shifted back west.

There have been only 3 other instances where the EPO dropped to under -400 in January for at least a few days. Each instance featured widespread cold:  1963, 1974 and 1991.  Notice the southeast ridge attempting to push warmer air further west in 1974 and 1991.

The models, both the EURO and the GFS kept the trough west until January 1st when it began ejecting the trough east.

EURO output for January 7th. 12-26 and 1-1

The Greenland block suggests a -NAO (North Atlantic Oscillation) which connects to colder east. The southeast ridge should not be this strong. Yet the southeast ridge continues to linger for the last several weeks.  A Greenland Block argues against the southeast ridge. But the weak La Nina signal argues for it. Have there been instances historically in January where the EPO goes strongly negative (-300 or below) similar to the current situation with a positive NAO (stubborn southeast ridge)?  Yes.

The battle goes on. The key, I believe, lies in the cool pool in the northern Pacific Ocean. It has prevented a strong ridge tendency across the western US which locks in the trough across the north and central US. The southeast ridge is hard to overcome.

What does all this mean long term through the end of January?

1) The lack of change in the sea surface temperatures in the northern Pacific Ocean will make western US ridge development difficult. 2) The trough will continue to drift east bringing with it shots of cold but it will be transient. 3) The southeast ridge will continue to play havoc with forecasts reducing long bouts of cold across the eastern US for the foreseeable future. The NAO will have more of an influence the second half of winter.  Look for more panhandle-type systems the rest of the month similar to the one this weekend.