Thursday, May 16, 2024

Rainfall: Tale of Two Different Periods


Its been more dry than normal in recent days overall. However, rainfall across northern Ohio and much of the lower Great Lakes was well above normal from mid March to mid April:



The overall pattern has shifted since April 15. Rainfall with the exception of a few locations in Holmes, Tuscarawas counties has been below normal: Dark circles indicate above normal rain areas.





Days with rain in April. Notice the high frequency of rain in the first half of April.


From April 15 to May 15, the story has been opposite:


Akron rainfall since April 15:



Wednesday, May 01, 2024

Ohio Tornado Recap Through April 30


So far this year, the Ohio tornado count has been record setting.  Preliminary numbers put the total at 43 although official tornado track analysis puts the exact number closer to 35. Either way, we haven't had a year anywhere close to this since...well, last year. 

Ohio counties that have been under a tornado warning at some point this year: 55 of the 88 counties.




Here are the totals year by year since 1950. Red bar represents total tornadoes through April 30.  The green bar are the EF2 or greater tornadoes each year.


Here is the average number of tornadoes per state through April 30:


Here is the actual number this year through April 30:



Why so many tornadoes this year?

First, we have been transitioning out of a very strong El Nino period and rapidly heading into a La Nina. These changes in the equatorial Pacific have impacted the jet stream across the central US. Throughout the winter, the storm track was absent across the US as evident by below normal snowfall across the central US.

Notice how the jet intensity was abnormally strong in mid March and April across the mid-west. Warmer colors indicate well above normal jet intensity.

The lifted index (degree of instability) was extremely favorable for rising air and storms across the Ohio Valley in mid March. Colder colors indicate rapidly rising air.


The MJO might have been a factor. Higher amplitude phase 4-6 in mid March. Moderate amplitude phase 8-1-2 in late March. However, according to this paper, the connection in March and April might be smaller. Bold print below is important:

The physical mechanism proposed in this study cannot explain the MJO–U.S. tornadogenesis relationship in the boreal early and middle spring months (March and April). Compared to MJJ, the Pacific jet is strengthened and shifted southward in March and April, but the anomalous subsidence over the northeast Pacific is very weak in March and April. Therefore, it is more likely that the relationship between MJO and U.S. tornadic environmental parameters in March and April is largely influenced by extratropical stationary Rossby waves forced by MJO-induced diabatic heating anomalies over the Maritime Continent. Thus, it is also likely that natural atmospheric variabilities originated from high latitudes such as North Atlantic Oscillation (e.g., Lin et al. 2009) and Artic Oscillation (e.g., Zhou and Miller 2005) interfere with the MJO-induced extratropical teleconnection to the United States in March and April, and thus may weaken the relationship between MJO and U.S. tornadogenesis. Additionally, in March and April, tropical Pacific sea surface temperature anomalies associated with El NiƱo–Southern Oscillation (ENSO) are of key importance in modulating the spatiotemporal variability of U.S. tornadogenesis (e.g., Weaver et al. 2012Lee et al. 20132016Barrett and Gensini 2013Allen et al. 2015Lepore et al. 2017Molina et al. 2018Chu et al. 2019).


Speaking of high latitudes, check out the height anomalies in the higher latitudes since early 2024. Heights rise, Arctic Oscillation drops. Frequent troughs track across the mid latitudes. Notice all but one of the top 7 tornado days occurred when the northern height anomalies were high. 


Here are the mid latitude 500 mB heights vs normal on those top 7 tornado days with SPC storm reports for each period:

#1 - April 26-27 (143 tornadoes)




#2 - April 1-2 (97 tornadoes)



#3 - March 14 (36 tornadoes)



#4 - April 16 (24 tornadoes)



#5 - February 27 (24 tornadoes)




Gulf of Mexico water temperatures were well above normal in March especially. Some cooling has occurred since but overall temperatures are still above normal. 


We also transitioning out of El Nino and into La Nina territory over the last 2-3 months. Notice the warmer water eroding away along the equator. This probably played a factor in the overall jet stream direction and intensity changes across the central US.








Monday, April 01, 2024

Total Solar Eclipse Part III: How Often in Northern Ohio?


The last Total Solar Eclipse to pass over northern Ohio was in 1806. Thomas Jefferson was President. Here are the next TOTAL SOLAR ECLIPSES with the PATH OF TOTALITY to cross northern Ohio

There are only 5 in the next 2000 years!

What are the types of solar eclipses? (descriptions and images courtesy NASA)

TOTAL SOLAR ECLIPSE


A total solar eclipse happens when the Moon passes between the Sun and Earth blocking the face of the Sun. If a location is in the center of the Moon’s shadow when it hits Earth they will experience a total eclipse. The sky will darken as if it were dawn or dusk. Weather permitting, people in the path of a total solar eclipse can see the Sun’s corona, the outer atmosphere, which is otherwise usually obscured by the bright face of the Sun.

ANNULAR SOLAR ECLIPSE


An annular solar eclipse happens when the Moon passes between the Sun and Earth, but when it's at or near its farthest point from Earth. Because the Moon is farther away from Earth, it appears smaller than the Sun and does not completely cover the Sun. As a result, the Moon appears as a dark disk on top of a larger, bright disk, creating what looks like a ring around the Moon. 

HYBRID SOLAR ECLIPSE


Because Earth's surface is curved, sometimes an eclipse can shift between annular and total as the Moon’s shadow moves across the globe. 

Here are two great videos from NASA on Total Solar Eclipses:



Here are some nice eclipse tools from NASA:

Total Eclipse Explorer - Interactive

Total Solar Eclipse Viewer



Wednesday, March 27, 2024

Eclipse Day Cloud Outlook - 12 Days Out

You've heard me say this countless times over the years. I really don't put a ton of trust in daily model data further out than 7 days. (Contrary to popular belief, 7 day forecasts are far more accurate than they were 15-20 years ago.)  They do give a nice overall picture of the pattern across a large region like the mid-west or Great Lakes. This provides information like "above normal rainfall or below normal temperatures" which are definitely usable. However, deriving a detailed hourly forecast this far out will always invite problems. Keep this in mind as we close in on Eclipse Day.

For what its worth, here is what the GFS model is showing from late Saturday April 6 through late afternoon Monday April 8th. This is middle altitude cloud cover percentage.

I wouldn't use this information to plan your eclipse viewing as we still have time before the hourly forecast details become better in focus.  If this verifies, cloud cover will be a problem

Another update on Friday.



Eclipse Path


Monday, March 25, 2024

Total Solar Eclipse Part I: What's The Weather Typically Like on April 8th?

NASA

As of this writing it's still a bit too early for a super detailed daily forecast for April 8 in northern Ohio. However it doesn't keep us from looking back at past April 8 weather history.

Here's the weather for April 8 over the last 20 years in northern Ohio:



The NWS office in Wilmington, Ohio has some nice past satellite images showing the wide variety of cloud cover regimes on April 8th.  Here is one comparing 2020 to 2021.


Historically, a cloud free day around the Great Lakes is not very high.

Image courtesy:  Brian Brettschneider, Climatologist

Here is a nice summary of April 8 weather for Cleveland:


Not that I put tons of (little if any actually) weight on deterministic model output but for semi-entertainment use, here is what the American model (GFS) is showing for Monday afternoon, April 8th. What is my confidence of this verifying?  Not high as of this writing. More to come.






Friday, March 22, 2024

Many Tornadoes In Ohio Thus Far. How Does This Compare to Past Years?

 


Uncharacteristically, late February and March thus far, has been a very active period for severe weather across Ohio. While we do see more frequent day-to-day weather fluctuation across the southern Great Lakes and Ohio this month (and April) than in any other month, severe weather doesn't always accompany these changes.

The first severe weather event occurred on February 28th. 

Only 2 hail reports with this first round in late February. No tornadoes.  Most of the storm reports (hail, wind and tornadoes) were across central Ohio.


The second round was far more extensive March. A total of 18 tornado warnings across Ohio and 6 in northeastern Ohio. The NWS in Cleveland also has a great recap here.



5 tornadoes were confirmed in northeastern Ohio. A total of 15 across Ohio.

Storm Reports in March 2024




Radar - March 14, 2024
So far this year's Ohio severe weather reports:



Plymouth, Ohio damage from March 14, 2024 tornado

Is the number of tornado unprecedented for Ohio through late March?  I looked back at the total OHIO tornado count through March since 1950 and separated the totals (red)  with the EF2+ totals (green).  Here is what I found:

Ohio Tornado Count: 1950 - 1985 (thru March)

Ohio Tornado Count: 1986 - 2024 (thru march)

There were brief upticks in tornadoes in the mid 50s and a few instances in the 70s but nothing        really high.  The peaks were 1985, 1986, 2012, 2016 and 2017. Here is the early season 1986 tornado tracks:



Here are some additional bullet points on the graphics above:

*  Two of the three tornadoes in 1992 were EF2+.  One was an EF4.
*  The 1991 tornado was an EF3
*  Six of the nine early season tornadoes in 1986 were EF2+

However, over the last 2 years, early season Ohio tornado counts have rose significantly.  17 in 2023.  26 in 2024 through March. Five of those were EF2 tornadoes. One was in Crawford/Huron counties.

For spatial perspective here is the January through March tornado locations for 2023 and 2024:

Jan, Feb, March Tornado Locations - 2023


Jan, Feb, March tornado locations - 2024

Tornado warnings in 2023 through mid March vs tornado warning in 2024 through mid March:

2023




What were the causes of the uptick last year and this year?  Is this a fluke increase or something that we will see more in the years ahead?

One piece to the puzzle may be the Madden Julian Oscillation (MJO). This was in a high amplitude state in both years.  First image is last Jan through March 2023, second image is this year through late March. (More on this in the weeks ahead)

Strong Phase 7,8 and 1 in March of 2023

Strong phase 4,5 and 6 in March 2024


In my opinion, it's hard to draw a long term conclusion based on only a few severe weather events over a few weeks. So while we had two years with an uptick in early season tornadoes in Ohio, we need to monitor the next 3-5 years to see if a trend develops.