Tropical Storm (Depression) Bertha will impact our Thursday and Friday weather. It will bring periods of rain showers and humid conditions. The weekend is looking much better and cooler.
This week’s big weather news was in Tennessee. Early Tuesday morning a line of streaming showers due to an elongated trough of showers and thunderstorms entered the Tennessee Valley. All-day Nashville and the surrounding counties had been under heavy rain and some thunderstorms. Little did anyone know what was coming later that evening.
Yet, the one agency that is supposed to inform and give the proper time protections misjudged the storms and this led to at least 25 fatalities, a spawn of several tornadoes of greater than EF-1 strength and one confirmed EF-4 which led to millions in damage, destruction, and all, in the middle of the night.
“It slipped through the cracks at NOAA, so, therefore, when there’s no activation warning from their end, the community outdoor sirens do not activate,” said Ronnie Pearson, director of Warren County Emergency Management.
There it is. An admission of failure on the part of the NOAA. Folks in Warren County, Tennessee knew nothing of what was coming their way. Little did anyone in the counties hit hard to know to prepare properly. There were strong thunderstorms or severe thunderstorms warnings but no tornado watches the entire day even though the severity indices showed the high potential. Nobody can know for sure. There was a 2 percent chance according to the SPC (Storm Prediction Center) in Norman, Oklahoma of tornado development all day, but that wasn’t enough according to the standards of the NOAA in Nashville to issue anything but a severe weather statement all day. There were tornado warnings issued for the western part of the state but were canceled by 12:15am Tuesday morning.
Warning Coordination Meteorologist Joe Sullivan issued a statement saying conditions over south-central Kentucky were less favorable for tornadoes, but storm projections did support large hail and possibly a few strong to severe wind gusts. Sullivan did note that ” The storm that produced the tornado was not of the same type (supercell) that produced the tornadoes that night in Tennessee or near Crofton in northern Christian County, KY,” explained Sullivan. “This tornado was the result of the intersection of storms moving in two different – nearly perpendicular – directions. While the intersection of storm boundaries is not entirely uncommon, only rarely do they produce tornadoes.”
Nashville Weather Service forecasters sniffed this out in their Monday morning update, writing “the primary risk appears to be hail, but locally damaging winds and even a couple of tornadoes would be possible should capping erode.” It was a very low-probability but high-impact potential. Granted, you can’t issue a tornado warning until one hits the ground somewhere, but even as the day wore on not even the slightest indication of a tornado watch was issued. Those can last up to 12 hours at a time.
A rapidly-evolving environment
As late as 10:35pm news outlets were still clamoring at the severity levels of the storm:
“Storm mode looks to become increasingly messy, with multi-cell clusters eventually forming into a broken line,” the Nashville Weather Service had written in their meteorological forecast discussion at 10:14 p.m. “Damaging winds and hail continue to be the main concern, though an isolated tornado cannot be ruled out.”
Thus, there it is. As late as 10:35pm the NWS still had more than two hours to give some people still up warning.
A warning was finally issued for the Nashville metro area at 12:36am Tuesday morning. The tornado hit at 12:41am. And a lot of people were asleep. And a lot of people didn’t have an NOAA radio available. Yet, what good is any of this if you are asleep.
This image shows the radar at the time the tornado entered Nashville which had NO warnings even though this debris ball (area in pink and purple with the white dots) of tornado induced debris traveled for 275 miles for 4 hours towards Nashville that started in the western part of the state.
This was the TWEET earlier in the day on Monday which was put out. You can clearly see the areas in yellow had a “slight” risk of severe weather and those were the areas impacted. However, all other risk factors were higher except tornado development which stayed at a “low” threat.
At 11:45om a tornadic supercell was detected on radar heading towards Nashville. STILL, no warning issued by NOAA at this point for the Nashville metro area.
Sources and Pictures from The Washington Post. Matthew Cappucci
The Winter of 2019-2020 was never going to be one. And, in the future, when I look at the teleconnections in November and they look almost the same as they do as we enter March then that’s probably telling us all something. I’ve learned my lesson.
The teleconnections are one small piece of the puzzle of forecasting in meteorology. They provide us with a snapshot of what the atmosphere is doing.
The PNA is the Pacific-North American index. This tells us what kind of ridging is taking place. A (+) PNA tells us there is high ridging out west allowing storms to come in, up and over the Rockies, and down the shute towards the middle of the country and East Coast. A (-) PNA tells us the opposite. There is no ridging. Meaning there are flat waves coming in from the Pacific. It’s most progressive.
The NAO is the North American Oscillation index. It gives us a view of high latitude blocking over Greenland. A (-) NAO tells us there is blocking. A (+) NAO tells us there is hardly any block. This is key in that if a storm is coming up the East Coast it doesn’t allow it to cut towards the Great Lakes or through the Appalachians. Both cases provide us with mostly rain.
And the last the EPO is our cold air source. (+)EPO tells us there is no cold air source. A (-)EPO says there is a cold air source and it has staying power depending on how negative it is.
These are two indices from the last two weeks. And, as you can see, none of them are good for East Coast storms/snow in the winter months. If there is no cold air, if storms are just coming in and coming out, and if there is very little blocking then you can almost book it there won’t be any snow coming our way anytime soon.
And this has been the story the entire winter. It’s officially over in a couple of weeks, but meteorology winter is over tomorrow- March 1st.
Folks, it’s over okay. That’s it.
It is what it was. The DEAD winter of 2019-2020 with an official grand total of 0.9 inches of snow in the state of Delaware.
A fairly strong upper-level low with some vertical wind shear threatens the MId-Atlantic with some high winds and rain for Wednesday afternoon/early evening. A strong 998mb low is forecast to develop somewhere along the PA/WV border and produce cold, heavy snow to areas like Ohio, Indiana, western PA, and upstate New York. Yet, on the other side of that front is warmer air pushing from the Gulf and Atlantic waters. And whenever you get warm air and colder air in the same area together it could produce a KABOOM! with severe thunderstorms, or high winds. More on this tomorrow.
500mb chart showing the upper level low colliding with the eastern branch of the southern jet later Wednesday night. It could produce some severe storms Wednesday evening.
Storm Prediction Center depiction showing the area of marginal severe storm risk on Wednesday.
Delaware weather is a paradox. Literally, in three parts of the state, we can have three different types of weather in a single day. Yet, living in Delaware is becoming increasingly clearer as we approach the Spring and Summer months. Delaware is a state with very severe weather risk.
Unlike say Tornado Alley between the MId-West and the plains like Texas, Oklahoma, Kansas, etc.. Delaware is starting to see more and more of its a fair share of severe weather. In the last two years, we have had at least three recorded tornadoes. One an EF-2 last May on Memorial Day weekend down near Laurel. And it happened at night which is more terrifying and rare. The most common severe weather that Delaware’s faces are thunderstorms, straight-line storms, and Derechos. I want to discuss Derechos.
In late June of 2012 Delaware and much of the lower half of the Mason-Dixon states experienced what is called a Derecho severe weather event. It started early in the morning out of thunderstorms in eastern Iowa. Derechos form because of elevated thunderstorms. They are, in a sense, strong thunderstorms that last hours and are damaging by the intensity of the size of the storm. They also spread over hundreds of miles.
The picture below shows how air billows upon a high-pressure system over the East Coast. This building of airflow above the front can lead to the formation of abnormally higher than the normal mixed layer that leads to intense Derechos.
Add in unbreathable heat and humidity and there is always the possibility of a Derecho of any kind in the Spring and Summer months.
The radar echo shows a progressive derecho forming as a bow that drops from NW to SE. Straight lines just move in one “straight” direction via the winds and upper-level jet.
The Derecho event in June of 2012 moved over 700 miles in 10 hours and killed 22 people and left hundreds of thousands without power.
We are sure to see something like this as storms are growing more powerful overheated Gulf moisture and heated ocean waters.
The Madden-Julian Oscillation which determines the eastward propagation of storms from Asia to the Pacific will be entering into the “Circle of Death” after spending some time in Phase 7 which is a neutral zone indicating probable transition into either a colder phase like 8-9-1-2. Yet, all ensembles are pointing inward towards the circle which means it has NO influence on weather patterns.
Likewise, our teleconnections which have been horrible ALL winter are indicating that winter is just simply dead in the Eastern 2/3 of the country. There is no ridging (-PNA), there is no high block in Greenland (+NAO) and no cold air (+EPO). And this goes through the 5th of March. And if you add in all of the other factors not favoring anything significant in the East like a coastal storm as we are going into March, then it’s all over folks.
Winter 2019-20 is dead. Adios!
Above is a picture of the major cities of the East Coast. The very fine white area is called the “Fall Line”. Can weather really straddle a line? Does one or two degrees west or east of the line make a difference? The two answers is Yes, and Yes. If you look to the west of the “Fall Line”, you will see that the land rises-elevation. Temperatures are impacted by that small difference. In Philadelphia, it could be 34 degrees as a storm approaches. Fifteen miles west of Philadelphia in Montgomery County it could be 32 degrees and falling as a storm approaches. You could have snow in Lower Merion, and rain in Center City-cold rain at that. In that case, if it’s 34 degrees in Philadelphia you can rest assured it’s 35 in Wilmington, DE almost a certain rain event as you can see Wilmington, DE almost is sinking in the sediment of the Delaware River. Yet, at the same time, it could be 35 in Wilmington, DE and further north and west of Wilmington, DE in Chadds Ford just a mere 6-8 miles from Wilmington to its south could be startling the freezing line and could either bet wet snow or even just snow.
So, the weather follows I-95 because of I-95 changes in elevation. It’s the strangest, but the most fascinating piece of geography that no other part of the country has.
Snowstorm along the I-95. Arctic cold air is the solution if you want big snows in the megalopolis cities of Washington, D.C. to New York City.
Winter 2019-2020 in the Mid-Atlantic from Washington D.C. to Boston, Mass has been, simply, strange or has it?
According to early winter predictions the NOAA stated in October 2019 very clearly:
“neutral conditions are in place this year and expected to persist into the spring. In the absence of El Nino or La Nina, long-term trends become a key predictor for the outlook, while other climate patterns, such as the Madden-Julian Oscillation and Arctic Oscillation (AO), will likely play a larger role in determining winter weather”
In other words, instead of La Nina or El Nino we’ve had “La Nada”. Nothing. The Pacific waters have had no impact on our winter. The jet streams have been let loose and are so divergent north and south they can’t see each other. Judah Cohen from the Atmospheric Environmental Research is an expert in the area of the AO index. He stated in his most recent blog:
“I know I sound like a broken record when I start every blog by how surprised I am by the stratospheric PV remains on the strong side of normal and even at times near or at record strong for the date. Today there has been some chatter/news about a record daily high for the AO today. But the incessant stretch of positive to strongly positive AO since late December, based on the polar cap geopotential height anomalies (PCHs) plot originated in the polar stratosphere with cold/negative PCHs/strong PV back in mid-December that propagated to the surface over a course of two weeks.”
The graphic above shows the GEFS ensemble for temperature variation over the globe. (Courtesy of https://www.aer.com/science-research/climate-weather/arctic-oscillation/)
In other words, there has been a pool of cold air sitting on top of the North Pole just swirling around the Arctic Ocean and there has been nothing to push it south enough to allow any major, long sustaining cold weather to give the East wintry precipitation. The extent of the cold has been kept out West and it just seems to be that way this winter 2019-2020.
There have been at least eleven winters in the Philadelphia/Wilmington, DE area of fewer than four inches of snow with 1997-98 being at the top with only 0.8 inches that year. It looks like we could beat that this winter.
Thus, the predominant notion that global warming has caused this snowless winter in the NE corridor from Washington, D.C. to Boston which has had snow but not their gigantic February numbers of recent years, is by far not the culprit.
It’s just this winter.
First in a series of posts about how weather impacted events in our history.
September 11th, 2001 was a day we would like to forget. Yet, just like a lot of historical events in history, weather played a critical role.
The surface map shows the weather map at 7am on September 11th, 2001. In the blue, we can see a massive round high-pressure system in the Mid-West this gave us and most of the country a beautiful, clear blue sky day. In red is a cold front that had moved through the night before which actually gave NYC rain that night. Also, just to the east in the Atlantic was Hurricane Erin. Erin was threatening the East Coast until that cold front swept it way out to sea. It’s very possible that IF that cold front had not pushed through Erin would have threatened the East Coast with at least high, thick clouds all down the Eastern seaboard. This could have either thrown off the attackers and given authorities more time to uncover the attack. It was close to being a ring for the FBI and CIA. They were about to grab some of the attackers.
Yet, it was a beautiful sunny day. Hurricane Erin missed the East Coast.
Until 8:46am. Born on that day were 2,996 angels.