The video explains it.
Wednesday, February 29, 2012
Severe Weather Possible Again
It is Déjà vu all over again. Warm moist air will again surge northward Friday and invade the tristate. At this point it looks like we have two chances for severe storms. The first chance is about midday with the warm front and the second is late evening with the cold front.
The video explains it.
The video explains it.
Tuesday, February 28, 2012
Thinking About Severe Weather
A strong velocity max (aka upper level disturbance) embedded in the jet stream with wind speeds approaching NASCAR velocity, 200 mph, is powering a strong surface low towards the Great Lakes.
North of the storm Winter Storm Watches and Warnings have been issued along with a large area under Blizzard Warning (in white) over parts of South and North Dakota.
Along the cold front from Oklahoma to Nebraska Tornado Watches have been issued. This is a typical late winter storm and severe weather is likely from the plains to the East Coast as the storm advances over the next several days.
The video has more on forecasting severe storms with this and similar systems.
Along the cold front from Oklahoma to Nebraska Tornado Watches have been issued. This is a typical late winter storm and severe weather is likely from the plains to the East Coast as the storm advances over the next several days.
The video has more on forecasting severe storms with this and similar systems.
Monday, February 27, 2012
Getting Stormier
This is the time of the year that the cold air draped across the north pole begins to noticeably shrink back towards the pole as the late winter solar radiation gets stronger by the day.
The result is that the unstable tropical air that has stayed south through the dead of winter begins to be seen more and more frequently pushing northward deep into the continent.
The northward withdrawl of the cold air of winter is often slower than the invasion of tropical air from the south and in spring, more often than at any other time of the year, the two clash in the vicinity of The Ohio River Valley.
The result is that the unstable tropical air that has stayed south through the dead of winter begins to be seen more and more frequently pushing northward deep into the continent.
The northward withdrawl of the cold air of winter is often slower than the invasion of tropical air from the south and in spring, more often than at any other time of the year, the two clash in the vicinity of The Ohio River Valley.
Moist tropical air gives birth to thunderstorms as the heat used to evaporate water molecules is released back to the thunderstorm environment when the molecules condense forming the torrential rains that fall from the storms.
If you throw in additional lift from a front, the dynamics of a jet streak (aka upper level disturbance) and the energy of the sun you may conjure up severe thunderstorms.
The video has more.
Wednesday, February 22, 2012
The Wettest 12 Months Ever for Cincinnati
This post departs from my regular routine and does not coincide with my Inside The Forecast segment for the day.
We all know that Cincinnati had the wettest year ever in 2011 recording 73.28" of rain. Included in the total of course is melted snow and ice.
But if you think about it a year is an artificial division of time relative to weather. In fact so are weeks months and 24 hour days. It is not a difficult concept weather events are not confined to time intervals humans define.
But .... we have to organize the information some way so we talk about wettest days, months and years.
The reality is that by looking at rain totals over intervals of 12 consecutive months we can gain better insight.
That is just what I did. Reliable monthly rainfall data goes back to November 1834 and official monthly data back to November 1870. The earlier data set was observed by teachers at Woodward College (later High School) in Over The Rhine, Downtown Cincinnati. The official data was less than half-mile away also in Downtown Cincinnati. The Woodward data later moved to near the entrance of Eden Park about one mile into Walnut Hills from Downtown.
The data sets overlap from November 1870 through December 1902. I mention this because it allows us to compare the two and judge the accuracy of the unofficial data. The two are comparable.
For 12-consecutive month periods the wettest is 77.09" from Feb 2011 through the end of Jan 2012 almost 4" greater than the wettest year in history at 73.28".
The Table below lists the 20 wettest 12 month periods in Cincinnati history. The columns are year, ending month, total rainfall and departure from the normal annual rainfall for the 1981-2010 normal period.
We all know that Cincinnati had the wettest year ever in 2011 recording 73.28" of rain. Included in the total of course is melted snow and ice.
But if you think about it a year is an artificial division of time relative to weather. In fact so are weeks months and 24 hour days. It is not a difficult concept weather events are not confined to time intervals humans define.
But .... we have to organize the information some way so we talk about wettest days, months and years.
The reality is that by looking at rain totals over intervals of 12 consecutive months we can gain better insight.
That is just what I did. Reliable monthly rainfall data goes back to November 1834 and official monthly data back to November 1870. The earlier data set was observed by teachers at Woodward College (later High School) in Over The Rhine, Downtown Cincinnati. The official data was less than half-mile away also in Downtown Cincinnati. The Woodward data later moved to near the entrance of Eden Park about one mile into Walnut Hills from Downtown.
The data sets overlap from November 1870 through December 1902. I mention this because it allows us to compare the two and judge the accuracy of the unofficial data. The two are comparable.
For 12-consecutive month periods the wettest is 77.09" from Feb 2011 through the end of Jan 2012 almost 4" greater than the wettest year in history at 73.28".
The Table below lists the 20 wettest 12 month periods in Cincinnati history. The columns are year, ending month, total rainfall and departure from the normal annual rainfall for the 1981-2010 normal period.
20 Wettest 12-Month Periods
| 2012 | 1 | 77.09 | 34.57 |
| 2011 | 12 | 73.28 | 30.76 |
| 2011 | 11 | 68.53 | 26.01 |
| 2011 | 10 | 67.14 | 24.62 |
| 1847 | 10 | 66.59 | 24.07 |
| 1847 | 11 | 66.28 | 23.76 |
| 1880 | 6 | 65.46 | 22.94 |
| 1847 | 12 | 65.18 | 22.66 |
| 1880 | 7 | 65.17 | 22.65 |
| 1848 | 3 | 65.15 | 22.63 |
| 1848 | 1 | 65.05 | 22.53 |
| 2011 | 9 | 64.60 | 22.08 |
| 1848 | 5 | 64.41 | 21.89 |
| 1848 | 2 | 63.80 | 21.28 |
| 1848 | 4 | 63.58 | 21.06 |
| 1882 | 9 | 62.31 | 19.79 |
| 1882 | 8 | 61.25 | 18.73 |
| 1880 | 5 | 60.82 | 18.30 |
| 1847 | 7 | 60.74 | 18.22 |
| 1882 | 5 | 59.95 | 17.43 |
By the way the driest 12-month period in Cincinnati history enede November 1901 with only 15.63" of rain while the driest year in Cincinnati was 1901 with 17.99" of rain.
So you see consecutive 12-month periods tell a more extreme story than calendar year data.
Here are the 20 driest 12-month periods in Cincinnati history. The columns are the same as for wet periods.
20 Driest 12-Month Periods
| 1901 | 11 | 15.63 | -26.89 |
| 1902 | 3 | 17.71 | -24.81 |
| 1901 | 12 | 17.99 | -24.53 |
| 1902 | 2 | 18.25 | -24.27 |
| 1902 | 4 | 18.65 | -23.87 |
| 1902 | 1 | 19.22 | -23.30 |
| 1901 | 10 | 19.39 | -23.13 |
| 1901 | 8 | 19.61 | -22.91 |
| 1931 | 2 | 20.14 | -22.38 |
| 1931 | 3 | 20.20 | -22.32 |
| 1901 | 9 | 20.25 | -22.27 |
| 1857 | 3 | 21.13 | -21.39 |
| 1941 | 5 | 21.20 | -21.32 |
| 1931 | 1 | 21.21 | -21.31 |
| 1857 | 2 | 21.88 | -20.64 |
| 1905 | 3 | 22.07 | -20.45 |
| 1931 | 4 | 22.08 | -20.44 |
| 1871 | 6 | 22.33 | -20.19 |
| 1857 | 1 | 22.39 | -20.13 |
| 1902 | 5 | 22.57 | -19.95 |
Tuesday, February 21, 2012
The West to East Jet Stream Continues
The fanatical relationship between humans and weather has been part of almost all cultures as far back as archaeologists have evidence.
About 5000 years ago the saying we know as, "Red sky at night, sailors delight ..." was inscribed on Babylonian stone tablets. Years later Aristotle repeated the saying in his treatise Meteorologica.
The saying also appears in the Bible, Matthew 16, 1-3, and William Shakespeare penned a version in his 1592 poem, Venus and Adonis.
The folkloric rhyme it seems has been with us since the beginning and that makes sense, because long before all of the above recalled the weather forecasting rhyme, nomadic tribes had to know weather patterns and seasonal changes to survive. The sacred oral traditions were passed from one generation to generation the next.
Fast forward to today and modern humans cyber-digital relationship with weather is as fanatical as our earliest ancestors.
All this is a long way to get to an outlook for the next 10 days and whether there will be a big snow.
When the 20th Century dawned we had no knowledge of fronts, highs and lows and the weather they cause. In the years before and after WWI in Bergen, Norway a group of meteorologists developed the next-to-last big block in the structure of modern meteorology.
They developed the concept of fronts as the battle ground between contrasting air masses. The horrid trench warfare of "The War to End All Wars" had left its mark on meteorology.
The only problem is that when tested with equations the Bergen School's approach could not account for how strong cyclones, those low pressure storms you see on weather maps, would become.
They were not wrong, they just did not have enough information. After WWII at the University of Chicago the role of the jet stream and those mysterious entities TV meteorologists call upper level disturbances was unraveled and the final building block was in place.
And the video below tells you why I am not encouraged about the possibity of a "big one", a snowstorm that is, before it is too late this season. It is not impossible just not likely.
About 5000 years ago the saying we know as, "Red sky at night, sailors delight ..." was inscribed on Babylonian stone tablets. Years later Aristotle repeated the saying in his treatise Meteorologica.
The saying also appears in the Bible, Matthew 16, 1-3, and William Shakespeare penned a version in his 1592 poem, Venus and Adonis.
The folkloric rhyme it seems has been with us since the beginning and that makes sense, because long before all of the above recalled the weather forecasting rhyme, nomadic tribes had to know weather patterns and seasonal changes to survive. The sacred oral traditions were passed from one generation to generation the next.
Fast forward to today and modern humans cyber-digital relationship with weather is as fanatical as our earliest ancestors.
All this is a long way to get to an outlook for the next 10 days and whether there will be a big snow.
When the 20th Century dawned we had no knowledge of fronts, highs and lows and the weather they cause. In the years before and after WWI in Bergen, Norway a group of meteorologists developed the next-to-last big block in the structure of modern meteorology.
They developed the concept of fronts as the battle ground between contrasting air masses. The horrid trench warfare of "The War to End All Wars" had left its mark on meteorology.
The only problem is that when tested with equations the Bergen School's approach could not account for how strong cyclones, those low pressure storms you see on weather maps, would become.
They were not wrong, they just did not have enough information. After WWII at the University of Chicago the role of the jet stream and those mysterious entities TV meteorologists call upper level disturbances was unraveled and the final building block was in place.
And the video below tells you why I am not encouraged about the possibity of a "big one", a snowstorm that is, before it is too late this season. It is not impossible just not likely.
Monday, February 20, 2012
ZONAL FLOW
The next 7 days should be dominated by numerous small storms with a bit of precipitation possible each day but no big storms and no temperature extremes.
Why? Because the jet stream flow is mostly west to east or what meteorologists call zonal. West to east jet stream flow is approximately parallel to the climate zones determined by latitude. In zonal flow most of the very cold air stays way north and the most of the very warm air stays far south. Without the jusxtposition of the very cold and the very warm the thermal energy difference across the jet is insufficient to drive big storms.
This week will be dominated by zonal flow.
High amplitude jet stream flow or flow where the jet pushs way to the north and way to the south in big ridges and trofs (meteorologists' shorthand) is called meridional flow. In this type of regime warm air pushes way north and cold air pushes into the deep south. The difference in temperature across the jet helps power big storms.
In addition meridional flow and help bring Gulf of Mexico moisture northward to produce precipitation and release heat as the water vapor condenses to liquid or directly to frozen precipitation. Theis "latent heat" that condensing moisture releases also helps drive storms.
The video has more.
Why? Because the jet stream flow is mostly west to east or what meteorologists call zonal. West to east jet stream flow is approximately parallel to the climate zones determined by latitude. In zonal flow most of the very cold air stays way north and the most of the very warm air stays far south. Without the jusxtposition of the very cold and the very warm the thermal energy difference across the jet is insufficient to drive big storms.
This week will be dominated by zonal flow.
High amplitude jet stream flow or flow where the jet pushs way to the north and way to the south in big ridges and trofs (meteorologists' shorthand) is called meridional flow. In this type of regime warm air pushes way north and cold air pushes into the deep south. The difference in temperature across the jet helps power big storms.
In addition meridional flow and help bring Gulf of Mexico moisture northward to produce precipitation and release heat as the water vapor condenses to liquid or directly to frozen precipitation. Theis "latent heat" that condensing moisture releases also helps drive storms.
The video has more.
Thursday, February 16, 2012
Looking 90 Days Ahead
Around the middle of each month NOAA's Climate Prediction Center (CPC) issues seasonal outlooks for a variety of time periods in the future.
Producing these outlooks is very different from forecasting. Forecasting weather is basically the application of physics and math to the atmosphere through the tool of numerical models.
Seasonal outlooks like the ones for March, April and May can use a number of tools including historical analogues and statistical methodologies, and the persistance of typical flow patterns.
Also important are patterns of atmosphere-ocean interaction. To the public the most recognizable pattern is El Niño/La Niña.
There are others like the Madden-Julian Oscillation of the tropics, the Arctic Oscillation, the Antarctic Oscillation, the North Atlantic Oscillation and the Pacific North American Pattern. Essentially these all describe and quantify atmospheric flow patterns and their persistence in different geographic regions of the globe.
For example La Niña interacting with the North Atlantic Oscillation is blamed for the relatively harsh winter of 2010-2011 in Cincinnati. For the winter of 2011-2012 La Niña interacted differently with the North Atlantic Oscillation, because the NAO had changed, and though both winters were La Niña winters they were very different.
If a blocking pattern is expected to persist only slow changes to the jet stream flow may occur and as a result changes in the weather will be forecast to be slight or very slow.
Using all these tools the CPC issues extended outlooks from 5 days to 1 year in the future.
Here is what March, April and May are expected to bring:
The top map, precipitation outlook shows the La Niña "bullseye" of precipitation (as I call it) will continue over the Tristate. It is smaller and weaker as the La Niña. pattern starts to ease.
Temperatures here are expected to be warmer than average.
So at this point a repeat of the record-setting wet weather of Spring 2011 seems unlikely.
By the way CPC thinks Cincinnati will have about normal precipitation and warmer than normal temperatures for Summer 2012.
Producing these outlooks is very different from forecasting. Forecasting weather is basically the application of physics and math to the atmosphere through the tool of numerical models.
Seasonal outlooks like the ones for March, April and May can use a number of tools including historical analogues and statistical methodologies, and the persistance of typical flow patterns.
Also important are patterns of atmosphere-ocean interaction. To the public the most recognizable pattern is El Niño/La Niña.
There are others like the Madden-Julian Oscillation of the tropics, the Arctic Oscillation, the Antarctic Oscillation, the North Atlantic Oscillation and the Pacific North American Pattern. Essentially these all describe and quantify atmospheric flow patterns and their persistence in different geographic regions of the globe.
For example La Niña interacting with the North Atlantic Oscillation is blamed for the relatively harsh winter of 2010-2011 in Cincinnati. For the winter of 2011-2012 La Niña interacted differently with the North Atlantic Oscillation, because the NAO had changed, and though both winters were La Niña winters they were very different.
If a blocking pattern is expected to persist only slow changes to the jet stream flow may occur and as a result changes in the weather will be forecast to be slight or very slow.
Using all these tools the CPC issues extended outlooks from 5 days to 1 year in the future.
Here is what March, April and May are expected to bring:
The top map, precipitation outlook shows the La Niña "bullseye" of precipitation (as I call it) will continue over the Tristate. It is smaller and weaker as the La Niña. pattern starts to ease.
Temperatures here are expected to be warmer than average.
So at this point a repeat of the record-setting wet weather of Spring 2011 seems unlikely.
By the way CPC thinks Cincinnati will have about normal precipitation and warmer than normal temperatures for Summer 2012.
Wednesday, February 15, 2012
A Look At The Weekend
Each Wednesday I look ahead to, what in my opinion, is the best part of a week - The Weekend! It is not that I do not like my job, truthfully after nearly 35 years in TV I still like each and every day. It is that weekends are the time to kick back and enjoy the parts of life we do not have time for the other 5 days.
The coming weekend is a bit of a question mark. The GFS (global forecast system) or what I often call on the air the "American Model" to distinguish it from the European Model and the Canadian Model.
The American Model from this morning (12z or 7am EST run) had the FOX19 viewing area on the northern edge of precipitation from a storm that will cross Georgia into the Carolinas Sunday. The European and the Canadian both had the storm farther south and the precipitation shield smaller resulting in a dry weekend.
The midday run of the American Model (18z or 1PM EST) pushed the rain shield to Lake Erie Saturday and had it moving out of the tristate early Sunday.
In my experience the European and Canadian models often play "catch up" with the American, not always but much of the time. So even though the score is 2 dry models to 1 wet model I am leaning towards some light rain or sprinkles for Saturday. Also we have a saying that "the trend is your friend", meaning as the day gets closer the models begin to zero in on what will really happen. The trend in the American model is for wet weather over the weekend.
Before I am convinced I want to see a few more runs but right now (Wednesday evening) I am leaning towards some rain.
The video has more.
The coming weekend is a bit of a question mark. The GFS (global forecast system) or what I often call on the air the "American Model" to distinguish it from the European Model and the Canadian Model.
The American Model from this morning (12z or 7am EST run) had the FOX19 viewing area on the northern edge of precipitation from a storm that will cross Georgia into the Carolinas Sunday. The European and the Canadian both had the storm farther south and the precipitation shield smaller resulting in a dry weekend.
The midday run of the American Model (18z or 1PM EST) pushed the rain shield to Lake Erie Saturday and had it moving out of the tristate early Sunday.
In my experience the European and Canadian models often play "catch up" with the American, not always but much of the time. So even though the score is 2 dry models to 1 wet model I am leaning towards some light rain or sprinkles for Saturday. Also we have a saying that "the trend is your friend", meaning as the day gets closer the models begin to zero in on what will really happen. The trend in the American model is for wet weather over the weekend.
Before I am convinced I want to see a few more runs but right now (Wednesday evening) I am leaning towards some rain.
The video has more.
Tuesday, February 14, 2012
The Next Storm Brings Rain
Extended range forecasting has come a long way since I started in the weather business. In 2012 we are easily more accurate 7 days out than we were 3 days out in 1977.
We still cannot accurately time the start of end of a snow event a week away. Commonly it may arrive a day earlier or a day later than a particular model run predicts.
The job of a meteorologist in extended forecasting is to let you in to our thought processes, let you know "something" may happen on a particular day then update the progress of the forecast as the storm gets closer. The goal is no surprises.
For example I was asked today by an elementary school child if there will be any snow days this year. Coincidentally the models are kicking out information on what could be a big storm in the U.S. Wednesday through Friday of next week, that is 8 to 10 days in the future. Only a fool would emphatically pronounce a prediction of a big snow storm starting any of those days. But i could tell her it would rain Thursday with no chance of a snow day and next week there is a chance. Stand by.
There are three things in general that determine if a storm will bring snow or if it will bring rain.
Now don't get me wrong it is much more complex than that once the storm is a few hours away but in general for the extended forecast three things dominate my thinking. I cover them in the video.
We still cannot accurately time the start of end of a snow event a week away. Commonly it may arrive a day earlier or a day later than a particular model run predicts.
The job of a meteorologist in extended forecasting is to let you in to our thought processes, let you know "something" may happen on a particular day then update the progress of the forecast as the storm gets closer. The goal is no surprises.
For example I was asked today by an elementary school child if there will be any snow days this year. Coincidentally the models are kicking out information on what could be a big storm in the U.S. Wednesday through Friday of next week, that is 8 to 10 days in the future. Only a fool would emphatically pronounce a prediction of a big snow storm starting any of those days. But i could tell her it would rain Thursday with no chance of a snow day and next week there is a chance. Stand by.
There are three things in general that determine if a storm will bring snow or if it will bring rain.
Now don't get me wrong it is much more complex than that once the storm is a few hours away but in general for the extended forecast three things dominate my thinking. I cover them in the video.
Thursday, February 9, 2012
Wet Snow Friday - Slick Streets Saturday Morning
A weak to moderate upper level disturbance will push a low eastward across Tennessee Friday into Saturday bringing the Cincinnati Tristate wet snow.
The good news is that there will be NO SNOW for the Friday morning commute and only wet snow (translated wet roads) for the homebound commute.
The bad news is that untreated roads will ice up for early Saturday morning as meltedsnow freezes when the temperature drops quickly before dawn Saturday morning.
The video explains it.
Tuesday, February 7, 2012
Impact Is More Important Than How Much Snow Falls
Here in Cincinnati we are just far enough north to get disruptive snow events almost every winter and just far enough south that sometimes we are dealing with the icy stuff.
By icy stuff I mean the precipitation that is transitional between snow and rain. Because of the geometry of storm systems in the middle latitudes the cold air at the surface is sometimes overrun by warmer air. When snow falls through the warm layer it can melt into rain and then when it hits the colder-than-freezing surface splat and freeze into a glaze of ice. Glaze is the agreed upon international name for waht we call freezing rain.
If the cold air at the surface is deep and well below freezing the snowflakes that melted to raindrops can refreeze into small ice pellets, which is the internationally agreed upon name for them. We call it sleet.
Everyone knows the helpless feeling of hitting a patch of friction-free glaze ice on foot or worse in a car and that is almost always worse than several inches of snow.
By icy stuff I mean the precipitation that is transitional between snow and rain. Because of the geometry of storm systems in the middle latitudes the cold air at the surface is sometimes overrun by warmer air. When snow falls through the warm layer it can melt into rain and then when it hits the colder-than-freezing surface splat and freeze into a glaze of ice. Glaze is the agreed upon international name for waht we call freezing rain.
If the cold air at the surface is deep and well below freezing the snowflakes that melted to raindrops can refreeze into small ice pellets, which is the internationally agreed upon name for them. We call it sleet.
Everyone knows the helpless feeling of hitting a patch of friction-free glaze ice on foot or worse in a car and that is almost always worse than several inches of snow.
Monday, February 6, 2012
Upper Level Disturbances
This post covers what you have heard TV Meteorologists call "Upper Level Disturbances". These mysterious entities go by other names like "short wave", an "impulse", a "velocity maximum" or a "jet streak". I like to call them "bundles of energy" because the energy part of the name tells the viewer that these jet stream-level disturbances energize the low pressure systems you see on weather maps at the surface along with their companion cold fronts and warm fronts.
It is within the bundles of energy that the highest jet stream wind speeds are observed, thus one of the names, "velocity maximum". So you have a jet stream and these bundles of energy follow the jet. What makes the forecast sometimes difficult is that the upper disturbances also can modify the jet if they are strong enough.
To be sure there is no confusion the upper level disturbances do NOT power tropical systems. In the tropics storms are driven by the energy released when water vapor (humidity) condenses back to liquid.
The way these bundles of energy work is beyond the scope of this post but with each one comes some lift and the chance for precipitation is there is sufficient moisture. This week moisture is scarce so precipitation will be light or non-existent.
The video describes how this week looks.
Wednesday, February 1, 2012
Ground Hog Day Eve! And No Snow In Sight
After two days in the 60s, high temperatures 20° and 22° warmer than normal, the weather will cool, but not too much. The La Niña pattern continues to dominate the global jet stream pattern. Basically brief intrusions of cold air push into the "Lower 48" and occasional surges of moist air bring episodes of rain. What is missing are big winter storms.
The coming weekend one of those surges of moisture will come our way and bring a period of rain lasting about 24 hours.
This discussion is specific to the weekend forecast, however it illustrates in general how "return flow" around an anticyclone, coming off the Gulf of Mexico transports moisture deep into the continent for rain.
The video below explains it.
The coming weekend one of those surges of moisture will come our way and bring a period of rain lasting about 24 hours.
This discussion is specific to the weekend forecast, however it illustrates in general how "return flow" around an anticyclone, coming off the Gulf of Mexico transports moisture deep into the continent for rain.
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