Atm Ocn 100 Edition 1nd Lecture 23 Outline of Last Lecture I Weather of the day II A little more about Tornados a Enhanced F Scale for Tornado Damage b Tornado Frequency III Hail and Lightening IV Origins of hail V Ways that ice interacts with supercooled liquid water VI Hail a How big VII Supercell structure VIII Hail Swaths Outline of Current Lecture II Weather of the day III Hail some radar information IV Where does hail occur V Lightning VI Where lightning occurs a United States VII More Lightning Current Lecture Reminders Homework due today Test 2 is next Friday Weather of the day We can see isotherms and isobars We can see that there is strong high pressure dropping to the south through North Dakota Nebraska and so on Right now the frontal zone at midnight last night is moving across us It brought us snow last night It was always a possibility that we saw from last week but we didn t predict it to be last night 1000 500 mb thickness is a good map of telling the temperature The cold tongue pushing south is an indication of cold air from the artic going south We can look at thickness to find the rain snow line When the cold air moves over the warm lake instabilities develop and there can be showers from this Lake effects don t always bring snow but we may see it in the next day or two This will be one of the first blasts into the Gulf of Mexico Very typical weather we usually see this cold right around Halloween By Sunday may be a little warmer There will be some warmer air towards us We can see the magenta coloring right on top of us but we are recovering quickly It will get warm again at 850 mb by Monday night This morning there were stratocumulus clouds Now a lot of clouds are forming outside The warm ground will keep the air warmer then it would normally be with the same temperatures in the winter This will produce an instability that causes overturn We may have snow later today from this instability At night ground cools so instability stops So there shouldn t be snow later tonight But there is potential for getting super cold tonight maybe even into the 20 s Back to lecture Hail some radar information How we observe hail with radar Radar measures reflectivity measures power returned Radar receives and transmits information It listens and receives the echo from a pulse that it emitted It is a continuous pulsing and a very high frequency and then there is a return From a frequency shift you can see Doppler The radar beam reflection is due to scattering of targets and some of it reflects back which is detected The size of the particle matters for a radar If you use longer wavelength radar a different reflectivity comes back than short wave radar There is a strong dependence between wavelength and droplet size Droplet size is not uniform could be bigger on horizontal axis compared to vertical axis On the polarized beam out we focus on detecting the horizontal axis that affects reflectivity Hail particles tend to be more spherical than rain droplets The larger ones are oblique The larger the rain droplet gets the more oval shape it becomes orientated with the big axis horizontal The smaller the rain droplet the more spherical it would be If you compare horizontal to the vertical you can get a measure of how big the rain droplets are And then that can tell you as well how fast they are falling The weather service converted to the polarized radar only a few years ago This is about 20 years old Doppler radar is nearly 40 years old We are looking at 3 pictures of the same cloud derived from polarized radar The top one is reflectivity factor It is a cloud with hail in it large reflectivity means large hail If ice is undergoing wet growth which is collecting water super cool liquid water as it falls it is collected on falling ice particle and doesn t freeze If it freezes immediately than that is dry growth because the particle never gets wet If there is a ton of liquid water heat cannot be transferred fast enough so the particle will warm to 0 degrees Celsius where rain cannot freeze Then the particle will keep warming and then stay there Even if the temperature of the air is 20 A reflectivity factor of 60 or 70 shows hail which is pictured in the first cloud on this picture We can see the differential reflectivity between horizontal and vertical polarized beams At the bottom part of the cloud we see the greatest difference in differential reflectivity because rain is happening down there The 3rd picture is labeling the different things in the cloud like hail The orange is light rain We see big differential reflectivity and it shows the type of precipitation that is occurring New radar science differential reflectivity it is a new thing for weather service offices Now forecasts of hail or precipitation will improve a lot from these radars because they can detect the sizes Where does hail occur 3 inch hail or bigger is considered a severe storm Hail occurs really between Texas and Oklahoma Supercells are big hail producers This is why you get supercells too When you get large storms large supercells it occurs a lot in Northern Texas This is very similar to tornado bowl Lightning Lightning is the number one killer compared to any other weather But it is not considered severe for a storm to have lightning Where lightning occurs Frequency being the reds or up to the blacks are the most frequent Lightning is only over land Why What is going on here is the thunderstorms over land are stronger than over water They are stronger thunderstorms and they have more ice What is different over land Land is much warmer than the ocean Land creates heat masses that can contain contribute a lot to a thunderstorm During the warmest part of the day the land is warmer than the ocean ever gets The land produces the warmest and coldest temperatures The largest features will appear over land where the air gets the most warm When you go over ocean in the afternoon it is not warmer than it is at night And we see them concentrated in the areas where the inner tropical convergence zone is In Florida sea breeze fronts Over water we get weaker thunderstorms that really have to work hard to get up the equilibrium Over land updrafts stronger and more violent thunderstorms United States Lightning is concentrated over Florida This is a result of the sea breeze front over Florida Everyday there is a line of thunderstorms from both coasts that move inland Sea breeze front on the West coast moves a little bit and