Lecture 35Outline of Last Lecture I. RemindersII. Weather of the dayIII. Air Masses and Frontsa. Illustration of different frontsIV. Extratropical CyclonesOutline of Current Lecture II. AnnouncementsIII. Weather of the dayIV. Some ReviewV. Troughs…CyclonesVI. Summary For Cyclone East of RockiesVII. Cyclones Forming Along Gulf and East CoastsCurrent LectureAnnouncementsHomework due todayThere is a new homework that only half will be due next week. The other half will be optional, if turned in we get extra credit. Homework Due Friday, December 12, 2014TYU Ch 13: 2 ,4, ,6, 7,18 ; TYPSS 3 TYU Ch 16: 1, 2, 3, 7, 11 ; TYPSS 2Extra Credit, (Not to be covered in Class):TYU Ch 17: 1, 3, 5, 13 TYU Ch 15: 1, 2, 3, 4, 5, 6, 7 Weather of the day Atm Ocn 100 1nd EditionYesterday we can see a storm that started off as a category 5 tropical cyclone. It is supposed to hit the Philippines. The eye dissipates as it weakens. The clouds around it how they look make it seem like there is something fromthe west causing the storm to weaken. Another map is the sheer map; it shows the difference of wind speed there is from upper levels to low levels. The streamlines are the direction the wind is coming from. The wind is weakening, but the Philippines will still be hit with a category 3 tropical cyclone. This was one of the strongest recorded super typhoons, but now it is dissipating a little bit so it will be more like a category 3 instead of a category 5. The sea surface temperatures are warm, but they aren’t a lot warmer then normal. So it is interesting we are getting these really strong typhoons so late in the season. Typhoons take warm water and turn that warm water into vapor. The sun warms the water and then it evaporates, that evaporation turns into vapor and then it condenses and turns it back into heat. This warms the air and transmits back to the atmosphere.The water cycle warms the atmosphere. Hurricanes suck energy right out of the water and then go into the atmosphere. Where does the energy go after that? The air has warm and gone upward, the only way to get rid of that is transfer it to space. It gets transferred around the tropics, the energy will then be transmitted and make a strong subtropical jet. This will get into the Westerly’s and create waves that will affect us. What is going to happen here?If a big amount of energy is expelled it could produce a strong jet surge into the polar regions that would push a very strong ridge up over the Gulf of Alaska, Eastern Siberia. Last winter attributes in part because of typhoon that hit the Philippines. This winter is different because we have an El Nino. The forecast for the next couple weeks is a very zonal type flow. But this typhoon may change this. We aren’t sure what is going to happen yet. This is a complex situation of how this will interact. Last year the typhoon didn’t get down to a category 3. The week before Xmas is when we may feel the effects of this typhoon.Back to lecture:Some ReviewCold Front CloudsSteep frontal slope(50:1 or about 1 km up in about 50 km horizontal distance)Warm Frontal CloudsSlope less than a cold front 100:1 or about 1 km up in 100 km horizontal distance)Special Setup for Cyclones East of RockiesWhen things go over the mountains they stretch and spin up and see low form. They often go into Gulf of Alaska…Often there is a trough over North America and the upper air is compressed…Tend to have low pressure at upper elevation like at 500 mb and above. And lower pressure over North America, a trough, and the lows would come across the mountains and get caught in northwestern flow and gosouthward, circle through planes. The jet stream steers this whole process. Troughs…CyclonesThere are troughs of different scales. North America would typically have a trough at 500 mb. The trough would usually come down to the right of the mountains. When the low comes in there is a trough within a trough. There is a little trough where a low would in the trough. Between the beginning and the end of the trough is called a long wave trough. And the space between the middle of the trough is called the short wave trough. The individual storm is associated with the short wave trough, it moves faster and moves through the long wave trough and circles around through the bottom of it and then goes to the right.The long wave trough would normally be associated with a high amplitude low index pattern. There are about 5 of these throughout the world. A clipper moves so quickly…something can be in Alberta and move to New York in like 3 days. There is a cold front from the Artic air to the north. When it goes to the other side of the mountains there is a front and a dry line. As the cold front crosses the Rockies, it then drives cold air down south. Another place that this happens frequently is in Colorado. In many places there is a trough over the great basinand then it will span like Alberta, to the eastern side of Colorado. These then span cyclones. The Colorado low when it goes south it goes near the Gulf of Mexico. This is a completely different situation. When the Alberta clipper goes south, it has downward motion…How much rainfall/snowfall will it produce coming from the north? It starts really far from oceans. No moisture gets across the Rockies that can precipitate on the other side. Most snow comes from the plains if there is any water in the air and it is lifted. Not much water from the west. A foot of snow for us will come from a Colorado low that takes a drink from the Gulf. Need moisture for that to happen. Precipitation shield forms on dry line, not cold frontCreates conveyor belt of moisture and drops a huge snow band on the north and west side of the stormwhich is where we would lie. To the east of this would be mostly rain. Rain itself will be 20 degrees like the air temperature; it would freeze immediately when it hits the ground. That is known as freezing rain. Summary For Cyclone East of Rockies• Special conditions present alteration to Norwegian cyclone model• Lower portion of cold front unable to move across from Pacific, i.e. cut-off by Rockies• Dry line forms on west side of Rockies• Arctic Pulse of cold Canadian air mass plunges south on lee of Rockies• Movement of air over mountains causes “lee cyclogenesis” or stretching of vorticity downward, causinginitial spin-up of cyclonic flowChapter 11 Cyclones Forming Along Gulf and East CoastsThey get very