DISCUSSION: When it comes to the global observation of extratropical cyclone formation and evolution thereof, there is no question that cyclone structure can be one of the more interesting marvels of modern atmospheric science dynamical observations. During the heart of a given Northern Hemispheric Winter season, there can often be situations wherein low, mid, and upper level atmospheric support comes into place for the successful development of more intense extratropical cyclones. One of the premiere factors involved with the development of such intense Pacific low-pressure systems has to do with the presence of upper-level features most commonly referred to as an upper-level trough. An upper-level trough is an atmospheric feature which helps to amplify the degree of mid- and/or upper-level instability by way of increasing the mid- to upper-level temperature contrast.
A mid- to upper-level temperature contrast is the primary catalyst which leads to a mid- to upper-level pressure contrast which leads to a more dynamically unstable mid- to upper-level atmospheric environment. As a result of these changes which sometimes occur at times over larger oceanic basins such as the Pacific and the Atlantic Ocean basins, there can also sometimes be the development of larger-scale low-pressure systems. When such low-pressure systems develop, you can sometimes observe more rapid development of such systems as is captured in the satellite imagery gif which is attached above (courtesy of The Weather Channel). In this water vapor satellite imagery gif attached above (courtesy of the Himawari-8 satellite imager), you can clearly see how rapidly such systems can develop when all the necessary factors come into place. From going to the adolescent phase of this system to the mature phase of this extratropical cyclone, you can see how quickly the structure of a developing oceanic cyclone can change. Moreover, you can also see how quickly the well-defined center of this low-pressure system formed and the corresponding convection which wrapped right around the immediate center of this system’s circulation. Currently, this system has deepened (i.e., has further intensified) all the way down to an estimated 937 mb low. Thus, there is no debate that this is a very powerful low-pressure system to say the least. It goes without saying that it is incredible to observe the gradual as well as real-time development of such low-pressure systems as they are truly a perfect case and point for how the atmosphere can sometimes perform at an incredibly high level. To learn more about other neat weather observation topics from around the world, click here! © 2019 Meteorologist Jordan Rabinowitz
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 DISCUSSION: Earth's atmosphere can be divided into four layers based on how temperature changes with height. In the lowest layer of the atmosphere (troposphere), temperature generally decreases with height. Above that is the stratosphere where temperature increases with height. Then above the stratosphere is the mesosphere and thermosphere where temperature decreases and increases with height, respectively. In order for clouds to form, there must be water vapor in the air. Since the source of water vapor is the surface, most of the water in the atmosphere and associated clouds occur in the troposphere. However, on rare occasions, the small amounts of vapor in higher layers of the atmosphere can lead to cloud development. In particular, noctilucent clouds are thin clouds that occur in the mesosphere (~50 miles above the ground). When these clouds form, they tend to occur near the poles where the extremely low temperatures help them to develop. In addition, these clouds are extremely thin due to the extremely low amounts of vapor in the mesosphere. Hence, they can't be seen when the sun is high in the sky. Instead they are illuminated when the sun is low in the sky or below the horizon, which occurs a lot in polar regions. While noctilucent clouds almost exclusively appear in polar regions, certain conditions may allow them to form at lower latitudes. For example, the picture above shows a noctilucent cloud near San Francisco, CA. In this case, as a meteor burned up high in Earth's atmosphere, it created the right conditions for a noctilucent cloud to form at an unusually low latitude. Rocket launches can also help to generate these clouds in places where you wouldn't normally expect them to form. The picture below from spaceweather.com shows such a noctilucent cloud formation over Orlando, FL as a result of a rocket launch from Cape Canaveral. To learn more about other weather observation topics from around the world, be sure to click here! © 2019 Meteorologist Dr. Ken Leppert II  |
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