Mid‐latitude Cyclonic Storm SystemThe Cloud Shield is Usually Comma Shaped with the Head around the Low Pressure Center and the Tail Just ahead of the Cold FrontLow Pressure Center and the Tail Just ahead of the Cold Front08_15ab.jpgMid Latitude Cyclone Storm System (MLCSS)•It has several names. Cyclone, Cyclonic Storm, Cyclonic System, Depression.•Cyclonic Storms are the weather maker for mid-latitude locations and create fthe changeable pattern of weather there.•The cyclonic storm consists of a center area of low pressure which anchors the fronts attached to the low This gives a comma shaped cloud shield on thefronts attached to the low. This gives a comma shaped cloud shield on the satellite image.•The cyclonic system pulls air masses of very different character together. This results in local thunder storms along the fronts.•The cyclonic system can destabilize the atmosphere over a large region of the U S causing many areas of thunderstorms that arenotlocated along frontsU.S. causing many areas of thunderstorms that are notlocated along fronts.•The cyclonic systems are short lived (1 week) and migrate moving generally west to east.•Cyclonic systems are created by the westerlies and jet stream aloft. The surface low pressure cell is connected to a trof aloft and is created by the trof.Strong Cyclonic System over Eastern U.S.With Counterclockwise Pattern of Rotation around LowWith Counterclockwise Pattern of Rotation around LowClockwise Circulation around AnticycloneCentered over IndianaStages in Life Cycle of a Cyclonic System1. Cyclogenesis. Low develops along frontal boundary with winds showing rotation.winds showing rotation.2. Mature or Open. Classic fully developed cyclonic system with pronounced warm sector of maritime tropical air wedged between the fronts.3 Occl sion or Occl ded Sstem Cold front has3. Occlusion or Occluded System. Cold front has overtaken the warm front and lifted it off the surface System is also losing upper air supportsurface. System is also losing upper air support as it approaches the crest of the next ridge.Stages in the Life Cycle of a g yCyclonic Storm SystemThe cold front moves faster than the warm front eventually overtaking it and lifting it off the ground forming and lifting it off the ground formingan occluded front.Norwegian Cyclone ModelThe Norwegian cyclone model, so named to honor the Norwegian meteorologists g y , g gwho first conceptualized the typical life cycle of cyclones in the 1910s and 1920s, presents the evolution of a cyclone. In this model, there will initially be a boundary, or front, separating warm air to the south from cold air to the north. The front is often stationaryoften stationary. A wave on the front will form as an upper level disturbance embedded in the jet stream moves overdisturbance embedded in the jet stream moves over the front. The front develops a "kink" where the wave is developing. This process is called cyclogenesis. Precipitation will begin to develop with the heaviest occurrence along the front (dark green).As the wave intensifies, both cold and warm fronts become better organized.The wave becomes a mature low pressure system, while the cold front, moving faster than the warm front, "catches up" with the warm front. As the cold front overtakes the warm front, an occluded front forms.cold front overtakes the warm front, an occluded front forms.The cold front under runs the warm front and lifts it off the ground. The occluded front is actually a messy sandwich of frontal boundaries and air massesfrontal boundaries and air masses.As the occlusion process continues, the system looses its upper level support from the jet stream and the core pressure begins to rise.Stages in the Life Cycle of a Cyclonic Storm SystemSince cyclonic systems move from west to east the cyclogenic systems form farther westSince cyclonic systems move from west to east, the cyclogenic systems form farther west and the occluded systems farther east. Note the block diagrams. The lifting along the cold front is under‐running while along the warm front it is over‐running.Cyclogenic System Forming in Wyoming. This is Cl iCyclogenesis.Note incipient counter clockwise pattern of rotation around this low and also the fairly well defined clockwise pattern around the High over Wisconsin. Classic Open Stage of Cyclonic System.Cold Front is About Ready to Pinch Off the Warm Front in Kansas. There is a strong line of thunderstorms in the narrowing warm sectorstrong line of thunderstorms in the narrowing warm sector.Occluded Cyclonic System with Occluded Front Arcing from Low in Wisconsin to New York.Note Reinf orcing Cold Front from Michigan to OklahomaMeandering of the Westerlies Creates Areas ofConvergence and Divergence Displaced to the East of g g pCorresponding Upper‐Level FeatureStrong Divergence Field from N. Texas to MissouriStrong ConvergenceField across Great LakesStrong Convergence Field across Great LakesDivergence Aloft Causes Low in TX PanhandleConvergence Aloft Causes High Over Gt. Lakesg gSurface Map for Same Day Shows Family of Cyclones Associated with a Trof Aloft.OiC Bdf Sh i MN & WIOverrunning Causes Band of Showers in MN & WI.The severe storms in the warm sector are related to the trof aloft (dashed yellow line).Types of Cyclonic Systemsf i h li1. Trof Type is the most common. Cyclonic system develops near the base of the trof and moves up the east side No closed isobars aloftup the east side. No closed isobars aloft. These often exist as families. (6 Oct. Maps)2. Long Wave Type is big and tends to occur during cooler half of year. Key is upper level support showing at least one closed isobar aloft. Often have more than two closed isobars.3. Short Wave Type is smaller, form rapidly, and move quickly.It is connectedto short wave aloft.quickly. It is connected to short wave aloft. Since these often form quickly, they are called the forecaster's nightmare. 300 mb Chart for 2 Sept, ’08. Showing Trof across Northern Great Plains Advancing towards Midwest. It Has a Divergence Field Across Southern Manitoba and Ontario. “L” Indicates Position of Surface Low. Since the Trof Contains No Closed Isobars, the Cl t th Sf Wldb TfT (N t Slid )Cyclone at the Surface Would be a Trof Type (Next Slide).LLSurface Map for 2 Sep, “08. Strong Cyclonic System in Southern Canada Wedged between Two Strong Anticyclones. Hurricane Gustav is over Louisiana and Arkansas. Cyclone is a