This document includes all weather changer writings. 20 weather changing events are discussed in these writings. (1) WX CHANGERS: FRONTS This series of hints goes over processes that can cause dramatic changes in the weather. This writing discusses fronts. Fronts can result in a dramatic change in the weather. The passage of a cold or warm front can cause a dramatic shift in wind, temperature, humidity and weather. With adequate moisture, precipitation is common along the frontal boundary. The most noticeable weather change with a frontal passage is temperature. The fastest temperature changes tend to occur with cold fronts. Temperature can drop 10s of degrees within an hour or two. In some cases, there can be more than a 20 degree F temperature drop in just minutes. The gusty winds can bring the wind chill down also thus the weather outside feels significantly colder than before frontal passage. Strong rain bands can develop on and near the frontal boundary. The weather can go from mild and partly cloudy to windy with heavy rain as the front passes. The strong wind can blow in sheets of heavy rain. The intense lifting that the front can produce helps lead to the big change in weather. A warm front passage is typically not as violent as a cold front passage but significant weather changes can still occur. The weather can go from damp and cold to warm and partly sunny in the matter of minutes as the front passes. Strong storms can also occur near the warm front boundary due to the lifting that the warm front provides. Flash flooding is one of the most dangerous forms of changing weather. Along with lightning and tornadoes, flash floods are responsible for a high percentage of weather storm deaths. Flash flooding and lightning deaths tend to not get as much media coverage as compared to tornado deaths but flash flooding and lightning are serious weather related risks. Flash flooding is a sudden rise in water level within creeks, streams and other low lying water flowing regions. The rush of the water and the turbulence of the water make it difficult to survive when a person on foot or in a car is trapped in the rushing water. It is important to not drive through water of unknown depth and to seek higher ground when thunderstorms occur. When visiting or moving to an unfamiliar area, it is important to locate the regions that could be influenced by flash flooding. These areas should be avoided when heavy rain occurs, whether on foot or driving. A flash flood can change a dry creek bed into a rushing torrent of water. The creek or stream can flash flood even if it is not raining at that particular location since the water source can be from a nearby thunderstorm. Flash flood watches and warnings are issued when the weather has the potential to generate heavy rain that can produce flooding. Being at a safe location, higher ground or home instead of driving can reduce the risks from flash flooding. (2) WX CHANGERS- CHINOOK AND UPSLOPE EVENTS Chinook and upslope events can result in dramatic changes in weather in a short amount of time. A Chinook event has some similarities to a dryline passage such as the dewpoint dropping and the wind coming from a higher elevation source. A Chinook is associated with a strong downsloping wind. Air that sinks will decrease in relative humidity and increase in temperature. This can occur when air in high elevation regions such as over the mountains, sinks down into the surrounding lower elevation regions. The effect can be more pronounced when the wind speed is strong since there will be a fast and widespread replacement of the cold air with warmer and drier air. These Chinook or downslope episodes can dramatically warm the temperature, quickly melt snow away that is on the ground and dry the air. This can be welcome air in the winter since the air with a Chinook can replace very cold air that was in place. This can make winter feel like spring for a day or so. The downsloping air can result in temperatures increasing by 10s of degrees in a short time period. An upslope event has the opposite impact. Rising air cools, helps produce clouds/precipitation and moistens the air. An upslope event occurs when a persistent wind flows from lower elevation regions toward higher elevation regions (such as a mountain range). An upslope event can bring flooding rains in the warm season and very heavy snows in the cool season. A slow moving low pressure system that is advecting in moisture can produce many hours of favorable upslope conditions and thus heavy amounts of precipitation. A weather forecaster looks for the number of hours upslope conditions will be in place (via wind direction), the moisture associated with the air and how quickly the air is rising in order to assess the significance of the upslope event. (3) WX CHANGERS- SHALLOW INVERSION A shallow inversion can cause a dramatic change in the weather when it develops and when it mixes out. A shallow inversion can be created by overnight cooling or a shallow layer of cool air moving in at the surface. There is a much different air mass above the inversion. For example, it may by 25 F at the surface while it is 45 F just a few hundred feet up. One way the shallow inversion can be mixed out is through solar heating. When the sun heats the surface, it will cause vertical circulations that cause the air to mix. This can cause the shallow layer of cold air at the surface to mix with much warmer air aloft. Since the volume of the warmer air aloft is much greater, the temperature of the mixed air will be closer to that of the warm air. This can cause the surface temperature to sky rocket in the morning. For example, warming from 20 F to 45 F in just a couple of hours in the morning. Other ways a shallow inversion can be set up include shallow cold fronts and cold air ponding into a valley. Strong winds and solar heating are two processes that can mix out this shallow cold air and cause the temperature to jump up. What can start out as a cold morning can quickly turn into a mild day when the rapid warming takes place. What can be thought of as the opposite of an inversion is a dry adiabatic layer or superadiabatic layer. This layer at the surface will show a rapid decrease of temperature with height (warm at ground surface with rapid cooling aloft). This can be caused by intense solar radiation when winds are weak. When the sun sets, a rapid cooling can take place. In the evening, the temperature can rapidly decrease as a cool inversion layer forms at the surface. This can commonly occur in dry areas in summer such as in desert and semi-arid location. This is why desert and semi-arid locations can have such a big temperature difference between the high and low temperature. It can occur to a lesser extent in other areas also when the weather is sunny and dry. (4) WX CHANGERS- SUNSHINE The difference between the high and low temperature is often between 15 and 30 units of F. Much of this difference can be attributed to the daily cycle of sunlight and darkness. Other example factors include cloud cover, fronts, wind direction influences, humidity and weather events. Sunlight though typically accounts for much of the difference when averaged over a year. The high and low temperature is one of the important pieces of weather data that is included with a weather summary. Sunlight helps warm the temperature thus the high temperature typically occurs when the sun is out and cumulative warming from the sun has taken place. The low temperature typically occurs at night when radiation cooling lowers the temperature gradually at night. The lowest temperature typically occurs around sunrise. The significant difference in temperature between the high and low temperature due to sunlight makes this factor a weather changer. It is the most common weather changer since it happens each day. Some days are more influenced by the sun than others. On days with thick clouds and the same air mass, the difference between the high and low temperature may only be a few degrees. On clear dry days, the difference between the high and low temperature may be 10s of degrees F, such as a morning low of 65 F and a high of 95 F. Clear skies, long hours of daylight and dry air (and dry soil) allow for the maximum of warming by the sun. Thus, desert and semi-arid regions tend to have the biggest difference between the high and low temperature. For example, the low temperature could be 50 F with a high of 90 F in a arid location which results in 40 units F of warming due to sunlight. A humid location with significant cloud cover and wet soils will reduce the amount of warming, though it can still be 20 units of F or more of warming that can be attributed to sunlight. (5) WX CHANGERS- DOWNDRAFT A downdraft from a thunderstorm can dramatically change the weather. A downdraft is produced by evaporative cooled air that falls to the surface from a thunderstorm. Downdrafts can be refreshing on hot summer days. For example, temperatures can cool from the 90s F to the 70s F when the downdraft air moves in. The temperature change occurs within minutes. Air mass thunderstorms are most likely to develop when temperatures are at their warmest during the day. This makes the downdrafts all the more refreshing when a very hot day is turned into a mild day. The cooling from the downdraft can be as significant as the entire cooling that it takes in the overnight hours. A downdraft is hours of overnight cooling compacted into just a few minutes. The downdraft also tends to bring gusty winds. The windy conditions can make it feel cooler also. Downdrafts are common from warm season convective storms. These winds can be a weather changer in another way. That way is that they can produce severe convective wind gusts. These wind gusts can produce damage to property and vegetation. The wind can go from fairly light to very strong in the matter of seconds as the downdraft gust front moves through. They can also spin up brief gustnadoes which can produce damage. Severe downdraft winds can occur from a grouping of storm cells called multi-cells. Multi-cells forming a squall line, a derecho, or a mesoscale convective system can produce sudden damaging wind. (6) WX CHANGERS- EVAPORATIVE COOLING Evaporative cooling is a cooling of the air due to latent heat absorption of water molecules. When water evaporates, the evaporation process requires taking heat from the environment in order for the evaporation to occur. With the removal of heat from the air, the air cools. The amount of water that is able to evaporate into a volume of air impacts the cooling. Evaporative cooling can occur until the relative humidity reaches 100% (saturated air). Thus, initially dry and warm air will produce the greatest amount of evaporate cooling when this air is saturated through the evaporation process. This is because dry air can evaporate a greater amount of moisture as compared to less dry air when both are initially at the same temperature and warm air can evaporate a greater amount of moisture as compared to cold air. One reason rainfall is associated with cooler air is because the rain cools the air through evaporative cooling. When rain falls into dry air it will dramatically change the weather of that air. This makes it a significant weather changer. Rain falling into dry air will increase the dewpoint and lower the temperature. The wet bulb temperature is the temperature that the dewpoint and temperature will meet at when complete saturation occurs. Another reason that evaporative cooling is a significant weather changer is that it can cause a cold rain to turn into wintery precipitation. Evaporative cooling can be enough to cause the ground surface temperature to drop below freezing which leads to ice on the ground and travel problems. For example, the temperature could be 34 F with a dewpoint of 10 F. When rain falls into this air, evaporative cooling will cause the dewpoint to increase and the temperature to decrease. After saturation, the new temperature will be below freezing. This can change precipitation type from rain to snow, sleet or freezing rain. Weather forecasters keep a close eye on the evaporative cooling potential when the temperature is initially just above freezing since the weather could change dramatically to icing conditions after evaporative cooling. (7) WX CHANGERS- CAP BREAK The cap is a layer of warm air aloft that resists the mixing between planetary boundary layer air and air in the middle and upper troposphere. It is also called a lid and an elevated warm layer. The cap is a weather changer since when it breaks the weather can go from warm and nice to very stormy. This transition can occur in the course of minutes. Energy and moisture can build under the cap during the day. The cap helps contribute to clear or partly cloudy skies. This allows solar energy to build in the planetary boundary layer and at the earth’s surface. Moisture can build up also as moisture advects in from a moisture source. This energy helps to erode the cap during the day. If the cap is strong enough, it will not break. If just enough energy can build up, the cap will explosively break like Mentos placed in a can of diet coke. The explosive convection can lead to severe weather such as strong straight line winds, hail, torrential rain and tornadoes. Triggers such as fronts, dry lines, convergence boundaries, upper level divergence, influx of moisture, and low level warm air advection can combine with sunshine to help break the cap. The most likely time of the day for the cap to break is from about noon and into the afternoon. A cap breaking in the afternoon can sometimes lead to stronger storms since the energy has had more time to build up during the day. The cap, a huge potential weather changer, is monitored by weather forecasters closely since it has such a dramatic influence on the forecast. (8) WX CHANGERS- MARINE LAYER The marine layer is a cool and humid layer produced by cooling from a cool ocean current and evaporation from the ocean that humidifies the air. This layer of air can stay off shore or move well inland depending on the wind direction. When the marine layer is in place, it is often accompanied by cloudy and/or foggy conditions. This causes the weather to be cooler since sunlight is not effective in warming the surface. What makes the marine layer a weather changer is that this layer moving in or moving out causes a dramatic change in the weather. One location that is influenced by the marine layer is the West Coast of the U.S. For the West Coast, the marine layer can cause some of the biggest shifts in weather. When the marine layer is in place, the weather can be cool, cloudy and damp. When the marine layer retreats or mixes out, then the weather can be hot, clear and dry. The marine layer can cause havoc with weather forecasting since an incorrect forecast on marine layer timing can cause the forecasted high temperature to be way off. For locations near the coast, the marine layer will often be in place in the morning and then by afternoon the sun’s influence will be enough to mix out the marine layer. If the marine layer is strong enough though then it will not mix out and the entire day can end up being cool, cloudy and damp. For example, this layer mixing out or not can mean the difference between a high of 75 F and a high of 90 F. (9) WX CHANGERS- PASSAGE OF 32 F LINE The 32 F line is the isotherm on the surface chart where the temperature on one side is at or below freezing and the temperature on the other side is above freezing. It is also called the freezing line. In actual practice the 32 F line is more of a zone where the temperature is just above or just below freezing. The passage of the 32 F line is a weather changer since it can contribute to icing of the ground surface and can cause precipitation to change from rain/drizzle to freezing rain/freezing drizzle. The movement of the 32 F line is accomplished through cold air advection, evaporative cooling, any other cooling processes and any processes that could warm the air such as warm soil temperatures. The 32 F line will tend to advance forward when significant cold air advection is taking place. When the air mass becomes more stagnant then the progression of the 32 F line will tend to be much slower and can retreat due to warming processes such as solar radiation, soil temperature above freezing and rain falling through a warm layer aloft before falling to the surface. When the air mass is dry at the surface and rain aloft falls into the dry air, the 32 F line will tend to advance forward due to evaporative cooling. Other warming and cooling processes will need to be considered when determining how far the 32 F line will advance forward. On TV weather maps, many times, especially in cases of potential winter weather, the weather broadcaster will have the 32 F isotherm drawn on the surface temperature chart and a time lapse into the future shown so that viewers can see its position relative to where they live. The position of the 32 F line is important to the National Weather Service when it comes to issuing travelers and winter weather advisories. Critical changes in weather can occur when the surface temperature drops below freezing, thus the passage of the 32 F line is a significant weather changer. (10) WX CHANGERS- DENSE FOG Fog is a cloud on the ground. Fog can range from very light to very dense. Dense fog can cause serious travel problems. The visibility can get so low that it is difficult to see a car even a short distance ahead. When an accident occurs, a chain reaction of accidents one right after the other can occur since there is not enough time to brake before hitting the car in front. Conditions that typically cause dense fog include high moisture, relatively light wind, and some lifting. Moisture can be supplied by wet soils, precipitation falling or moisture advection. Light wind reduces the mixing of saturated air with drier air. Stronger wind helps promote evaporation which will tend to reduce fog density unless conditions are very saturated. Some lifting can be supplied for example by upslope flow, warm air advection, or surface convergence. This lift helps sustain the saturation of the air. Sinking air will decrease the relative humidity and cause fog to dissipate. Dense fog can occur anywhere but is most common near oceans, in valleys, near mountains, near rivers, and bodies of water due to moisture or lifting that can be present at these locations. Dense fog can change a good day into a day with severe travel headaches. This makes dense fog an important weather changer. (11) WX CHANGERS- LAKE-EFFECT SNOW Lake-effect snow is as big as a weather changer can be, especially white-out lake-effect bands. Lake-effect snows only occur in particular regions called snow belts, thus the residents in these areas are typically well versed on the consequences of living in the snow belt. Visitors or new residents to these regions are often in for a shock when a winter in these regions is experienced. Lake-effect snow occurs due to very cold air picking up moisture from a huge lake and then depositing that moisture on and near the lakeshore downwind of the wind direction. The lake supplies a continuous supply of moisture. Moisture is often a limiting factor in snow events as a whole (non lake-effect events). However, in a lake-effect situation, the almost unlimited moisture can produce huge snowfalls and very heavy snow rates. A long fetch over the relative warm waters of a great lake can bring a continuous supply of moisture that can be uplifted and deposited as heavy snow in lake belt regions. The weather can go from cold but nice to dangerous in a matter of minutes or a couple miles in a lake-effect event. It can be impossible to see while traveling in the heavy snow bands. The snow can accumulate in feet which make snow removal more challenging. One of the biggest weather changers that can be witnessed is traveling into a lake-effect snow band or observing one move in. (12) WX CHANGERS- HEAT BURST A heat burst is a rare event and a dramatic weather changer. A heat burst is a special type of downdraft that, instead of producing refreshing cooler air, produces extremely hot and dry air. When air sinks, it warms adiabatically. In a normal downdraft, the air is cold enough that even though it warms while sinking it will still end up being colder than the air it is replacing. Also, a normal downdraft will often contain precipitation. The evaporation of precipitation as the air sinks contributes to the air not warming as much as it otherwise would. In the case of a heat burst, the downdraft begins higher aloft than a normal downdraft and typically at the stage when thunderstorms are dissipating. Evening and early night is a typical time they can occur. A heat burst will begin with air high aloft that rapidly accelerates toward the surface. Since storms are dissipating, this downdraft will not have much precipitation thus evaporative cooling will be much more limited as compared to a normal downdraft. The heat burst downdraft also starts high aloft, in the upper troposphere. These two factors (less moisture, a long distance to fall) allow a dramatic warming of the air as it sinks to the surface. One factor that makes heat bursts rare is that many times they don’t make it to the surface since the downdraft will lose negative buoyancy when it becomes warmer than the surrounding air. Thus, another factor in producing a heat burst is that the downward momentum must be extreme enough to allow it to reach all the way to the surface. A dramatic change in weather is in store for heat bursts that reach the surface. A heat burst reaching the surface can cause relative humidities to fall near zero and temperatures to increase to well above 100 F. The strongest heat bursts will cause surface temperatures to climb to between 100 F and 120 F. These conditions can persist for a couple of hours or so along with strong wind before the temperature returns back to normal. The strong wind combined with heat and extremely low relative humidity can quickly dry out vegetation. It is often dark outside when these events occur which makes them feel all the more unusual. (13) WX CHANGERS- NOR’EASTERS Nor’easters are a type of mid-latitude cyclone that can bring enormous changes to the weather. They are most common in the cool season (colder half of the year) and they derive their energy from two sources which include the temperature gradient between cold and warm air masses and also the latent heat energy supplied by warm ocean currents. The location they occur is along and near the East Coast of North America and they get their name from the northeast wind direction that is experienced along and near the coast. Locations that are noted for receiving these storms include U.S. states and Canadian Provinces that border the Atlantic Ocean and with the influence extending one to several hundred miles inland. Since they are more common in the cooler part of the year (mid-Fall to mid-Spring), these storms can produce significant snow accumulations. They can be referred to as “white hurricanes” since characteristics include strong surface winds and heavy snow. The low pressure structure differs from a hurricane though in that Nor’easters take on the low pressure structure of an intense mid-latitude cyclone with differential advections. Nor’easters can range from wet Nor’easters to white Nor’easters depending on how much cold air is in place and how much cold air is advected into the system. Commonly Nor’easters produce both heavy rain and heavy snow with a tendency for snow to be more prevalent in the direction of the colder air advecting into the system. In the case of a wet Nor’easter, most of the heaviest precipitation falls as rain. Coastal areas receive significant rainfall with snow more likely further inland closer to the cold air source. In the case of a white Nor’easter, heavy snow is experienced even at coastal locations and areas out over the ocean. Another tendency is that snow is more likely to occur at the coast the farther north a location is (higher latitude). Each Nor’easter is different though in that certain areas will tend to be favored for the heaviest rain or snow in any one event. The heavy precipitation tends to fall in bands. If the Nor’easter is slow moving, huge rainfall and snowfall accumulations can occur at certain locations. The dramatic weather changes that can occur make Nor’easters a significant weather changer. They can cause coastal beach erosion, heavy flooding rain, travel crippling snowstorms, dangerous sea waves, and structure / tree damaging wind. Like hurricanes, Nor’easters can explode in intensity in the span of a few hours. The interaction between latent heat energy from the Gulf Stream, the low pressure center and cold air advecting toward the coast can create a rapidly developing intense storm system. As they develop and mature they tend to move toward the north, northeast or east from the influence of the polar jet stream mid-latitude winds. They can leave behind significant damage and precipitation totals. (14) WX CHANGERS- HABOOB Haboob is one of the more interesting words in meteorology and what it refers to is more commonly known as a dust storm. Previous weather changes have involved the influence of the downdraft. A thunderstorm downdraft is one of the events that can create a haboob event. They can also occur from the gusty winds behind a cold front or dryline passage. Haboobs are most likely to occur in arid and semi-arid locations. The time before thunderstorm development can include light winds and clear weather. The gusty winds, low visibility and blowing dust that are associated with a haboob make it a weather changer. Locations in arid locations have soil and dirt that is not well supported by vegetation. The power of the wind to pick up dirt and dust increases exponentially with wind speed increase. The winds from the downdraft of a thunderstorm can be very gusty. In arid locations, the dry air can evaporate the rain within a downdraft before it reaches the surface. Thus, the downdraft reaches the ground surface as a dry downdraft. With no rain to help remove dust from the air, the gusty winds rapidly pick up dust from the ground surface and transports it into the air. The dust can be thick enough to significantly reduce visibility. The dust can cause problems such as restricting travel due to low visibility, clogging air filtration devices, leaving behind a dusty layer and making outdoor activities very uncomfortable. They can cause the weather to go from nice and sunny to dusty and windy in the span of a few moments. (15) WX CHANGERS- DRYLINE The dryline is a dramatic weather changer and can be a convergence zone for severe storms to fire up. A dryline separates air masses with very different moisture characteristics. Since the dryline is more noted for its advancing stage instead of retreat stage, it is known as a dryline instead of a moistline. The dryline typically advances during the day and then retreats at night. In the advancing stage, the dryline will replace warm and humid air with warm and dry air. The dryline is found most notable in the spring and is a relatively common feature in Western Texas, Oklahoma, and Kansas. The dryline can advance to the east of this region but it will inevitably retreat back toward the source region after sunset. The dryline is a dewpoint change line and a convergence axis. The dewpoint can vary dramatically from one side to the other. For example, the dewpoint could be 68 F on the moist side and 25 F on the dry side. The passage is often accompanied by gusty winds, dust and sometimes storms if enough convergence takes place. The dryline can change a humid hot day into a dry dusty day in just moments after passage. Storms can fire up on and near the dryline boundary thus the storms represent another sudden change that can occur in the weather. A dryline separates warm and moist mT air (warm and moist Gulf of Mexico ocean air mass known as maritime tropical) from high plains and high elevation cT air (warm and dry continental tropical air). The cT air will flow over the mT air, thus the influence of the dry air mass can extend well east of the surface dryline boundary. This dry air aloft produces convective instability when it flows over the top of warm and humid air. Thus, the dryline environment is often associated with a severe storm environment, especially when the dryline is being forced forward by a developing low pressure system. (16) WX CHANGERS- HURRICANE EYE The region in and around a hurricane’s eye is a region famous for incredible weather changes. The center of a hurricane, especially a strong hurricane, is noted for having a low cloud density region called an eye. In the eye the winds are fairly light and if it is daytime the sun can come out. Just a few miles in all directions though the fierce winds and heavy rains of the eyewall are being experienced. Experiencing the eye requires having to go through the eyewall, thus often damage has taken place by the time the eye is overhead. Unfortunately, as the eye moves out, the extreme winds of the eyewall will return one more time before the storm ends for that location. Thus, any birds, other animals or people that come out during the eye’s arrival will have to shelter one more time before the storm ends. Winds can go from over 75 miles per hour, to nearly calm, to over 75 miles per hour again as a hurricane’s eye approaches, moves overhead and then moves past. The forward motion speed of the hurricane will determine how quickly this process takes place. It is possible that the process can occur slowly or the eye can stall temporarily and this allows much more time to document the experience. (17) WX CHANGERS- SUPERCELL A supercell is an intense thunderstorm that has a mesocyclonic circulation. They tend to be long lived since the updraft and downdraft are in separate regions of the storm. They can produce heavy rain, hail, strong convective wind gusts, vivid lightning and tornadoes. They are a significant weather changer due to the damage they can produce. They can bring flash flooding rain, hail large enough to do damage to cars and roofs, wind gusts that can damage structures and tornadoes that can produce significant damage. The strongest tornadoes are produced by supercells. Supercells are of great interest due to the damage and loss of life they can produce. Severe thunderstorm and tornado warnings are commonly issued when a supercell develops. A supercell can change the weather from stormy to tragic in seconds. These are storms that are important to take cover from. Supercells are most common in spring and early summer when there is the greatest combination of instability, moisture, wind shear and lifting mechanisms. Instability is created by warm surface temperatures with cooler air high aloft. Moisture is transported in from evaporation from warm ocean water. Wind shear is supplied by fronts, convergence boundaries, low pressure systems and the jet stream. Lifting mechanisms are supplied by low level warm air advection, surface convergence boundaries and upper level divergence. Supercells are the storms that inspire storm spotters and storm chasers since incredible photos and videos can be obtained of these storms. (18) WX CHANGERS- SEA BREEZE A sea breeze is a mesoscale front produced by the contrast between the relatively cooler water of the ocean and the relatively warmer land surface during the day. The sea breeze is most pronounced in the afternoon when the temperature difference between ocean and land is at its greatest. A sea breeze can have a similar impact as a cold front since it brings in cooler air and storms can develop on its boundary. Sea breezes are common in summer in a location such as Florida which is surrounded by water on three sides. The sea breeze is found in coastal area and they can move several miles inland during the day. A sea breeze can bring in a refreshing change in the weather. The lifting from the boundary tends to increase cloud cover and the chance for thunderstorms. The cooler air is denser, thus the surrounding hot air will lift over the sea breeze boundary. A faster moving and more pronounced sea breeze will tend to produce more convergence and storms. The cooling from the sea breeze is more pronounced when precipitation occurs since the evaporation will cool the air even more. The opposite of the sea breeze is the land breeze. At night, the land cools more than the ocean thus the land breeze will push cooler air over the ocean. The land breeze tends to be weaker than the sea breeze and the land breeze does not tend to generate thunderstorms. Thus, the sea breeze is typically more talked about. (19) WX CHANGERS- MID-LATITUDE CYLONE A mid-latitude cyclone brings in clouds and precipitation. It is a low pressure system that has a lifecycle of many days and can travel over 1000s of miles. They are most common in the middle and high latitudes and the season they are most common is in the cooler half of the year when the jet stream is more active. The regions that mid-latitude cyclones tend to develop are near mountain ranges, at ocean/land boundaries and along troughs in the jet stream. Mid-latitude cyclones are a common weather changer mechanism in the middle-latitudes. They bring in fronts and precipitation systems that can turn sunny weather to cloudy and damp weather. Mid-latitude cyclones tend to move toward the east or northeast once they mature. Due to the movement, they tend to influence the weather for a day or two. It is common that the weather will be nice, followed by a day or two of inclement weather and then followed by the return of nice weather. Mid-latitude cyclones are a major reason that the weather forecast changes in the future. A cold front and colder air often follows behind a mid-latitude cyclone thus warmer weather is typically followed by colder weather when a mid-latitude cyclone is forecasted to influence the forecast region. (20) WX CHANGERS- FLASH FLOODING Flash flooding is one of the most dangerous forms of changing weather. Along with lightning and tornadoes, flash floods are responsible for a high percentage of weather storm deaths. Flash flooding and lightning deaths tend to not get as much media coverage as compared to tornado deaths but flash flooding and lightning are serious weather related risks. Flash flooding is a sudden rise in water level within creeks, streams and other low lying water flowing regions. The rush of the water and the turbulence of the water make it difficult to survive when a person on foot or in a car is trapped in the rushing water. It is important to not drive through water of unknown depth and to seek higher ground when thunderstorms occur. When visiting or moving to an unfamiliar area, it is important to locate the regions that could be influenced by flash flooding. These areas should be avoided when heavy rain occurs, whether on foot or driving. A flash flood can change a dry creek bed into a rushing torrent of water. The creek or stream can flash flood even if it is not raining at that particular location since the water source can be from a nearby thunderstorm. Flash flood watches and warnings are issued when the weather has the potential to generate heavy rain that can produce flooding. Being at a safe location, higher ground or home instead of driving can reduce the risks from flash flooding. |