One aspect of weather that makes it so captivating is that it can get sensational, dangerous and down right freakish! This page has all 10 local freakish weather writings on one page. 1. LOCAL FREAKISH WX SERIES: EXTREME HAIL This series looks at freakish weather events that can occur locally. The weather event is freakish in that it display an extreme weather characteristic. It is local is that it can occur in one location and a mile away there can be nothing or a much reduced intensity of the weather. This writing looks at extreme hail. The hail size that falls from a supercell storm is highly variable. The hail sizes experienced will vary dramatically over the region the storm moves over. One person may report marble size hail, another may report quarter size hail while even another could report tennis ball size hail. Why is the hail produced from a supercell not uniform in size? The location that receives the largest hail will have the best combination of the storm being at its most intense and where the updraft and growth factors are maximized. A storm is a process that varies in intensity during its lifecycle. A storm will tend to increase in intensity, then reach maximum intensity and then decrease in intensity. This is only a generalization though since storms are continuously varying in intensity as they evolve and move. Locations directly under the hail core will often get larger and more hail than locations on the periphery. The wind interactions with the hail stones will help determine where they fall after the stones grow in the updraft region of the storm. A stronger updraft will typically develop larger hailstones. The updraft will typically be stronger in the core of the updraft than at the outer edges. Stones in the core of the updraft can be suspended longer and thus have more opportunity to cycle through the updraft and continue to grow. The size of this core region is localized within the storm, thus when this hail falls out it will influence a local region below it. Since a storm will typically have a forward motion as the hail falls out, the hail will fall in a more or less linear but narrow path over the ground surface. The intense and turbulent winds aloft can influence where the hail stones move and how some are recycled back into or away from the updraft. This can cause some hail to fall farther from the storm core than expected. Huge hail stones can devastate local regions along with linear path while just half of mile away from the path there may be no hail at all. Neighbors just a few houses away from each other can report different hail sizes. The question to ask is this, what is the largest hail stone that landed on the ground from the storm? Often this largest stone is not found if it lands for example in an empty field. If this largest hail stone and stones that are similar in size to it land on a car, in a front yard or on a roof then it is much more likely it will be observed. Depending on the strength of the storm and the location with respect to the storm, the largest hail stone may be golf ball size or it could be grapefruit size for example. It is difficult to know the largest hail stones produced until pictures and reports come in. 2. LOCAL FREAKISH WX SERIES: TORNADO Tornadoes are rare events for any local point. They can seem more frequent since they can often be seen from a distance and the number of observers documenting the event is significant. There are several ways in which tornadoes are freakish events. First, the damage and personal lose they produce can be intense. Second, the distance between two close locations can suffer dramatically different damage. For example, a house can be severely damaged while a house a couple of houses down only has minor damage. Third, of all meteorological phenomena they can be the most stunning. Like hail, tornadoes tend to follow a streaked pattern along the ground. They do often deviate from a straight path at the start or end of the path but much of the path follows the motion of a straight or gradually curving path while it is on the ground. Like hail again, the path of damage width tends to be narrow when compared to the length of the path. However, some tornadoes do make a quick touchdown before retreated from the surface. Some very rare monster tornadoes can be a mile wide. One point I really want to stress is that tornadoes will do the unexpected. A forecaster that thinks they have tornado forecasting figured out often makes mistakes. The saying I like to go back to is, “any strong or severe storm is capable of producing a tornado”. Knowing for certain what environments and storms will produce tornadoes and will not produce tornadoes is not a certainty. There is a balance between over-warning and under-warning. On one extreme, too many storms are tornado warned and on the other extreme not enough are tornado warned. There is an element of judgment when deciding to warm on a storm. One mistake is to think a strong thunderstorm environment will not produce tornadoes when in fact it does. Another mistake is to overplay the threat and it does not materialize. Forecasters have to be ready to change their judgment at a moment’s notice. Tornadoes are such freakish events and forecasting them has it challenges in that there is an expectation for a forecast to be more specific and quicker than it is. Tornado forecasting requires moment by moment monitoring of radar, spotter reports and knowing the history and environment that a storm has. Many freakish reports occur from tornadoes. Some classic examples are the sound of a freight train, the debris reports, miraculous survival stories, heartbreaking deaths, and dramatic rescues. Tornadoes are a primary reason for the interest many people have in weather and storms. 3. LOCAL FREAKISH WX SERIES: 4+ INCHES OF RAIN IN AN HOUR A freakish weather event that can occur includes extreme rainfall on a local area. The extreme rainfall can be generated by moisture converging into a stationary lifting mechanism, a stalled strong thunderstorm or a rain band from a tropical storm system. These freakish events can fill up a backyard rain gauge in an hour. There can be for example a 5 inches rainfall gauge that fills up and overflows due to a freakish rainfall event. An example of moisture converging into a stationary lifting mechanism is when a moisture rich flow collides into a mountain range. The steady supply of moisture and lifting can generate extreme rainfall amounts. This can occur for example along the Rocky Mountains and mountains of the Pacific. This can generate prodigious flash floods as the water moves down mountain streams. A strong storm with slow movement can generate prolonged heavy rain over a location. This type of heavy rain event will commonly lead to flash floods. Typically storms have enough forward motion so that the heaviest of the rain lasts for less than half an hour at any one location. A slow moving storm though can allow the heavy rain core to stay over a location or a solid hour or more and this can generate the 4+ inches of rain in an hour. Training of storms can also produce very heavy local rainfall. Training occurs when storms keep developing and dumping rain over the same region. This can occur even when the individual storms have a progressive forward motion. Tropical systems are also notorious for generating very high rainfall rates. The tropical storm brings in a deep layer of moisture. The lifting along with the moisture will generate very heavy bands of precipitation. If these bands occur over the same region then rainfall rates can exceed 4+ in an hour. As the tropical moisture collides into additional lifting mechanisms such as higher elevations or a front then this can also cause tremendous rainfall rates. 4. LOCAL FREAKISH WX SERIES: 6+ INCHES OF SNOW IN AN HOUR Very heavy snow can occur in association with optimized lake effect snow, as thundersnow or in an intense snow band created by very strong uplift. A freakishly heavy snow event will have large flakes, will have numerous flakes and conditions will sustain itself for an hour or more. These three factors combined can produce snows of greater than 6 inches in just an hour. A really good snow rate is 2 inches per hour, thus the snow rate in a freakish event is really eye opening. A heavy lake effect snow occurs as frigid air moves over a large fetch of relatively warm water and then this air converges over the land as it continues to lift. Convective style lifting can wring out large amounts of snow. The bigger events can result in snow measured in feet instead of inches. One reason for this is because the conditions responsible for the snow can sustain itself for many hours. Another form of snow that is not lake effect but is convective in nature is thundersnow. This can result in very large snowflakes and numerous snowflakes that accumulate quickly. If the snow rate is able to sustain itself for an hour or more, many inches of snow can pile up within an hour. Due to poor visibility and a piling accumulation, these snows can temporarily cripple an urban area. Heavy snow in association with a mid-latitude cyclone tends to fall in bands. Locations under the bands can get several more inches of snow than surrounding areas. These bands can result from intense dynamic lifting that in turn leads to a type of convective uplift called slantwise convection. When these bands are slow moving or training than many inches of snow can occur at a location in a short amount of time. 5. LOCAL FREAKISH WX SERIES: 3+ INCHES OF GRAUPEL IN AN HOUR The experience with graupel is that it is a combination of a large snowflake and a small hailstone. They fall faster than snowflakes but a little slower than hail. Sometime graupel is called “soft hail”. It forms by large snowflakes that are suspended aloft that grow by supercooled water drops freezing on the snow. This allows graupel to have a bright white color and a faster fall rate than snow. This type of storm is more common in higher elevation regions since there is an absence or a significant reduction in the amount of warm air the precipitation needs to falls through to reach the surface. In a lower elevation location, it is more likely the graupel will melt into heavy rain before reaching the surface. Relatively strong lifting is needed to form graupel, thus when it does form, many times a heavy shower of graupel will be experienced. Graupel can accumulate on the ground in a similar fashion to heavy snow. Several inches can fall in an hour especially if the storm is slow moving. It can look like several inches of snow occurred. Unlike snow though, it is not good for making snowballs and is denser than snow. In a freak graupel storm, a convective storm will form in an environment that supports frozen precipitation that can reach the surface. Heavy precipitation forms in the updraft. The strong updraft and cold temperatures allow for a heavy winter precipitation to develop aloft. Instead of the heavy rain that a thunderstorm would have, heavy graupel falls to the surface. It can accumulate quickly. In the bigger storms, snow plows will be needed to remove the accumulation from roadways. 6. LOCAL FREAKISH WX SERIES: LIGHTNING STORM A thunderstorm has lightning but each storm can produce a varying amount of lightning depending on several storm characteristics. One character is CAPE. The greater the instability then generally the more numerous the lightning strikes will be. Another character is the temperature difference between the bottom and top portions of a thunderstorm. A greater temperature difference will tend to produce more lightning. Strong storm speed and directional wind shear will help increase storm intensity and this helps increase lightning generation. A freak lightning storm can have cloud to ground lightning vivid enough to occur every few seconds. Cloud to cloud lightning can be so numerous that the cloud continuously stays lit and partially lit. In some cases the sky can appear to glow green as the continuous lightning lights up precipitation in the storm. These storms produce ferociously intense lightning strikes, the power typically goes out temporarily and damage is done from the numerous strikes. Lightning is a major cause of deaths in thunderstorms. This is another reason for why lightning storms are so dangerous. The worst place to be during lightning is outside. 7. LOCAL FREAKISH WX SERIES: 2+ INCHES SLEET STORM Sleet (a.k.a. ice pellets) occurs when snowflakes partially freeze as they fall through an above freezing layer of air and then freeze back into a solid spherical shaped ball of ice before reaching the ground surface. They have the appearance of a frozen raindrop. They are denser than snowflakes and fall with a speed more similar to that of raindrops. They have a unique light pinging sound as they bounce off objects they hit on the surface. They can accumulate on the ground making travel hazardous. A significant accumulate will appear fairly white on the ground. Unlike snow, it is very difficult to create snowballs with sleet. Unlike sleet, they do not accumulate as well on power lines and in trees and this is one aspect that can make it less of a nuisance than a freezing rain event. To be freakish, generally the sleet needs to fall at a heavy persistent rate and be accompanied by thunder. Heavy thundersleet is a freakish weather event to witness. The large sleet balls accumulate quickly and cause many traffic problems. In a more phenomenal event, hail or graupel will fall with the sleet during a thunderstorm creating the ultimate of ice craziness. A persistent sleet storm can dump several inches of thick ice. 8. LOCAL FREAKISH WX SERIES: WHAT THE HECK? Sometimes freakish weather is an event that does not happen or an event that happens when nothing was expected. There can be an expectation for wild weather to occur and it can look like most indications are for a wild weather event but then nothing happens. There can be no threat and then a big weather event ends up happening. Below are some examples (along with a sarcastic statement) and then possible reasons the event did or did not materialize: 1. A forecast for no snow and 6 inches occurs. (I’m shoveling 6 inches of partly cloudy!) Some explanations: Big snow just missed forecast area in another direction; specific forecast was made too far in advance of event; storm system stalled over forecast area 2. A forecast for a high chance of thunderstorms and nothing occurs. (We canceled our outdoor plans for nothing!) Some explanations: Cap was too strong, Cold and/or dry air worked into the area too quickly, Event just missed forecast area in another direction 3. Freezing rain warning and no freezing rain occurs. (We panicked for just a cold rain!) Some explanations: Temperature stayed just above freezing, ground temperature was too warm, cold air at surface was modified by a layer of above freezing air aloft 4. Forecast for sunny conditions and cloudy conditions occur. (The skies sure don’t look blue!) Some explanations: Ground fog did not mix out during the day, layer of cirrus occurred, lifting was stronger than anticipated, specific forecast was made too far in advance 9. LOCAL FREAKISH WX SERIES: ZERO VISIBILITY FOG Fog is a cloud that is on the ground. Just like a cloud, it is composed on tiny numerous water droplets. Fog varies in visibility from only reducing the visibility slightly to producing low visibility even a few feet away. Fog is often thicker in warm air since more moisture can be evaporated into warm air. The moisture sources for fog are moisture evaporating off the ground, moisture evaporating in the air from rain and then recondensing on small cloud droplets, and moisture being transported in from a moisture source such as a warm ocean. Dynamic uplift, saturated soils, persistent rain, being night, and plenty of condensation nuclei from smoke and emissions are other factors that can contribute to a thicker fog. This writing looks at freakishly low visibility fog. Extremely low visibility fog is very dangerous when traveling. It can be so dense that the tail lights of a car are faint even when a few feet away. Major pileup accidents occur as a car slows down and then gets rear ended by a car behind. A chain reaction of dozens of cars can crash and pile up. It is important to be extremely cautious when driving through dense fog. Often the densest fog occurs near a river valley, near a lake/ocean, in a highly vegetation area, or in a lower elevation region that is surrounded by higher elevations. Roadways can experience denser fog when driving near these locations. It can be so foggy that only faint lights can be seen in the distance. These conditions can bring roadways and airports to a standstill. It is best to not travel during freakishly low visibility fog. 10. LOCAL FREAKISH WX SERIES: HEAVY FREEZING RAIN Freezing rain can be the most dangerous of winter weather events, especially when all objects on the ground are below freezing. One factor that makes it so dangerous is the accumulation of ice on objects such as trees, power lines and antennas. This can cause significant damage to trees, power lines being brought down, electricity going out for an extended amount of time and crippling impacts on transportation. The heavier the precipitation, then the more significant and destructive the event can be. Many freezing drizzle/rain events consist of drizzle and light freezing rain. In some situations though, heavy freezing rain can occur. This results in a freakish ice storm. The heaviest of freezing rain will result from a strong convective thunderstorm. The troposphere aloft can be warmer and moist due to the transport of warm air and moisture. This layer of air can flow over a subfreezing layer of air that is hugging the ground surface. These events can be accompanied by thunder and lightning. The heavy freezing rain produces crippling impacts that occur very quickly. Whole branches on trees crack to the ground, power lines are brought down and roads are coated in ice. Travel becomes very difficult if not impossible due to vehicles being unable to drive on the ice. The power can go out for days as trees crash down on power lines. Severe damage occurs to vegetation and property. The witnessing of a freezing rain thunderstorm with heavy rain is freakish indeed. |