October 2017

Meeting Notes for October 2, 2017

17 in attendance (including one guest, Derek’s grandmother!)

Financials:

Sept. 1 $2248.31 opening balance

A check was presented for BYA T-shirt payment for $32.00 but it was a pass-through in the books

One renewal of $30.00

Ending balance $2278.31

Dues are due next month. Students are 10.00 and a family of 2 is 30.00. A family of 3 or more is 30.00.

Board officer elections are also next month.

Karen Cruce is the Club contact for the Astronomical League. She would like it very much if someone would be able to take this over in November. Responsibilities of this position include sending an updated membership list at the end of each quarter. You don’t get a reminder from them to do this—you just do it. Once in a while, she will also receive an email of general interest which she forwards to the membership. Dues are also due once a year.

Steve’s report on Girl Scout star party at Wah-Sha-She Sept. 29:

Had 6 scopes, 8 people from the club. Had to start leaving 9:30-10 due to cloud cover. Did see the moon though and good views of Saturn.

Rick’s report on the BYA participation at the Pawhuska rocket launch and star party at the Pawhuska airport:

The BYA had 3 rockets, 6 launches, all successful. They took a video. There may be one potential new member from this event. They also participated in the star party organized by the Tulsa Astronomy Club—although they only had about an hour of viewing due to clouds (thicker than at the star party Friday night). There may be two potential new members from this event.

Star party at Tri-County Oct. 27 for Cornerstone Classical Academy:

There will be 30 students and at least one adult per student. 60-90 people total? Start 7:30. Darryl will bring 2 scopes. Students will be K-5^th grade. Half of the students in this academy are home-schooled.

Copan school event—no updates this month. Daryl working on this.

Darryl said that on October 15 Moon will occult Regulus in Leo around 3 am

Denise has contacts with Young Professionals of Bartlesville that she will approach about doing a star party for them.

Rick and Denise have received info from Warren Neff about wanting to do a presentation for STEM for math classes. Rick has talked to him about doing more general presentations first. Daryl and Denise will work on this with Warren.

Abby’s astronomy news highlights:

Australia is starting a space agency

The giant telescope in Puerto Rico sustained some damage to a line feed antenna with hurricane Maria.

Last image from Cassini of Saturn before it crashed itself into the planet Sept. 15. Abby pointed out that this was a very poignant event for her and Derek as Cassini had been active for their entire lives since birth!

Images of—

Storm systems on Neptune

Saturn nebula in Aquarius

Various galaxies

Main presentation by Denise Gregg on Clouds:

Why talk about clouds? If you were a Martian, our planet Earth would be another world!

How do you classify clouds? Clouds may be may be classified by form and by height. Luke Howard (1772 - 1864), a British pharmacist was the first to describe cloud forms using Latin terms such as cirrus, cumulus or stratus. The division of clouds into ten basic cloud forms, or cloud genera is based on his publications.

Clouds form in three basic patterns—

Cirrus, from cirro, meaning curly or fibrous.

Stratus, from strato, suggesting sheets or layers.

Cumulus, from cumulo, indicating heaped or piled.

And in three basic altitude ranges--

The highest clouds in the atmosphere are cirrocumulus, cirrus, and cirrostratus.

Mid-level clouds include altocumulus and altostratus.

The lowest clouds in the atmosphere are stratus, cumulus, and stratocumulus.

There are ten major cloud types—cirrus, stratus, cumulus, nimbus, cirrostratus, cirrocumulus, altostratus, altocumulus, stratocumulus, nimbostratus, cumulonimbus (Actually this list has 11!)

Cirrus is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word cirrus, meaning a ringlet or curling lock of hair. Cirrus clouds are the most common type of high clouds and are composed of ice crystals that originate from the freezing of super-cooled water droplets. They are typically found at heights greater than 20,000 ft. They are blown by high winds into long streamers and are usually white. The dryness of the air higher in the atmosphere contributes to their wispy look. What can you learn from them? They generally predict fair to pleasant weather. By watching the movement of cirrus clouds you can tell from which direction weather is approaching.

Cirrus uncinus--Mare’s tails--can indicate the approach of precipitation. These clouds are generally sparse in the sky (but not here!) and are very thin.

Cirrus fibratus is a type of cirrus cloud. The name cirrus fibratus is derived from Latin, meaning "fibrous". They appear as fibers or threads. The way to distinguish cirrus fibratus from other subtypes of cirrus clouds is to look at the ends of the strands. In fibratus, the filaments do not descend from fluffy tufts of cloud as in cirrus floccus, nor do they curve down from thicker heads to give the hooked, comma-like appearance of cirrus uncinus (mare’s tails). Fibratus are simply thin, delicate strands of high cloud. They do not indicate precipitation. Their purpose is to look spectacular and amaze people. The images shown tonight were not doctored, stacked, layered, had their mid-tones stretched, or altered in any other way. And they were taken with an iPhone.

Cirrus castellanus is a species of cirrus cloud. Its name comes from the word castellanus, which means “of a fort, of a castle” in Latin. Like all cirrus, this species occurs at high altitudes. It appears as a series of dense lumps, or "towers" of cirrus, connected by a thinner base. These clouds do not indicate precipitation.

Cirrus floccus is a type of cirrus cloud whose name is derived from Latin, meaning a lock of wool. Cirrus floccus occurs as small tufts of cloud, usually with a ragged base. Cirrus floccus can have virga falling from it. The individual tufts are usually isolated from each other.

Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. The word stratus comes from the Latin prefix strato-, meaning layer. Stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color from dark gray to nearly white. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over a region. Stratus clouds may produce a light drizzle or small amount of snow. While light rain or snow may fall, this cloud does not indicate much meteorological activity.

Cumulus clouds--Cumulo- in Latin means “heap” or “pile”. Cumulus clouds are often described as puffy, cotton-like or fluffy in appearance, and have flat bases. Cumulus clouds, being low-level clouds, are generally less than 6600 feet in altitude unless they are the more vertical cumulus congestus form. Cumulus clouds may appear by themselves, in lines, or in clusters. Cumulus clouds are often precursors of other types of cloud, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. Normally cumulus clouds produce little or no precipitation but they can grow into the precipitation-bearing congestus or cumulonimbus clouds. Cumulus clouds can be formed by water vapor, super-cooled water droplets, or ice crystals, depending on the ambient temperature. They generally cool the earth by reflecting incoming solar radiation. Cumulus clouds are part of the larger category of free-convective cumuliform clouds, which include cumulonimbus.

Cumulus humilis is a cumuliform cloud with little vertical extent that is commonly referred to as fair-weather cumulus. This cloud type is common in the summer. While they generally indicate fair weather, if they do develop into cumulus mediocris or cumulus congestus, thunderstorms could develop later in the day. Denise calls cumulus humilis “happy clouds”.

Cumulus mediocris is a low to middle-level cloud, with some vertical extent, of the genus cumulus. It is larger in vertical development than cumulus humilis. Cumulus mediocris may also exhibit small protuberances from the top. These clouds may or may not show the cauliflower form characteristic of cumulus clouds. These clouds are common in advance of a cold front or in unstable atmospheric conditions, such as an area of low pressure. They can grow into larger clouds (cumulus congestus) which could bring rain, winds and, in worse cases, thunder and lightning. If these clouds are present in the morning or early afternoon they show a significant instability in the atmosphere, likely leading to storms later in the day if the cloud is thickening. If thinning, though, can lead to calm weather.

Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus cloud that can be based in low or middle height ranges. They achieve considerable vertical development in areas of deep, moist convection. They are an intermediate stage between cumulus mediocris and cumulonimbus. Because they are produced by strong updrafts, they are typically taller than they are wide. Cloud tops can reach 20,000 feet or higher in the tropics. Cumulus congestus clouds are capable of producing severe turbulence and showers of moderate to heavy intensity.

Cumulonimbus, from the Latin cumulus "heap" and nimbus "rainstorm, storm cloud" is a dense towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus clouds progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell.

A supercell is a thunderstorm characterized by the presence of a mesocyclone—a deep, persistently rotating updraft. These storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms—supercell, squall line, multi-cell and single-cell, supercells are the overall least common type and have the potential to be the most severe. Supercells are often isolated from other thunderstorms and can dominate the local weather up to 20 miles away. Supercells are often put into three classification types—classic, low-precipitation and high-precipitation. Low-precipitation supercells are usually found in climates that are more arid, such as the high plains of the U.S. High-precipitation supercells are most often found in moist climates. Supercells can occur anywhere in the world under the right pre-existing weather conditions, but they are most common in the Great Plains of the U.S. in an area known as Tornado Alley, and in the Tornado Corridor of Argentina, Uruguay and southern Brazil.

An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus. Arcus clouds typically form along the leading edge or “gust front” of thunderstorm outflow. Roll clouds may also arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts.

Nimbus clouds are clouds that already have rain or snow falling from them. The Latin word nimbus means precipitation. You often see the name of this cloud type combined with other cloud types, such as a cumulonimbus cloud with rain falling from it, or a nimbostratus cloud, which is a stratus cloud with rain falling from it.

Nimbostratus clouds are middle or multi-level stratus type clouds. Although usually a low-based cloud, nimbostratus actually forms most commonly in the middle level of the troposphere and then spreads vertically into the low and high levels. (The troposphere is the lowest region of the atmosphere, extending from the Earth’s surface to a height of about 3.7-6.2 miles. This is the region where vertical mixing of hot and cold currents takes place. Temperature in the troposphere usually decreases with increasing altitude.) Nimbostratus clouds usually produce precipitation over a wide area. Nimbostratus clouds often have very few visual features.

Cirrostratus clouds are high, thin, generally uniform stratiform type clouds. Cirrostratus clouds are composed of ice crystals. This cloud type is difficult to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no halos if it is thicker cirrostratus fibratus. On the approach of a frontal system, cirrostratus often begins as nebulosus and turns to fibratus. If cirrostratus begins as fragmented fibratus it often means that the front is weak. Cirrostratus is usually about 18,000 feet in altitude and its presence indicates a large amount of moisture in the upper atmosphere.

Cirrocumulus clouds are high patches or layers of cloudlets that appear tiny, on account of their distance from the ground. The best way to distinguish cirrocumulus from altocumulus is the size of the cloudlets, as well as the area of the sky covered by the layer as a whole. Since these clouds are at such a distance from the ground (often around 6 miles), the cloudlets of cirrocumulus appear so small that you often have to look carefully to notice the grainy texture. For the cloud to be cirrocumulus, these cloudlets must appear no larger than the width of a finger, held at arm’s length, when they are more than 30 degrees above the horizon. Composed almost entirely of ice crystals, cirrocumulus is a rare and fleeting cloud.

Altocumulus clouds, from the Latin altus for “high” and cumulus for “heaped”, are middle-altitude clouds that belong to the straticumuliform category characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. Altocumulus clouds signify convection. A sheet of partially conjoined altocumulus periucidus is sometimes found preceding a weakening warm front, where the altostratus is starting to fragment, resulting in patches of altocumulus periucidus between the areas of altostratus. Altostratus is also commonly found between the warm and cold fronts in a depression, although this is often hidden by lower clouds. Towering altocumulus, known as altocumulus castellanus, frequently signals the development of thunderstorms later in the day, as it shows instability and convection in the middle levels of the troposphere, the area where towering cumulus clouds can turn into cumulonimbus. Altocumulus is one of the three warning clouds often recorded by the aviation industry (the other two are towering cumulus and cumulonimbus). Altocumulus clouds generally form about 6,600-20,000 feet above the ground. Extensive altocumulus formations, particularly if they take the form undulates, are often referred to as altocumulus mackerel sky.

Altocumulus perlucidus are clouds which form at the middle level, between 6,000 and 16,000 feet.

Altostratus clouds are a middle altitude cloud type belonging to the stratiform category characterized by a generally uniform gray to bluish-green sheet or layer. Altostratus clouds are lighter in color than nimbostratus and darker than high cirrostratus. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus), as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened or upper-level warm front.

The most widespread of all cloud types, stratocumulus is a low layer patch of cloud that has a well-defined, clumpy base. The patches are either joined up or have gaps in between. High stratocumulus that have cloudlets with gaps in between—a variety known as perlucidus—can be confused with the mid-level cloud altocumulus. Stratocumulus is usually less orderly in appearance and its cloudlets are bigger, appearing larger than the width of three fingers, held at arm’s length, when they are more than 30 degrees above the horizon.

Mammatus are known as supplementary features that hang down from a layer of cloud in smooth or rough patches that often have the appearance of udders, which is what mamma means in Latin. They can be found on a wide range of cloud types but the most dramatic examples occur on the underside of the huge anvils known as incus that spread out at the top of mature cumulonimbus storm clouds and can cover all the visible sky. (The incus is the huge canopy of ice crystals that spread out at the top of a thunderstorm. Incus means “anvil” in Latin.) Some people claim that mammatus are harbingers of stormy weather, but they tend to form at the rear, rather than at the front, of storms. Once you see mammatus formations above you, the storm has usually passed you over or missed you entirely. (However, this is not always the case; Denise’s own experience has been that if you see mammatus, keep a close eye on the weather and be prepared to take cover.) Each lobe of mammatus is typically two miles across, and appears for around ten minutes.

Horseshoe vortex—The rare and fleeting horseshoe vortex cloud appears for just a minute or so before evaporating. This cloud forms in a region of rotating air, or vortex. While the familiar orientation for a vortex is vertical, it can occasionally develop on a horizontal axis. This is when the gently rotating crescent of the horseshoe vortex cloud can form. The movement of air seems to result from an updraft that is sent into a spin when it reaches a sudden change in the horizontal winds above. The air in the upper arc of the vortex cools enough to develop a rotating crescent of cloud. One of the best places to spot these is near supercell storms. The winds rushing in to feed the storm's growth can lead to just the right sort of shearing air currents. This cloud type may not lead to any precipitation, however. I call this kind of cloud a "croissant cloud".

Kelvin-Helmholtz Waves--Clouds that indicate a large change in wind speed over small increases in altitude (National Audubon Society Field Guide to Weather by Dr. David M. Ludlum and contributors) Kelvin-Helmholtz’ distinctive breaking-wave appearance is caused by wind shear. When cloud develops at an abrupt boundary between layers of colder air below and warmer air above, and the upper layer is moving more rapidly than the lower one, undulations can develop along its surface. If there is enough shearing, these can roll up into a succession of vortices. (The Cloud Collector’s Handbook by Gavin Pretor-Pinney) You can see them in all seasons of the year, at any time of day from morning to sunset Particularly when the air is dry, but they can occur even in rain/storm clouds! Look for clouds that look like rings of cigarette smoke all lined up, or that look like a row of breaking ocean whitecaps. Look for impulses Can be found in cirrus, altocirrus, stratocumulus or even cumulus clouds They can be discreet or attached to a larger cloud base.

Crepuscular rays appear when the path of sunlight is made visible by tiny atmospheric particles too scarce to appear as a cloud, but plentiful enough to scatter the light noticeably. In spite of being almost parallel, these rays seem to radiate out from behind the cloud. This is the same perspective effect as railway tracks seeming to widen as they get nearer. Anti-crepuscular rays appear to emanate from a point directly opposite the sun. These are shadows cast by clouds behind you. Perspective makes them converge in the distance.

Excerpts from a presentation by George Flickinger to Astronomy Club Feb. 11, 2012, about tornadoes:

Approaching tornado clues—If it is not appearing to move, it is coming toward you. Take cover. If it is a gray color, it is either approaching or moving away from you. Take cover. If it is a white color, it is moving away from you. (Although this could also mean it is just forming—take cover.) If it is a black it is moving toward you. TAKE COVER. The darker the gray, the more (urgently) you should take cover.

Hail--

Hail is formed by wind (updrafts) picking up raindrops and as they go up, they cool and freeze. Then they drop back down as more water is added to the raindrops and then they get thrown back up again and they freeze even more and get bigger. The cycle continues. The larger the hail is, the more likely a tornado is. Quarter size hail or smaller generally means a smaller tornado risk. Tennis-ball size hail: 50/50 chance of tornado forming. Softball-size hail: Updraft wind at that point is over 80 mph. When that wind twists, it forms a tornado and it could be huge.

Joplin tornado 2011: 4-inch hail. Moore tornado 1999: 4 ½-inch hail.

If you are in a car and spot a tornado--

If you can drive away, drive south and east. Most tornadoes go SW to NE or W to E. If you are driving and see a tornado, if you are clustered together with a bunch of cars (like in heavy rush-hour traffic) don’t get out of your car; stay clustered. Snuggle next to the other cars. It is harder for wind to get underneath a whole bunch of cars stuck together. Cars may be damaged but you are more likely to survive. Stay low in your car. You don’t want to be in a car with no other cars around. The wind could get underneath it. (But I have also heard not to get out of your car and walk under an underpass. Underpasses serve as wind tunnels.)

Beware of supercells merging. Tornadoes can develop quickly if cells merge. This happened in Joplin.

At home—

The garage door is most vulnerable. This is where damage will start. If you go to a bathroom, go to one farthest from your garage. Concrete-reinforced buildings are survivable. Also safe rooms.

Denise’s favorite weather forecast site—the National Weather Service weather forecast. It has a link to the Hazardous Weather Outlook, that tells it like it is. Links at the bottom of the page to the Forecast Discussion (was very nice in preparation for the total solar eclipse) and to the Decision Support Page where you can see the maximum amount/severity of any weather danger that could be anticipated. For example, maximum hail size. Forecast page for Bartlesville is http://forecast.weather.gov/MapClick.php?CityName=Bartlesville&state=OK&site=TSA&textField1=36.7378&textField2=-95.9482&e=0#.WdJIcWyWy70

Recommended books—

The Cloud Collector’s Handbook by Gavin Pretor-Pinney. You can give yourself points for “collecting” certain types of clouds! Highest- point-value cloud? Kelvin-Helmholtz! Great images.

National Audubon Society Field Guide to Weather by David M. Ludlum. A very comprehensive guide to weather, with great images.

Denise’s parting advice? Look up!