 On September 28th, 2019 the college town of Davis, California was taken by surprise when a tornado warning was issued by the Sacramento National Weather Service. Situated just outside of Sacramento, the area is not one typically known for tornadoes, especially not in the fall month of September. The California valley only averages about 10 tornadoes a year, the majority of those occurring during the spring, and more so towards the northern apex of the valley in Butte, Calaveras, and Amador counties thanks to the Buttes and Coastal Mountain range there that help drive orographic lift. Although tornadoes in California are not unheard of, they are certainly few, and even fewer in the fall! So what exactly occurred with this wild weather?
Around 4:30pm, 10 miles north of Davis, California in the city of Woodland, California a large storm cell began to take form and inundated the city with precipitation. The storm rapidly developed into a severe thunderstorm and left streets flooded with rain and hail. Cloud to ground lightning was reported as the storm continued to grow and swell throughout the late afternoon. At approximately 5:30pm, the cell had drifted southwest towards the town of Davis, home of the University of California, Davis, passing over highway 113 as it lumbered on. A large hail shaft was evident in the storm, dropping one half to one inch sized hail as it crossed the highway bridge between the two cities, bringing traffic to a near stop as hail pummeled the thoroughfare. Banks of hail formed, taking on the appearance of snow drifts as the hail and graupel continued to fall. From this inundation, cars would later be found to be spun-out, having lost control on the icy roads. Come 6pm, the storm had strengthened immensely, and reached just short of Davis. A large anvil was evident, stretching and creeping along the skyline. Thunder and lightning activity intensified with increased cloud-to-cloud strikes occurring and precipitation continued to dominate the center of the storm. Nearby temperatures dropped with the Sacramento International Airport reporting a record-breaking low of 45 degrees Fahrenheit. At 6:37pm, the storm had gone tornado warned as radar-indicated rotation. Multiple gustnadoes were reported from 6:15 until approximately 6:40pm, all precursors to the tornado that touched down at 6:41pm. The touchdown occurred in North Davis along county road 29 in agricultural fields where the twister tossed tumbleweeds and brush into the air, but did no serious harm. With wind speeds up to 74 miles per hour, the tornado was assessed to be an EF-0 and dissipated at about 6:55pm. The twister, although short-lived and weak, was none-the-less an exciting introduction to Davis for many of the incoming and returning students to the university who had just begun their first week of the fall quarter. Although not quite a rarity, a California tornado is certainly a surprise to all when they come about. The September 29th tornado took many by surprise that day, but is forever etched into the memories of those who witnessed and experienced the exciting atmosphere that day. To read more about historical weather events, click here! https://www.globalweatherclimatecenter.com/weather-history-topics © 2019 Weather Forecaster Alexis Clouser
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Thirty years ago on September 22, 1989, Hurricane Hugo made landfall in the United State on Sullivans Island, SC as a category 4 hurricane causing impacts through both North Carolina and South Carolina. Although this storm was a major hurricane on the Saffir-Simpson scale, the amount of rainfall it brought to these areas was significantly less compared to more recent storms that also impacted these areas such as Hurricane Florence in 2018, which made landfall in North Carolina as a category 1. What could have caused this categorically “weaker” storm to have a more significant rainfall-related flooding impact than a major hurricane? On September 10, 1989, a tropical depression that was soon to become Hugo developed southeast of the Cape Verde Islands. By the next day, this storm had become Tropical Storm Hugo before rapidly intensifying and reaching hurricane strength by September 13. Hugo made its first landfall between Guadeloupe and Montserrat as a category 5 hurricane before making another landfall in St. Croix less than a day later. Hugo then made subsequent landfalls that same day in Puerto Rico. On September 22, Hugo made landfall once again at Sullivan’s Island, South Carolina as a category 4 hurricane with sustained maximum winds of 140mph and a minimum central pressure of 934millibars. The storm weakened rapidly as it moved inland, however, it was still a category 1 by the time it impacted Charlotte, North Carolina the same day as its South Carolina landfall. By September 23, Hugo had weakened to a remnant low and had then dissipated south of Greenland by September 25, 1989. On August 31, 2018, Tropical Depression Six formed south of Santiago in Cape Verde traveling on a west-northwest trajectory. By September 1st, this storm officially became a named storm as Tropical Storm Florence before undergoing an unexpected rapid intensification September 4th and 5th. At this point, Florence was a category 4 with estimated maximum sustained winds of 130mph and a central pressure of 950millibars. By September 12th, Florence had rapidly weakened due to increasing wind shear, strengthened once again to a category 4, reaching its peak strength of 150mph maximum sustained winds and a central pressure of 937millibars, before dropping back below major hurricane status. On September 14, 2018, Florence made landfall south of Wilmington, North Carolina as a category 1 hurricane with maximum sustained wind speeds of 90 mph and a central pressure of 956millibars. Florence slowly made its way inland, weakening to a tropical depression by September 16th and later dissipating over Massachusetts by September 18th.
Although both of these storms impacted many areas, including areas outside of the United States, the rainfall-related impacts focused on in this article will be on North Carolina and South Carolina since these were areas greatly impacted by both Florence and Hugo. Hurricane Hugo brought anywhere from 1-10 inches of rain to North Carolina and South Carolina with a maximum rainfall measurement of 10.28 inches in Edisto Island, South Carolina, southwest of Sullivan’s Island where Hugo had made landfall. The majority of heavy rainfall was relatively localized in the southeastern coastal region of South Carolina with many of these areas seeing between 3-7 inches of rain. While Hugo was a major hurricane and was incredibly destructive, it produced significantly less rainfall than the categorically weaker Hurricane Florence. The maximum measured rainfall was 35.93 inches in Elizabethtown, North Carolina. Surrounding areas in central North Carolina to southeastern coastal areas of North Carolina and northeastern coastal areas of South Carolina saw between 10-35 inches of rain during Florence’s time in these areas. Although Florence was a “weak” category 1 hurricane in terms of wind speed and minimum central pressure, the flooding impacts brought on by this intense rainfall were particularly significant. So, how could a category 1 hurricane produce significantly more rainfall in an area and have similarly destructive impacts as a major category 4 storm? The primary key was the speed at which the storms were moving. Hurricane Hugo quickly made its way from its landfall in South Carolina through inland North Carolina within a day while Florence moved at a much slower pace. This slow speed allowed for Florence to continue to produce large amounts of rain in the same areas, leading to significant flooding.
To learn more about other past historic weather and science events from around the world, be sure to click here! ©2019 Meteorologist Stephanie Edwards  Photo: Lauren Long https://www.syracuse.com/news/2014/07/deadly_tornado_smithfield_new_york_weather_madison_county.html July 8th, 2014 was a typical summer day for Central New York State; hot, humid, with a slight risk of thunderstorms in the air as a cold front was expected to cross over the region. But that typical summer day quickly turned into an event that would change the perception of severe weather events for many people and local meteorologists for years to come. A series of severe storms were expected to occur across the Northeast that afternoon with threats for widespread damaging winds, a couple of tornadoes, and isolated cases of large hail possible. A public severe weather outlook had mentioned that severe thunderstorms were expected over parts of the north-central Appalachians that afternoon, and a slight risk issued by the NOAA SPC in previous outlooks was later upgraded to a moderate risk that included much of central and western NY, as well as the Southern Tier. Below is one of the SPC mesoscale discussions issued for that day:  All the ingredients for severe weather and tornado development were present, and several meteorologists were aware of but caught off guard by the turn of events that would later unfold.  Credit: NOAA SPC Base reflectivity from 13Z 20140708 to 05Z 20140709 Nearly five years ago this July, as the line of storms made its way across the region, an EF-2 tornado with winds up to 135 mph touched down at around 7:02 PM EDT in Smithfield, Madison county NY. This tornado killed four residents of the community, destroyed several homes and property, and is known to this day as one of the deadliest tornadoes ever to occur in New York State. Several severe thunderstorm warnings were issued throughout the area. Madison county was included in the warning as the storms swept through. Neighboring counties had tornado warnings issued for storms showing signs of radar indicated rotation. This tornadic event however was unusual in the fact that it “spun-up” from the ground up and was not formed in the usual way out of a strong, rotating thunderstorm called a supercell. While several forecasters were already occupied on a separate tornado warned storm approaching Onondaga county, the storm over in Madison county that was merely severe thunderstorm warned dropped the unexpected and deadly tornado over Smithfield where it disappeared before anyone could be warned about it. This tornado was hard for meteorologists to see, because it had occurred along the Smithfield ridge sitting at 1400 feet high where the National Weather Service radar took approximately five minutes to make a complete scan of the area. With the radar beam at the Binghamton airport sitting at an angle of 0.5 degrees and scanning several thousands of feet into the air, this made anything occurring below the height of the ridge difficult to see if at all, and when the tornado finally showed up on radar it was already happening, and within minutes it was too late. This line of storms produced five tornadoes total in New York State all in one day; four in central NY and one in Warren county. Below is an image from the SVRGIS page from the NOAA SPC United States severe report database:  This graphic represents the tornado paths recorded from 1950 to 2017 in the U.S. What many people often forget is that the typical areas that get the most frequent cases of tornadic events are not the ONLY places that get can and do get tornadoes that can cause loss of property and life. When tornadoes happen in the Northeast their lifespan is often shorter, and blocked by trees and other topographic barriers making it more difficult to seek shelter from. However, it’s important to recognize this event not only as an anomaly but as a tragic event that should remind everyone to take every warning and watch seriously no matter where they are and what they’re doing. More awareness needs to be made that tornadoes can and DO happen outside of typical areas like tornado alley in the great plains. A quote by New York State governor Andrew Cuomo strikes the feeling of this reality all too well as he once stated, “We don’t get tornadoes in New York, right? Anyone will tell you that. Well, we do now.” Forecasting for rare events like these remains a difficult issue for meteorologists to this day, and goes to show how the strength and speed of nature’s greatest forces can overwhelm our best efforts of prediction even in places outside of Tornado Alley. To learn more about other past, historical weather events, click here! @2019 Weather Forecaster Christine Gregory Sources: https://www.syracuse.com/news/2014/07/deadly_tornado_smithfield_new_york_weather_madison_county.html https://weather.com/storms/tornado/news/deadliest-tornado-new-york-history-20140709 https://www.weather.gov/bgm/pastSevereJuly82014 https://www.spc.noaa.gov/gis/svrgis/ https://www.spc.noaa.gov/exper/archive/event.php?date=20140708 https://www.daculaweather.com/4_spc_meso_archive.php On this past 4th of July, the temperature in Alaska’s largest city, Anchorage, soared higher than at any other point on record as record-crushing heat sprawled across the “Last Frontier” state. The observed high temperature at the Ted Stevens Anchorage International Airport climbed to a mind-boggling 90 degrees crushing its previous all-time record high of 85 degrees set 50 years prior on June 14th, 1969. This high temperature also crushed the daily record high for Anchorage on July 4th which was 77 degrees set back in 1999. And just to put this into perspective, the average high in Anchorage on July 4th is 65 degrees. Anchorage was so warm, that it tied a few other places across the United States that also topped out at 90 degrees on the 4th. This includes West Palm Beach, FL, Memphis, TN, and Rockford, IL. The source of this record-setting heat is due to the placement of the jet stream. Typically, the jet stream is located south of the state which keeps all the “scorching heat” away from Alaska. That wasn’t the case on this Independence Day. A rise in the jet stream has allowed an expansive dome of high pressure to form over Alaska. Underneath this high pressure system, sinking air has suppressed rain chances which has led to plenty of sunshine and record heat.  Anchorage wasn’t the only one posting record heat on America's birthday. Below is a graphic created by the National Weather Service in Anchorage, AK showing other places around southern Alaska that broke all-time records on Thursday: King Salmon: Observed high: 89°. Previous record: 88° (June 27th, 1953). Kenai: Observed high: 89°. Previous record: 87° (June 26th, 1953). Gulkana: Observed high: 88°. Previous record: 86° (1956).  This dome of high pressure and heat wave is forecast to peak this weekend and last through the middle of the month. The Climate Prediction Center’s outlook (below) calls for the abnormal warm trend to stretch through the next 6-10 days. High temperatures for Anchorage are set to top out in 80s for the next several days before the it is set to subside late next week.  To learn more about other past historic weather and science events from around the world, be sure to click here!
©2019 Meteorologist Joey Marino On May 20th, 2019, NOAA's Storm Prediction Center (SPC) released their severe weather outlook. This outlook called for a high risk of a severe weather outbreak. The last time that the SPC went high-risk was on May 18th, 2017. The SPC only chooses to forecast for a high-risk day when they are confident in the chances of numerous long tracked tornadoes or a long-lived thunderstorm system such as a derecho. The high-risk forecast occurs when they see the four main ingredients, shear, lift, instability, and moisture in excess and if they could cause these storms to last.  Looking back on forecasts for May 20th, they showed a low-pressure system that would be position in the upper part of the Great Plains. This low-pressure system had a central pressure less than 1000 millibars. Systems with pressure less than 1000 millibars can help to initiate storm development. Often with a low-pressure system, fronts start to form, where they are connected to the low-pressure system. Fronts can also provide a way for the storms start, after all, they are a boundary where two different types of air masses meet. Looking at another ingredient for severe weather on this day, moisture, the lower portion of the Great Plains has a special type of boundary called a dryline. The dryline is a boundary that divides the warm, moist air from the warm, dry air. As a result, the dew points on either side can not only provide a measure of the moisture in the air, but the dryline can also provide another lifting mechanism for parcels of air to rise. The dew point values in the area highlighted by the Storm Prediction Center were into the upper 60’s to lower 70’s, showing that there was plenty of moisture for convection to occur. These high dew points also added more instability into the atmosphere as well. So in order for severe weather to happen, one more ingredient was needed: shear.  Analyzing the soundings from the NWS offices located in this area, the winds were moving from a slight southeast direction the surface to turning more towards the southwest as the weather balloon moved higher up into the atmosphere. Not only that, the speed of the wind increased as the parcel of air rose.
So all four ingredients were present, now why was May 20th not as devastating when looking at the tornadic potential? These storms, produced baseball-sized hail, numerous flooding incidents, and a couple of tornadoes, kept merging together. As a supercell started to show signs of becoming tornadic, it would merge with another cell. After this pattern occurs, instead of discrete supercells, there would be a quasi-linear convective system. These systems can produce rapid spin-up tornadoes and hail, but these types of severe weather are often limited due to the fact that they are in a line and connected to one another. The linear nature of the storms on May 20th caused heavy downpours, leading to multiple flash flood warnings throughout the high-risk area. While any type of severe weather is damaging, the high-risk area did not see long-lasting tornadoes, instead, the high-risk area got hail and rain, leading to a major flooding event. These areas did experience high wind gusts along with a few brief spin-up tornadoes. These areas did not have to experience the results of a long track tornado as the SPC predicted. To Look Back on More Historical Weather Events, Make Sure to Check Out https://www.globalweatherclimatecenter.com/weather-history-topics ! Sources: NOAA SPC, https://blog.nssl.noaa.gov/ewp/2019/05/21/nucaps-data-from-yesterdays-may-20th-event/ ©2019 Weather Forecaster Shannon Sullivan How 2 Tornadoes Helped Initiate Severe Weather Forecasting in the U.S. (Credit: The Weather Channel)5/25/2019  DISCUSSION: In the early 20th century, official tornado warnings were not allowed in the U.S. because the Weather Bureau (precursor to today’s National Weather Service) didn’t want to cause panic based on low-confidence forecasts (given our limited understanding of tornadoes). However, two tornadoes struck Tinker Air Force Base (AFB) in Oklahoma in March 1948 while two prominent Air Force meteorologists (Major Ernest Fawbush and Captain Robert Miller; pictured above) were stationed there that would begin to change that.
Initially, there was no mention of thunderstorms in the forecast for the evening of 20 March 1948. Later that evening, reports came in of a tornado that had damaged an airport to the southwest of Tinker AFB and was moving to the northeast toward Tinker. Unfortunately, those reports came in too late to warn and prepare the AFB. The result was $10 million in damages including the destruction of 52 aircraft. After this event, a study was put together to determine if better severe storm forecasts could be issued to prevent such damage in the future. Fawbush and Miller identified several large-scale conditions that tended to precede the formation of tornadoes and observed these conditions form again five days later on 25 March. The two base meteorologists decided to issue a forecast similar to today’s tornado watch. This forecast was a success when a second tornado in five days struck Tinker. This tornado still caused $6 million in damage, but there were no injuries likely due to the base preparations that were enacted after the forecast was issued. According to information from Tinker AFB, 89% of the tornado forecasts issued by Fawbush and Miller verified, which is pretty incredible given the rudimentary observing system and infancy of severe weather science at that time relative to today’s tools and understanding. This success led to the development of the Severe Weather Unit of the Weather Bureau in 1952 which is the precursor to today’s Storm Prediction Center. Essentially, two tornadoes that occurred in 1948 prompted two Air Force meteorologists to study the conditions under which tornadoes form and issue the first official tornado forecast. This successful forecast and subsequent successful ones helped spawn the severe weather forecasting enterprise that currently exists in the U.S. and which has undoubtedly helped save countless lives. To learn more about other past historic weather and science events from around the world, be sure to click here! ©2019 Meteorologist Dr. Ken Leppert II July 4 Snowfall in Minnesota: Fact or Fiction? (Credit: National Weather Service Archives)4/30/2019 Winter in the United States is an interesting topic. In the South, winter lasts for maybe a month, and then it’s gone; however, in the Northwest, Midwest, and Northeast, that is a completely different story. Most people associate winter beginning in November and ending around mid-April. Now depending upon how the trough and ridge are set up for the season will depend on how long winter lasts. Before going further, troughs and ridges are a part of the jet stream over North America. When there is a valley in the flow, that is a trough. Troughs are normally associated with a low-pressure while ridges (the hills in the wave) are associated with high-pressure. During the summer, the jet stream becomes zonal over the mid-latitudes and during the fall and into the spring, the jet stream develops wave-like patterns. With that being said, typically by May the flow becomes zonal as spring is coming to an end. This is why snow is unlikely past this point because there aren’t any troughs to bring that arctic air further south to cause air masses to clash which inevitably leads to snowstorm development. So, while it isn’t necessarily common, it isn’t a rarity to have a few outlier snowfalls that can continue into May for some. When delving deeper into this topic, the question came to mind, “How late in the year has there been a recorded snowfall?” After spending some time on researching this, there was an article about many people reporting snowfall on July 4 in 2008, but the article was vague if it occurred or not. Thankfully, XMACIS (NCDC) is a very useful tool when trying to find out any kind of climatological data. From what was found, there was evidence that there was 16” of snowfall recorded at a COOP station in Pelican Rapids, MN on this day. It still sounded very odd to not have come across actual news reports of this day, as this would be quite a headliner to receive 16” of snow in early July in the United States, even if it is bordering Canada. When checking out previous surface maps from this day from the National Weather Service Archives and SPC Outlooks, there was nothing to back this statement up. Looking at the event, the low-pressure system/cold front was too far south to have an impact in Minnesota this day. Going back a few days to when the cold front was passing through the area, on July 2, the surface maps still failed to support that the air mass behind the cold front was cold enough to cause wintry precipitation on this day (let alone on Independence Day). The images above support this thesis by showing temperatures throughout the country, including behind the front.   Minimum temperatures on July 2nd, 2008 prove to be entirely too warm to support snowfall in the coming days. The average maximum temperature was in the 80s, while the minimum temperature was in the 60s, and behind the front was 50s. Even if there was a significant polar vortex moving through that area on the 4th, the soil/ground temperatures would be entirely too high to support any accumulation.
Unfortunately, it appears that the rumor of Minnesota receiving 16” of snowfall on July 4 has been squashed. The latest recorded snowfall event was May 2, 2013 where the northern parts of the state received between 1-2”. Although, that doesn’t rule out that this could happen within the next few years as the troughs over the last couple winters have been pushing further south than normal. To learn more about other interesting tropical cyclone topics and events from around the world, click www.globalweatherclimatecenter.com/weather-history-topics. ©2019 Weather Forecaster Ashley Lennard  DISCUSSION: Late January and early February of this year brought an outbreak of frigid arctic air to a large portion of the U.S. with temperatures in the north-central portion of the U.S. the coldest that they have been in over 20 years. Specifically, the coldest temperature measured this year occurred at Cotton, Minnesota of -56F on 27 and again on the 31 January. Including these temperatures this year, temperatures between -55 and -59F have been officially recorded 34 times in our ~150-year observation record over the continental U. S. (there are additional unofficial and/or unverified temperatures that have been measured below -55F). Given that we are past the climatologically coldest part of the year, this current outbreak of unseasonably cold air across the U. S. probably won't set any new record cold temperatures for the year.
For someone who lives in Louisiana, -56F is unimaginably cold. But, even colder temperatures have been recorded in the lower 48 states of the U. S. The map above shows the locations of the 15 official temperatures that have been measured at or below -60F. For the dates when these all occurred, please click here. Of particular note is the coldest temperature ever recorded in the continental U. S. of -69.7F on 20 January 1954 at Rogers Pass, Montana. This was so cold that the indicator of minimum temperature along with the fluid in the thermometer actually retreated into the bulb of the thermometer. The station that recorded this value existed in that location for only a short time from 1 May 1953 to 28 June 1956. It was installed next to a new mine which turned out to not be very productive. So, the mine and observation station were shuttered after only a short time. In order to achieve such an extreme temperature, conditions have to be just right. Otherwise, such a temperature would occur more often. Indeed, the weather conditions at Rogers Pass the night/morning of 20 January 1954 were ideal for generating extreme cold. In particular, there was fresh snow on the ground, a dry, cold air mass in place, no clouds, and no wind, all conditions very conducive to radiational cooling. In addition, the station was located in a depression allowing the coldest air to sink toward the station. Despite these conditions, and as is typically the case for record observations, this particular observation underwent a robust verification process by the Weather Bureau (precursor to today's National Weather Service). For example, the instrument was tested to make sure it was working correctly and the measurement was checked for consistency with other nearby stations. The above is a small glimpse into the coldest temperatures recorded in the continental U. S. and a little bit of the story surrounding the record coldest temperature. I suppose one take away from this is that no matter how cold it gets wherever you are in the lower 48 states of the U. S., it could always be worse (i.e., colder). To learn more about other past historic weather and science events from around the world, be sure to click here! ©2019 Meteorologist Dr. Ken Leppert II  Discussion: As the Midwestern United States begins to warm up, 30 years ago much of Alaska was following suit in what was a brutal end to the month of January. During the latter half of January 1989, temperatures across the interior portions of the state were reported as low as the negative mid-70s degrees Fahrenheit, which is shy of the record low of negative 80 degrees Fahrenheit in the state, but nonetheless an impressive and dangerous feat. Wind chills were even worse as an example below will illustrate. During this cold air outbreak, the highest pressure ever documented in North America (at the time) was recorded on January 31, 1989 in eastern Alaska at Northway. The pressure read 1078 mb (a reanalysis image shows the high pressure in red situated over Alaska). To put this in perspective, Siberia, where the highest pressures on Earth are typically recorded has maxed out in the mid 1080 mb range.  The above image was taken from Iowa State’s ASOS archive site. This is an observation from Cantwell, Alaska on January 28th, 1989. Notice the strong north/northeasterly winds with the temperature -43 degrees Fahrenheit making for treacherous wind chills.  What was the setup for this cold outbreak? High pressure leaked into Alaska from Siberia and the Beaufort Sea, locking cold air in place for about two weeks. This, along with a strong surface low pressure system (cool colors) to the south and a bit east of Alaska during the 28th created a difference in pressure which lead to a strong and persistent northerly to northeasterly wind (surface pattern and setup featured above). The observation above from PATW outlines what this particular day (the 28th) was like in central Alaska. To put this in perspective, a temperature of -43 degrees Fahrenheit and winds gusting up to 40 knots correlates to a treacherous wind chill of around -91 degrees Fahrenheit based on the National Weather Service Wind Chill Temperature calculator.  The last image shows the averaged 500 mb height anomalies across the region from the two-week period between January 17th to January 31st of 1989. A huge negative anomaly, signifying the polar vortex, has parked itself right over Alaska and areas to the north keeping the brutal and long-lasting cold air across much of the state. This was an impressive cold stretch, even for Alaska’s standards.
Be sure to stay tuned to GWCC for more interesting historical weather here! ©2018 Meteorologist Joe DeLizio Sources: https://www.adn.com/features/article/recalling-frigid-1989-alaska-winter/2011/11/21/  On January 31, 1958, the United States successfully launched the Explorer I satellite. As the country’s first successful satellite, Explorer I effectively marked the beginning of the U.S. Space Age. Additionally, the launch of Explorer I came as a direct response to the Soviet Union’s launching of Sputnik 1 & 2, launching the U.S into what was known as the Space Race. Following the success of Explorer I, the U.S. began developing and launching additional satellites, eventually paving the way for the satellites used in meteorology today.
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