JPSS (SNPP and NOAA-20)

Popocatépetl, the Smoking Mountain

Posted on May 11, 2012 by Curtis Seaman

According to legend, Popocatépetl was a great warrior whose girlfriend, Iztaccíhuatl, died because her father was a jerk who lied. (An alternate story is that it was a rival warrior who was a jerk who lied.) Either way, Iztaccíhuatl was erroneously told that Popocatépetl died in battle, which caused her to die of grief. When Popoca, as he was known to his buddies, returned to find out that she was dead, he was very sad. Reports on what followed differ, but Popoca either died of grief himself, or committed suicide at the thought of living without Iztaccíhuatl. To commemorate these events, the gods turned them both into mountains. To this day, the mountain Popocatépetl spews out rock and ash and fire either because he’s still mad at what happened, or because it is his way of looking out for his girlfriend.

The name Iztaccíhuatl literally means “White Woman,” and is the name of the snow-covered mountain ~40 miles southeast of Mexico City. Popocatépetl literally means “Smoking Mountain,” and is the name given to the volcano just to the south of Iztaccíhuatl. It is one of Mexico’s most active volcanoes. Ole’ Popoca has recently begun to remind us that he is mad (or eternally vigilant).

The alert level was raised in mid-April after the volcano was heard rumbling and once again began spewing ash over the region. If you clicked on that link, you might have noticed this sentence:

“The joint NOAA-NASA Suomi NPP satellite snapped a picture of the ash cloud coming from Popocatépetl on April 16.”

Although they forgot to include the picture in the article, VIIRS on board Suomi NPP did see the ash cloud. Here’s an image of the I-01 reflectance (white = 1, black = 0) taken by VIIRS on 16 April 2012 at 20:25 UTC:

Image of Popocatépetl's ash plume from VIIRS channel I-01, 20:25 UTC 16 April 2012

Image of Popocatepetl's ash plume from VIIRS channel I-01, 20:25 UTC 16 April 2012

The ash plume is pushed to the east by the winds surrounding the cloud-covered volcano (where the arrow is pointing). On a clearer day, you can see Popocatépetl, Iztaccíhuatl, Matlacuéyatl, and the tallest volcano in Mexico, Pico de Orizaba:

False-color RGB composite (I-01, I-02 and I-03) from VIIRS taken at 19:53 UTC 23 May 2012

False-color RGB composite (I-01, I-02 and I-03) from VIIRS taken at 19:53 UTC 23 April 2012

The above image is a false-color RGB composite of VIIRS channels I-01, I-02 and I-03 taken at 19:53 on 23 April 2012. The volcanoes and nearby urban centers have been identified and labelled. Pico de Orizaba, Popocatépetl, and Iztaccíhuatl are the first, second and third tallest mountains in Mexico, respectively, and are normally the only mountains in Mexico to be snow-covered year-round. The snow on top of Pico de Orizaba and Iztaccíhuatl is clearly visible in the image. Popocatépetl lost its snow during the 1990s when it became more active. But, you can see the cloud of ash and steam from the volcano in the image, which is not being blown around in the wind as much on this day. In fact, you can watch a time-lapse video of the steam and ash cloud from a Mexican government webcam from around the time of the Suomi-NPP overpass where you can see the clouds produced/influenced by The Smoking Mountain.

On 20 April 2012, a photographer captured this amazing image of Popocatépetl’s eruption of lava at night. Being near a new moon (which occurred on 21 April), the Day/Night Band (DNB) was able to see this lava eruption:

VIIRS Day/Night Band image of the Popocatépetl eruption from 07:58 UTC 20 April 2012

VIIRS Day/Night Band image of the Popocatepetl eruption from 07:58 UTC 20 April 2012

VIIRS I-01 image of Popocatépetl taken at 19:53 UTC 23 April 2012

VIIRS I-01 image of Popocatepetl taken at 19:53 UTC 23 April 2012

In the above images, the red arrows are pointing to the same spot – the top of Popocatépetl. The upper image is from the DNB at 07:58 UTC on 20 April 2012, the lower image is from I-01 at 19:53 UTC on 23 April 2012 (the same time as the RGB composite). If you were to overlay the images on top of each other, you would see that the light source visible in the DNB image is right at the top of the volcano. Since there are no towns up there, and people surrounding the volcano have been evacuated, the light is coming from the erupting lava.

CIMSS provided these images of the volcano and ash plume at night (the same time as the DNB image above), which were visible in channels I-04 and I-05:

Image of Popocatépetl from VIIRS channel I-04, 07:58 UTC 20 April 2012 (courtesy William Straka, III / CIMSS)

Image of Popocatépetl from VIIRS channel I-05, 07:58 UTC 20 April 2012 (courtesy William Straka, III / CIMSS)

The upper image is the I-04 image. Channel I-04, at 3.74 µm, is very sensitive to hot spots such as wildfires or, in this case, volcanic eruptions. The dark (warm) spot identified is the heat signature of the molten rock that is erupting from the volcano. The cooler (brighter) ash cloud is visible in the I-04 image, but it shows up more clearly in the I-05 (11.45 µm) image underneath it.

Someone compiled a time-lapse series of images (14 April – 22 April) of Popocatépetl from a “NASA satellite” (presumably GOES-13) and posted the video to YouTube, which you can watch here.

Given its proximity to Mexico City, Popocatépetl is on the list of dangerous volcanoes to watch out for. The folks at WIRED are keeping their eye on it. Hopefully, Ole’ Popoca is just letting off a little steam, and not planning to get real violent. His girlfriend died a long time ago – it’s time to just let it go already.

Posted in Uncategorized | Tagged ash detection, day/night band, false color, GOES, I-1, I-4, I-5, mexico, RGB composite, VIIRS, volcano | Comments Off

Remote Islands, part I: Easter Island

Posted on April 26, 2012 by Curtis Seaman

With the I-bands having ~375 m resolution at nadir, VIIRS is a powerful instrument. We have already seen the detailed imagery it produces of severe thunderstorms and tropical cyclones. But, you might ask (particularly if you’re thinking you need a vacation), what remote islands is it able to see?

Well, it can see Easter Island. Yes, the one with all the big-headed statues (moai).

False color RGB composite (I1-I2-I3) image of Easter Island, 20:44 UTC 25 April 2012

At approximately 24.6 km x 12.3 km, VIIRS has no problem identifying the triangular island, as this false color (I1-I2-I3) RGB composite shows. In this image, taken at 20:44 UTC on 25 April 2012, the 163 km² island appears to be dwarfed by a thunderstorm just to its north. If you zoom in, you can see several small cumulus clouds over the island along with their shadows. Unfortunately, it is not quite the resolution needed to see the individual moai.

As Easter Island is in the southern hemisphere, it is autumn there now. The average high temperature is down to 76 °F (from a summertime peak of 79 °F in February). April and May are listed as the wettest months, so an image of Easter Island not obscured by clouds this time of year may be a rare occurrence.

Posted in Uncategorized | Tagged false color, remote island, resolution, RGB composite, thunderstorm, VIIRS | Comments Off

The Last Line of Storms from the 14 April 2012 Tornado Outbreak

Posted on April 18, 2012 by Curtis Seaman

The second major tornado outbreak of the year took place on 14 April 2012 (after the 2 March outbreak that slammed Indiana and Kentucky). At last count, 115 tornadoes were reported from Oklahoma to Iowa. Credit must be given to the Storm Prediction Center, National Weather Service offices, and local TV and other media outlets for accurately predicting the severe weather event and keeping people informed as it happened, and the people of the area for paying attention to the weather. It must be counted as a success on many levels that 115 tornadoes over 4 states only resulted in 6 deaths (and those deaths occurred in the toughest situation to warn people – a rain-wrapped tornado in the middle of the night where the tornado sirens were disabled due to a lightning strike earlier in the day).

The last bout of severe weather occurred with a squall line that formed in the late evening (~02:30 UTC 15 April 2012) along the dry line in western Texas and quickly expanded into Oklahoma and Kansas. This line produced the deadly tornado in Woodward, OK, along with many reports of 1-2″ diameter hail. Suomi-NPP passed over this line of storms between 07:45 and 07:50 UTC (15 April). The high resolution infrared window band, I-5 (11.45 µm), shows the immense scale of this storm system stretching from Wisconsin and Minnesota to Texas, in great detail. Be sure to click on the image, then on the “1497×1953” link below the banner to see it in full resolution. (The full resolution image is ~2MB in size.)

View of a squall line over the Central Plains from VIIRS channel I-5, 7:45 UTC 15 April 2012

View of the squall line over the Central Plains from VIIRS channel I-5, 7:45 UTC 15 April 2012

The color scale here is the same one used for the 2 March 2012 tornado outbreak image and the 25 January squall line over southeast Texas. The darkest blue pixels visible amongst the white overshooting tops (more easily visible on the southern end of the squall line) have a brightness temperature below -77 C, indicative of very strong convection.

Posted in Uncategorized | Tagged great plains, I-5, overshooting tops, resolution, severe weather, squall line, VIIRS | Comments Off

VIIRS view of Invest 97S at night

Posted on April 10, 2012 by Curtis Seaman

On 5 April 2012, the Joint Typhoon Warning Center was watching an area of the Mozambique Channel for possible development of a tropical cyclone. This area was named Invest 97S. As 6 April 2012 was a full moon, this is a good case to test the capabilities of low-light visible imagery channels for detection of tropical cyclone development at night.

The Operational Linescan System (OLS) aboard the Defense Meteorological Satellite Program (DMSP) satellite F-18 has a low-light visible channel (that inspired the development of the Day-Night Band (DNB) for VIIRS). The image below is from this channel on F-18, taken at 17:22 UTC, 5 April 2012 (courtesy the Naval Research Laboratory).

DMSP OLS low-light visible image of Invest 97S, taken at 17:22 UTC, 5 April 2012. Image courtesy Naval Research Laboratory.

The landmass on the right of the image is Madagascar with Mozambique on the left side of the image. A low-level circulation is visible in the clouds just off the coast of Madagascar in the center of the image.

Suomi-NPP passed over the area at 23:02 UTC. The images below are taken from the VIIRS DNB, which is a low-light visible channel (centered at 0.7 µm) with higher radiometric resolution, a higher signal-to-noise ratio and higher spatial resolution. The second image is a zoomed-in version of the first.

VIIRS DNB image of Invest 97S taken at 23:02 UTC, 5 April 2012. Image courtesy Dan Lindsey and Steve Miller.

Zoomed-in image of Invest 97S from the VIIRS DNB taken at 23:02 UTC, 5 April 2012. Image courtesy Dan Lindsey and Steve Miller.

In the nearly six hours that elapsed between the DMSP OLS image and the VIIRS DNB image, you can see that the line of deeper convection to the southwest of the circulation center has moved further south away from the center of the circulation and outflow from these storms has cleared out the low level clouds from where the storms used to be.

Compare these images with the high-resolution infrared window channel (11.45 µm), I-5, from VIIRS, seen below.

VIIRS channel I-5 image of Invest 97S, taken at 23:02 UTC, 5 April 2012.

The low level circulation is difficult to distinguish, given that there is no significant temperature contrast between the low level clouds and the background (ocean) surface. The deeper convective clouds are easy to spot in I-5, however.

The information provided by the VIIRS DNB near full moon events would be a great help to tropical cyclone forecasting in cases such as this where, typically, only IR data is available at night. Assuming latency issues with VIIRS can be solved, of course.

In the end, Invest 97S failed to develop into a tropical cyclone, which spared Madagascar and Mozambique – both of which had been affected by the cyclones Giovanna and Funso earlier this year.

Posted in Uncategorized | Tagged day/night band, DMSP, I-5, OLS, tropical storm, VIIRS | Comments Off

Time-lapse of the Lower North Fork Fire

Posted on April 3, 2012 by Curtis Seaman

On 26 March 2012, strong winds, high temperatures and low humidities re-ignited embers from a controlled burn that took place the previous week near Conifer, CO. The Lower North Fork fire quickly spread in the high winds, eventually burning more than 4000 acres and damaging or destroying 27 homes. Three people were killed, presumably because they were unable to evacuate before their homes were engulfed in flame. One family’s daring escape from the fire was caught on a cell phone camera and made national news (CAUTION: strong language has not been edited out). Many interesting pictures of the fire may be found here, here, and here.

Channel I-4 of VIIRS (centered at 3.74 µm) captured the hot spot from the Lower North Fork fire on each of Suomi-NPP’s afternoon (ascending) overpasses last week. These images make up the loop shown below.

5-day loop of I-4 images of the Lower North Fork fire

5-day loop of afternoon I-4 images of the Lower North Fork fire

In this image loop, the color scale represents observed brightness temperature such that warmer pixels appear darker and cooler pixels appear lighter. Pixels warmer than 330 K appear black, and pixels colder than 250 K appear white. The time between each image in the loop is approximately 24 hours.

The first image in the loop, taken at 20:24 UTC on the 26th, captured the hot spot shortly after the fire was first reported. The hot spot as seen by I-4 expanded significantly during the first 24 hours, before lighter winds and firefighting efforts greatly limited the growth of the fire. Over the last three frames, the hot spot can be seen to cool and shrink slightly.

Low (liquid) clouds can be seen as dark splotches on the images from the 28th and 29th of March, which should not be confused with fires. This is due to the fact that liquid clouds are highly reflective at 3.7 µm, and the reflection of solar radiation during the day increases the observed brightness temperature, so they appear darker. The persistently bright sideways “C” shape to the northeast of the fire is Chatfield Reservoir, which has a low brightness temperature due to the low water temperature in the reservoir and the relatively low emissivity of liquid water at this wavelength. Cherry Creek Reservoir (to the northeast of Chatfield Reservoir) and Marston Lake (to the north of Chatfield Reservoir) can also be seen.

With clear skies, the burn area shows up quite clearly in the I-band false color RGB composite of I-1, I-2 and I-3, taken at 20:06 UTC 27 March 2012 – the same time as the second frame of the loop above.

RGB composite of VIIRS channels I-1, I-2 and I-3 of the Lower North Fork fire, 20:06 UTC 27 March 2012

The burn area shows up as a sizeable dark brown spot in the forests (which show up as green) southwest of Denver.

After the driest and warmest March on record in Denver, hopefully this is not the start of a long, devastating fire season (link goes to PDF file).

Posted in Uncategorized | Tagged false color, fire, I-4, RGB composite, VIIRS | Comments Off

I- and M- Band Views of the Heartstrong Fire

Posted on March 20, 2012 by Curtis Seaman

The Heartstrong Fire in Yuma County, Colorado, 18 March 2012 (uncredited photo)

On 18 March 2012, very warm, very dry and very windy conditions existed throughout eastern Colorado. Surface observations showed temperatures in the 70s and 80s, dew points in the teens and 20s, and sustained winds at 20-30 knots (gusting over 40 knots). Wind gusts up to 60 knots (~70 mph) were reported.

Surface observations, 19:00 UTC 18 March 2012 (courtesy UCAR)

A red flag warning was issued for nearly all of eastern Colorado. And with good reason! A grass fire started in Yuma County, CO (which borders Nebraska and Kansas) in the early afternoon, and quickly grew out of control. The media dubbed it the Heartstrong Fire. An area 14 x 16 miles had to be evacuated, although only 2400 acres actually burned. The smoke plume was easily visible from the Goodland, KS, National Weather Service radar. Two homes were destroyed, and three firefighters were injured battling the blaze.

Radar image of smoke from the Heartstrong Fire, 21:17 UTC 18 March 2012

Radar image of smoke from the Heartstrong Fire seen by the Goodland, KS, NWS radar, 21:17 UTC 18 March 2012 (courtesy UCAR)

"True Color" image of the Heartstrong Fire, 19:34 UTC 18 March 2012

"True Color" image (RGB composite of VIIRS channels M3, M4 and M5) of the Heartstrong Fire, 19:34 UTC 18 March 2012

Even though cirrus clouds covered the area (as seen in the true color image above), VIIRS observed the fire in its two 3.7 µm channels. The VIIRS images shown here, from 19:34 UTC, were taken roughly 20 minutes after the fire was first reported. The moderate resolution band M-12 (centered at 3.7 µm) identifies a hot spot (which shows up as black in the image below) that is approximately 6 pixels by 3 pixels. With ~750 m resolution at nadir in this band, that corresponds to a total area of 10.2 km² of pixels that contain a fire signal.

Image of the Heartstrong Fire from VIIRS channel M-12, 19:34 UTC 18 March 2012

The high resolution imagery band I-4 (centered at 3.74 µm) also identifies the hot spot. In this case it is approximately 11 pixels by 5 pixels in size. At ~375 m resolution at nadir, this corresponds to an area of 7.7 km² of pixels that contain a fire signal.

Image of the Heartstrong Fire from VIIRS channel I-4, 19:34 UTC 18 March 2012

Image of the Heartstrong Fire (indicated by the red arrow) from VIIRS channel I-4, 19:34 UTC 18 March 2012

Thus, the difference in resolution between these two channels leads to a difference in the apparent size of the hot spot as seen by satellites. However, it should be noted that this apparent size is only an estimate of the size of the hot spot visible in the satellite image, not the actual size of the fire. Fires move in narrow flame fronts that cover only a small percentage of the pixel area. From a firefighting perspective, detecting which pixels actually contain fire and where the actual burning occurs within those pixels are two different things.

Of additional interest is the difference in observed brightness temperatures between these two channels. The warmest pixel in M-12 was 327 K, while the warmest pixel in I-4 was 342 K. As the observed brightness temperature is related to the fraction of each pixel covered by fire, the higher resolution images produce higher brightness temperatures in the hot spot.

This means that, to a human observer, the hot spot appears larger in the M-band image, while, from an automated algorithm point-of-view, the I-band image has a larger number of pixels within the hot spot, and higher brightness temperatures. The difference in the appearance of the hot spot between these channels is more clearly seen in the figure below. Be sure to click on the image, and then look for the “1700×702” link above the image title and click on that to see the comparison in its highest quality.

Comparison between the I-4 and M-12 views of the Heartstrong Fire. The previous I-4 and M-12 images (taken at 19:34 UTC, 18 March 2012) have been zoomed in for additional clarity.

As an additional note, band M-13 (centered at 4.05 µm) is the primary band used in active fire detection. This band was designed specifically to measure the radiative signal of hot spots without sensor saturation. The M-13 image of the fire is shown below.

Image of the Heartstrong Fire taken by VIIRS band M-13, 19:34 UTC 18 March 2012

Image of the Heartstrong Fire from VIIRS channel M-13, 19:34 UTC 18 March 2012

There is a dedicated team of researchers actively exploring fire detection from VIIRS. You can learn more about fire detection and the status of their current fire detection products by visiting viirsfire.geog.umd.edu.

Posted in Uncategorized | Tagged fire, I-4, M-12, M-13, resolution, true color, VIIRS | Comments Off

Aurora Borealis from the Day-Night Band

Posted on March 12, 2012 by Curtis Seaman

On 6 March 2012, a massive solar flare erupted and an associated coronal mass ejection was launched toward Earth. Video of the solar flare from NASA’s Solar Dynamics Observatory can be viewed here. NOAA’s Space Weather Center forecast the coronal mass ejection to reach Earth on 8 March 2012, which you can view here. In another video, Joe Kunchas of the Space Weather Prediction Center talks about the solar flare, coronal mass ejection and possible impacts of the these events – including re-routing of aircraft, the effect on electric power grids and the best conditions to view the aurora. ABC News made it sound like the world was going to end.

Fortunately, the world did not come to an end and Suomi NPP sufferend no significant ill effects from the solar activity. In fact, the Day/Night band on VIIRS caught the aurora borealis, even in the presence of a full moon.

VIIRS Day/Night band image of the aurora over Saskatchewan and Manitoba, 9 March 2012

The Day/Night band (DNB) is a visible-wavelength band, centered at 0.7 µm, that is highly sensitive to low levels of light, so that it behaves like a visible channel even at night when the moon is out. As seen in the image, the DNB clearly shows the location of towns and cities at night. Since 8 March 2012 was a full moon, clouds, snow and ice (particularly over Lake Winnipeg) are also visible. The brightest swirl, extending from north of Saskatoon, over Reindeer Lake and into northwestern Manitoba is the aurora borealis.

On its previous orbit, the DNB captured the aurora over Ontario and Quebec, although it is more difficult to distinguish from the underlying clouds.

VIIRS DNB image taken at 7:35 UTC, 9 March 2012

A VIIRS Day/Night band image taken at 7:35 UTC, 9 March 2012

In this image, the bright swirls extending from north-central Ontario, over James Bay and into northern Quebec are elements of the aurora. It is expected that auroras would be more visible in the DNB during new moon events, where the aurora would be the only light source (apart from cities, towns and other point-source human activity).

Many amateur and professional photographers got a good look at the auroras, including this video taken from the shores of Lake Superior and this one taken near Wasilla, Alaska. Imagine if we had two more DNB channels at shorter wavelengths, so that we could capture the amazing colors of the aurora that these videos show.

Posted in Uncategorized | Tagged aurora, day/night band, ice and snow, VIIRS | Comments Off

VIIRS View of March 2 Tornadic Storms

Posted on March 5, 2012 by Dan Lindsey

NPP/VIIRS passed over Southern Indiana on March 2 about thirty minutes before the most devastating tornadoes struck the towns of New Pekin and Henryville (among others). At 1935 UTC, a pair of rotating thunderstorms, also known as supercells, were advancing eastward across Indiana. The easternmost storm spawned the most damaging tornadoes. Below is a VIIRS true color image from the NPP pass at 1935 UTC.

VIIRS True Color image of the severe storms on 2 March 2012 at 1935 UTC.

A zoomed-in visible view of the storms is below.

VIIRS I-band 1 (375-m resolution) from 2 March 2012 at 1935 UTC

The infrared (I-band 5) image is below, along with some annotations pointing out the two active supercells discussed above. Note that the brightness temperatures associated with the overshooting top (OST) of the westernmost storm are colder than the easternmost storm, although both storms were quite strong at the time and the eastern storm ended up producing the deadlier tornadoes. OSTs are transitory, so it’s possible that a new cold OST formed with the eastern storm shortly after the NPP pass. These very high resolution infrared views of tornadic storms are among the first documented, given the recent launch of NPP.

VIIRS I-band 5 Infrared view from 2 March 2012 at 1935 UTC

To illustrate the effect of high resolution in the IR, below is a GOES-13 10.7 micrometer IR image from 1932 UTC, which has 4-km resolution at nadir. The coldest brightness temperature in the westernmost storm in southern Indiana from GOES is 206.6 K, but with VIIRS it’s 195 K.

GOES-13 4-km IR Image from 1932 UTC on 2 March. Compare this image to the 375-m VIIRS image above to see the improvement provided by VIIRS over GOES.

The day after the tornadoes, relatively cloud-free skies in eastern Kentucky allowed VIIRS to see some of the tornado tracks. In the image below, the faint white lines circled in red in Kentucky and West Virginia denote the new tornado damage paths. When green vegetation is disrupted/destroyed, the result is typically a brighter scene at visible wavelengths.

VIIRS I-band 1 from 3 March 2012 over eastern KY and western WV. The tornado tracks are circled and show up as faint white lines

Posted in Uncategorized | Tagged IR window, overshooting tops, severe weather, true color, VIIRS, visible | Comments Off

A Tropical Winter Wonderland

Posted on February 20, 2012 by Curtis Seaman

It’s not every day the official National Weather Service forecast from Honolulu, HI calls for freezing rain and snow in parts of Hawaii, but that’s what happened 19 February 2012 for the Big Island. Mauna Loa and Mauna Kea both received snow over the last 24 hours, and VIIRS shows both volcanoes are covered with the white stuff.

True color image of the island of Hawaii from VIIRS, taken at 23:16 UTC, 19 Febraury 2012

A false color image of the island of Hawaii taken from VIIRS at 23:16 UTC, 19 February 2012

False color (or "pseudo-true color") image of the island of Hawaii from VIIRS at 23:16 UTC, 19 February 2012

The top image is an RGB composite of moderate resolution channels M3 (blue), M4 (green) and M5 (red). As these channels observe radiances in the blue (0.488 μm), green (0.555 μm) and red (0.865 μm) portions of the visible spectrum, respectively, the image represents what the human eye sees, and is thus a “true color” representation.

The bottom image is an RGB composite of high resolution channels I-1 (blue), I-2 (green) and I-3 (red). These channels observe radiances centered on 0.64, 0.86 and 1.61 μm, respectively. As a result, differences in the optical properties of liquid droplets and ice particles at these wavelengths allow liquid and ice clouds (and snow) to be distinguished more easily. Liquid clouds appear white (or a dirty, brownish-white), while ice clouds appear blue. The snow on top of Mauna Loa and Mauna Kea stands out as a deeper blue. Vegetation still shows up as green, and barren ground as brown, producing an image that may be called “pseudo-true color”.

Both peaks, which are more than 13,600 ft above sea level, receive snow during most winters. The Mauna Loa observatory, at 11,100 ft above sea level, averages 3.7 inches of snowfall each year. While there are many observatories on Mauna Kea with weather stations, none of them seem to collect routine snowfall information. You can find the latest webcam imagery of Mauna Kea by clicking here to find out how much snow there is in the tropical paradise now. Aloha!

Posted in Uncategorized | Tagged false color, Hawaii, ice and snow, RGB composite, true color, VIIRS | Comments Off

Tropical Cyclone Giovanna

Posted on February 14, 2012 by Curtis Seaman

Back in January, Madagascar was brushed by tropical cyclone Funso, which caused periods of heavy rain, but was a bigger deal for neighboring Mozambique. This time around, Madagascar took a direct hit from tropical cyclone Giovanna, which reached “Super Cyclone” status as category 4 storm just prior to making landfall.

VIIRS got a great look at Giovanna while it was a category 4 storm.

A visible image of Super Cyclone Giovanna from VIIRS channel I-1 taken at 09:47 UTC, 13 February 2012 (Thanks to Dan Lindsey)

IR-window image of Super Cyclone Giovanna taken by VIIRS channel I-5 at 09:47 UTC, 13 February 2012 (Thanks to Dan Lindsey)

Fortunately, Giovanna weakened rapidly upon making landfall. Moving east to west across the center of the island and over the mountains of central Madagascar, Giovanna could not maintain its Super Cyclone status. At the time of this post, Giovanna was located over the west coast of Madagascar and down to sustained winds of 35 knots, making it a weak tropical storm. Early reports suggest between 2 and 5 people were killed, and some towns on the east coast had 60% or more of their buildings damaged or destroyed.

All things considered, the situation could have been much worse, considering residents were only given a half a day’s warning, and the primary method for disseminating weather warnings is through the use of town criers.

Posted in Uncategorized | Tagged category 4, giovanna, IR window, Madagascar, tropical storm, VIIRS, visible | Comments Off