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Ephemerata Weather Radar will likely be affected by a planned outage by the US National Weather Service as they migrate some of their data services to a new server configuration. EWR uses data from these servers. Most of this conversion effort will occur in the evening of July 19, 2010 EDT local time. If the data conversion goes without incident, the outage should be short lived.

EWR users are therfore cautioned that radar maps later today and through the overnight may not be updated and therefore not be current. Ontario users of EWR may wish to refer to the Environment Canada sites listed in the sidebar on the alerts archive if weather is threatening and an official statement is needed.

NOUS41 KWBC 141335

935 AM EDT WED JUL 14 2010



FOR JULY 20 2010






PHONE: 301-713-0864 X 114





Update 2010/07/10: There have been some concerns expressed over recent seismic activity at Volcano Katla. There is nothing being reported from the Icelandic Met Office that indicates a concern. Active volcanos tend to have regular periods of seismicity. These recent events are of low magnitude and are not believed to be indicative of imminent eruption of Katla. The earthquake charts on the Met site are updated constantly (near real-time according to the Met Office) and the colours do not indicate severity, only time elapsed since last occurred. Earthquakes greater than magnitude 3 are indicated by a star icon.

Update 2010/04/24: Note: This will be EWR’s last report on the current event sequence at Eyjafjallajökull unless there is a substantial change in events. I invite you to explore the links included throughout this post to develop an understanding of the Eyjafjallajökull event. The Active Monitoring sidebar will continue to list the quicklinks for NORDVULK and the webcams. This post will be added to the general Active Monitoring list for quick access as the EWR blog moves forward.

The bulk of the information presented has been drawn from situation reports of the Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland. Certain links contained below represent specific research efforts of indviduals and are attributed where appropriate. As has been noted in this latest sitrep, the eruption has not ceased and there remains concern about future activity. While Katla is not considered at immediate risk of eruption, the association with Eyjafjallajökull means it will continue to be monitored.

Status report 24 April 2010

from Icelandic Meteorological Office and Institute of Earth Sciences, UofI
Compiled by: MTG / HB
Based on: IES/IMO Inspection flight with aircraft from Ernir at 1600-1700
IMO seismic monitoring
IES/IMO GPS monitoring
IMO river gauges

Eruption plume:
Height( a.s.l): 13000 feet (4 km)
Heading: SW
Colour: Grey

Tephra fallout: Minor (plume dark but no reports of fallout in districts around volcano)
Meltwater: 100-120 m3/s, based on gauge at old Markarfljót bridge and a rough estimate of base flow.

Conditions at eruption site: North crater still active. Mild explosive activity with spatter thrown to 100 m height above crater. Shockwaves occur every few seconds. North of crater a roughly 300 m long and wide depression has been melted out in the last three days. Steam plumes rise from the depression, especially at the margins. This is explained by lava flowing northwards from the crater with the steam rising where lava meets ice.

Seismic tremor: Magnitude similar to what it has been over the last few days.

GPS deformation: Indicates slow subsidence towards the center of the volcano.

Magma flow: Eruption plume: less or equal to 10 tonnes/s.
Lava flow: 10-30 tonnes/s
Total magma flow: 20-40 tonnes/s

Overall assessment: Magma flow rate has remained at similar level over the last few days. Plume activity is gradually declining. Flow of lava is considered to have began around noon on Wednesday 21 April. Timing is based on: a) onset of semi-continuous discharge of meltwater from Gígjökull, b) Observations of steam rising at northern margin of ice cauldon at 1300 on 21 April, and c) a change occurs in fluctuations in tremor amplitude at this time. No signs of melting or meltwater discharge towards south. No signs of termination of eruption.

Eruption update 21 April

Eruption continues with less explosive activity. Eruption rate is inferred to have declined over last few days and now be an order of magnitude smaller than during the initial 72 hours of the eruption. Present eruption rate is estimated to less than 30 m3/s of magma, or 75 tonnes/s , with a large uncertainty.

Eruptive style: The northernmost one of two main craters in the summit caldera is active. Phreatomatic explosive activity occurs with some lava spatter at craters.

Plume height: about 3 km

Tephra dispersal: local towards the south

Meltwater: minor, but what is melted flows down into Markarfljót, no signs of water accumulation in craters

Seismic tremor recorded by the Icelandic Meteorological Office: some fluctuations but mostly stable. Tremor is not decreasing and does not reflect the decline as inferred for the eruption rate.

GPS-measurements: indicate continuing small pressure decrease under the volcano at a similar rate.

Composition of erupted material: Samples collected April 19 show same composition as early in the explosive phase, but fluorine content is higher. Samples collected 19 April have 850 mg/kg (initially it was 25-35 mg/kg). This is due to the change in eruptive style – tephra is now not washed to the same extent by water in the eruptive plume.

Amount of erupted material: Uncertain but on the order of 100 millon cubic meters. Tephra next to craters is 20-30 m thick.

Compiled by: Freysteinn Sigmundsson, Magnús Tumi Guðmundsson, Guðrún Larsen, Níels Óskarsson, Sigurður Reynir Gíslason, Páll Einarsson, Sigrún Hreinsdóttir, Rikke Pedersen, Ármann Höskuldsson, Guðrún Sverrisdóttir, other staff of Institute of Earth Sciences and collaborators.

Radar images acquired yesterday, 20 April, by the Icelandic Coast Guard showed no changes in the size of the cauldron at the eruption site of Eyjafjallajökull, compared with images from 19 April – Eyjólfur Magnússon

20. April 2010: Latest results from GPS stations around Eyjafjallajökull show deflation associated with the eruption. No movements associated with the Katla volcano are presently observed – Benedikt Ófeigsson, Sigrún Hreinsdóttir and Bryndís Brandsdóttir

Eyjafjallajökull frá Hvolsvelli

Screencap 2010/04/17 8:45 EDT of Eyjafjallajökull from Hvolsvelli, Iceland. Mila webcam

Eyjafjallajökull frá Valahnúk

Screencap 2010/04/17 8:45 EDT Eyjafjallajökull from Valahnúk, Iceland. Mila webcam.

Update 2010/04/17:– stable eruption, change in wind conditions

Explosive activity at the eruptive site and seismic tremor continue at a relatively stable rate without a decline overnight. Air space over large part of Europe continues to be closed. Eruption plume loaded with tephra (ash) rises to more than 8 km, with tephra fallout in inhabited areas around the volcano. Over 20 lightning recorded in the eruption plume over a 4 hour period. Overnight wind conditions at the eruptive site change. Steady easterly wind that have prevailed since the onset of the explosive eruptive phase replaced by northerly winds that carry the eruption plume away from the volcano to the south. A MODIS satellite image at 03:41 GMT shows the eruption plume bending from south to east, and a NOAA AVHRR satellite image acquired at 07:01 GMT shows plume heading from the volcano towards the south.

Impact on European Air Travel 2010/04/17 13:25 UTC. Normally the airspace over the United Kingdom, Scandanavia and northern Europe is full of planes.

Ash cloud over Europe April 16, 2010, NASA Earth Observatory photo.

Ash Cloud from Iceland volcano April 15, 2010. NASA Earth Observatory photo

Update 2010/04/16: From Icelandic media sources and the Nordic Volcanic Center, Institute of Earth Sciences [more at link, and check the webcams in the Active Monitoring sidebar.]:

Media: Britain closes airspace as volcanic ash spreads.

The Boston Globe has some good shots in their Big Picture series and here too.

Many good shots here too (this is the Flickr Volcano pool – many recent uploads for Iceland)

Video clips:


Iriya:1:Flickr [Good!], Iriya:2:Flickr [Good, too!], Iriya:3:Flickr
Tackii:1:Flickr, Tackii:2:Flickr
And this one from the Nutter Isles…

Video of the eruption from the air
airflight 2
Ground effect
local views

GPS measurements from Thorvaldseyri (THEY), south of the Eyjafjallajökull volcano, now show displacement towards north. The station had been moving south since the intrusion activity started in the end of December. This change suggests that an equillibrium has been reached in magma flow in and out of the volcano.
Plot showing the displacement (pdf file – data from Sigrún Hreinsdóttir,

Eyjafjallajokull Volcano – GPS Time Series (by Sigrún Hreinsdóttir)

New map of the lava flow from 21 – 24 March 2010 (by Eyjólfur Magnússon, pdf file)

Results from observations flights over the eruption site 21 and 22 March 2010 (pdf file compiled by Eyjólfur Magnússon)

Radar observations at the Eyjafjallajöklull eruption site 14 Apríl 2010 – Eyjólfur Magnússon

Eyjafjallajökull eruption: A new phase started on 14 April 2010
A new phase of the Eyjafjallajökull eruption started around midnight on the 14th of April, where melt penetrated its way to the central crater beneath the glacier. Bad weather makes visual observations difficult, but surveillance flights with radar and temperature sensors will shed light on the new conditions later today.

Eyjafjallajökull eruption: 20 March to present
Compiled by Freysteinn SigmundssonInformation sources: Nordic Volcanological Center, Institute of Earth Sciences; Icelandic Meteorological Office (seismic and hydrological observations) and many others.

20 March, late evening: An eruption begins on Fimmvörðuháls located between the Eyjafjallajökull and Mýrdalsjökull ice caps. The eruption was initially detected visually; a red cloud above eruptive site was seen around 23 GMT. The onset of the eruption was gentle, following a period of weeks and months prior to the eruption of high seismic activity and high crustal deformation rates in the Eyjafjallajökull volcanic system. Seismic tremor begins around 22:30 and rises gently. Seismicity was not enhanced significantly immediately prior to the eruption compared to the weeks prior to the eruption. However, the depth of earthquakes decreases and earthquake propagate from magma upwelling area under Eyjafjallajökull towards the eruptive site.

21 March:
Observations from air in early morning reveal a short (<500 m) NE-SW oriented effusive eruptive fissure with fire fountaining and Hawaiian eruptive style. Fire fountains occur from 10-12 vents, with lava jets reaching up to about 100 m hight. The eruption appeared stable from 4-7 AM when viewed from air. The eruption tremor rose gently until reaching a maximum around 7-8 AM. No further lengthening of the fissure was detected. Lava is limited to immediate surroundings of the eruptive craters (less than few hundred meters). Minor amount of ash falls within few km to the west of the eruption site, carried by easterly winds. No ice melting is occurring as the eruptive fissure is just outside the ice covers of Eyjafjallajökull and Mýrdalsjökull.

22 March:
Initial observations from ground. Activity had focused on a series of closely spaced vents. Prevailing easterly winds lead to maximum scoria accumulation on a linear rim west of the NE-SW oriented fissure. Lava flows (Aa type) towards the Hrunagil canyon with initial view on a spectacular „lava fall“ as molten lava flows off steep cliffs into the canyon.

23 – 31 March:
Steady eruptive activity in initial craters with gradual focusing towards fewer vents. Lava flows towards north into two canyons, Hrunagil and Hvannárgil, with intermittent spectacular „lava falls“ as molten lava flows off steep cliffs into both canyons. Extensive steam plume generation when magma melts snow in front of advancing lava, mostly in the canyons. Two or three plumes observed (one at the eruptive craters, others more pronounced in front of the advancing lava). Meltwater released in batches into rivers in the canyons. Relatively steady eruption tremor recorded by seismometers.

Evening of March 31:
Opening of a new short fissure immediately north of the previous one probably relating to changes at shallow depth in the feeder channel (few hundred meters?). No change in eruption tremor.

31 March – April 6: Activity continues in both the old and new eruptive craters, in a similar manner as before, with lava mostly flowing towards the NE, and pronounced „lava falls“ in Hvannárgil. Last active phase of the of the lava fall into Hrunagil on 31 March.

April 5: Eruption tremor (1-2 Hz frequency band at nearest seismic station Godabunga) begins to decline in a gradual manner.

April 7: Activity has stopped in the original craters of the eruption, and is limited to craters on the new fissure formed on 31 March. Lava flows cover an estimated area of 1.3 square kilometers, with estimated average thickness of 10-20 m. Maximum elevation of scoria craters formed in the eruption is 82 m.

April 9:
After little change in deformation rates during the eruption, timeseries at continuous GPS-stations north of the volcano show sudden change, partly jumping back to pre-eruptive levels. Signals may relate to decreasing pressure in the magma conduit feeding the eruption.

April 11:
Eruption tremor approaches pre-eruptive levels, but visual observation reveal eruptive activity in late afternoon.

April 12: Seismic tremor reaches a minimum – eruption temporarily stops

April 13: Extensive seismic swarm begins around 23:00 under the central part of Eyjafjallajokull.

April 14: Onset of seismic tremor shortly after midnight of increasing amplitude, in association with an eruption from a new vent under the central ice-capped crater of Eyjafjallajokull. The eruption is visually confirmed in early morning – eruption plume rises above Eyjafjallajokull. Meltwater forms a jokulhlaup.

Map of the lava flow on Fimmvörðuháls from 21 March – 7 April 2010 (by Eyjólfur Magnússon, pdf file)
A view from space on the crustal deformation associated with magma intrusion – preceding the March 20th eruption
First interferometric analysis of synthetic aperture radar images acquired by satellites reveal extensive deformation associated with a magmatic intrusion under Eyjafjallajökull preceding the eruption. The deformation signal appear as colour fringes, where each fringe represents a change in range from ground to satellite of 1.5 cm. Extensive deformation is observed both north and south of Eyjafjallajökull. The two images show a large change in range from ground to satellite between September 1999 and March 20, 2010, just prior to the eruption that began around 22:30 GMT. These are the first in a series of interferograms anticipated to be formed showing the course of the eruption.
The interferograms are formed by analysing images from the German TerraSAR-X satellite. The research is a collaborative project between the Nordic Volcanological Center at the Institute of Earth Sciences, University of Iceland, the Technical University of Delft, Netherlands, and the University of Wisconsin-Madison, USA. The initial interferograms have been formed by Andy Hooper at Delft.
Contact persons:  Rikke Pedersen (, Martin Hensch (, Andy Hooper (, Kurt Feigl (, Amandine Auriac (, Freysteinn Sigmundsson (


Saturday night, Mar 21, 2010, at about 11:30, residents of Fljotshlid, Iceland, noticed an orange flare from the vicinity of the Eyjafjallajökull glacier.

A kilometer long fissure has opened in a passage in Fimmvörduhals, between glaciers Eyjafjallajökull and Mýrdalsjökuland and volcanic magma was erupting up through the fissure.

Scientists say the eruption seems to be small and since it is not under a glacier, the danger is less than it might have been.

An Icelandic Coast Guard aircraft flew over the eruption early this morning. For three hours the plane circled the area and Karl Sigurbjörnsson of RÚV filmed this dramatic video of the eruption (do watch the video – the images are quite spectacular).

The immediate area was evacuated and has been closed to travel. This is a popular tourist area of Iceland, and there is a well-known hiking trail in the vicinity of the eruption. Residents have been allowed to return, but the area remains closed to tourists.

There are concerns that the eruption could spread to beneath the glacier, and there also a watch on Katla (see also Katla Volcano at the Institute of earth Sciences ), a nearby large, presently dormant, volcano. Katla has erupted before, and eruptions under glaciers are especially serious due to rapid melting of large volumes of ice, creating near instant high volume floods.

There have been small earthquakes and seismic activity in the area. Seismic activity in Eyjafjallajökull has been intensive for the past three weeks and most of the earthquakes have been located between 7 and 10 km depth. On March 19th a seismic swarm began east of the top crater, originating between 4 and 7 km depth. The activity migrated eastwards and towards the surface on Saturday, March 20th. At 22:30 GMT a slightly increased tremor was detected on three seismic stations, located within 20 km from the volano’s top crater, and within the next two hours reports on an volcanic eruption were received. (from Icelandic Met Office)

Additional Resources:

Icelandic Met Office
University of Iceland Institute of Earth Sciences, ongoing activity
Katla monitoring
Nordic Volcanological Center Icelandic fissure eruption triggers worries

The Iceland Review Online is running constant updates as more information comes available.

Observe the Katla Volcano in Iceland from the Katla webcam

The onset of the doldrums of summer in the Great Lakes is due largely to weather patterns that set up a repeating scenario that draws very warm and moist Gulf of Mexico air directly into the Great Lakes basin. The forecast map below (courtesy NCAR) for July 5, 2010, illustrates precisely the establishment of the “Mississippi Heat Pump” – an atmospheric engine that churns this moist warm air northward.

Mississippi Heat Pump - NCAR map

Low pressure systems (“L” on the map) are a standard feature of the continental weather system for North America (the infamous “Colorado low” for example), and due to the rotation of the earth, they form in the lee of the Rocky Mountain cordillera and advance their way eastward.

In the northern hemisphere, low pressure areas (areas of rising air) rotate counterclockwise (“cyclones”), and high pressure areas rotate clockwise (“anticyclones”). Since air nearer the ground tends to contain more moisture, as its moves upward in a low, gets cooler, forms clouds, rain and stormy weather. In highs, the opposite is true -upper air, being cooler, descends and warms. As it does so, its capacity to hold moisture increases. Clouds dissipate, and if the air dries enough, we get the clear blue skies of a great summer day. Where the pressure difference is not great between the high and an adjacent low, we get hazy, more humid weather.

Turning back to the map, we see several areas of low pressure stretching from Texas to northern Quebec. The yellow arrows show the rotation and air flow about the lows. Note that there is a tendency in each case to draw Gulf air northward in the rotation up the Mississippi valley. What is important though, for the heat pump, is the formation of a strong high off the Atlantic seaboard (“H”- sometimes called a “Bermuda high” if they centre far enough off the coast). These highs, when they form, tend to be very stable and last several days . Note that rotation and air mass flow around the high is clockwise, as shown by the yellow arrow. You therefore have a situation where rotation about the lows over the central US coincide with the rotation around the seaboard high, forming a strong flow northward from the Gulf (magenta lines), up the Mississippi and into the Great Lakes basin. In this particular case, the draw is further augmented by a strong low over northern Quebec.

Since the lows are also drawing cooler air from the north (“cold fronts”), the interface between the lows and the high can set off very turbulent weather including strong convective and tornadic storms. From June on, these are characteristic for the upper US Midwest, upper Mississippi and Ohio valleys. Eastward flow of weather brings them across the Great Lakes, especially in the lee of lakes Erie and Ontario. Its easy to see that this repetitive seasonal weather pattern goes a long way to maintaining the rainfall load that sustains the Great Lakes, the Mississppi, and other large mid-continent river systems.

We are apparently experiencing another round of what Bell Canada laughingly calls “DSL internet service”. Ephemerata Weather Radar may show delays in updating imagery due our inability this morning to hold an internet connection. Our system has automated restarts built in several times a day to attempt to deal with these DSL issues, but at times, the outages are severe enough to make the system very erratic. We can’t rule out throttling either, although neither Bell nor the ISP will admit it.

First Atlantic region (actually, Gulf of Mexico) hurricane for 2010.

2010-07-02: Declared dissipated at 10:00PM CDT

2010-07-01: Reached cat 2 prior to landfall, now downgraded to tropical storm. Came ashore about 10:15 EDT June 30 south of the US/Mexico border south of Brownsville. 14″ rain in areas north of Brownsville by 11 PM, projected to reach 20″ in isolated areas. Sustained winds of 100mph at landfall with higher gusts.

Radar base reflectivity image of Hurricane Alex as cat 2, just prior to landfall on the northeast coast of Mexico, 7:31 CDT, July 1, 2010. Warning blocks are flood warnings for the Brownsville, Tx, area. Storm is much larger than radar implies. Range limits of KBRO Brownsville radar site means beam overshoots storm at limit of range.

Radar animation of Hurricane Alex covering the period from 10 AM CDT June 30 to 7:30 AM July 1, 2010. During this period, Alex increased in strength to a category 2 hurricane. You can see the eye form up and hold until landfall, finally breaking down as it ran into the dry mountains of Mexico. (Please note: this is a large file, 16.6mb. Allow time to load. If animation doesn’t run in thread, click on image to download full size file to view).

Hurricane Alex June 2010

Base Reflectivity radar animation of Hurricane Alex 9:59 AM CDT June 30, 2010 to &:31 AM CDT July 1, 2010 KBRO, Brownsville, Tx. Created from data supplied by the US NWS

The storm extent is much broader than the radar images indicate (as can be seen by the marine warning blocks that pop up off Louisiana to the north). As the radar beam reaches further out from the radar site, it begins to overshoot the tops of the storm. The edges of the pattern will show less activity than is actually happening at the fringe.

A later animation of Alex dissipating over northern Mexico and SW Texas (same radar paremeters):


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