The northerly flow of arctic air over the still-unfrozen waters of Lake Superior was aiding the development of lake effect snow (LES) bands, some of which were moving inland over the eastern portion of the Upper Peninsula of Michigan. One of the more well-defined LES bands was seen to be moving across the Grand Marais area — a cooperative observer 10 miles south of the city reported 8.5 inches of new snow during the 24-hour period from 12 UTC on 16 January to 12 UTC on 17 January.Looking farther to the south, an interesting feature was seen in the southern part of ice-covered Green Bay, Wisconsin (below): a channel through the ice (red arrows) had been cut by the US Coast Guard icebreaker Mackinaw during the evening of 14 January, to allow passage for a ship to unload cargo at a dock along the mouth of the Fox River (which empties into the southern end of Green Bay). Hat tip to the NWS Green Bay for providing the information on which icebreaker was involved. Finally, a look to the southern portion of the overpass: the Mississippi River, between the states of Louisiana and Mississippi. The Landsat satellites fly over the same portion of the Earth every 17 days, so taking advantage of this fact we can visualize the profound changes in the southern Mississippi River due to the flow of large amounts of water resulting from heavy rainfall farther to the north — over the Middle Mississippi River and Ohio River Valley regions — during December 2015 (as discussed in this blog post). Water appears as darker shades of blue in these particular Landsat RGB images, aiding in the identification of areas where flooding is occurring.
A comparison of Aqua MODIS true-color (created using bands 1/4/3) and false-color (created using bands 7/2/1) RGB images on 02 January (below) demonstrated the advantage of the false-color imagery for detection of the extent of river and lake flooding. The high sediment content of the area lakes and rivers made them appear as varying shades of tan to brown on the true-color image, making their boundaries more difficult to distinguish from the similar shades of the surrounding bare ground surfaces. (Note: when GOES-R is launched in late 2016, similar spectral bands on the ABI instrument will allow the creation of these types of true-color and false-color RGB images)A more detailed view of flooding across the eastern portion of the MODIS images (in southern Indiana and northern Kentucky) was provided by 30-meter resolution Landsat-8 false-color imagery, as visualized using RealEarth (below). A magnified view of the Evansville, Indiana / Owensboro, Kentucky area can be seen here. Maps of total observed precipitation and departure from normal (below) during the same 14-day period as the 2 MODIS false-color images shown at the top of the blog post revealed that widespread areas received upwards of 8-10 inches of rainfall, which was 6-8 inches above normal for that 2-week period of time. As a result of water runoff from the heavy precipitation, new records for maximum river gauge height were set for the Mississippi River at Cape Girardeau, Missouri and Thebes, Illinois (below). Additional information is available from the NWS Paducah.
Persistent southerly to westerly flow over the Pacific Northwest has allowed a series of disturbances to produce rain each day so far this month in Seattle, including a record rainfall on December 7th (a day that was particularly dark, given the extensive clouds and the low sun angle: Link). (Update: Seattle also had record daily rainfall on 8 December.) The GOES-15 Water Vapor animation, above, from 0000 UTC on 6 December through 2100 UTC on 8 December (available here as an mp4 file) shows that series of impulses on the south side of a strong circulation in the Gulf of Alaska (Surface Analysis), and later scenes suggest a jet extending to the southwest. MIMIC Total Precipitable Water, below, for the 72 hours ending at 1700 UTC on 8 December, shows the signature of an atmospheric river moving moisture towards the Pacific Northwest coast, auguring rain. The broad southerly and southwesterly flow has meant above-normal temperatures as well (Seattle recorded a daily record high maximum — 60 F — on December 8).
The Aqua Satellite, carrying a MODIS (MODerate resolution Imaging Spectroradiometer) instrument, overflew the Pacific Northwest at about 2045 UTC on 8 December. The MODIS instrument senses radiation at 1.38 µm, a water vapor channel that is particularly sensitive to Cirrus Clouds (GOES-R will also detect radiation at this wavelength). The toggle below, between the 1.38 µm near-infrared and the 0.64 µm visible, shows that the storm in the Gulf of Alaska and the jet moving in from the southwest are prolific cirrus producers! Cirrus is present almost everywhere. The cirrus channel on MODIS is dark (that is, it is not detecting upper-level clouds that are inferred to be cirrus) only over the central Plains, over the Pacific Ocean west of California/Oregon and over parts of north-central Oregon and western Washington.
Historic rainfalls associated with tropical moisture and a surface low pressure system inundated portions of South and North Carolina over the weekend. During the first four days of October, Charleston SC had 17+” of rain, Downtown Charleston had more than 16″, Columbia had 11″, Myrtle Beach had 14″. In fact, new records were set for greatest 1-day, 2-day, 3-day and 4-day rainfall at Charleston and Columbia (and storm-total rainfall amounts were as high as 26.88 inches in Charleston county; click here for a YouTube video showing radar reflectivity from 1-6 October). The toggle above shows the Suomi NPP VIIRS Day/Night Band (with and without 24-hour precipitation totals ending 5 October, after the heaviest rain had moved north of Charleston) and Suomi NPP VIIRS 11.45 µm infrared imagery at 0630 UTC (2:30 am local time) — overshooting tops are evident within a band of strong convection offshore that was moving westward (inland) around the upper-level low pressure system located east of Jacksonville FL (as seen in the larger-scale version of the Day/Night Band image below).
The animation of GOES-13 10.7 µm Infrared imagery, below (click to view mp4 loop; very large animated gif file available here; a YouTube video of all GOES-13 RSO Infrared magery from 1-4 October is here), shows the evolution of the atmospheric flow pattern, from thunderstorms moving southwest-to-northeast along the coast on 1 October to thunderstorms moving directly inland, first from southeast-to-northwest late on 3 October and then to east/northeast-to-west/southwest along the coast at the end of the animation as an upper-level low developed east of Jacksonville. Multiple rounds of heavy rains occurred as the orientation of the rain bands pivoted, always overlapping South Carolina.
Much of the rain over Charleston fell between 0300 UTC on 3 October and 0700 UTC on 4 October, in two distinct events, as shown in the hourly GOES-13 Infrared image animation below. During the first bout of heavy rain that occurred late on the 2nd/early on the 3rd of October, cells moved over Charleston from the south; during the second bout of heavy rain, from the 3rd into the 4th, cells moved over Charleston from the southeast (this toggle of Total Precipitable Water from the GOES Sounder shows the convection offshore in regions of abundant moisture). The change in direction of cell motion was driven by the development of an upper-level low pressure system, as shown in the Water Vapor Imagery animation farther below. Both the thunderstorms over South Carolina and the thunderstorms supporting the evolution of Hurricane Joaquin benefited from the very moist tropical air mass that was over the Atlantic Ocean off southeast coast of the US.
A composite of the MIMIC Total Precipitable Water product and WSR-88D radar reflectivity visualized using SSEC RealEarth, below, showed how the offshore plume of high TPW became very narrow and focused on South Carolina during the 44-hour period from 18 UTC on 02 October to 14 UTC on 04 October.