Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 1:33 PM GMT on June 20, 2012
Tropical Storm Chris formed Tuesday evening from a extratropical storm that spent enough time over waters of 24 - 26°C to acquire tropical characteristics. Chris is headed eastwards, out to sea, and will not trouble any land areas. Only twice before, in 1887 and 1959, has the third storm of the season formed earlier than this date. Formation of three tropical storms so early in the year is not necessarily a harbinger of an active season; 1959 was close to average, with 12 named storms, 7 hurricanes, and 2 intense hurricanes (average is 11 named storms, 6 hurricanes, and 2 intense hurricanes.) Unusual levels of early season activity in the Caribbean and between Africa and the Lesser Antilles usually portends a very active hurricane season, but this year's storms have not formed in this region. Alberto, Beryl, and Chris all formed off the U.S. East Coast.
Figure 1. Morning satellite image of Chris.
Disturbance near Cuba will bring heavy rains to Florida
An area of low pressure and heavy thunderstorms centered just south of Cuba has changed little since Tuesday, and is bringing sporadic heavy rains to Jamaica, the Cayman Islands, South Florida, the Southern Bahamas, and Cuba. This disturbance will need to be watched for development as it drifts slowly northwest at about 5 mph and enters the Gulf of Mexico late this week. The disturbance is poorly organized, and has only a modest area of heavy thunderstorms. Wind shear is a moderate to high 15 - 25 knots over the region, and the shear is predicted to remain in the moderate to high range for the next three days along the disturbance's path. Water vapor satellite loops show a region of dry air over the Southern Gulf of Mexico; strong upper-level winds out of the northwest are bringing some of this dry air into the vicinity of the disturbance, which is interfering with development. NHC is giving the disturbance a 20% chance of developing into a tropical depression by Friday morning. As the disturbance reaches the waters off the southwest coast of Florida this weekend, a strong trough of low pressure pushing off of the U.S. East Coast will be capable of grabbing the storm and accelerating it to the northeast. This is the solution of the GFS model, which takes the storm across Florida on Sunday, and into the waters off the coast of South Carolina by Monday, with the disturbance developing into a tropical or subtropical storm off the coast of South Carolina. None of the other reliable computer models is showing development of the disturbance into a tropical depression. I think it is unlikely that heavy rains from this disturbance will affect Louisiana and Texas, but it will bring heavy rains to Southwest Florida and Cuba over the next five days.
Figure 2. Morning satellite image of the tropical disturbance near Cuba.
Figure 3. Rainfall for the 5-day period ending at 8am EDT Monday as predicted by NOAA's Hydrometeorological Prediction Center. Amounts in excess of five inches (orange colors) are predicted for Southwest Florida, with an area of ten inches (yellow colors) just off the coast.
Major flooding in Duluth, Minnesota
A serious flood emergency is occurring in Duluth, Minnesota. A series of "training" thunderstorms that all passed over the same region have dumped 4 - 5 inches of rain over a wide swath of Northern Minnesota overnight and early this morning. Nearly 8 inches of rain fell in the Denfeld area of western Duluth. This is more rain than fell in the city's previous worst flood on record, which occurred August 20, 1972. Major flooding is occurring, and only emergency travel is recommended in the city due to flooded roads. A flash flood warning from the Duluth National Weather Service issued at 7am CDT said this:
We cannot stress what a major threat this is for the city of Duluth
and along the North Shore. Aging infrastructure will also play a
part in the flood threat... especially on the hillside. Highway 61
remains closed in spots with washouts... overflowing streams and
rivers...washed out culverts and washed out roads. Just because you
might be able to travel to a destination now... does not mean you
will make it in one to two hours. This is how fast this situation
may deteriorate as more rainfall moves in from the west. There is
the potential for several more inches of rain today and the utility
system and the saturated ground cannot take much more rain.
According to wunderground's weather historian, Christopher C. Burt, the all-time 24 hour precipitation record for Duluth is 5.79" on 8/22 - 8/23 1978; 4.14" was recorded on Tuesday at the airport.
Figure 4. Radar-estimated rainfall from the Duluth, Minnesota radar.
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