Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 3:31 PM GMT on November 26, 2013
The weather gods are interfering mightily with the busiest travel period of the year in the U.S., as powerful Winter Storm Boreas plows up the Eastern seaboard, bringing a nasty mix of snow, sleet, freezing rain, heavy rain, high winds, and severe thunderstorms. Woe to ye who attempt to traverse the Pennsylvania Turnpike through Western Pennsylvania; my award for worst weather of the day goes to Somerset, PA. Tuesday's forecast calls for freezing rain of up to 1/10" ice accumulation, accompanied by 1 - 3" of snow, followed by rain and freeing rain Tuesday night, followed by another 2 - 4" of snow on Wednesday. Dangerous snowy and icy travel will dominate all the high elevation areas from the Smoky Mountains to Maine. The worst freezing rain will be in the mountains of Western North Carolina, where up to 1/4" of ice accumulation is expected. The greatest snows of 6+ inches will fall in Western New York and Northwest Pennsylvania. Rochester, NY is expected to get up to a foot of snow, due to strong northwest winds off of Lake Ontario that will add a extra lake effect boost. Six plus inches of snow are also a good bet in Pittsburgh and Buffalo.
Figure 1. Crews spray deicing solution onto an American Airlines 737 before departure at Dallas-Fort Worth International airport, Nov. 25, 2013. (AP Photo/Brandon Wade)
A very wet and windy storm for the coast
Boreas has tapped into an "Atmospheric River" of very moist air from the Gulf of Mexico, and the amount of water vapor available to make rain (the "Precipitable Water") will be near record highs (for November) along the East Coast. For example, in New York City, the Precipitable Water is expected to be near 1.7" on Wednesday morning; there has been only one higher value of Precipitable Water recorded there in November since 1948 (2.02" on November 11, 2003.) All this moisture will generate heavy rains for coastal New England and the Mid-Atlantic, with rain amounts of 3 - 4" commonplace. The low clouds and strong winds accompanying these rains will slow air travel throughout the Mid-Atlantic and Northeast. Fortunately, river levels are low due to moderate drought in much of the Northeast, and only minor flooding is expected from the heavy rains.
Accompanying the heavy rains along the coast will be high winds; a Wind Advisory for sustained winds of 20 - 30 mph, with gusts up to 50 mph, is in place along much of the coast from Delaware to Maine. While the rains will be gone on Thursday in time for the Macy's Thanksgiving Day Parade in New York City, winds will still be strong, making conditions potentially too dangerous for the balloons used in the parade. These balloons are not allowed to fly if the city experiences sustained winds of 23 mph with gusts of 34 mph. The forecast calls for sustained winds of 15 - 20 mph gusting to 40 mph on Thursday.
Figure 2. Predicted precipitation for the 3-day period ending Friday, November 29, 2013. This week's storm is expected to dump heavy rains of 3 - 4 inches along a long swath from North Carolina to Maine. Image credit: NOAA.
Category 1 Cyclone Lehar headed towards India
Dangerous Category 1 Cyclone Lehar is slowly intensifying as it heads west-northwest at 10 mph towards India's Bay of Bengal coast. Satellite images show that Lehar--which is the Hindustani word for "wave"--continues to have a large Central Dense Overcast (CDO) of high cirrus clouds over its center, which is characteristic of intensifying tropical cyclones near Category 1 hurricane strength. Lehar has not been able to form a prominent eye, and is likely having problems getting organized in the face of moderate wind shear of 10 - 20 knots. Ocean temperatures are a very warm 28 - 29°C, and Lehar should be able to attain Category 2 strength before landfall. Cooler waters near shore and an increase in wind shear as the storm nears landfall will likely mean that Lehar will be weakening as it comes ashore. Landfall is expected to occur near 06 UTC Thursday, November 28, in the Andhra Pradesh state of India. This is the same portion of the coast that Cyclone Helen hit on Friday as a tropical storm with 40 mph winds. Helen's heavy rains killed eleven people, caused widespread severe agricultural damage, and left the soils saturated, which will make the rains from Lehar doubly dangerous. Also of concern is the storm surge, which will impact a portion of the coast that is heavily populated and low-lying. The India Meteorological Agency (IMD) is predicting a storm surge of up to 2 - 3 meters (7 - 10 feet) to the right of where the eye makes landfall.
Figure 3. Cyclone Lehar over the Bay of Bengal at approximately 04:30 UTC November 26, 2013. At the time, Lehar was at Category 1 strength with top winds of 85 mph. Image credit: NASA.
An unusually active tropical cyclone season for India
In addition to Cyclone Helen, India's Bay of Bengal coast also was hit this year by Tropical Cyclone Phailin, a Category 4 storm with 140 mph winds, which killed 44 people and did $1.1 billion in damage on October 12, 2013. It's unusual for India to get hit by so many named storms in one year; the last time three or more named storms did so was in 1996, when six storms of at least tropical storm intensity hit. Only four Bay of Bengal tropical cyclones have hit India at hurricane strength since 2000, if we include Cyclone Phailin from 2013. The others were:
Category 1 Cyclone Aila of May 25, 2009, which hit near Kolkata, killing 96, causing $553 million in damage.
Category 1 Cyclone Thane, of December 30, 2011, which hit Southeast India, killing 48, causing $376 million in damage.
Category 1 Cyclone 05B, which hit Southern India on November 29, 2000, killing six.
The last major tropical cyclone to hit the portion of the coast that Lehar is threatening occurred on June 14 1996, when Category 4 Tropical Cyclone 07B struck, killing 731 people. Wunderground's weather historian Christopher C. Burt has a detailed post on India's tropical cyclone history. During the past two centuries, 42 percent of Earth's tropical cyclone-associated deaths have occurred in Bangladesh, and 27 percent have occurred in India (Nicholls, R.J.N., N. Mimura, J.C. Topping, 1995, "Climate change in south and south-east Asia: some implications for coastal areas," J Glob Environ Eng 1995;1:137–54.)
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