WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

91L develops a closed circulation; monsoon floods in India kill over 250

By: Dr. Jeff Masters, 2:06 PM GMT on October 06, 2009

A tropical wave (91L) near 17N, 52W, about 550 miles east of the Lesser Antilles Islands, continues to generate considerable heavy thunderstorm activity as it moves northwest at 15 mph. The wave is under high wind shear, 20 - 25 knots, and is over warm waters, 29°C. This morning's QuikSCAT pass showed no closed circulation, and top winds of 30 mph. However, satellite loops show that 91L now has a closed surface circulation, though strong upper-level winds out of the west are keeping the heavy thunderstorm activity confined to the east side of the center. Since there is not much dry air to the storm's west, the shear will not have as great a negative impact as we've seen in similar high-shear situations this year.

None of the computer models develop the wave, and they show moderate to high wind shear affecting 91L over the next 2 - 3 days. The storm will be steered northwest for the next 2 - 3 days by a trough of low pressure passing to the north. The northern Lesser Antilles may see some heavy rain showers and gusty winds from the southern portion of 91L on Thursday and Friday. By Friday, the trough will have passed far to the east, and high pressure will build in, which may force 91L to the southwest into the Caribbean, according to some model projections. Wind shear is expected to fall to the low to moderate range 3 - 5 days from now. If 91L holds together for the next 2 - 3 days and avoids interaction with the high mountains of Hispaniola late this week, the storm could be trouble. NHC is currently giving 91L a low (less than 30% chance) of developing into a tropical depression by Thursday, and the Hurricane Hunters are not on call to fly the storm. I think the storm has more potential to develop than NHC does, and put the odds of development over the next two days at medium (30 - 50%).

Figure 2. latest images of Invest 91L.

Pacific typhoons
In the Philippines, Tropical Storm Parma circled back and has struck the northwest corner of the Philippines' Luzon island today. Parma dumped over sixteen inches of rain on northern Luzon in its first pass over the island last weekend, and is expected to dump another 1 - 2 inches today.

Typhoon Melor has weakened to a Category 3 typhoon south of Japan, and is expected to hit Japan Thursday morning as a Category 2 storm. Melor is expected to track near or over Tokyo as a tropical storm on Thursday afternoon.

Monsoon floods in India kill 269
India's monsoon officially ended on October 1, but an unusually slow-to-depart monsoon dumped unprecedented rains in Karnataka and Andhra Pradesh states in southern India over the past week, generating massive flooding that has killed at least 269 people and left 2.5 million homeless. Rainfall last Thursday in the city of Karwar exceeded .5 meters (19 inches) in a single day. Rain from the deluge ran off into the Krishna River in Andhra Pradash state, where the local information minister stated, "This is known as PMF or possible maximum flood, which happens once in 10,000 years".

Disastrous monsoon floods are common in India and surrounding nations, and the annual death toll from monsoon floods exceeds 1,000 in India, Bangladesh, Nepal, and Pakistan. Over 2,000 people died last year in monsoon floods in South Asia. The greater concern is when the monsoon rains fail, as sometimes happens during El Niño years. This year's El Niño led to substantial drought over much of India, and the 2009 Indian Monsoon is among the five worst monsoons in the recorded history (since 1871). The five worst monsoons along with the rainfall deficits for India have been:

1) 1877, -33%
2) 1899, -29%
3) 1918, -25%
4) 1972, -24%
5) 2009, -23%

Up until the late 1960s, it was common for the failure of the monsoon rains to kill millions of people in India. The drought of 1965 - 1967 killed at least 1.5 million people. However, since the Green Revolution of the late 1960s--a government initiative to improve food self-sufficiency using new technology and high-yield grains--failure of the monsoon rains has not led to mass starvation in India. While there are concerns about food shortages due to the summer drought, and now the October monsoon floods, the days of mass starvation in India due to drought and flood are past, thankfully.

Climate change poses a significant challenge to India, as more intense droughts and greater floods are likely to occur in India as the climate warms. Wunderground's climate change blogger Dr. Ricky Rood just completed a trip to India, and wrote a nice 3-part series about the challenges India faces due to climate change.

Figure 2. Rainfall this year in India has been 23% below average, the 5th worst monsoon since 1871. Image credit: India Meteorological Department.

A plug for Portlight
The Portlight.org disaster relief charity has been doing some great work this past week, and delivered a truck full of relief supplies over the weekend to victims of the Atlanta, GA floods. Portlight is also preparing a shipment of supplies for disabled people to the tsunami victims of Samoa. If you haven't stopped by their blog lately, take a look at the latest stories and photos.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.