Arizona wildfires spread smoke 1,000 miles; 94L little threat to develop

Smoke from Arizona's third largest fire on record, the massive Wallow fire, has now blown downwind over 1,000 miles to Iowa. The fire, which is 0% contained, is expected to rage full-force for at least three more days due to unfavorable weather. Hot, dry, and windy weather is predicted again today over Eastern Arizona, where NOAA has issued red flag warnings for critical fire conditions. A large trough of low pressure is anchored over the Southwest, and several disturbances rippling along this trough will bring strong southwesterly surface winds of 20 - 30 mph, with gusts near 35 mph, through Thursday. Extremely low humidities of 5 - 15% and hot summer temperatures are also expected, creating a dangerous fire weather situation. Yesterday, Luna, New Mexico, located about 50 miles northeast of the fire, had wind gusts in excess of 30 mph for 8 hours, temperatures near 80°F, and humidities as low as 12%. During the day yesterday, the fire grew from 300 square miles to 365 square miles, 30% of the size of Rhode Island. A separate fire burning in Southeast Arizona, the 163-square-mile Horseshoe Two fire, is the state's 5th largest fire on record. According to the Interagency Fire Center, 3.5 million acres have burned in the U.S. so far this year, the most on record for this early in the year--and more than double the 10-year average from 2001 - 2010 of 1.4 million acres. Extreme to exceptional drought conditions over most of Texas, New Mexico, and Eastern Arizona are largely responsible for the record fire season.


Figure 1. Active wildfires and smoke as visualized at 9am EDT June 7, 2011 using our wundermap for the U.S. with the Fire layer turned on. Smoke from the Wallow fire and Horseshoe Two fire in Arizona extended more than 1,000 miles, covering most of the Midwest.


Figure 2. Smoke billows from the rapidly growing Wallow fire in Eastern Arizona in this image taken by NASA's Aqua satellite on June 6, 2011. The fire beneath the smoke is outlined in red. A large pyrocumulus cloud spawned by the fire is visible along the Arizona-New Mexico border. Pyrocumulus clouds are produced by the intense heating associated with fires or volcanic eruptions. Image credit: NASA Natural Hazards website.

Caribbean disturbance 94L little threat to develop
The large, disorganized tropical disturbance (Invest 94L) in the Western Caribbean near Jamaica is looking much less organized this morning, but is still capable of bringing heavy rains as it pushes slowly northwards at less than 5 mph. Satellite estimates of rainfall for the 24-hour period ending at 8pm EDT Monday night run as high as 5 inches for northeastern Nicaragua and Honduras, with 2 - 4 inches falling over portions of Jamaica and southeast Cuba. Satellite loops show a decrease in the heavy thunderstorm activity and organization of 94L in recent hours, and the storm's low-level spiral bands and upper-level outflow are very poorly defined. The storm's center of low pressure is located about 100 miles south-southeast of Grand Cayman Island. Water vapor satellite loops show the Caribbean is quite moist, and water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm. Wind shear has edged into the high range, 20 - 25 knots, which has probably contributed to 94L's deterioration.


Figure 3. Morning satellite image of 94L.

Since 94L is so large and poorly organized, today's mission by the Hurricane Hunters has been cancelled. The storm is moving slowly to the north, into a band of very high wind shear of 30 - 50 knots that lies over Cuba and the southern Bahama Islands. The SHIPS model predicts shear will rise above 30 knots by late tonight, which will make development into a tropical depression difficult. This morning's 00Z and 06Z model runs were unimpressed with 94L, with most of them showing little or no development. The 00Z run of the NOGAPS model predicts that a gap may open up in the shear sufficient for the storm to organize into a tropical depression late this week, but this is looking increasingly unlikely. At 8am EDT today, NHC gave 94L a 20% chance of developing into a tropical depression by Thursday. Regardless of development, 94L is capable of bringing heavy rains of 2 - 4 inches to Jamaica, eastern Cuba, the Cayman Islands, and Haiti through Thursday. These rains will probably spread northwards into the Bahama Islands, and possibly South Florida, by Thursday or Friday.

Jeff Masters