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 , 4:54 PM GMT on August 05, 2011
Tropical Storm Emily degraded into an open tropical wave yesterday afternoon, after Hurricane Hunters could no longer locate a center of circulation at the surface. Through the morning yesterday, the storm appeared to lose most of its strong thunderstorm activity on the north side, and mid-level circulation was broad (tropical cyclones need a tight, coherent circulation to maintain themselves). Soon after the Hurricane Hunters took a pass through the storm, the National Hurricane Center demoted Emily from a tropical storm to a remnant low, while continuing to stress the rainfall threat to Hispaniola and eastern Cuba. Today it appears the center of the remnants are located just north of eastern Cuba in the southern Bahamas, although thunderstorm activity continues across eastern Cuba. Hispaniola probably saw rain and thunderstorms again early this morning, the strongest of which were on the eastern side of the island. New thunderstorm activity is starting to develop in the southeast Bahamas. Given Wednesday's rain gauge analysis from CPC, Hispaniola probably saw at least an additional 5 inches of rain yesterday.
Environmental conditions remain pretty much the same as yesterday, but are expected to become more favorable for Emily's remnants, and redevelopment of the storm is possible. Circulation from the low to mid-levels is still broad and tilting to the east with height due to the lingering moderate westerly wind shear. However, this shear is expected to dissipate some over the next 24 hours, and signs of this are already present to the west of the remnants. The dry air that has been following the storm since its inception has dissipated, as well.
Figure 1. Satellite imagery of the remnants of Tropical Storm Emily as they move northwest away from Cuba and Hispaniola and into the Bahamas.
Forecast for Emily's Remnants
Interestingly, the models have come into better agreement on the forecast for former Emily now that it has lost its surface circulation and degenerated into a tropical wave. The ECMWF, which has come out ahead in this forecasting game so far, is optimistic today that Emily will redevelop. Other global models—GFS, CMC, and FIM—also redevelop the storm. Consensus on timing of redevelopment seems to be when the wave reaches the northern Bahamas in 24 to 48 hours. At 12Z (8am EDT), the high-resolution HWRF model run forecasted a track that was furthest to the west of all the models, scraping eastern Florida as it travels northwest. The most probable track and intensity forecast that I see at this point is north-northwest movement over the next 24 to 36 hours, at which point the system will take a fairly sharp turn to the northeast and out to sea. Without an already established, coherent circulation, it appears unlikely that if Emily is reborn it will intensify into anything more than a moderate tropical storm. However, there is some potential as the system moves out to see that it could gain some strength and develop hurricane-force winds before it transitions into an extra-tropical cyclone.
Typhoon Muifa passes to the south of Okinawa, heads into East China Sea
The center of Typhoon Muifa passed to the south of Okinawa earlier this morning (Eastern time) and it continues to batter the islands with high winds and torrential rain. Local radar estimate rainfall rates as high as 80 mm/hour (approx. 3 inches/hour) in the strongest rain bands. Kadena Air Force Base near the city of Okinawa has been reporting sustained winds of 47 mph with gusts up to 72 mph. Muifa is expected to turn northwest today as it enters the East China Sea as a category 1 on the Saffir-Simpson scale, and then intensify into a category 2 as it passes close to eastern China. This morning, the forecast is that Muifa will probably not make landfall anywhere as a typhoon.
Figure 2. Radar imagery from the Japan Meteorological Agency around 1am JST. Scale is in millimeters. Highest rainfall rates appear to be approximately 3 inches/hour.
South-Central U.S. continues to bake
The extreme heat continues again today after 269 high maximum and 250 high minimum temperature records were set yesterday, 19 and 29 of which were all-time records, respectively. 206 of yesterday's records were 110°F or higher. Yesterday, Reuters was reporting that Texas was one power plant shutdown away from rolling blackouts. The forecast today doesn't look any better. Heat index values up to 125° are forecast in eastern Texas and the Lower Mississippi Valley.
Particularly toasty heat index values from yesterday:
• Mobile, Alabama: 120°
• Arkadelphia, Arkansas: 121°
• Bay St. Louis, Mississippi: 121°
• Memphis, Tennessee: 122°
Figure 3. Heat index forecast from the ECMWF for today. Scale is in degrees Fahrenheit. You can plot model forecasts using Wundermap by choosing the "Model Data" layer.
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