NASA - National Aeronautics and Space Administration

Debby's Demise on Sunday Aug. 27

The last advisory from the National Hurricane Center (NHC) on what was Tropical Depression Debby as Sun. Aug. 27, at 4:00 p.m. EDT, as Debby lost most tropical characteristics. At that time, the center of Debby was located near latitude 31.5 north, longitude 48.6 west or about 1300 miles west-southwest of the Azores islands. The depression was moving toward the north near 17 mph, and Debby had maximum sustained winds of 30 mph. Estimated minimum central pressure was 1012 millibars. By 5:00 p.m. EDT, the NHC reported that because of the lack of persistent organized convection, Debby was no longer a tropical cyclone.

---

Tropical Storm Debby to Curve Toward North Atlantic

Tropical Storm Debby is spinning in the open Atlantic Ocean and poses no threat to the U.S. mainland. These two satellite images are from two different satellites, giving a top-down and sideways view of Tropical Storm Debby, spinning in the open Atlantic Ocean on Aug. 25, 2006.

Two Satellite Views: Top and Sideways


Click image to enlarge.

The top image is from the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES) to give an idea of how the storm looked from the top. This data was processed by NASA's GOES Project at the Goddard Space Flight Center, Greenbelt, Md. The bottom images are from CloudSat.

The CloudSat image (bottom) was taken from NASA's CloudSat satellite on Aug. 24 at approximately 12:18 a.m. EDT (04:18 UTC). The black line depicts where CloudSat looked at Tropical Storm Debby, closer to the left edge of the storm. That being the case, the CloudSat image shows less cloud cover to the left, which matches with the clouds (blue) in the GOES image above left of the black line.

The red and purple areas on the CloudSat image (bottom) indicate large amounts of cloud water. The blue areas along the top of the clouds indicates cloud ice, while the wavy blue lines on the bottom center of the image indicate intense rainfall. Notice that the solid line along the bottom of the panel, which is the ground, disappears in these areas of intense precipitation. It is likely that in the area the precipitation rate exceeds 30mm/hr (1.18 inches/hour) based on previous studies.

Where is Tropical Storm Debby and What is Her Future?

The National Hurricane Center (NHC) forecast for Tropical Storm as of 5:00 a.m. EDT (09:00 UTC) on Aug. 25, places Debby's center near 22.9 North and 42.3 West. She's about 1285 miles west-northwest of the Cape Verde Islands (off the African coast). Debby's movement is toward the west-northwest near 17 mph. Debby's estimated minimum central pressure is 1000 millibars, and maximum sustained winds are near 50 mph.

The NHC forecast discussions on Aug. 24 at 5 a.m. EDT referred to looking at data from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite, that showed the low and middle parts of the storm don't line up well. That means that higher in the atmosphere (where the middle part of the storm is) winds are blowing in a different direction (southerly in this case), and "shearing" or pulling at the storm, weakening it. However, Debby is about to move over warmer waters and that could help the cyclone to strengthen a little. Image credit: NASA/JPL/The Cooperative Institute for Research in the Atmosphere (CIRA), Colorado State University/NOAA (+ Large Version of Image)

---

Tropical Depression #4 Now Tropical Storm Debby in the Atlantic Ocean

The National Hurricane Center (NHC) reported that Tropical Depression Four became Tropical Storm Debby on Tuesday night at 10 p.m. EDT.

At 4:00 a.m. EDT, on Wed. Aug. 23, Tropical Storm Debby was located near 15.9 North latitude and 30.1 West. Debby was moving toward the west-northwest near 16 mph, and had maximum sustained winds near 45 mph. Minimum central pressure was 1002 millibars. NHC forecasters looked at NASA's Aqua satellite microwave data (like these images) and determined Debby continues to improve and get organized. A satellite overpass during the early morning of Aug. 23 detected a fairly well organized system with well defined rain bands around Debby's center.

Where is Debby Headed?

According to the latest NHC Forecast track, Debby will likely strengthen into a minimal hurricane by Sunday, Aug. 27, and begin turning northward into the northern Atlantic, staying far to the east of Bermuda.



An Inside Satellite Look at Debby's Clouds

This is an infrared image of Tropical Depression Debby in the Atlantic, from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite on Aug. 22, 2006. This AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud- free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. The infrared signal does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the Earth, revealing warmer temperatures (red). At the time the data were taken from which these images were made the eye had not yet opened but the storm is now well organized. The location of the future eye appears as a circle in the microwave image just to the SE of the Azores (Islands).



Where is Debby's Heaviest Rainfall?

The second image is created from microwave radiation emitted by Earth's atmosphere and received by the instrument. It shows where the heaviest rainfall is taking place (in blue) in the storm. Blue areas outside of the storm where there are either some clouds or no clouds, indicate where the sea surface shines through.



What Does Debby Look Like to the Eye?

Tropical Depression Debby is captured here by the visible light / near-infrared sensor on the AIRS instrument. This is what Debby looks like to the naked eye. Image Credit: NASA/JPL. Caption Credit: NASA/JPL/ Rob Gutro Goddard

---

Hurricane Season Kicking Up on Both Coasts

Click image to enlarge.

Tropical Depression Four formed in the far eastern Atlantic Ocean the evening of Aug. 21, 2006, is headed into the open Atlantic, and is expected to strengthen. There are now two storms in the eastern Pacific Ocean, Hector and now Ileana.

This is an image from the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES) on Tues. Aug. 22. This data was processed by NASA's GOES Project Science Office at the Goddard Space Flight Center, Greenbelt, Md. In this GOES satellite image of the northern hemisphere, Tropical Depression #4 (TD4) can be seen on the far right off the African coast. On the far left, off the southwestern coast of Mexico, is Tropical Storm Ileana.

Tropical Depression #4 In the Atlantic Set to Strengthen

At 7:00 a.m. EDT, on Aug. 22, Tropical Depression Four (TD#4) had maximum sustained winds are near 35 mph (55 km/hr) with higher gusts. The depression is forecast to become a tropical storm during the next 24 hours, according to the National Hurricane Center.

At 8:00 a.m. EDT, TD #4 continues moving west-northwestward near 16 mph to the south of the Cape Verde islands. A turn toward the northwest is expected today. The center of tropical depression four was located near latitude 13.0 north, longitude 25.2 west or about 130 miles south-southwest of the southernmost Cape Verde Islands, off the African coast. Estimated minimum central pressure is 1007 millibars.

A tropical storm warning remains in effect for the Cape Verde Islands today, Aug. 22, as TD #4 is currently passing to the south and southwest of them. Outer rain bands and squalls will continue to affect the southern Cape Verde Islands today. Rainfall amounts of 2 to 4 inches, with isolated maximum amounts of 6 inches in areas of higher terrain are possible over the southernmost Cape Verde Islands in association with the depression. These rains could cause life-threatening flash floods and mud slides.

NASA is On-Location at the Cape Verde Islands for TD #4

Coincidentally, NASA scientists are currently operating a field mission to study the birth of hurricanes. The mission, called NAMMA, the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign is a NASA-sponsored field research investigation using multiple research and observation methods to study the formation and evolution of tropical hurricanes in the eastern and central Atlantic; their impact on the U.S. east coast; the composition and structure of the Saharan Air Layer; and how aerosols may affect cloud precipitation and cyclone development. + NAMMA website

Ileana and Hector Churn in the Eastern Pacific

Meanwhile in the eastern Pacific Ocean, there are two systems that the National Hurricane Center is watching, although both are not expected to affect land. Tropical Storm Ileana as of 2:00 a.m. PDT (9:00 UTC) on Aug. 22, was located off the south-western Mexican coast near 14.0 North and 105.6 West. Ileana can be seen in this satellite image, churning to the left of Mexico. Ileana's movement is toward the west-northwest at around 12 knots (14 mph). Ileana's maximum sustained winds were 45 knots (52 mph) with gusts to 55 knots (63 mph).

Tropical Storm Hector has been struggling in the last couple of days, but the National Hurricane Center predicts dissipation by Aug. 23 or 24 as Hector enters cooler waters and stable air. At 2:00 a.m. PDT on Aug. 22, Hector was located far west of Ileana in the open ocean, near 22.4 North and 136.5 West. Hector isn't visible on this satellite image, because he's hidden by the curvature of the Earth and far to the left of Ileana. Hector's movement is toward the west-northwest at around 4 knots (5 mph). Hector's maximum sustained winds were 35 knots (40 mph) with gusts to 45 knots (52 mph). Credit: NASA GSFC/NOAA. Caption: Rob Gutro, NASA GSFC.