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Hurricane Season 2008: Hurricane Bertha (Eastern Atlantic Ocean)
07.03.08
 
July 21, 2008

Bertha Now Far in the Northern Atlantic Ocean, Fizzling

Satellite image of Bertha Credit: NASA/JPL
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The National Hurricane Center issued their final advisory on Tropical Storm Bertha on Sunday, July 20 as she had moved into the colder waters of the Northern Atlantic Ocean.

At 15:00 UTC (11:00 a.m.) EDT on Sunday July 20, Tropical Storm Bertha was still packing maximum sustained winds near 70 mph (110 km/hr) with higher gusts. Bertha has lost tropical characteristics and is expected to slowly weaken during the next day or so.

The center of Tropical Storm Bertha was located near latitude 51.3 north and longitude 35.7 west or about 850 miles (1,365 km) east-northeast of Cape Race Newfoundland and about 1020 miles (1,640 km) southwest of Reykjavic, Iceland.

Bertha was moving toward the northeast near 36 mph (57 km/hr) and this motion is expected to continue through Tuesday as she fizzles. Estimated minimum central pressure was 987 millibars on July 20.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 20 at 4:53 UTC (12:53 a.m. EDT) and Bertha was due south of Greenland. This infrared image also clearly shows that Bertha still had good circulation on Sunday the 20th.

The AIRS images show 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 Bertha. The AIRS data creates an accurate 3-D map of atmospheric temperature, water vapor and clouds, all of which are helpful to forecasters.

The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 18, 2008

NASA'S CloudSat Gives a Side View of Bertha

Bertha east of Bermuda Credit: NASA/JPL
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NASA's CloudSat satellite's Cloud Profiling Radar captured a sideways look across Bertha on July 15 as it was east of Bermuda.

The top image is from the Geostationary Operational Environmental Satellite (GOES) - 12, supplied through the U.S. Naval Research Laboratory and shows the top of Bertha at the same time as the CloudSat image below it, shows what Bertha looked like sideways.

The red line through the GOES-12 satellite image shows the vertical cross section of radar, basically what Bertha's clouds looked like sideways. The colors indicate the intensity of the reflected radar energy. The top of Bertha's clouds reach more than 13 kilometers, more than 8 miles high!

The blue areas along the top of the clouds indicate 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 this area of intense precipitation. It is likely that in the area the precipitation rate exceeds 30mm/hr (1.18 inches/hour) based on previous studies.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 16, 2008

Tropical Storm Bertha Threatens to Regain Hurricane Status

Hurricane Bertha on July 14 Credit: Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center
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Tropical Storm Bertha swept past Bermuda on July 14, 2008. The storm system had fallen from hurricane strength, but it still packed winds of 100 kilometers per hour (55 miles per hour) around the storm center. The island of Bermuda is no stranger to severe storms, and had battened down in preparation. There were widespread power outages, but no serious damage or injuries were reported, according to the Associated Press on July 15. Rip tides and surf were unusually strong not only in Bermuda, but along much of the east coast of the United States, due to the winds and waves from the storm system.

This natural-color satellite image, obtained by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite shows Tropical Storm Bertha as it appeared at 12:05 p.m. local time (15:05 UTC) on July 14, 2008. The storm system shows the hallmark spiral shape of a tropical storm system and remnants of a central eye, but its appearance was more ragged than a well-formed hurricane. As of July 15, forecasters at the National Hurricane Center were anticipating that the storm system would move away from Bermuda and rebuild in strength slightly to reach Category 1 hurricane status once again.

Text credit: Jesse Allen



July 16, 2008

Bertha's Rise and Fall

Four TRIMM images of Hurricane Bertha Top (L to R): Bertha on July 4 and 7. Bottom (L to R): July 9 and 13.
Credit: Hal Pierce
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This series of images chronicles the development and decay of the first hurricane of the 2008 Atlantic hurricane season, Hurricane Bertha. The images were taken by the Tropical Rainfall Measuring Mission (TRMM) satellite, which uses microwave and radar sensors to see both the swirling clouds and bands of rain that define the structure of the storm.

TRMM captured the first image, top left, on July 4, a day after Bertha had become a tropical storm. As shown in the large image, which covers a broader area, the storm was immediately west of the Canary Islands off the coast of West Africa. The cluster of thunderstorms had just started to take a circular shape. While the spots of red indicate there were regions of heavy rain, little organization was evident.

Bertha strengthened as it slowly moved west over the warm waters of the Atlantic Ocean. When TRMM captured the next image on July 7 at 17:03 UTC (1:03 p.m. EDT), top right, the storm was approaching its maximum intensity. Between July 7 and July 8, Bertha grew from a tropical storm with winds of 100 kilometers per hour (63 miles per hour or 55 knots) to a major hurricane (Category 3 storm) with winds of 195 km/hr (120 mph or 105 knots). At the time of the image, Bertha was intensifying from a Category 1 to a Category 3 hurricane, according to the National Hurricane Center. Not surprisingly, the storm was much more organized on July 7 than it was on July 4. A circular band of dark red defined the northern edge of the eyewall, where rain and winds were most intense. Other bands of heavy rain (yellow and green) circled the center of the storm.

The eye was larger and cloud-free when TRMM captured its next image of the storm on July 9, lower left. The eyewall was crisply defined in an arc of dark red, indicating extremely intense rain. The heavy rain in the eyewall is a good indication that a lot of heat was being released into the storm’s core, driving its circulation. This circulation was evident in the surrounding rain field, which curves around the storm in distinctive bands. When TRMM captured this image at 23:20 UTC (7:20 p.m. EDT) on July 9th, Bertha had regained Category 2 intensity with winds estimated at 170 km/hr (104 mph or 90 knots) by the National Hurricane Center.

The final image in the series was taken on July 13 at 16:20 UTC (12:20 p.m. EDT). At this stage, the storm was almost completely devoid of rain near its center. Instead, only the remains of the large outer eyewall (as evidenced by the ring of light to moderate rain shown in blue and green, respectively), wrapped around the eastern side of the storm. This is typically where the strongest winds reside, which at this time were estimated at 100 km/hr (63 mph or 55 knots) by the National Hurricane Center.

As Bertha continued to drift towards Bermuda, it began to take a more northerly track. The center passed east of the island on July 14, bringing tropical-storm-force winds that knocked out power. The storm also produced dangerous rip currents along the East Coast of the United States, likely contributing to the drowning of at least one person along the New Jersey shore, said the Associated Press. As of July 15, Bertha was expected to strengthen slightly as it pulled away from Bermuda off to the north-northeast.

Text credit: Steve Lang and Holli Riebeek



July 15, 2008

Tropical Storm Bertha Becomes Longest-Lived July Tropical Storm Ever

Hurricane Bertha, July 15, 2008 Credit: NASA/JPL
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Tropical Storm Bertha has now become the longest-lived July tropical storm in Atlantic history, surpassing the previous record of 12.25 days set by storm number two in 1916.

Bertha may still become a hurricane within the next day or so before encountering a more hostile environment.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 15, 2008 at 06:17:25 UTC.

The 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 Bertha. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

Text credit: Alan Buis, NASA/JPL



July 14, 2008

Tropical Storm Bertha in Bermuda: Rain, Wind and Heavy Surf -- Then Moving On...

Satellite image of Hurricane Bertha Credit: NASA/JPL
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On Monday, July 14, 2008, Tropical Storm Bertha was raining and blowing on Bermuda. At 8:00 a.m. EDT, tropical storm force winds were battering Bermuda, and the island was under a tropical storm warning.

At 9:05 a.m. EDT, the forecast from Bermuda Weather noted "Tropical Storm Bertha will deliver high winds and heavy rain to the Island today and tonight. Conditions improve tomorrow, but Bertha will continue to maintain an unsettled theme for the next few days." At that time at the weather station at the L.F.Wade International Airport in Bermuda reported rain with a temperature of 76 degrees Fahrenheit (24 degrees Celsius), 90% humidity, and winds from the north-northeast at 29 knots (33 mph) gusting to 41 knots (47 mph).

The latest report from the National Hurricane Center at 8:00 a.m. EDT noted that Bertha is a strong tropical storm. Maximum sustained winds are near 65 mph (100 km/hr) with higher gusts. Little change in strength Is forecast during the next couple of days.

That report placed the center of Tropical Storm Bertha near latitude 31.6 north and longitude 63.8 west or about 75 miles (120 km) southeast of Bermuda. Although Bertha's center is 75 miles away from Bermuda, its tropical storm force winds extend outward up to 140 miles (220 km) from the center, which is why the island is getting slammed with them. Sustained winds of 50 mph, with gusts to 68 mph were also recently reported at Commissioner's Point in Bermuda.

Bertha is moving toward the north-northwest at 8 mph (13 km/hr) and a turn toward the north is forecast today, followed by a gradual turn toward the northeast on Tuesday July 15. Estimated minimum central pressure is 990 millibars.

Winds aren't the only thing Bertha is bringing to Bermuda. There are large ocean swells and high surf. These dangerous conditions are expected to continue for the next day or two as Bertha starts moving past the island. Rain is another issue. Bertha is expected to produce rainfall amounts between 3 and 5 inches.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 13 at 17:29 UTC (1:29 p.m. EDT).

The 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 Bertha. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 11, 2008

Slow-Moving Bertha Expected to Pass East of Bermuda

TRIMM image of Hurricane Bertha Credit: Hal Pierce (SSAI/NASA GSFC)
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Bertha, which became a hurricane back on the 7th of July 2008, continues to slowly make its way through the central Atlantic in the general direction of Bermuda. The center of the storm is expected to pass well east of Bermuda, but tropical storm force winds could reach the islands as the system slowly drifts in the general vicinity of Bermuda over the next few days.

After becoming a hurricane on the morning of the 7th, Bertha quickly intensified and became a Category 3 storm by that same evening; however, cooler water, wind shear and dry air combined to quickly weaken Bertha back down to a Category 1 storm a day later. Continuing westward, Bertha once again found warmer waters and a more favorable low wind shear environment and responded by restrengthening back to a Category 2 storm on the evening of the 9th. The Tropical Rainfall Measuring Mission satellite (known as TRMM) has been monitoring Bertha's progress in the Atlantic. This first image was taken at 23:20 UTC (7:20 pm EDT) on July 9th, 2008 and shows Bertha after it had regained Category 2 intensity. At the time this image was taken, Bertha's maximum sustained winds were estimated at 90 knots (104 mph) by the National Hurricane Center (NHC). TRMM reveals an area of intense rainfall in the northwestern half of the eyewall (shown by the dark red arc) surrounding a well-defined, cloud-free eye (dark center). Excellent banding (curvature) is also evident in the surrounding rain field. The heavy rain in the eyewall is a good indication that a lot of heat is being released into the storm's core, driving its circulation. It can also allow for future intensification. However, despite remaining over warm water, Bertha once again weakened in response to wind shear and dry air. TRIMM image of Hurricane Bertha, southeast of Bermuda Credit: Hal Pierce (SSAI/NASA GSFC)
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In addition, on the 10th, the storm began to undergo what is known as an "eyewall replacement cycle" wherein a larger eyewall forms farther out from the center of the storm and chokes off the inner eyewall. This results in a reduction in peak intensity but a broadening of the wind field. Given time and favorable conditions, the outer eyewall can contract and become a new inner eyewall, allowing the peak intensity to rebound. The next image from TRMM was taken at 22:25 UTC (6:25 pm EDT) on 10 July. The large outer eyewall is clearly evident by the arc of heavy rain (dark red semi- circle) north of the center. A small part of the inner eyewall still remains (smaller area of moderate intensity rain shown in green near the center). At the time of this overpass, Bertha's sustained winds were estimated at 75 knots (86 mph) by NHC.

After becoming a hurricane back on the 7th, Bertha began to slow down and turn more northward due to a weaking in the subtropical ridge to its north. Weaker steering currents have allowed the storm to slow even more and Bertha is expected to drift slowly northward in the coming days but remain east of Bermuda.

TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Text credit: Steve Lang, NASA's Goddard Space Flight Center/SSAI



July 10, 2008

Bertha Forecast to Pass Just East of Bermuda and into Northern Atlantic

Credit: NASA/JPL
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A Tropical Storm Watch was posted for Bermuda on Friday, July 11, 2008 as Bertha crept closer to the island. Bertha is bringing high surf and large swells there already and that will continue into the early part of the week of July 14.

A tropical storm watch means that tropical storm conditions are possible in the watch area in 36 hours. AT 11:00 a.m. EDT (1500 Zulu Time) the center of Hurricane Bertha was located near latitude 28.5 north and longitude 62.0 west or about 310 miles (500 km) south-southeast of Bermuda.

Bertha is moving toward the northwest near 6 mph (9 km/hr) and this general motion is expected to continue today with a gradual turn to the north during the next 24 hours. On this track, Bertha's fringes will be nearing Bermuda on Saturday. Once Bertha passes Bermuda, she'll head into the open waters of the North Atlantic Ocean.

Maximum sustained winds are near 85 mph (140 km/hr) with higher gusts. Bertha is a category one hurricane on the Saffir-Simpson Scale. Estimated minimum central pressure is 980 millibars.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 10 at 16:59 UTC (12:59 p.m. EDT).

The 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 Bertha. The yellow circle in the center of the image is Bertha's eye.

Satellite image of Hurricane Bertha Credit: NASA/Jesse Allen MODIS Rapid Response Team
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The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

This natural-color image of Hurricane Bertha was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on July 9, 2008, at 14:45 UTC (10:45 a.m. Eastern Daylight Time). Shortly after, the National Hurricane Center estimated that Bertha was a Category 1 storm, with maximum sustained wind speeds of 75 miles per hour. Bertha was compact when MODIS observed it, a small ball of clouds with a long line of thunderstorms trailing away to the southeast. The eye of the storm had clouded over.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center / Rebecca Lindsay, MODIS



Hurricane Bertha Bringing Dangerous Surf to Bermuda

Satellite image of Hurricane Bertha Credit: NASA/JPL
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Even though Hurricane Bertha won't make a direct hit to Bermuda, it doesn't mean vacationers have a free pass to ocean fun. In fact, as Bertha passes to the east of Bermuda, she's kicking up dangerously large ocean swells and high surf. Those conditions will persist for the next several days as Bertha continues on her northern track.

At 11:00 a.m. EDT, the National Hurricane Center warned Bermudans in its public advisory, "It is still too early to determine the extent to which Bertha could impact Bermuda. Interests on that island should closely monitor the progress of Bertha during the next several days."

The Royal Gazette on the island of Bermuda reports that "The emergency measures organisation of the Home Affairs Minister, and representatives from the Weather Service, Harbour Radio, Police, Fire and the Regiment urged the public to continue to monitor the storm and to stay out of the sea."

At that time, on July 10, the center of Bertha was located about 485 miles (785 kilometers) southeast of Bermuda, or near latitude 26.5 degrees north and longitude 60.2 degrees west.

Bertha is moving toward the northwest near 9 mph (15 km/hr). A gradual turn toward the north and a decrease in forward speed are expected during the next couple of days, thus, the expected high surf conditions will linger in Bermuda a little longer.

Maximum sustained winds have decreased to near 90 mph (150 Km/hr) with higher gusts. That makes Bertha a category one hurricane on the Saffir-Simpson scale. While Bertha has weakened this morning, forecasters say that it could re-intensify during the next 24 hours. Estimated minimum central pressure is 977 millibars.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 10 at 5:59 UTC (1:59 a.m. EDT).

The 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 Bertha. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 9, 2008

NASA Satellites Provide Two Views of Bertha's Clouds as it Nears Bermuda

Satellite image of Hurricane Bertha Credit: NASA/JPL
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NASA can analyze hurricanes from two sides, from the top down and sideways. An instrument on NASA's Aqua satellite provides a look at the temperatures of Bertha's cloud tops, while NASA's CloudSat gives a sideways slice of the storm. Both provide indications of the storm's strength.

At 11:00 a.m. EDT on Wednesday, July 9, Hurricane Bertha seemed to again be getting better organized after reaching Category 3 strength earlier in the week before falling to Category 1 strength yesterday.

The National Hurricane Center noted in its discussion on July 9 at 11:00 a.m. EDT, "Bertha's cloud pattern has improved this morning and the eye appears to be reforming. The initial intensity remains at 75 mph… but Bertha looks to be in the process of strengthening. The intensity forecast continues to be challenging."

At 11:00 a.m. EDT the center of Hurricane Bertha was located near latitude 24.2 north and longitude 57.5 west or about 550 miles (885 km) northeast of the northern Leeward Islands and about 715 miles (1,150 km) southeast of Bermuda.

Maximum sustained winds are near 75 mph (120 km/hr) with higher gusts. Some strengthening is forecast during the next 24 hours.

Bertha is now moving toward the west-northwest near 12 mph (19 km/hr). A gradual turn toward the north-northwest with a decrease in forward speed is expected during the next couple of days. Estimated minimum central pressure is 987 millibars.

In this infrared image from July 9 at 5:17 UTC (1:17 a.m. EDT), was created by data from the Atmospheric Infrared Sounder (AIRS), another instrument on NASA's Aqua satellite. It provides a top-down look at the hurricane.

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 Bertha. This infrared image shows large areas of stronger convection surrounding the core of the storm (in purple). There is no visible eye in this AIRS image, as it would appear as a yellow dot in the center of the blue and purple area.

Satellite image of Hurricane Bertha Credit: NASA/JPL/Colorado State University/Naval Research Laboratory-Monterey
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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).

NASA's CloudSat satellite's Cloud Profiling Radar captured a sideways look across Hurricane Bertha as she continues to approach Bermuda.

The top image is from the European Space Agency's Meteosat Second Generation (MSG) - 2 satellite from July 5 and the image was supplied through the U.S. Naval Research Laboratory.

The image on the bottom is from NASA's CloudSat satellite also taken on July 5. The red line through the MSG-2 satellite image shows the vertical cross section of radar, basically what Bertha's clouds looked like sideways. The colors indicate the intensity of the reflected radar energy. The top of Bertha's clouds are just over 14 kilometers, or approximately 8.7 miles high.

The blue areas along the top of the clouds indicate cloud ice. Notice that the solid line along the bottom of the panel, which is the ground, disappears in the center area of heavy precipitation. It is likely that in the area the precipitation rate exceeds 30mm/hr (1.18 inches/hour) based on previous studies.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 8, 2008, second update

Atlantic's Big Bertha Back to Category 2

Satellite image of Hurricane Bertha Credit: NASA/Jeff Schmaltz, MODIS Rapid Response Team
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By mid-day on July 8, Hurricane Bertha was still packing maximum sustained winds near 105 miles per hour, making her a Category 2 hurricane on the Saffir-Simpson scale. Earlier in the day she was a Category 3 storm with sustained winds near 10 mph.

At 11:00 a.m. EDT (1500 Zulu Time) on July 8, the center of Hurricane Bertha was located near latitude 22.1 degrees north and longitude 53.8 degrees west or about 660 miles (1.065 km) east-northeast of the northern Leeward Islands and about 975 miles (1,570 km) southeast of Bermuda.

Bertha is moving toward the northwest near 10 mph...17 km/hr...and it's expected to continue tracking in that direction over the next couple of days, but at a slowing pace. Estimated minimum central pressure is 970 millibars.

Forecasters at the National Hurricane Center noted in their discussion that "conventional and microwave imagery show a rapid degradation of Bertha's structure during the last 6 hours. The eye has disappeared and cloud tops have warmed considerably." They noted that Bertha has encountered the wind shear (winds that blow in different directions at different levels of the atmosphere that weaken or tear a storm apart) that they had forecast it would encounter.

Right now, Bertha is forecast to pass to the east of Bermuda over the weekend while maintaining hurricane strength. That would mean some very rough and dangerous waters would be generated for vacationers on the island.

This natural-color satellite image, obtained by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite shows Hurricane Bertha as it appeared at 1:30 p.m. local time (16:30 UTC) on July 7, 2008. The hurricane was a Category 1 storm at this time, but it intensified to Category 3 within hours of this MODIS observation. Bertha appears as a well-developed system, with tightly wound spiral arms wrapping around a well-formed and distinct eye at its center. The afternoon sun shining on the cloud tops also casts a deep shadow into the center of the storm where the steep eyewall begins.

Text credit: Rob Gutro and Jesse Allen, NASA's Goddard Space Flight Center



July 8, 2008, first update

Bertha Bumps to a Category Three Hurricane in the Atlantic

Hurricane Bertha bumped up in strength from a Category one hurricane on July 7 to a Category three storm on July 8.

At 5:00 a.m. Atlantic Standard Time (5 a.m. EDT), Hurricane Bertha was located near latitude 21.4 north and longitude 53.3 west or about 675 miles (1,085 km) east-northeast of the northern leeward islands and about 1035 miles (1,660 km) southeast of Bermuda.

Maximum sustained winds are near 120 mph (195 km/hr) with higher gusts. Bertha is a category three hurricane on the Saffir-Simpson Hurricane scale. The National Hurricane Center notes that "some fluctuations in intensity may occur today, but a gradual weakening trend is expected to begin within the next couple of days."

Bertha is moving toward the northwest near 10 mph (17 km/hr) and this general motion is expected to continue for the next 48 hours. Minimum central pressure is 955 millibars.

Bertha's History

On Monday, July 7th, 2008, Tropical Storm Bertha, which had been steadily making its way westward across the central Atlantic over the past several days, finally intensified and became the first hurricane of the 2008 Atlantic season. Bertha began as the 2nd tropical depression of the season (td #2). Td #2 formed on the morning of July 3, 2008 about 250 miles south-southeast of the Cape Verde Islands from a strong tropical wave moving off of the coast of Africa. Storms that form in this region are known as "Cape Verde" storms. Although not unusual, Cape Verde storms most often occur in August and September during the height of the season.

Soon after it formed, td #2 became a little better organized and was upgraded to Tropical Storm Bertha. Over the next few days, Bertha continued to track to the west-northwest along the southern periphery of a subtropical ridge to its north. The storm's intensity varied little despite a low-wind shear environment due to marginal sea surface temperatures.

Satellite image of Hurricane Bertha Credit: Hal Pierce, NASA/SSAI
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The Tropical Rainfall Measuring Mission satellite (known as TRMM) is a joint mission between NASA and the Japanese space agency JAXA that scientists use to study the rainfall in hurricanes and tropical cyclones. TRMM was placed into service in November of 1997. From its low-earth orbit, TRMM has been providing valuable images and information on tropical cyclones around the tropics using a combination of passive microwave and active radar sensors, including the first precipitation radar in space.

This set of images was taken by TRMM at 16:37 UTC (12:37 p.m. EDT) July 4, 2008 as Bertha was moving through the central Atlantic. The first image shows the horizontal pattern of rain intensity. Rain rates in the center swath are based on the TRMM precipitation radar (PR), and those in the outer swath on the TRMM microwave imager (TMI). The rain rates are overlaid on infrared (IR) data from the TRMM visible infrared scanner (VIRS). Despite the cyclonic pattern in the clouds (white semi-circular arcs) and the weak banding (curvature) evident in the rain field (green arcs), the center lacks any semblance of an eye and the overall rain area (blue and green areas) is rather limited. An area of intense rain (darker reds) is located near the center.

Satellite image of Hurricane Bertha Credit: Hal Pierce, NASA/SSAI
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The second image was taken at the same time and shows a 3d image of the storm courtesy of the TRMM PR. The most prominent feature is a deep convective tower (shown in red), which reaches over 15 kilometers (9.3 miles) high. This is associated with the area of intense rain in the previous image. These tall towers are associated with convective bursts and can be a sign of future strengthening as they indicate areas within the storm where heat, known as latent heat, is being released.

This heating is what drives the storm's circulation. However, Bertha was also in the process of passing over cooler sea surface temperatures, which kept intensification in check. At the time of these images, bertha was a moderate tropical storm with maximum sustained winds reported at 45 knots (52 mph) by the National Hurricane Center (NHC).

As Bertha continued on its westward track, it finally began to encounter warmer waters, allowing it to intensify. A weakness in the subtropical ridge is expected to allow the storm to recurve to the north over the next few days, although it could still pose a threat to Bermuda. On average, the first hurricane of the season usually forms by mid-August. Last year, dean became the first hurricane of the season on august 16th. Back in 1996, the first hurricane of the season also formed on July 7th and was also named Bertha. Hurricanes names are recycled every six years unless retired.

Text credit: Steve Lang, NASA's Goddard Space Flight Center/SSAI



July 7, 2008

Bertha: The Atlantic's First Hurricane in 2008

Satellite image of Hurricane Bertha Credit: NASA/JPL
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Tropical Storm Bertha formed in the far eastern Atlantic on July 3 and strengthened quickly into a tropical storm that same day. By 4:00 a.m. EDT on Monday, July 7, Bertha became a hurricane.

By 10 a.m. EDT on July 7, forecasters at the National Hurricane Center noted that Bertha could strengthen to a Category 2 hurricane. Meanwhile, Bertha was located at 10:00 a.m. EDT near latitude 19.6 north and longitude 51.3 west or about 775 miles (1250 km) east of the northern Leeward Islands.

Bertha was moving toward the west-northwest near 15 mph, and a gradual turn towards the northwest with a reduction in forward speed is expected over the next couple of days.

Maximum sustained winds are near 90 mph with higher gusts. Some strengthening is forecast during the next 24 hours...and Bertha could become a category two hurricane later today or tonight. Estimated minimum central pressure is 975 millibars. Bertha is currently forecast to pass just east of Bermuda on Saturday, July 12, but the forecast track is subject to change.

This infrared image of Bertha was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. The image was created on July 7 at 16:23 UTC (2:23 p.m. EDT).

The 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 Bertha. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center



July 3, 2008

Eastern Atlantic Ocean Births Bertha: 2nd Atlantic Named Storm Forms

GOES image of Tropical Storm BERTHACredit: NOAA/NASA GOES Project At 11:00 a.m. EDT, the day before Independence Day, July 3, Tropical Storm Bertha was born in the far eastern Atlantic Ocean.

Bertha is the second tropical storm of the 2008 Atlantic Season. She formed near the Cape Verde Islands, off the western African coast. At the time of her birth, she was already raining on the southern Cape Verde Islands with her outer rainbands. Locally heavy rainfall and gusty winds will continue in portions of the Cape Verde islands until noon Eastern Daylight Time on July 4.

Specifically, Bertha's center was located near latitude 13.3 north and longitude 24.7 west or about 190 miles (310 km) south-southwest of the Cape Verde Islands. Bertha is moving toward the west-northwest near 14 mph (22 km/hr) and is expected to continue doing so over the next couple of days. Her maximum sustained winds are near 40 mph (65 km/hr). Estimated minimum central pressure is 1006 millibars. The National Hurricane Center forecasts some gradual strengthening over the next day or two.

This satellite image was captured on July 3 at 1:23 p.m. EDT from Geostationary Operational Environmental Satellite (GOES-11). In the image, Bertha is located in the far right of the satellite image, just west of the African coast. GOES is operated by the National Oceanic and Atmospheric Administration. It was created by NASA's GOES Project, located at NASA's Goddard Space Flight Center, Greenbelt, Md.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center