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Bertha (Atlantic Ocean)
August 6, 2014

[image-172]Satellite Shows Bertha Merged with Frontal System in North Atlantic

A visible satellite image from NOAA's GOES-East satellite shows that Post-Tropical Storm Bertha was merging with a frontal system in the North Atlantic Ocean.

The visible image from 1200 UTC (8 a.m. EDT) on August 6 was created at the NASA GOES Project, located at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The image was created from data from NOAA's GOES-East satellite and the circulation center of Bertha is barely discernable. Bertha's circulation was connected to a stationary front that stretched from northeastern Canada to the Bahamas creating what looks like a giant tail stretching from the low pressure area. Satellite imagery showed that there were no strong thunderstorms associated with Bertha's center.

At 11 a.m. EDT, the National Hurricane Center (NHC) noted that Bertha acquired extra-tropical characteristics. Bertha had maximum sustained winds near 50 mph (85 kph). It was centered near 40.2 north latitude and 62.7 west longitude, about  305 miles (495 km) south of Halifax, Nova Scotia, Canada.  Bertha had maximum sustained winds near 50 mph (85 kph) and was speeding to the northeast at 31 mph (50 kph).

The NHC noted that the low is moving toward the northeast and is being steered by the mid-latitude westerlies [winds]. Most of the global models keep the post-tropical cyclone moving rapidly northeastward and then eastward over the North Atlantic.

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


[image-140][image-156]Aug. 05, 2014 - NASA's Aqua Satellite Puts Two Eyes on Hurricane Bertha

Two instruments or "eyes" from NASA's Aqua satellite were peering at Hurricane Bertha in the North Atlantic Ocean shortly after it became the season's second hurricane. Bertha's hurricane status didn't last long as it weakened to a tropical storm today, August 5.

The Atmospheric Infrared Sounder or AIRS instrument aboard Aqua provides infrared data, while the Moderate Resolution Imaging Spectroradiometer or MODIS instrument provides visible data. Together, these instruments give scientists and forecasters a good look inside and outside of the storm to help determine what's happening. 

At 11 a.m. EDT (1500 UTC) on August 4, reports from NOAA and air force hurricane hunter aircraft indicated that the maximum sustained winds had increased to near 80 mph (130 kph) and Bertha became a hurricane. 

NASA's Aqua satellite passed over Hurricane Bertha at 1:47 p.m. EDT and the AIRS instrument gathered infrared data and cloud top temperature data on the storm, while the MODIS instrument snapped a visible image of the storm three minutes later. The MODIS image did not reveal an eye, and showed a thick band of thunderstorms wrapping into the center of circulation from the southeast.

When Aqua cast an infrared eye on the storm using the AIRS instrument, it provided information on cloud top heights and temperatures. The highest, coldest cloud top temperatures appeared around the center of circulation and in the eastern quadrant of the storm. The AIRS image also showed high clouds in a line off the U.S. East Coast from a stationary front.

On August 5 at 5 a.m. EDT (0900 UTC), Bertha had weakened back into a tropical storm. At that time Bertha's maximum sustained winds were near 65 mph (100 kph) over a small area northeast of the center.

The center of tropical storm bertha was located near latitude 33.4 north and longitude 72.9 west. That puts the center about 475 miles (765 km) west of Bermuda. Bertha was moving toward the north-northeast near 22 mph (35 kph) and the NHC expects a turn to the northeast and increase in forward speed.  The minimum central pressure recently reported by a U.S. Air Force Reserve reconnaissance aircraft was 1005 millibars.

The National Hurricane Center has forecast gradual weakening over the next two days.

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


Aug. 04, 2014 - NASA Sees Tropical Storm Bertha Leaving the Bahamas

[image-36][image-108][image-124]Tropical Storm Bertha took a "vacation" in the Bahamas on August 3 and NASA's Terra satellite captured an image of the storm that appeared be centered over "Crooked Island."

On August 2, before Bertha visited the Bahamas, the western half of the storm passed over Puerto Rico. A visible image captured by NASA's Terra satellite showed Bertha's clouds stretched from Puerto Rico east, over the British Virgin Islands. NOAA's National Weather Service office in San Juan, Puerto Rico reported 1.36 inches of rainfall from Bertha on August 2.

On August 3 at 15:35 UTC (11:35 a.m. EDT), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Terra satellite captured a visible image of Tropical Storm Bertha over the Bahamas. The visible image showed powerful thunderstorms around Bertha's center, and southeast of the center. Those powerful storms southeast of the center were being pushed there from wind shear coming from the northwest.

Forecaster Stewart at the National Hurricane Center or NHC noted in the Discussion on Bertha on August 4 at 5 a.m. EDT, "Convection has been pulsing near the center, but the overall convective cloud pattern of Bertha has changed little since the previous advisory due to moderate northwesterly wind shear."

At 5 a.m. EDT (0900 UTC) the center of Tropical Storm Bertha was located near latitude 26.1 north and longitude 73.6 west. That puts the center of Bertha about 220 miles (350 km) east of Great Abaco Island, Bahamas. Bertha is moving toward the north near 16 mph (26 kph) and is expected to continue moving in that direction today according to NHC. NHC noted that Bertha will continue to move away from the Bahamas today and pass about midway between the U.S. east coast and Bermuda on August 5.

Reports from a NOAA hurricane hunter aircraft indicate that maximum sustained winds have increased to near 70 mph (110 kph) and additional strengthening is expected during the next day or two, so Bertha is expected to reach hurricane force later today, August 4 before weakening in a day.  

The NHC noted that Bertha continues to move around the western edge of the stationary summertime big Bermuda-Azores high pressure system. Bertha is expected to continue moving around it in a clock-wise direction until Wednesday, August 6, when it is forecast to move northeastward into the mid-latitude westerlies (winds), keeping it off-shore from the U.S. East Coast.

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

 


[image-51][image-78][image-94]Aug. 01, 2014 - NASA Finds Heavy Rainfall and Wind Shear in Newborn Tropical Storm Bertha

The Tropical Rainfall Measuring Mission satellite known as TRMM found rain was falling heavily in the Atlantic Ocean's second tropical storm of the hurricane season. Bertha was close to the Lesser Antilles, prompting warnings and watches.

The National Hurricane Center (NHC) upgraded a well-defined low pressure center east-southeast of Barbados to Tropical Storm Bertha on July 31, 2014 at 0300 UTC (11 p.m. AST). Bertha's development is inhibited by upper-level shear that may weaken as the tropical storm moves over the northeastern Caribbean Sea.

Watches and Warnings in effect as of August 1 at 11 a.m. EDT (1500 UTC) include a Tropical Storm Warning for St. Lucia, Dominica, Martinique, Puerto Rico, Vieques, Culebra, the U.S. Virgin Islands and the British Virgin Islands. A Tropical Storm Watch is in effect for the eastern Dominican Republic from Cabo Frances Viejo to Isla Saona.

At 11 a.m. EDT (1500 UTC) the National Hurricane Center noted that the center of Tropical Storm Bertha was located near latitude 14.0 north and longitude 58.9 west, about 70 miles (110 km) southeast of Barbados. It was moving toward the west-northwest near 21 mph (33 kph) and that general motion is expected to continue for the next couple of days. NHC noted that Bertha is expected to move through the central Lesser Antilles during the night (August 1) and approach the Virgin Islands and Puerto Rico on Saturday, August 2. The estimated minimum central pressure is 1008 millibars.

The TRMM satellite, managed by both NASA and the Japan Aerospace Exploration Agency had an excellent view of tropical storm Bertha on August 1, 2014 at 0713 UTC (3:13 a.m. AST). Rainfall from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) revealed that rain was falling at a rate of over 109 mm (about 4.3 inches) per hour northeast of the sheared storm.

The National Hurricane Center noted Bertha is currently experiencing about 15-20 knots of southwesterly vertical wind shear which is pushing the heaviest rainfall northeast of the center. NHC also noted that water vapor imagery showed dry mid-/upper-level air near the storm. The forecast track calls for Bertha to interact with one or two upper-level troughs (elongated areas of low pressure) during the two to three days, which should cause some vertical wind shear and dry air to continue affecting the storm. Those are two factors that will limit the development and strengthening of the storm.

Radar reflectivity values from TRMM's Precipitation Radar (PR) instrument were used to create a 3-D view of the storm to show the structure of precipitation within Tropical Storm Bertha. The 3-D image showed that intense thunderstorms or "hot towers" were reaching heights of over 15km (about 9.3 miles). This kind of chimney cloud is called a "hot tower" because it releases a huge quantity of latent heat by condensation. The latent heat released in the center of tropical cyclones is usually an indicator of future intensification but vertical shear is expected to be a limiting factor for Bertha.

The NHC expects little change in Bertha's strength over the next two days.

Text credit:  Harold F. Pierce
SSAI/NASA's Goddard Space Flight Center

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This animation of NOAA's GOES-East satellite imagery from Aug. 2 through 4 shows Tropical Storm Bertha moving over Puerto Rico, Hispaniola and the Bahamas. It became a hurricane Aug. 4 at 11 a.m. EDT when NOAA and air force hurricane hunter aircraft indicated that winds reached near 80 mph.
Image Credit: 
NASA/NOAA GOES Project
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TRMM image of Bertha
On Aug. 1, rainfall data from TRMM, combined with an infrared image from the GOES-East satellite showed rain was falling at a rate of over 109 mm/4.3 inches (red) per hour northeast of the sheared storm.
Image Credit: 
SSAI/NASA, Hal Pierce
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3-D TRMM image of Bertha
This 3-D view of Tropical Storm Bertha on Aug. 1 was created from TRMM satellite data. It shows (from the south) intense thunderstorms were reaching heights of over 15km (about 9.3 miles).
Image Credit: 
SSAI/NASA, Hal Pierce
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This 3-D flyby of Tropical Storm Bertha on Aug. 1 was created from TRMM satellite data. It shows (from the south) intense thunderstorms were reaching heights of over 15km (about 9.3 miles). TRMM showed rain was falling at a rate of over109 mm/4.3 inches (red) per hour northeast of the sheared storm.
Image Credit: 
SSAI/NASA, Hal Pierce
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MODIS image of Bertha
On Aug. 3 at 11:35 a.m. EDT, NASA's Terra satellite captured this image of Tropical Storm Bertha over the Bahamas.
Image Credit: 
NASA MODIS Rapid Response Team
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MODIS image of Bertha
On Aug. 2 at 10: 55 a.m. EDT, Tropical Storm Bertha's western quadrant of clouds had blanketed Puerto Rico as seen in the MODIS image from NASA's Terra satellite.
Image Credit: 
NASA MODIS Rapid Response Team
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MODIS image of Bertha
This visible image of Hurricane Bertha off the Bahamas at 1:50 p.m. EDT was taken by the MODIS instrument aboard NASA's Aqua satellite.
Image Credit: 
NASA Goddard MODIS Rapid Response Team
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This false-colored infrared image from NASA's Aqua satellite shows powerful thunderstorms (purple) around Bertha's center on August 4 at 1:47 p.m. EDT, just after it became a hurricane.
Image Credit: 
NASA JPL, Ed Olsen
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Remnants of Bertha
This GOES-East satellite image shows that Post-Tropical Storm Bertha has become associated with a frontal system and has acquired extra-tropical characteristics about 300 miles south of Halifax, Nova Scotia, Canada.
Image Credit: 
NASA/NOAA GOES Project
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Page Last Updated: August 6th, 2014
Page Editor: Lynn Jenner