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Hurricane Season 2008: Tropical Storm Cristobal (Eastern Atlantic Ocean)
 
July 23, 2008

Cristobal's Curtain Call in the North Atlantic Ocean

Tropical Storm Cristobal was becoming "extratropical" in the northern Atlantic Ocean on Wednesday, July 23, 2008, and is expected to merge with a cold front over the ocean by July 25. That means it's losing its tropical characteristics.

According to the National Hurricane Center, the term "extra-tropical" implies both poleward displacement of the cyclone and the conversion of the cyclone's primary energy source from the release of latent heat of condensation to baroclinic (the temperature contrast between warm and cold air masses) processes. It is important to note that cyclones can become extratropical and still retain winds of hurricane or tropical storm force.

At 5:00 a.m. EDT on July 23, Cristobal's center was located near latitude 44.7 degrees north and longitude 55.9 west, or 380 miles (610 km) east of Halifax, Nova Scotia, Canada.

Cristobal was moving toward the east-northeast near 31 mph (50 km/hr). A turn toward the east is expected followed by a turn southeast. Maximum sustained winds are near 45 mph (75 km/hr) with higher gusts. No significant change in strength is forecast during the next 24 hours. Minimum central pressure was 1003 millibars.

By July 25, Cristobal will only be a memory in the northern Atlantic Ocean.

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



July 22, 2008, second update

Tropical Storm Cristobal Forms off Carolina Coast, Heads Out to Sea

Satellite image of Cristobal Credit: Hal Pierce (SSAI/NASA GSFC)
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The stage was set for what was to become Tropical Storm Cristobal when a persistent area of low pressure moved northeast out of the eastern Gulf of Mexico and across central Florida along an old frontal boundary. After exiting the northeast coast of Florida, the area of low pressure emerged over warm waters of about 27.5 C (or 81.5 F) off of the southeast coast of Georgia. Tropical cyclones require a minimum of 26.5 C (or 80 F) to form. As the low pressure center drifted northeastward just off of the Southeast coast, it remained over warm water and provided a focus for shower and thunderstorm activity. This allowed the process of tropical cyclone formation to proceed. On the evening of the 19th of July 2008 (local time), the area of showers and thunderstorms associated with the low became better organized and the third tropical depression of the Atlantic season (TD #3) formed. As the system continued to slowly make its way to the northeast parallel to the coastline, it slowly strengthened and by the afternoon of the 19th (local time), it had become Tropical Storm Cristobal and was due east of Charleston, SC. Over the next day, Cristobal continued to hug the Carolina coast as a weak tropical storm. On the evening of the 21st, it passed Cape Hatteras, NC and continued out to sea.

The Tropical Rainfall Measuring Mission satellite (known as 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 image was taken by TRMM at 15:24 UTC (11:24 am EDT) 21 July 2008 as Cristobal was pulling away from the outerbanks of North Carolina. It shows the horizontal pattern of rain intensity within the storm. 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). The area of cloudiness associated with the storm is rather small (white area). Within these clouds TRMM reveals that most of the rain is south of the center of circulation. There is some banding as evidenced by the curvature in some of the rain features (note the arc shape of the moderate to heavy rain band shown by the green and red areas, respectively). This feature, which is embedded in the storm's cyclonic circulation, is south of the center. At the time of this image, Cristobal was a moderate tropical storm with maximum sustained winds reported at 55 knots (63 mph) by the National Hurricane Center (NHC). Over the next day, Cristobal maintained its intensity as it tracked over the warm waters of the Gulf Stream but is now expected to weaken as it moves rapidly off to the northeast then east over cooler waters.

Text credit: Steve Lang, SSAI/NASA GSFC



July 22, 2008, first update

Cristobal Zipping Past New England, Creating High Surf

Tropical Storm Cristobal off the coast of New England Credit: NASA/JPL
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Tropical Storm Cristobal may not be making landfall in New England, but it's stirring up the waters off the coast as it moves northeast into the northern Atlantic Ocean.

High surf advisories and small craft advisories are posted for coastal Rhode Island and Massachusetts today, July 22. In addition, there is a moderate to high risk of strong rip currents along the south coasts of Massachusetts and Rhode Island today. The risk may continue during much of the week.

At 5:00 a.m. EDT the center of Tropical Storm Cristobal was located near latitude 39.1 north and longitude 68.2 west. The storm is parallel to the northern New Jersey coast. Specifically, its about 485 miles northeast of Cape Hatteras, North Carolina and about 450 miles (720 km) south-southwest of Halifax Nova Scotia, Canada.

Cristobal is moving toward the northeast near 21 mph (33 km/hr) and a turn toward the east-northeast with a further increase in forward speed is expected during the next day or two. He's expected to stay at sea and parallel the northern New England and Nova Scotia coasts before heading into the open northern Atlantic.

Maximum sustained winds are near 60 mph (95 km/hr) with higher gusts. Weakening is forecast during the next 24 hours as Cristobal loses tropical characteristics. Estimated minimum central pressure is 1002 millibars.

Cristobal's forecast track takes the cyclone over much cooler sea surface temperatures as it crosses the north wall of the Gulf Stream during the next day or so. Tropical storms and hurricanes need sea surface temperatures of at least 80 degrees Fahrenheit to maintain strength. Off the Massachusetts coast, sea surface temperatures are in the low to mid-70s, which means that Cristobal will weaken further as he passes east of the state and remains at sea.

By Friday, July 25, Cristobal is expected to merge with a cold front that is pushing southward over the eastern Atlantic Ocean.

This infrared image of Cristobal 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 22 at 6:23 UTC (2:23 a.m. EDT).

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 Cristobal. 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 21, 2008

Tropical Storm Cristobal Stirring up Strong Waves On Eastern U.S. Coast

Satellite image of Cristobal Credit: NASA/JPL
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In its fourth day of life, Cristobal, the third named tropical cyclone of the Atlantic Hurricane Season has been causing heavy surf along the mid-Atlantic coast, and creating dangerous rip tides along the beaches.

Cristobal was born on Friday, July 18 around 11:00 p.m. EDT, as a tropical depression about 65 miles (105 km) south-southeast of Charleston, South Carolina and about 330 miles (530 km) southwest of Cape Hatteras, North Carolina. Since then, Cristobal has been creating dangerous surf conditions, and bringing some much needed rainfall to coasts of both Carolinas.

On Monday, July 21, 2008, at 11:00 a.m. EDT, Cristobal was parallel to the border of North Carolina and Virginia. Specifically, he was located near latitude 36.6 degrees north and longitude 72.6 degrees west, or about 190 miles east-northeast of Cape Hatteras, North Carolina.

Cristobal was moving toward the northeast near 13 mph (20 km/hr) and this general motion is expected to continue for the next couple of days with an increase in forward speed.

Maximum sustained winds are near 65 mph (100 km/hr) with higher gusts. Little change in strength is forecast during the next 24 hours and Cristobal should start to lose tropical characteristics late on Tuesday as he moves into cooler waters and skirts the coast of Nova Scotia, Canada. This path will also carry Cristobal north of the warm Gulf Stream and into an environment with a stronger wind shear (winds blowing at different directions at different altitudes, that can weaken or tear a storm apart.).

This infrared image of Cristobal 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 21 at 7:17 UTC (3:17 a.m. EDT) and Cristobal was southeast of Cape Hatteras, North Carolina.

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 Cristobal. 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