Archive for July, 2008

Sunday Rain
July 28, 2008

Sunday’s approaching cool front triggered quite a bit of thunderstorm activity for about an eight hour period starting around lunchtime. There were numerous reports of severe weather across the region. Hail seemed to be the biggest component this time ’round but there were also reports of wind gusts in the 40-60 mph range as well. There were only a few tornado warnings issued with this outbreak. They were based on radar observations and no confirmed tornado reports have been submitted to the National Weather Service.

BWI-Marshall recorded .65″ rainfall, with .25″ measured at the Maryland Science Center and only .11″ on TV Hill. This range of rain totals pretty well represents the rain distribution around the area. Parts of Harford and Cecil counties received 1-2 inches of rain based on radar estimates and there was one thunderstorm cell that was parked over the Bay just north of the Bay Bridge that dumped an estimated 2.5-3 inches of rain during the storm.

The cool front that generated the storms will be stalled just south of the area for a few days. Waves moving along the front may produce a few thundershowers late Tuesday or early Wednesday. A stronger impulse on the front will increase the rain chances on Thursday.

Enjoy the week.

John Collins

Coolest Summer Ever? In Alaska!
July 28, 2008

Here in Baltimore the measuring stick for summer heat is the 90 degree mark. Three consecutive days in the 90s is generally considered to be a “heat wave”, and of course, the heat can go on much longer when the stubborn Bermuda High won’t budge. So, it might be hard to relate to a place where summer’s “warmth” is measured by the number of days the temperature hits 65! Welcome to southern Alaska!

When my family visited the 49th state on a cruise in the summer of 2004 we didn’t realize how odd and entire week of warm, sunny days was. I remember standing in sunny downtown Juneau sweating in record setting 85 degree heat. This year, however, the chill has returned to Alaska and apparently the natives are having a hard time re-adjusting. The headline in the Anchorage Daily News flashes: “Gloomy summer headed toward infamy”. Here in Baltimore we’ve had 19 days of temperatures at 90 or higher, so far this summer. In Anchorage, they haven’t had a day above 72 yet and they’ve hit the Alaskan benchmark for warmth, 65 degrees, just seven times! Here’s the link the the Anchorage Daily News story: http://www.adn.com/life/story/473786.html


Tom Tasselmyer

Thank You Dolly
July 28, 2008

Hurricanes are destructive and dangerous, especially in areas where coastal developers ignore the threat, so we frequently hear of the damage they do and the disruptions to daily life they cause. But, these storms are part of the natural earth-atmosphere system and they do provide some benefits. In Texas, for example, hurricane Dolly caused wind damage and flooding to the southeastern part of the state, but parts of Texas have been dealing with extreme drought conditions and in those areas the rain from Dolly was welcome. The National Weather Service reported these rainfall totals in the extreme drought areas:

Kingsville   5.48”
Rockport    4.68”
Freeport     2.81”
Angleton    2.55”
Palacios     2.34”
Alice          2.21”
Rockport    2.08”
Beeville      2.08”
Sugarland  2.03”
Houston    2.02”
Wharton    1.53”
San Antonio 1.03”

The complete report can be found here: http://www.noaanews.noaa.gov/stories2008/20080725_drought.html

A look at the drought conditions in Texas and across the nation:

Tom Tasselmyer

Dolly Totals
July 25, 2008

Dolly’s Winds…..

The highest winds were noted in the area where the eye of the storm crossed the barrier islands as the storm began to move inland.

Dolly’s Rainfall……..

The heaviest rains were measured in a narrow band north of Brownsville, roughly along the path of the eye of the storm as it began to move inland. Notice how the measured rainfall band lines up with the Doppler Radar estimates shown in a previous blog.

The above charts were produced at the National Weather Service office in Brownsville, Texas. For their report on the storm, go to http://www.srh.noaa.gov/bro/wxevents/2008/dolly/report1.htm

John Collins

Dolly Rain Estimates
July 24, 2008

The National Weather Service doppler radar calculates precipitation totals. Below is an image of the Brownsville radar’s storm total display from Wednesday evening.

A band of 12 to 20 inches of rain has been estimated to have fallen so far just north of Brownsville. This band is roughly along or just north of the path of the storm’s eye.

For updates on Dolly’s progress, check out our Hurricane Tracker page at ….. http://www.wbaltv.com/hurricanes/index.html

John Collins

Dolly Details
July 23, 2008

Dolly slammed into the Texas coast as a category 2 hurricane midday Wednesday. The image below is from the Brownsville, Texas, National Weather Service Doppler Radar.

Dolly as seen by Doppler Radar from Brownsville, TX coming onto the far south Texas coastline.

The image below shows the falling pressure and rising winds as the storm approached the coast.

Air Pressure and Wind Speed as Dolly Approaches

This graph from NOAA shows falling air pressure and rising wind speeds measured by a buoy station about 15 miles northeast of Brownsville, TX.

Environmental Impacts:
• According to the National Hurricane Center’s 2 p.m. ET advisory, Hurricane Dolly made landfall on South Padre Island, Texas as a Category 2 storm with sustained winds of 100 mph and gusts reaching 120 mph. Dolly is expected to bring 8 to 12 inches of rain to south Texas with some areas receiving up to 20 inches.
• Federal Emergency Management Agency (FEMA) has set up an operating facility in Austin, TX. According to local agencies, 18 schools have set up shelters and are in standby for evacuees. The American Red Cross has sent 46 emergency response vehicles to south Texas in response to Hurricane Dolly.
• Dolly was the fourth tropical cyclone to form during the 2008 Atlantic hurricane season, and was upgraded to tropical storm status at the same time it was declared to be formed. The storm made its first landfall as a tropical storm on the Yucatán Peninsula near Cancún early on July 21. The storm made its second landfall in southern Texas this afternoon, where 27,000 customers are currently without power. Heavy rain and high winds are currently affecting the coast, with high surf affecting all of the Texas coastline.

The images and environmental impact information above were provided courtesy of StormCenter Communications.

Below is a  late afternoon  NOAA visible light satellite image of Dolly showing the eye of the storm inland and north of Brownsville, TX. At this stage Dolly has been downgraded to category 1.

For more on Dolly check out our Hurricane Tracker page at ….. http://www.wbaltv.com/hurricanes/index.html

John Collins

Rough Day On The Gulf Coast
July 23, 2008

The Wednesday morning NOAA visible light satellite picture shows that hurricane Dolly is about to make landfall along the Texas/Mexico coast.

At 9am EDT Dolly was 40 miles east of Brownsville, Texas. Brownsville is inland and the satellite picture shows that the eyewall appears to be on the coast. The storm is moving northwest at 8 mph. Winds are 95 mph., making Dolly a category 1 storm. Forecasters think the storm could reach category 2 before weakening. Hurricane hunter aircraft have measured the central pressure of the storm at 28.56″

Check out our Hurricane Tracker page for the latest on Dolly ………. http://www.wbaltv.com/hurricanes/index.html

John Collins

Satellite Picture With A Bit Of Everything
July 23, 2008

A quick break from all of the hurricane news. I ran across an interesting satellite picture from last week. It is visible imagery and shows amazing detail of a number of weather related situations over the Pacific Northwest.

Smoke and haze from northern California wildfires are streaming toward the northern plaines. A little farther north, satellite sensors detected and displayed a stream of sulfur dioxide coming off the Pacific Ocean. It most likely contained volcanic ash from eruptions in the Aleutian Islands of Alaska. Low clouds and fog are evident along the Pacific coast. Last but not least, numerous thunderstorms are shown erupting in the Canadian Rockies and to a lesser extent in the mountains of Montana, Wyoming and Colorado.

It is just a neat picture. I hope you find it interesting.

John Collins

Dolly Update Tuesday Evening
July 22, 2008

Dolly is now a hurricane with 75 mph winds and a central pressure of 29.12″. At 5pm EDT Dolly was 165 miles ESE of Brownsville, TX and was moving northwest at 10 mph.

The storm is close enough to the coast that the Brownsville radar can detect the developing eye in the rain bands.

It is expected that Dolly will make landfall as a hurricane midday Wednesday somewhere along the Gulf Coast of south Texas or Mexico. It should be noted that Brownsville is not a coastal city and is not subject to possible storm surge as are the barrier islands to the city’s east and northeast. 6-10 inch rains with isolated amounts to 15 inches are possible across the region and that will likely be the biggest problem for the urban areas in both Texas and Mexico.

Tropical Prediction Center forecasters have produced the following forecast map for tropical storm force wind probabilities.

The graphics are courtesy of StormCenter Communications and are from the Local National Weather Service office in Brownsville, TX and the National Hurricane Center on July 22, 2008.

Check out our Hurricane Tracker page for the latest updates on Dolly……. http://www.wbaltv.com/hurricanes/index.html

John Collins

Dolly And Bertha Satellite Pictures
July 22, 2008

As of Tuesday morning it is apparent that Dolly has the potential to cause some problems along the Gulf coast of south Texas and Mexico. The storm continues to strengthen and is headed in the general direction of Brownsville.

The picture above is NOAA visible satellite imagery from early Tuesday morning. Check out our Hurricane Tracker page for the latest information on Dolly……. http://www.wbaltv.com/hurricanes/index.html

While on the subject of hurricanes I wanted to show you a different type of satellite image. Infrared sensors on weather satellites record sea surface temperatures(SST) and provide forecasters vital information on the environment tropical weather systems will be moving into. Water temperature is an important factor in the development of hurricanes.

The satellite image below is from Monday, July 21. It is color coded and shows SSTs over the Atlantic, Caribbean and Gulf of Mexico.

First, look at the western Gulf of Mexico. The color coding shows that the water temperatures are running around 27-30 degrees celsius(80-86 degrees fahrenheit). This is a perfect water temperature environment for hurricane development and is one of the factors taken into account in developing a forecast for Dolly. Notice that the temperatures cool slightly right along the Texas/Mexico coast.

Perhaps the most interesting feature displayed on this satellite image is the water temperature in the Atlantic Ocean just east of Bermuda. The island is the white speck just north of the 30th parallel and west of longitude 60. Just east of the island the satellite image shows a band of SST values of 23-25 degrees celsius(around 75 degrees fahrenheit). This north/south band of cooler water is positioned exactly along the track that Bertha took earlier in July. Bertha slowed down as it approached Bermuda and moved slowly northward as it passed just east of the island. This strip of cooler water is the result of Bertha’s churning of the ocean and bringing cooler water to the surface. The churning effect very likely played a role in weakening Bertha as it approached Bermuda. A loop of the satellite images showing the upwelling of this cooler water can be found at http://www.ssd.noaa.gov/PS/TROP/DATA/RT/sst-atl-loop.html

Satellite images like these are a beautiful demonstration of the interaction of the ocean and the atmosphere. It is a complex process and one that makes forecasting weather in the near or long term a challenge and, at times, less than perfect.

John Collins