Tropical Storm Bill

Tropical storm development
Tropical storm development shows how important atmosphere-ocean interactions are in climate and weather. Tropical storms introduce and transport enormous amounts of heat and moisture into the atmosphere.

The video below shows the formation of Tropical Storm Bill in June 15 through June 17, 2015  as it makes it way westward across the the Gulf of Mexico in the easterly trade winds (remember: easterly trade winds flow FROM the East carrying weather systems westward).  Note that this is not a hurricane. A hurricane would be rotating more quickly and have an "eye" in the middle as it intensifies. These systems can cause severe flooding because of the tremendous amount of water that evaporates from the warm ocean surface of ther Gulf of Mexico  in the atmosphere




Current satellite imagery
You will be able to see how this tropical system dies out as it makes it way northward and its moisture and cloud gets advected and dispersed (that is to say transported blown) eastward in the mid-latitude westerlies. A little guide to the imagery is provided below. Note that blue indicates cold cloud tops (the colder the higher) while red generally represents surface temperatures.   You should be able to see the cloud and precipitation due to the moisture of this system if you are in Southern New England.

Link to satellite imagery.

Polar and subtropical jets

A jet is defined as any core of fast moving air, often indicated by a curved arrows on maps and by television meteorologists. The line is drawn in the location of the strongest winds. Jetstreams are typically wider and not as distinct, but more of a region where the wind increases toward a core of the strongest wind. One way of visualizing this is consider a river. The river's current is generally the strongest in the center with decreasing strength as one approaches the river's bank. It can be said that jetstreams are "rivers of air".

Observation of winds from rawinsondes show that there are two principle regions in the upper troposphere where winds are strongest. The first is in the 50°-60° N/S region and is called the polar jet and is typically associates with the polar front. The second is called the subtropical jet and is located around 30°N. Jet streams vary in height of four to eight miles (about 500 to 200 mb) and reach a maximum at the tropopause, reaching speeds of more than 275 mph.

The actual appearance of jet streams result from the complex interaction between many variables - such as the location of high and low pressure systems, warm and cold air, and seasonal changes. They meander around the globe, dipping and rising in altitude/latitude, splitting at times and forming eddies, and even disappearing altogether to appear somewhere else. Jet streams also "follow the sun" in that as the sun's elevation increases each day in the spring, the jet streams shifts north moving into Canada by Summer. As Autumn approaches and the sun's elevation decreases, the jet stream moves south into the United States helping to bring cooler air to the country.

Source: NWS

Observations of jet stream: Satellite Imagery

This high resolution visible satellite imagery of VT and HM shows the sun going down at the end of today. It confirms oue obervations of clouds being moved from west to east by the mid-latitude westerlies. A stratocumulus cloud mass (meteorologists sometimes call it a "blob of cloud" for obvious reasons) passes over the Northeast Kingdom of stratocumulus late in the day.

You can see current high resolution visible satellite imagery of New England at the Meteorology Department's Satellite page.

Observations of jet stream: WebCams

LSC Webcam imagery for Monday, 8 Sept 2008. Click here for current animation.

The LSC webcam is in the staff room on the 4th floor of the Vail Building looking southeastward over the campus in summer and eastward towards Burke Mountain in the winter. It's a good way of watching clouds develop, storms pass, and the day go by. You can guess at which direction the jet stream is moving too.

The clouds seen in this video are generally stratocumulus clouds: sometimes they look like puffy cottonballs (cumulus clouds), and sometimes they flatten out into a flat cover (a stratus deck). It looks like they are low, maybe a mile or two above the surface.

Note that even though the wind was relatively calm all day on the ground, they are moving at a good clip due to a strong westerly jet stream, pushing them towards the east. This is the norm in the middle latitudes. Winds usually increase with height in the lower 10 miles of the atmosphere due to the jet stream.