Some schools and businesses have already closed in the Mid-Atlantic states of Maryland, Virginia, Delaware, Pennsylvania, New Jersey, and the District of Columbia ahead of a powerful snowstorm that is forecast to strike that region starting this afternoon.

Today’s weather will be influenced by the passage of an occluded front, as the center of a low pressure system passes to our north. An occluded front is formed in a mature cyclone (low pressure system) when the cold front associated with the system overtakes the warm front, causing the two fronts to merge. Unlike a cold or warm front, an occluded front usually does not result in a large temperature difference at the surface upon its passage, since there is relatively cold air on either side of it. However, there is often a pocket of warm air pushed aloft in association with the occluded front, which can lead to precipitation along the frontal boundary.

November has arrived, and this week will begin the slow descent from brisk autumn temperatures to those more typically associated with chilly New England winters. The steadily decreasing amount of daylight present during this time of year contributes to a drop of 10°F (5.5°C) in normal temperatures over the course of the month. The winter solstice will be here soon enough, but until then, 4:30 p.m. sunsets will be a regular feature.

So far this week, we have seen a departure from the sunny, enjoyable autumn weather of early October for cloudy skies and chillier temperatures. This weather has been more reminiscent of late November than mid-October, but those looking for a reprieve will have to endure a few more days of cold. In fact, a bit of storminess will be added to the equation, as two low pressure systems will bring wind and rain to the Boston area over the weekend.

October has begun! Historically this month has been home to a wide variety of weather conditions for the New England region. This time of year has seen weather ranging from snowfall (on October 2, 1899), to 90 degree temperatures (on October 12, 1954), to hurricane landfalls (on October 20, 1770). As we transition from a warmer, calmer summer weather pattern to the cold, stormy winter pattern, it’s possible to experience all kinds of weird phenomena.

Today’s weather will offer a reprieve from the cool, dreary weather that MIT has experienced over the past couple days. A change in wind direction means that warmer air from over land will blow in from the West, instead of cool ocean air from the East. As a result, temperatures will reach the high 70s°F, instead of hovering around the 60°F mark as they did on Wednesday and Thursday.

While New England has recently felt the effects of Hurricane Bill and Tropical Storm Danny in the Atlantic, two other tropical cyclones are currently causing trouble in the Pacific Ocean. Recently, Hurricane Jimena has impacted areas of Northwest Mexico, strengthening to the verge of Category 5 status on the Saffir-Simpson Hurricane Wind Scale. On August 31, Jimena had sustained winds of 150 miles per hour while off of the Mexican West coast. Since then, the hurricane made landfall near Cabo San Lazaro, Mexico as a Category 2 storm. As of Thursday evening, Jimena continues to churn as a Tropical Storm over the Gulf of California. Meanwhile, in the East Pacific Ocean, Tropical Depression Dujuan formed on September 2nd about 80 km east of the Philippines, and is forecast to attain hurricane strength and impact the Japanese islands by the end of next week.

June has arrived! As summer nears, so does hurricane season. The National Weather Service has predicted the Atlantic hurricane season, which lasts from June to November, to be near-normal for 2009. According to forecasters at the Climate Prediction Center, there will be a 70 percent likelihood for the Atlantic to experience nine to 14 named storms, with four to seven of these becoming hurricanes.

This weekend’s weather will feature a sampling of typical spring conditions for New England. Sunny skies will be prevalent at times, but will be interspersed with clouds and rain. The average high temperature for this time of the year in Boston is around 65 degrees, and temperatures will range near this figure for most of the weekend. The Boston area will get a taste of partly sunny spring days today and tomorrow, but a thunderstorm or two are likely to make their way across the region this afternoon. Finally, a cold front will reach the area toward the end of the weekend, bringing with cooler temperatures, cloudy skies, and a even a few showers. Hence, our campus will experience warm, sunny weather, thunder and lightning, and a few spring showers over the course of a single weekend.

Severe weather has been wreaking havoc in the southeastern United States over the past few days. Over the weekend, severe thunderstorms caused widespread power outages, toppled trees, and spawned tornadoes as they carved a path through parts of Alabama, Georgia, Tennessee, Arkansas, and the Carolinas. Widespread damage and flooding was reported as were several deaths and injuries. The region was then battered by another storm system on Monday, with strong winds, heavy rain, and hail reported across Alabama, Georgia, Tennessee, Kentucky, and Florida. More severe weather was expected at the time of this writing Monday night, with severe thunderstorm and tornado watches posted by the National Weather Service across the Southeast.