First of all, congratulations and best wishes to all the graduates. The weather will fortunately allow for outdoor celebrations today. Although it will be cloudy, rain should remain to our south until the evening hours. A coastal storm will scrape us tonight, but pleasant conditions for the weekend will follow.
Stormy Out West, Quiet Over East
Today will feature two extremes over the eastern two-thirds of the country: a strong spring storm will be slow to move over the eastern Rockies/southern Plains, while the East Coast will experience a pleasantly warm day. The exact track of the spring storm out west is still uncertain, but the potential exists for a foot to over two feet of heavy wet snow over the mountains and along the foothills and adjacent plains in Colorado. Imagine trying to shovel that! Meanwhile. on the warm side of the storm, areas of Texas will receive beneficial heavy rain. The entire storm-affected area is currently in a moderate to severe drought, so any precipitation will be helpful.
Historical Perspective for 2008–2009 Seasonal Snowfall
Monday’s 8.5 snowfall brought our seasonal total to 63.7 , about 20" above an average winter season. The average additional snowfall from now until the end of the season is still another 8 . However, even if we were to receive no additional snow this winter, this year would still rank as the 18th snowiest season (snowfall records for Boston date back to 1871–1872). So if you feel that we’ve had a lot of snow this winter, you’re correct, although it could have been a lot worse! The highest snowfall for a season belongs to 1995–1996, when Boston recorded 107.6 of the white stuff. In case you’re wondering what the historical snowfall trends are for Boston, the answer is that the trend is fairly flat over the entire period of record 1871-2008, although four of the seven snowiest winters have occurred since the 1990’s (2004–2005, 1995–1996, 1993–1994, and 1992–1993).
Return to Winter
After not cracking 40°F (4°C) for the entire month of January, February in contrast has brought us a taste of spring so far. Maximum temperatures during the past two days have been in the 50s°F, but don’t expect that to last. A cold front moved through the area yesterday morning, ushering in more seasonable conditions. Where we had only a few showers with the frontal passage, parts of the South experienced severe weather and early-season tornadoes that killed several people.
Hanna is Coming
Flourishing tropical activity in the Atlantic basin over the past week has yielded a trio of storms: Tropical Storm Hanna, poised to become a hurricane and affect Boston Saturday night into Sunday, category 4 Hurricane Ike over the central Atlantic, and minimal Tropical Storm Josephine over the eastern Atlantic. Ike could potentially affect the east coast of the U.S. sometime during the middle of next week, but the main story right now is Hanna, packing sustained winds of up to 70 mph. Its projected path and intensity has the storm grazing the Carolinas as a category 1 hurricane early Saturday and potentially making a second landfall over southern New England as a tropical storm early Sunday morning.
Tropical cyclone activity in the Atlantic basin has recently surged. Tropical Storm Hanna formed yesterday northeast of the Bahamas and will possibly threaten the east coast of the U.S. sometime late next week. However, the main story is Tropical Storm Gustav, which made landfall in Haiti and Jamaica over the past few days and threatens to move into the Gulf of Mexico by the weekend. Oil companies have begun to evacuate some personnel, as the storm will likely impact the Gulf states early next week. The future intensities and exact paths of these storms are still highly uncertain, but they bear close monitoring.
Anomalously Snowy Winter?
With both winter and 2009 barely underway, Boston has already accumulated over 25 inches of snow. We are well ahead of a normal winter season’s pace of 9 inches up to this point. Interestingly, the 2007-08 winter season started at a similar pace, with about 28 inches reported by early January. That winter tallied over 50 inches, compared to the 40-inch average.
Clash of Extremes
A slowly moving low-pressure region currently over the Dakotas has set up a contrast of extremes in the middle of the country. Areas to the east of the low, in the warm sector of the storm, have set all-time November maximum temperature records. In contrast, areas just to the west of the low are receiving blizzard conditions. Some areas of the Dakotas have been getting pounded by several feet of snow and winds gusting over 55 mph at times. This storm is partly responsible for the above average temperatures that we have been feeling over the past few days, but thankfully it will lose its punch before approaching Boston.
Autumn Weather to Continue
Suddenly, summer warmth feels like a distant memory. Yesterday morning, Logan Airport recorded its first sub-40°F (4°C) temperature since April 16. The recent cold nights are not a great anomaly: average daily minimum temperatures are currently 45°F (7°C), and quickly fall by about 8°F (4°C) for each of the next 3 months.
On Sunday, Hurricane Kyle passed quietly off to our east by only 200 miles, bringing no more than a few showers to the Boston area during its passage. As we enter October tomorrow, weather phenomena such as hurricanes and thunderstorms in our vicinity become even a more remote possibility as the ocean cools and the solar angle rapidly decreases. October in Boston can still be very pleasant — combine fall foliage with average high temps in the mid 50s (13°C) to mid 60s (18°C) and it’s not hard to see why.
It’s Beginning to Feel Like Winter
Temperatures over the next few days will continue to be below average for a change. The month of October saw temperatures average more then five degrees above normal for Boston, mainly thanks to a dry high pressure pattern. That’s all a distant memory as far as the near-term weather is concerned. A low pressure system will be redeveloping off the mid-Atlantic coast today and track northeastward out to sea, although it will still provide us a chance of light precipitation Friday night and Saturday morning. If any precipitation does fall, it will likely be of the liquid variety, although temperatures may be marginal enough to have a few flakes mixed in as well. After the storm scrapes by us on Saturday, high pressure will settle into New England, yielding pleasant and sunny conditions for Sunday and the early part of next week. Enjoy the holiday!
The letters “wx” stand for the weather, hence the name WxChallenge, a national collegiate weather forecasting competition. MIT has competed in both this competition since its inception in 2006 and also its predecessor, the NCWFC (National Collegiate Weather Forecasting Competition). In fact, we have taken the national title five of the past six years. In the contest, we forecast for a different city every two weeks, estimating the high and low temperatures on any given day, the highest wind speed, and also the precipitation amount. The contest ends today, and what happens today at the Minneapolis-St. Paul airport will determine if MIT takes the title again, or if our rival, Mississippi State University, comes out with a narrow victory. The final results will be posted on the “cumulative results” page of the WxChallenge Web site tomorrow afternoon, so check it out: <i>www.wxchallenge.com</i>.
Old Man Winter Hangs On
The snow that impacted the Northeast last Friday officially left 8.9 inches in the Boston area, nearly beating the previous daily record of 9.0 inches set in 1893. A liquid equivalent of 0.75 inches fell, which means that the average snowfall ratio was 12:1 (12 inches of snow to one inch of rain): fairly typical of snowstorms in this area. Although it may not seem like it, the storm pushed Boston’s seasonal snowfall total to 50 inches, well ahead of an average year’s pace.
We are still in that time of the year when the diurnal, or daily, temperature range can be rather large. Clear skies and light winds are ideal conditions to make this happen, with abundant sunlight to warm the surface during the day, and good radiational cooling at night lowering temperatures. For instance, Bedford (10 miles to the northwest of Boston) reported a temperature of 26 degrees yesterday morning, while Martha’s Vineyard was even colder — an amazing 22 degrees Fahrenheit! Meanwhile in Boston, the ocean’s influence kept temperatures near 40. Within two hours of sunrise, all three locations were nearly the same temperature — about 50°F. So within the next few weeks, if the sun is setting upon clear skies and light winds, there’s a good chance it’ll be cold before sunrise.
Warm vs. Cold
As is frequent this time of the year, there can be a considerable difference in temperature over a short distance, i.e. a large temperature gradient. Fronts are usually responsible for these gradients, while the fronts are associated with low-pressure systems. One such low-pressure system located over the northern Great Lakes region yesterday sent a cold front plunging down into the Plains and Midwest. On the east side of the front, temperatures were generally in the 50s and 60s°F (10–20°C), whereas on the back side temperatures plunged as low as -30°F (-35°C)!
June or October?
Yesterday’s highs approached, and in some cases surpassed, the 80 degree mark yet again. Logan reached 81 degrees, nearly tying its record of 83 set in 1979. In fact, October to date has averaged more than 5 degrees above normal. Yesterday’s warm readings were typical of late June; our average highs should be near 60°F for late October, with average lows in the mid 40s°F. You can thank the unusual warmth of late on a persistent high pressure pattern that has been advecting the warm air into the Northeast. The warm air advection will be suppressed today by the passage of a cold front, bringing us a period of showers late this afternoon and evening. Expect the rest of the week to be more seasonable and pleasant. Our next chance of rain comes this weekend as a slow-moving system currently in the southern Plains moves our way.
Hasta La Vista, Summer?
Summer has come and gone as of last Sunday morning at 5:51 EST, but try telling that to the weather! We have been in an unusual high pressure pattern lately, which has allowed temperatures this week to soar and cut down precipitation to just 35 percent of normal since Aug. 1. Logan’s high of 88°F on Tuesday nearly tied the record high of 89°F for the same date in 1926. Again on Wednesday and Thursday, highs of 93°F and 85°F were only two degrees and one degree off from tying records, respectively. Thankfully, the muggy and rainy conditions today will usher in much drier and cooler air for the weekend.
So Long Summer
Although technically not yet autumn, temperatures over the foreseeable future will certainly make it feel like the fall season. Contrast this to just a few days ago when Logan tied a record high of 95°F, previously set way back in 1872. A cold front moved through early Sunday morning, bringing substantially cooler and somewhat drier air with its passage. The weekend also saw a weak Tropical Storm Gabrielle brush the North Carolina coast with mainly light rain and some gusty winds. Cape Hatteras recorded a top wind speed of 53 mph. Now a tropical depression, Gabrielle is currently racing off to the northeast and passed about 200 miles south of Nantucket last night.