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November 22, 2009

The Weather Page

The next good pass by the International Space Station over Baltimore will be Wednesday evening. Station and crew are hosting the shuttle Atlantis and its crew of seven. But the viewing weather looks poor. If things improve I'll post the times on MarylandWeather.com. Atmospheric "drag" has pulled the ISS 11 miles lower since January. It's now flying 211 miles above the Earth. A reboost is due.

November 20, 2009

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Don Gansauer in Canton wonders: "How accurate are local TV forecasts when they show the expected radar precipitation scans of the next 36 hours?" Those rain predictions are generated by computers, based on current conditions and past events under similar conditions. They're like kids: You're pretty sure where they are now, and how they usually behave. But 36 hours from now? Not so much.

November 19, 2009

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John Polyniak of Lake Shore says that in late fall, it often gets cold and frosty just before a warm front arrives. "Why?" he asks. Steve Zubrick, an NWS science officer, says it's a cycle. A cold front passes by, temperatures drop. High pressure moves in, skies clear, winds calm, frost forms. Then the high moves east, allowing the next low to approach. It drags in a warm front, just ahead of the next cold front. Cycles.

November 15, 2009

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The Leonid meteor shower peaks early Tuesday. Asia has the best view, but Marylanders could see rates topping 20 per hour between midnight and dawn on the 17th. No moon will interfere. If clouds threaten, try a day or two before or after the peak. Leonids emanate from Leo (NE after midnight), but can light up anywhere. Find a dark spot, dress warmly, stretch out, enjoy.

November 14, 2009

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Jay Slater of Baltimore watched Sunday's flyover by the International Space Station. He asks: "Whydoes it appear much lower and brighter than airplanes also in the sky?" A clear, dark sky provides no reference points by which to judge distance. So our brains interpret brighter as closer. A gigantic space station reflecting sunlight is far brighter than aircraft lights, so the ISS - 212 miles up - seems closer.

November 13, 2009

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Today is this year's third and final Friday the 13th, a day and date regarded by some as unlucky. Most years - 42 to 44 years per century - have just one or two Fridays that fall on the 13th. Only 14 or 15 years per century have three. The last of those was 1998; the next is 2012. Guy Ottewell's "Astronomical Calendar" notes that the 13th occurs on Friday more often than on any other day. Just our luck.

November 12, 2009

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Joe Bollinger writes from Glen Burnie: "What does the number +.5 mean with regard to a planet's magnitude?" The magnitude scale is a measure of an object's apparent brightness. Numbers run from negative digits (brightest), through zero, to positive digits (dimmest). The full moon is -12. Venus can reach -3.8. The North Star is a +2. The dimmest naked-eye objects visible under ideal conditions are +6.5.

November 8, 2009

The Weather Page

Space Cadets! The International Space Station is back in our evening skies tonight, flying high over Baltimore (and almost directly over Ocean City) on its way up the East Coast. If skies are clear, look for a bright, fast-moving "star" rising out of the southwest horizon at 6:14 p.m. It will climb above brilliant Jupiter – brightest object in the southern sky - by 6:17 p.m., just before vanishing into Earth's shadow.

November 7, 2009

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A reader recalls "summers that were much warmer in my childhood" during the 1970s and 1980s. He asks which decade had the most triple-digit highs. If we define "hot" by the number of 100-degree days, then his hottest decade was the '90s, with 13 at BWI. The '80s had 12, the '70s just one. Steve Zubrick at the National Weather Service says 1930 and 1988 were Baltimore's hottest years, each with seven 100-plus days.

November 6, 2009

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Old-timers in Baltimore may recall a storm that dropped 6 inches on Nov. 6-7, 1953 - the earliest heavy snowstorm on record here. Snow froze on the streets, snarling traffic for up to five hours. Three busloads of Towson High students didn't get home until 10 p.m. Cars, buses and trolleys were stranded amid a scarcity of cinder and sand trucks. Robert Larabee Jr., 8, died in a wreck on the new Baltimore-Washington Parkway.

November 5, 2009

The Weather Page

The low temperature at BWI on Wednesday morning was 32 degrees. It was the first time the airport has touched the freezing mark since April 13, when the low was 29 degrees. This first freeze was relatively late for Baltimore. The average is Oct. 28 for BWI (Nov. 13 for downtown). During the past six years, the first-freeze dates for BWI have ranged from Oct. 13 (2006) to Nov. 9 (2004).

November 1, 2009

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It's the first Sunday in November. Do you know how to turn your clocks back? It's also Samhain, a Celtic "cross-quarter day," halfway between the autumnal equinox and the winter solstice. It was celebrated as the start of winter and the new year. There were elements of a harvest festival, too, with large gatherings and bonfires, and a festival of the dead, with echoes in our Halloween.

October 31, 2009

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As kids, we loved it when Halloween fell on a Saturday. Our parents tried to hold us back, but we set out with our costumes and trick-or-treat bags as early as we could. After dark, a big moon made the neighborhood even spookier. We're two days short of the full moon this year. But if skies are clear, that will be good enough. We won't have a real full moon over our Halloweeen haunts until 2020.

October 30, 2009

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Parts of Colorado lie freezing beneath 2 to 3 feet of snow today. That's why we live here. The biggest October snowstorm of all time (at least since 1883) in Baltimore occurred on this date in 1925, leaving 2.5 inches on the ground. It arrived amid some very unseasonable cold. The day before the storm, the mercury stalled at 46 degrees - still the chilliest high on record for an Oct. 29 in Baltimore.

October 25, 2009

The Weather Page

It's the last Sunday in October, time for Europe to switch its clocks back an hour to standard time. We used to do the same thing, but since 2007 we've waited until the first Sunday in November to "fall back." We'll remain on Eastern Standard Time in Maryland until the second Sunday in March, when we'll "spring forward" again. Almost two-thirds of our year now falls within Daylight Saving Time.

October 22, 2009

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On this date in 4004 B.C. (Julian calendar), God began the creation of the universe, according to the "Annals of the Old Testament," written by Archbishop James Ussher in 1650. Cosmologists have arrived at a somewhat earlier, and less precise, date, based on observations of receding galaxies. They date the beginning of time and space to the Big Bang, 13.7 billion years ago, give or take a few million.

October 18, 2009

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If skies clear up, stargazers should watch this week for the annual Orionid meteor shower. Active from early October through early November, the shower peaks this week at 23 per hour in dark locations. The moon is new, so no moonlight will interfere. Look after midnight. Meteors - very fast, with half leaving persistent trails - will emerge from the constellation Orion, rising in the east after 11 p.m.

October 17, 2009

The Weather Page

If temperatures at BWI remain below 50 degrees through Sunday, we will have seen five consecutive days of record-low daily high temperatures. It would tie the record for consecutive record-low daily highs, set Feb. 9-13, 1899, when the warmest readings were 8, 3, 11, 11 and 10 degrees Fahrenheit. That 3-degree high remains the coldest high temperature for Baltimore since record-keeping began in 1871.

October 16, 2009

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James Chwirut writes from Baltimore: "We were debating in the office today about past temperatures for the summer ... When was the last 100-degree day of actual temperature - not heat index - in and around Baltimore?" Thankfully, we haven't been that hot at BWI since Aug. 8, 2007, when the mercury reached 102 degrees, setting a record for the date. It was 106 degrees that day at the Maryland Science Center.

October 15, 2009

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On Sunday, we listed a high temperature of 80 for Saturday in downtown Baltimore. That puzzled reader Fred Weiss. "My thermometer barely made it to 70 ... Where and what time was that 80-degree reading?" Darned if I know. Our data vendor claims it came from The Baltimore Sun's station at Calvert and Centre, but we never got that warm, either. All future "downtown" readings will come from the Maryland Science Center.

October 11, 2009

The Weather Page

Space Cadets! The weather isn't too promising, but with a few lucky breaks in the clouds Monday morning, we could catch the International Space Station on a very fine pass over Baltimore. Look southwest at 6:32 a.m. for a very bright, star-like object rising high in the sky. By 6:34 it will pass just above the waning moon and planet Mars, then head off to the northeast, disappearing at 6:37 a.m.

October 10, 2009

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Sam Cohen of Baltimore recalls a tremendous summer thunderstorm in the early 1970s. Trees fell, streets flooded and "in Dundalk they had 12 inches of hail and had to bring in a snowplow. ... Can you look this up and tell me I'm not crazy?" National Weather Service storm reports include one for July 8, 1972, noting "severe hail" in Harford and Baltimore counties: "In some places, it covered the ground." No mention of plows.

October 9, 2009

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Baltimore measured a trace of snow on this date in 1903, the earliest snowfall on record for the city. The average snow total for Baltimore, for the 30-year period from 1971 through 2000, is 18.2 inches. The last time we saw that much was the winter of 2005-2006, when 19.6 inches fell at BWI-Marshall. It's been seven years since we topped 20 inches for the season. That was in 2002-2003, when 58.1 inches fell.

October 8, 2009

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Roberta Vonderheide of Parkville still recalls the "magical moment" from 25 years ago. She watched from a boat as a reddened sun set in the west, while the full moon rose over trees to the east. "Is this a common occurrence? We never saw it again." Clouds might obscure it, but it happens every 29 days. Full moons always rise as the sun sets. What's uncommon is taking the time to watch.

October 4, 2009

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The moon was full at precisely 2:11 a.m. this morning, but we won't see it until it rises for Baltimore at 6:37 p.m. Out at the beaches, look for the moon to peek above the ocean at 6:32 p.m. And, because it's the full moon closest in time to the autumnal equinox, it's regarded as the Harvest Moon, the one that illuminated the fields as farmers worked late to bring in their crops.

October 3, 2009

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If you can roust yourself from bed before dawn on a clear, dry morning next week, you might catch a glimpse of the elusive planet Mercury, very low in the east, before sunrise. The nearest planet to the sun reaches its greatest "elongation" on Monday, which means its highest point in the sky and out of the sun's glare. Look due east, between 6 a.m. and 6:30 a.m., for a tiny point of steady light below bright Venus.

October 2, 2009

The Weather Page

October arrived this week, promising cooler, shorter days and, for snow fans, the first chance this season to utter the word "snow" in a forecast. The earliest trace of snow on record for Baltimore fell on Oct. 9, 1903. The earliest measurable fall was 0.3 inch, during the Orioles' 1979 World Series bid, on Oct. 10. There are nine dates in October with snow in the records. The most recent was a trace, on Oct. 22, 2003.

October 1, 2009

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We closed the books on September Wednesday night. The month ended just a shade drier and cooler than the long-term averages for Baltimore. The high was 85 degrees on Sept. 5. The low was 47 on the 20th and 29th. We averaged more than a half-degree cooler than the norm. BWI measured about 3.5 inches of rain, a bit below the average. Half the month's rain - 1.71 inches - fell on a single day, the 11th.

September 27, 2009

The Weather Page

If our skies clear, watch in the southeast for the next few nights as the waxing moon creeps closer to the brilliant planet Jupiter each evening. By Tuesday evening, Luna will be within just 2 degrees of Jupiter, the width of two fingers held at arm's length. Jupiter is currently almost 400 million miles from Earth. The moon on Tuesday will be about 250,000 miles away from us.

September 26, 2009

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A WeatherBlog reader, Hazmat77, takes issue with my reference to this season as fall. "Frank, the official name for this season is Autumn. 'Fall' is basically slang when used to describe Autumn." Really? It's the fifth definition of "fall" as a noun in my office dictionary. An older dictionary at home likes it, too, at least for use in the U.S. And the Associated Press Stylebook is okay with "fall" as a season (lowercase, please).

September 20, 2009

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Sid Carcress, in Catonsville, wonders whether the "butterfly effect" – that the flap of a butterfly's wings can stir up a faraway storm – could possibly be true. Perhaps. This poetic notion from chaos theory is called "sensitive dependance on initial conditions." In 1961, meteorologist Edward Lorenz made a minuscule change in a computer weather model and got a completely different outcome. He coined the term.

September 19, 2009

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Rosh Hashanah, the first day of the Jewish New Year 5770, began after sunset Friday night, when the sky grew dark enough for at least three stars to be seen. The date is timed to the first appearance of the young moon closest to the autumn equinox, which occurs on Sept. 22 this year. The formula was established by the Jewish religious leader Hillel II, in A.D. 363. Happy New Year!

September 18, 2009

The Weather Page

Forecasters have assigned alternating male and females names to hurricanes since 1979. Since then, Dennis Ferguson of Easton asks, "which 'gender' has caused the most damage?" Hurricane 'gender' is meaningless, so damage totals should be evenly distributed. But Katrina's $81 billion tab was three times the next-costliest storm's $26.5 billion (Andrew, 1992), so I suspect she wrecked the curve.

September 13, 2009

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Next weekend marks the sixth anniversary of Tropical Storm Isabel's deadly tromp across Central Maryland. The storm made landfall Sept. 18 near Ocracoke, N.C. with top winds of 105 mph. It quickly weakened. But Isabel's storm surge flooded the Chesapeake waterfront, including Baltimore, Annapolis and many bayshore communities. Seven people died in Maryland, and damages came to more than $1 billion.

September 12, 2009

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Verbraunia Rhodes of Baltimore is working on her "bucket list" and plans an Alaskan cruise to see the Northern Lights "before I pass on." She asks what time of year is best for aurora viewing. Good choice. Alaska is the best place in the U.S. to see the Northern Lights. Plan to go in September or March. Skies are dark, it's not too frigid and Earth's orbit is most likely to carry us through solar storms.

September 11, 2009

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One thing many people remember about the morning the World Trade Center in New York and the Pentagon were attacked was the exquisite beauty of that day. Skies on the East Coast were cloudless, with temperatures in the upper 60s or low 70s. Humidities were low. And after the FAA grounded all air traffic across the country, even the jet contrails disappeared. For days, the skies were a still, crystalline blue.

September 6, 2009

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Need to know how cold it was on Jan. 4, 1979? You can find hourly weather data for BWI-Marshall on The Baltimore Sun's weather page, MarylandWeather.com. Just scroll down to the daily temperature data, below the WJZ video forecast, and click on "Detailed History and Climate." The airport records, with some gaps, go back to 1948. (The low reading at BWI on Jan. 4, 1979 was 9 degrees, at 4 a.m.)

September 5, 2009

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Any bets on whether Baltimore will see any more 90-degree weather this year? The summer months (June through August) saw just 10 days in the 90s - none in June, four in July, and six in August. The average for that period in Baltimore is 25 days of 90 or higher. The three days in April that reached the 90s bring this year's total to 13. Will there be more? The average for September is 2.7 days in the 90s.

September 4, 2009

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The full moon rises over Baltimore today at 6:38 p.m. (five minutes earlier at the beaches). This being the last full moon before the autumnal equinox, it's often called the Fruit Moon, which shines, one presumes, on the ripening fruit. The Harvest Moon is defined as the full moon closest to the equinox, which falls this year on Sept. 22. So this year's Harvest Moon is still a month away, on Oct. 4.

September 3, 2009

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Today's weather comments, like Seinfeld's show, are all about nothing. Tonight, Saturn's rings are positioned exactly edge-on to our view from Earth for the first time since 1996. That makes them invisible to our gaze. Saturn itself is too deep in the sun's glare this week to see anyway, and you can't see much there without a telescope. So until late this month, Saturn, too, is all about nothing.

August 30, 2009

The Weather Page

Got an early wake-up Monday? Does the dog need a jog? Step outside just before dawn if skies are clear for a good look at the International Space Station as it makes a pass just a bit north of Baltimore. Watch for a bright, steady, starlike object rising above the northwest horizon at 6:17 a.m. It will climb to just north of straight up by 6:20 a.m., then pass between Mars and bright Venus before vanishing in the glare of sunrise in the southeast at 6:23 a.m.

August 28, 2009

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Sixty-one years ago this week, Baltimoreans sweltered through one of the hottest stretches of August weather on record for the city. For three days, instruments at the Customs House recorded the highest temperatures ever for the dates - 101 or 102 degrees each day from the 26th through the 28th. Overnight lows never sank below 77 degrees for four nights ending on the 29th, setting new "high minimum" records each time. All those daily records set in 1948 still stand today.

August 16, 2009

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Forty years ago tomorrow Hurricane Camille crashed ashore in Mississippi with 190-mph winds. It was the second-most-intense storm to hit the mainland U.S. and the most destructive of the time. It flattened nearly everything near the coast. But most of the deaths occurred days later when flash floods hit Virginia, killing 153 people. Freshwater floods after hurricanes kill more people than wind and tides.

August 14, 2009

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John Esch in Addison, Texas, is asking about water temperatures in Baltimore: "I'm moving my boat to Baltimore Inner Harbor for a year and am a little concerned about freezing water/ice." The state DNR tracks that. Between 1985 and 2008, the mean low temperature of the harbor's surface water was 37.9 degrees in February, but it dipped as low as 33.4. See the data at http://bit.ly/1Z8LGu

August 13, 2009

The Weather Page

Bud Schaefer, of Parkton, was born in 1930. He's noticed many high-temperature records were set that year: "Was that time period of the late 1920s and early 1930s unusually hot?" Yes, and through the '40s. Or so it seems. Baltimore's eight hottest years, and four of our six hottest summers, all fell between 1930 and 1949. Then again, 1950 was when they moved the official station from downtown to the airport.

August 9, 2009

The Weather Page

Seen any good meteors lately? We're nearing Aug. 11-12 peak of the annual Perseid meteor shower, and meteor rates are already rising. The Perseids occur as Earth passes through the dust trail of Comet Swift-Tuttle. The glare of moonlight will fade the faintest Perseids, so try looking between 9 and 11 p.m. Tuesday while Luna is low. Watch the whole sky with the moon at your back. Clear skies!

August 7, 2009

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The statistical peak of the hurricane season begins next week and runs into October. But we shouldn't read too much into this season's storm-free start. June and July produce fewer than two named storms a year on average. Hurricane Andrew, the first named storm of 1992, formed Aug. 17 and blasted South Florida on the 24th as a Cat. 4 storm, causing tremendous damage.

July 18, 2009

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Up early tomorrow with the dog? Step outside about 5 a.m. If skies are clear, look east for a fine, slender crescent moon rising just a few degrees north (left) of a brilliant planet Venus. To the right of Venus by the same distance is the bright star Aldebaran - the red eye of the bull in the constellation Taurus. Raise your gaze a similar distance above Aldebaran to find dim Mars.

July 17, 2009

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Last Friday was the 73rd anniversary of the hottest day on record for Baltimore. It was 107 degrees on July 10, 1936, and that blistering day followed a record 103 degrees on the 9th. The 10th was also the only day since record-keeping began in 1871 that we've ever reached 106. That's because the next-highest record highs were all 105 degrees, reached on Aug. 6 and 7, 1918, and again (thankfully, after the invention of air conditioning) Aug. 20, 1983.

July 16, 2009

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Richard Lelonek, in Baltimore, saw last week's comments on how thunderstorms and temperature inversions can cause static and interference on AM and FM radio. "How about digital transmissions of TV signals?" he asks. Brief "dropouts" and pixelation of weak digital TV broadcast signals can be caused by urban "heat island" effects - rising plumes of hot air over city streets and rooftops.

July 12, 2009

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Almost six weeks into the 2009 Atlantic hurricane season there is nothing stirring. The only tropical depression of the season so far appeared in May, then faded. The building El Nino in the Pacific will work to suppress hurricane formation in the Atlantic basin. But storm experts say early activity alone says little about what to expect during the season's peak, from August through October.

July 11, 2009

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Donald Gansauer in Canton hears "a lot of static on WBJC on occasional evenings. What is it about the atmosphere that causes AM/FM radio reception to go bad?" AM signals are vulnerable to electrical discharge (lightning) in thunderstorms. On FM, temperature inversions (warm air trapped above cold) can bend radio waves, causing interference. It's more common in cities, or near large bodies of water.

July 10, 2009

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Bill Edwards in Trappe saw a TV program about the use of chemicals "to divert or stop rain. ... I have noticed on many weekends that rain is predicted [but] it does not rain in this area. Curious." Forecasters can be wrong, and summertime showers can be hit-or-miss. The National Academy of Sciences found that, except for dissipating rare "cold fog," cloud seeding for weather control is "an act of faith," not science.

July 5, 2009

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Jane Buxton Brown of Lakehurst wonders about the solar system: "Will you tell me how planets got into their orbits originally, and why they stay in them?" The planets condensed and grew amid cooling and collisions of gas and dust in the rotating solar "nebula" that circled the infant sun. Momentum will keep them circling unless something - the pull of a passing star, perhaps - kicks them out.

July 4, 2009

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Jeff Brauner of Baltimore likes the name Hortense but hasn't heard of a Hurricane Hortense in a while. He wonders what became of the name. Alas, it was retired after flooding from a Hurricane Hortense in 1996 caused 39 deaths and $217 million in damage in the Caribbean. Puerto Rico saw 24 inches of rain; 20 inches fell in the Dominican Republic. Hortense was replaced by the name Hanna.

July 3, 2009

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Today the Earth is at aphelion, its farthest excursion from the sun this year. Astronomers calculate we are 94,206,500 miles from Old Sol. That's roughly 3.1 million miles farther than we are at "perihelion" - our closest approach, on Jan. 4. The extra distance doesn't cool us down much. The Northern Hemisphere's sunward tilt at this time of year is what really heats up the northern summer.

July 2, 2009

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In case you're keeping track, 2009 will be exactly half over today at 8 a.m. That assumes you're going by Universal Time. If you run your life on Eastern Daylight Time, as most of us around here do, the midpoint of the year comes at 1 p.m. Did you make any New Year's resolutions back on Jan. 1? If so, half the time available to make good on your promises has now slipped away.

June 28, 2009

The Weather Page

June ends this week, along with the second quarter and (for many) the fiscal year. It's been wet, but temperatures averaged out near normal. July is Baltimore's hottest month. Average highs peak at 88 on July 20; lows at 65. All but seven dates have record highs of 100 degrees or more. The oldest record still standing is the 2.28 inches of rain that fell July 28, 1871, the first year records were kept.

June 27, 2009

The Weather Page

Tonight's sunset will be the latest of the year in the Northern Hemisphere. For Baltimore, the last direct rays of sunlight will sink below a flat horizon at 8:37 p.m. EDT. At the beach, sunset occurs at 8:28 p.m. Total solar illumination has been diminishing since the solstice June 21, but the air and ocean are slow to respond. So average Maryland temperatures don't start cooling until after July 20.

June 26, 2009

The Weather Page

It's the lightning season again. Bolts from the sky kill more than 50 Americans each year, on average. Nine have died so far in 2009. Most are young males, and a third are struck at work. Ninety percent of those hit by lightning survive, but often with chronic pain, brain injury and thought-processing problems. Hear thunder? Go inside. Stay off (and unplug) hard-wired computers, phones or games.

June 21, 2009

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Ted Lingelbach in Parkville asks how a developing El Nino event in the Pacific will affect this hurricane season. El Nino conditions have already figured into forecasts of an average to slightly quieter-than-average Atlantic storm season. But El Ninos also tend to increase the chances for snowstorms of 8 inches or more in Baltimore. We could be in for some real snow, at last.

June 19, 2009

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After all this rain, Greg Koppenhoeffer of Ellicott City wondered whether Baltimore's reservoirs were full yet. He looked for numbers online but found none. The city hopes to post reservoir data on a new Web site sometime this summer. Call Public Works, and they'll say Loch Raven and Prettyboy are full. Liberty is rising at 98.9 percent. Combined, they're at 99.4 percent. Plenty.

June 18, 2009

The Weather Page

On Saturday I wrote here that the "equation of time" was zero on that date, so "solar time" and "clock time" were in agreement. I said our sundials should register 12 noon when our clocks did. Then Carl Yowell of Baltimore reminded me that our clocks are on daylight saving time. (Doh!) So, your sundial should have read high noon when your clock said 1 p.m. (noon, standard time)

June 14, 2009

The Weather Page

This morning's sunrise was the earliest of the year, at 5:39 a.m. EDT in Baltimore. But sunsets keep getting later, faster, for another week, so total daylight minutes will increase until the summer solstice June 21. We'll finally see the latest sunset June 27 at 8:37 p.m. EDT. The solar mileposts reverse with the earliest sunset Dec. 7; shortest day Dec. 21; latest sunrise Jan. 4.

June 13, 2009

The Weather Page

Today is the day to set your sundial. On this date the "equation of time" is zero. That means solar time and clock time are in agreement, and noon on your sundial should agree with noon on your watch. This is also true on Sept. 1, Dec. 25 and April 15. The rest of the year, your sundial might run as much as 16 minutes fast or 14 minutes slow. Blame Earth's tilt and elliptical orbit.

June 12, 2009

The Weather Page

Frances Bowman in Perryville wants to know "how often weather reports are actually correct, and how meteorologists defend their batting average." The NWS runs lots of stats to rate its forecast offices. But if tomorrow's high is 74 instead of 75, is that wrong? Is a 5-degree error on a seven-day forecast bad? We predict eclipses with precision because there are few variables. Weather variables are countless.

June 11, 2009

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Jeff Brauner in Baltimore asks "what actually converges" in the intertropical convergence zone where Air France Flight 447 went down. He wonders if it's safe to fly there. Northeast trade winds above the equator and southeast trades south of the line converge in the ITCZ. They force warm, humid air skyward, forming equatorial thunderstorms. There's normally little risk to modern airliners.

June 7, 2009

The Weather Page

If skies clear tonight, watch the full moon rise over Baltimore at 8:54 p.m. (At the beach? Look for it rising over the ocean nine minutes earlier.) This is the third full moon after the vernal equinox, and the last before the solstice June 21. That makes it the Flower, Strawberry or Rose Moon. Speaking of flowers, has anyone else noticed the gush of red roses on gritty Eden Street, south of Fleet? Beautiful.

June 6, 2009

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Carl Yowell of Baltimore asks: "In today's Sun ... the forecast is 'Rain 80%, Forecast: occasional rain.' What exactly does that mean? Eighty percent of the state will get occasional rain? Or an 80 percent chance of the forecast being correct?" A perennial question. It means that 8 out of 10 times in the past, when conditions were identical, the forecast area had intermittent rain.

June 5, 2009

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Frances Bowman of Perryville asks: "What kind of education does a meteorologist need?" It's no cakewalk. The National Weather Service wants a bachelor's degree in meteorology or atmospheric science. Course work must include thermodynamics, analysis and prediction, remote sensing, physics and calculus. Then choose three: hydrology, statistics, chemistry, oceanography, climatology, aeronomy or computer science.

May 31, 2009

The Weather Page

A long-range space-weather forecast: After the quietest low in a century in the 11-year cycle of solar activity, NOAA scientists predict the next solar peak will top out in May 2013 at the lowest level since 1928. But even "weak" solar cycles can act up. A similar cycle in 1859 produced a solar storm that set fires in telegraph offices and sparked Northern Lights bright enough to read newspapers by.

May 29, 2009

The Weather Page

The 2009 Atlantic hurricane season begins Monday. The first named storms will be Ana, then Bill. Military forecasters during World War II were first to give female names routinely to tropical storms in the Atlantic and the Gulf. In 1953, the U.S. adopted the practice, alternating with male names beginning in 1979. The 21-name alphabetical lists omit Q, U, X, Y and Z, and they repeat every six years.

May 28, 2009

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With days to go, this is already one of the wettest Mays since record-keeping began here in 1871. The airport total through Tuesday was 7.1 inches, drowning the long-term average of 3.89 inches. The record is 8.71 inches, set in 1989. The second-wettest was just last year, when 7.77 inches fell at BWI. The third-wettest was 7.26 inches in 1894. This month's dunking has tied with May 1960 for fourth place.