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April 30, 2008

A cold morning, but no record here

Woke up this morning to a chilly 35 degrees out on the WeatherDeck in Cockeysville. Started out the door with a light jacket, and my wife stopped me. "Is that going to be enough?" she asked me?

Now, you need to understand that she works for the Baltimore County schools, where they turn off the furnaces on April 15. The staff at her school has been freezing for two weeks. (Sorry. No pay raises, and no heat either for the folks who teach our kids.) She can't wear enough clothes to stay warm in the classroom. It took her all evening at home to warm up again. And our furnace kicked on last night.

But I digress. I stepped outside, and it was cold alright. But I kept the light jacket. The sun was bright and warm, and the air has warmed up quickly this morning. Downtown, at Calvert & Centre streets, the overnight low was only 47 degrees - about normal for this time of year.

Out at BWI, the thermometer slipped to 36 degrees this morning. But as chilly as that was, it was just shy of the record low for an April 30 at BWI, which was 32 degrees, set back in 1961, during the Kennedy Adminstration.

Here are some other overnight lows reported this morning from around the region:


Forecasters are looking for a high this afternoon around 60 degrees, about 10 degrees cooler than the longterm average.


Here's the good news. This month's Goldilocks weather has saved us a bundle in both heating and cooling expenses. The total of heating degree-days for April at BWI ran 25 percent below the longterm averages, meaning a 25 percent savings in consumption, all else being equal. And cooling degree-days were also very scarce, running 40 percent below the norm.

That silence from the furnace and the AC compressors is like the jingle of change in your pocket. Enjoy it.

Posted by Frank Roylance at 10:34 AM | | Comments (1)
Categories: By the numbers

April 29, 2008

April rain surplus tops 1.8 inches

Rain over the last three days has brought the month's total to more than 4.6 inches at Baltimore-Washington International Thurgood Marshall Airport. That's more than 1.8 inches of surplus for the month through Monday, and brings the deficit since Jan. 1 down to less than an inch. 

Here are the monthly surpluses (+) and deficits (-):

Jan.: -2.00 inches

Feb.: +0.78 inch

March: -1.56 inches

April: +1.84 inches (through Monday)

The 4.6-inch total for April also makes this the wettest April since ... well, since last year, when we absorbed 5 inches of rain. Normal for a complete April at BWI is 3 inches, but we've topped 4 inches of rain in April only seven times since 1980.

Here are some rain measurements for yesterday from around the region.

Maryland streamflow is abundant for the time being. Here's the realtime flow map. And groundwater reserves continue to rise.

Here's the chart for that monitoring well out in Granite, Baltimore County, we like to track. Looks like their gear failed Sunday just as the latest rains began. But it's up about 4 inches since April 1.


Posted by Frank Roylance at 4:50 PM | | Comments (0)
Categories: Drought

Clearing skies today, cold night ahead


It should begin to feel a little less like Ireland today. The clouds you see on top of us in the satellite image should begin to erode, the sun should reappear and the dank air will begin to dry out this afternoon. The cold front is past us now, and high pressure is building in.

The clearing skies, of course, will increase radiational cooling after dark tonight. That could mean some patchy frost west of the I-95 corridor. The forecast lows show 37 degrees at BWI, 36 at Westminster and 35 at Hagerstown. That's plenty cold enough for frost.

Wednesday may be our only truly sunny day this week. But it will be chilly. They're calling for highs of only 60 degrees tomorrow at BWI. That's almost 10 degrees below normal for this time of year. There will be clouds around Thursday and Friday, too, but we should see some sunshine as well. For those of us longing for some toasty weather amid all this Irish mist, Friday will be the warmest day of the week, reaching only 74 degrees.

Then, it looks like yet another damp weekend, with showers returning late Friday and lingering through Sunday as a new low out of the northern Plains states drags the next cold front through the region. Slainte!

Posted by Frank Roylance at 10:51 AM | | Comments (1)
Categories: Forecasts

April 28, 2008

Rain pelts pollen, petals

Rainfall yesterday and today has done a good job of knocking down last week's sky-high pollen counts. Unfortunately, it has also put an end to the spring blossoms we've enjoyed in recent weeks.

For some, like this driver this morning on Harford Road, it also offers an unexpected decoration for the old gray ride. The picture was taken by Kurt Kocher, spokesman for the city's Department of Public Works. Thanks, Kurt!

Kurt Kocher


Posted by Frank Roylance at 4:31 PM | | Comments (0)
Categories: Cool pictures

Perverse precipitation pattern persists

 NOAA weather radar

I need to start working weekends, and taking the middle of the week off. Maybe you've noticed. Most of our rain this month has fallen on or around the weekends, while the workweek has remained mostly sunny.

It's uncanny. And worse - the forecast for this week is shaping up along much the same lines. Rainy today and early tomorrow, then clearing for mid-week, and clouding up for more rain this weekend. Who wrote this script?

You can look it up:

* Fri-Sun, April 11-13:  0.18 inch rain

* Mon-Fri, April 14-18: Trace

* Sat-Mon, April 19-21: 1.97 inches rain

* Tues- Fri, April 22-25: no rain

* Sat-Sun, April 26-27: 0.49 inch rain

There may be some science behind the idea, too. In summer at least, there's evidence that human activity - particulate air pollution, which peaks during the workweek - can cause weekly cycles in rainfall in the southeastern U.S. Here's more.

And there's plenty more rain expected today. Showers and thunderstorms are likely after 2 p.m. this afternoon, perhaps extending into Tuesday morning as low-pressure pulls cool, damp air in off the ocean today, and drags a cold front across the area tonight.

Then things start to dry out for the middle of the week. The sun should be out by tomorrow afternoon. Clear skies by Tuesday night could produce lows in the 30s, and a patchy late frost by Wednesday morning west of the I-95 corridor.

The sunshine should persist through the rest of the week, with daytime highs crowding 80 degrees again by Friday (sounds just like last week, doesn't it?) But then clouds and moisture and showers move back into the region - you guessed it - for the weekend.

The good news, of course, is that we are gradually making up the rainfall deficit that had been accumulating since last May.

Since Jan. 1, BWI has recorded 11.38 inches of precipitation. That's less than 2 inches below the long-term average for the period, and we're likely to erase a good bit of that shortfall before the rain ends tomorrow morning.

And, while it may not have seemed like it late Saturday afternoon (as the north wind turned cold and dropped temperatures here at Calvert & Centre streets from nearly 80 degrees at 4 p.m., to just 65 degrees by 7:30 p.m.), April has been unusually mild - the 6th warmest April at BWI in the past 30 years, averaging 56.2 degrees. 

One more day of this cool, dank, marine weather, though, and maybe April won't be quite such a standout.

Posted by Frank Roylance at 10:37 AM | | Comments (0)
Categories: Forecasts

April 25, 2008

AccuWeather sees "slightly" more active hurricane season

Yet another crowd of tropical weather forecasters has chimed in with their predictions for the upcoming Atlantic hurricane season. Two weeks ago it was the Colorado State University team of Phil Klotzbach and William Gray, calling for a "well-above average" season.

Now it's's hurricane trackers, led by Joe Bastardi, who's expecting only "slightly more storms than average," with increased risk of U.S. landfalls, during the six-month season that opens, officially, on June 1.

For the record, "average" in the Atlantic basin during the period from 1950 to 2000, means 9.6 named storms, with 5.9 of those growing to hurricane force, and 2.3 of those, on average, reaching Category 3, with sustained winds of 111 mph or more.

Bastardi and his crew say both the waning La Nina conditions in the tropical Pacific Ocean, and a continuing warm-water cycle in the Atlantic argue for slightly more activity than the average, and increase the chances for U.S. landfalls.

More specifically, they note that the warm conditions are not uniform across the basin. "In some areas where hurricanes normally form - the central and eastern tropical Atlantic," Bastardi said, "ocean water temperatures are near or below normal. This should limit the number of storms." So don't expect a blowout season like 2005.

But "the warmest waters relative to normal will be in the northern areas of the Atlantic, especially toward the North American continent. This could potentially increase the threat of major landfalls to the U.S. coast."

Where the spread of storm tracks last year shifted southwest, sending a batch of powerful storms across the northern Caribbean, "this year, early indications show that the spread will move north and east, with a target closer to the Southeast U.S."

In their April 9 forecast, Klotzbach and Gray said there would be a 45 percent chance that a Cat. 3 storm or bigger would make landfall somewhere along the east coast, including Florida. The long-term average for the last century is 31 percent per season.

Bastardi and company say the conditions this year most resemble those in 1955, 1996 and 1999. (Klotzbach and Gray agreed on 1999, but also found analogs in 1950, 1989 and 2000.) NOTE: An earlier version of this post, relying on a release from AccuWeather included inaccurate dates. AccuWeather has since corrected its release, and those fixes are reflected here.)

In 1955, Hurricanes Connie and Diane struck North Carolina. And 1999 saw both Hurricanes Floyd and Dennis strike North Carolina. Here's the storm track for Floyd.


Hurricane season forecasting is, of course, a very young science. Weather and climate are vast, chaotic systems with more variables than even the most advanced computer models can capture with any certainty. These forecasters do their best with the knowledge they have (or think they have). And their efforts get lots of news play because hurricanes are big threats to life and property. There is always some benefit to alerting the public to the risks we face every year, in the hope we will pay attention, and prepare, when storms are on the move.

NOAA - AndrewWhen seasonal forecasts fall short of perfect, as they have in recent years, there's a risk that the public will scoff and pay less attention to the hazard in the future. That would be a mistake. Even a slow storm season can cough up one or two calamitous storms. See Hurricane Andrew in 1992. That's some of Andrew's aftermath at left.

Next up is the National Oceanic and Atmospheric Administration's forecast, due out next month.

Posted by Frank Roylance at 10:48 AM | | Comments (0)
Categories: Hurricane background

April 24, 2008

More on Sunday's rain, tornadoes

Imagine a 6 by 6 oak post, sunk three feet into the earth as a support for an outbuilding. Now imagine wind strong enough to suck it up out of the ground like a golf tee and toss it the length of four football fields. That's what the NWS surveyors found in Virginia where one of Sunday's three tornadoes struck. And that was only an EF-0 twister. Here's more on the Enhanced Fujita scale of tornado intensity.

The initial reports from the NWS Sterling forecast office are now available online. Click here. For the specifics on the Maryland damage, click here. For the Virginia details, click here.

There's also this nifty map of rainfall reports from the precip on Sunday and Monday.  It's a bit disorienting, covering just the Sterling office's forecast area. That's the Western Shore of the bay on the right, with Harford County at upper right, St. Mary's at lower right. The Pennsylvania line runs across the top, as far as Allegany County. (Garrett is covered by the Pittsburgh office.) The bulk of the map covers Northern Virginia.

National Weather Service

Posted by Frank Roylance at 5:39 PM | | Comments (0)
Categories: Tornadoes

Drought in So. Maryland recedes

The new Drought Monitor map is in this morning. As expected, it shows the recent rainfall (and there's more to come) has shrunk the region of the state that's still experiencing moderate drought conditions (tan on the map), from 27 percent to 22 percent.

Meanwhile, the region that is rated "abnormally dry" (yellow plus tan) has diminished from 51 percent to 36 percent. The portion of the state enjoying normal soil moisture and streamflow (white on the map) - including Baltimore and its suburbs - has jumped from 49 percent last week, to 63 percent this week. 

Streamflow looks better across most of the state, too. And the forecast promises more moisture this weekend, into Monday. Bad news for outdoor plans, but good news for gardens, crops, reservoirs and water tables. Here's a 30-day chart for a USGS monitoring well in Granite, Baltimore County.


Posted by Frank Roylance at 10:10 AM | | Comments (0)
Categories: Drought

April 23, 2008

Enjoy it now; cooler, wetter weather due

The Sun - Nanine Hartzenbusch 2003 

                                                                             Sun photo by Nanine Hartzenbusch 2003 

We're headed for the 70s today, with plenty of sunshine getting through amid increasing cumulous clouds. You can thank warm, moist air flowing up from the south and west.

But enjoy the next couple of days because forecasters see a series of cold fronts in our future, bringing chances for showers this weekend, and by next week a "soaking rain" before this balmy springtime weather returns.

But the work week (wouldn't you know) looks sunny and mild, with temperatures crowding 80 degrees by Friday. Plan your lunches for a sidewalk cafe somewhere, because you won't be eating al fresco this weekend.

They're calling for highs in the 60s and afternoon showers on Saturday as a high-pressure center over New England shoves what meteorologists call a "backdoor" cold front our way off the water. That happens when the clockwise circulation around the high to our north and east sweeps eastward around the high, bringing cool, wet air in off the Atlantic. This one's not too strong, so any precip will be isolated or scattered.

But there's another, stronger cold front approaching from the Great Lakes by late Saturday, increasing our shot for some showers on Sunday. And yet another cold front due here by Monday has plenty of moisture and forecasters are saying it "has the potential to bring a soaking rain to the region" early next week. The precise timing is a little vague at this point. But you'll likely need an umbrella at the bus stop next week.

There are still cooler conditions - highs in the 50s - and more puddles ahead later on next week. April showers, indeed.

Posted by Frank Roylance at 10:57 AM | | Comments (0)
Categories: Forecasts

April 22, 2008

Want to be a weather observer?


                                                                                                    Credit: CoCoRaHS 

Do you love weather? Do you like to work with numbers and weather instruments? Perhaps you'd like to become a volunteer weather observer in Northern Maryland for the Community Collaborative Rain, Snow and Hail Network (CoCoRaHS). 

Bruce Sullivan is reaching out to the WeatherBlog in the hope that our readers might include folks who would be interested in joining the CoCoRaHS team in this area. You would be contributing to the gathering of data such as these.

The group is organizing another training and information session for would-be observers, this coming Tuesday at 3 p.m., at the U.S. Geological Survey office near the University of Maryland Baltimore County. The address is USGS, MD-DE-DC Water Sciences Center, 5522 Research Park Drive, Baltimore, MD, 21228.

(An earlier version of this post listed a 4 p.m. start time. That is incorrect. Session begins at 3 p.m.)

You can also email Bruce at

Finally, you can read more about the organization here. And here.

Posted by Frank Roylance at 2:35 PM | | Comments (0)
Categories: Observer reports

Rains continue to boost reservoirs

Monday was the rainiest day at BWI-Marshall Airport since Feb. 1, and the improving precipitation picture is having the desired effect on the Baltimore region's reservoir system.

Rainfall over the past two days at BWI totaled 1.97 inches. That pushed the month's total to 3.25 inches, which is a quarter-inch wetter than the average April for the period 1971-2000. Monday's total was 1.32 inches. That was not quite a record for the date. Baltimore received 1.41 inches on April 21, 1918. 

Streamflow across the state is back in normal ranges, for now. But we remain in deficit for the calendar year-to-date, by about 2.5 inches.

The city's Department of Public Works reports the reservoir system is currently at more than 88 percent of its capacity, with more than 75 billion gallons in storage. That's up from 64 percent back in December, when authorities decided the continuing drought made it prudent to tap the Susquehanna River as a way to preserve supplies in the reservoirs.

Liberty Reservoir currently stands at 87 percent of capacity, up from 82 percent last month. Prettyboy is at 86 percent, up from 75 percent last month. Loch Raven stands at nearly 98 percent, up from 95 percent in March.

The new Drought Monitor map is being calculated today, and will be released Thursday morning. Here's how one of the city's reservoirs looked last fall.

Jed Kirschbaum 2007 

  Sun photo by Jed Kirschbaum

Posted by Frank Roylance at 12:18 PM | | Comments (0)
Categories: Drought

April 21, 2008

Wet until Wednesday

Those were some impressive showers yesterday. We totaled 1.8 inches here on the WeatherDeck in Cockeysville, with more rain due today as this low to our south keeps pumping wet air in off the Atlantic.

Down at BWI-Marshall they clocked just 0.65 inch by midnight last night, but other areas saw far more. Here is an accumulation map from the CoCoRaHS observers, with some observations topping 2 inches.

One report out of Sabillasville, in Frederick County exceeded 4 inches.

Here's a NWS accounting of some of the storm and damage reports yesterday, including several tornado sightings in Southern Maryland.

The forecast is another wet one, with more heavy showers likely today, wet again tomorrow, with the sun finally reappearing on Wednesday. The continued southerly flow off the ocean will bring a risk of minor coastal flooding at high tides today. Here's the list of advisories.

And I will be out in it today. My car quit on me. "Busted flat in Cockeysville, waitin' for a tow. Feelin' near as faded as my jeans ..."

Posted by Frank Roylance at 7:58 AM | | Comments (0)
Categories: Forecasts

April 18, 2008

Illinois quake details


This morning's Mag. 5.4 earthquake in Illinois occurred in an area with a history of small tremors - and some big ones - going back to the early 1800s.

Here's a link to the U.S. Geological Survey report on today's quake. And here's one to a description of the local geology and the history of tremors in the region.

Although we don't think of the middle of the country as being earthquake-prone, there have been some very powerful quakes in the region, centered mostly on the New Madrid, Mo., area. Historical accounts of New Madrid quakes in the early 19th century are quite astonishing. They were felt as far away as New England.

Here's what the USGS says about the area: "Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year. In addition, geologists have found evidence of eight or more prehistoric earthquakes over the last 25,000 years that were much larger than any observed historically in the region."

Emergency managers in Memphis and other communities in the area have recently begun to take the threat very seriously, and there has been a great deal of planning, and quake-proofing work in recent years to protect key Mississippi River crossings and gas and oil pipelines.

Posted by Frank Roylance at 8:35 AM | | Comments (2)
Categories: Events

Hot summer likely here, forecasters say

Long-range forecasters have a new prediction for this summer, just out this week. It's HOT.

The forecast for the June through August period says the probabilities point toward above-average temperatures for the northeastern United States. The same holds for the Western states and for Southern Florida. The map's below. Until recently, the forecast showed no clear trends on temperatures for our region. Now it does.

The same forecasters found no clear trends, however, on precipitation for the summer in these parts. The only strong trends seem to be in the Northwest states, which face dry conditions for the summer.


Posted by Frank Roylance at 8:24 AM | | Comments (1)
Categories: Forecasts

April 17, 2008

Second-warmest March globally, cool in US

The National Oceanic and Atmospheric Administration says March 2007 was the second-warmest on record globally, but cooler than the long-term average for the contiguous 48 states. In fact, the Western snowpack is the healthiest  in more than a decade, thanks to heavy snowfall in December, January and February.

Here's the full report.

And here are some highlights:

* Temperatures in the lower 48 states averaged 42 degrees in March, almost a half-degree lower than the average for the past 113 years.

* Alaska had its 17th-warmest March, 3.8 degrees above the mean from 1971-2000.

* Globally, land and surface water temperatures averaged 1.28 degrees above the 20th century mean, making it the second-warmest March globally. The average was pushed higher by much-warmer-than-normal temperatures in Eurasia.

* While the Western snowpack fared well in March, snow cover across the Northern Hemisphere was the fourth-lowest on record, consistent with the pattern of the past two decades, in which warming temperatures reduced the northern snow cover.

Extreme events during March included a rare downtown tornado in Atlanta, heavy rains in Missouri, widespread flooding from the Ozarks to Indiana, heavy snows in Kentucky and Ohio.

Here's a NOAA map of some other extreme March events around the world:


Posted by Frank Roylance at 3:20 PM | | Comments (0)
Categories: By the numbers

Offshore storm kicks up surf


One reason we're enjoying this beautiful stretch of dry, sunny weather along the East Coast is that the high-pressure system that's generating our delightful conditions is being held in place by a deep low off the coast, to our east.

From space, the big storm can be seen clearly as it spins in this satellite loop, counter-clockwise, almost like a hurricane. It's also churning up the ocean, and sending strong surf ashore along the Carolina coast, where high surf advisories are up.

The storm is slowly moving off to the northeast, and our fine weather will begin to deteriorate late Saturday as the next low moves our way, with rain due on Sunday and Monday. Sorry.

Posted by Frank Roylance at 2:47 PM | | Comments (0)
Categories: Cool pictures

Lighting ordinances can restore the night sky

USNO, FDSC, Lowell Observatory, Dan & Cindy Driscoe 

Fifty years ago, in 1958, Flagstaff passed the nation's first lighting ordinance designed to protect the night sky from the ravages of "light pollution." In truth, it was an effort to protect the view into space from the neaby Lowell Observatory. The pioneering work in Flagstaff has subsequently preserved the riches of the night sky for a growing list of observatories situated in the nearby mountains, and thereby encouraged the growth of an important local industry.

This photo shows in a very dramatic way (aided by both a truly light-pollution-free sky and a time exposure) just how glorious the night sky over Flagstaff can be now that outdoor lighting has been shielded - so that it points down, where it's needed, instead of up at the bellies of passing birds. It also happens to save energy and money, since you don't need as much candlepower if you're not sending light where it's not needed.

Here in Baltimore (below), and in most other cities, we delight in urban lighting programs that illuminate our buildings from below, with most of the glare shining up into the sky and erasing the stars ! When was the last time YOU saw the Milky Way?

You can learn more about outdoor lighting ordinances, from the International Dark Sky Association.

The Flagstaff image, credited to Dan and Cindy Durisco, the US. Naval Observatory, the Lowell Observatory and the Flagstaff Dark Skies Coalition, shows the San Fransisco Peaks beneath the Milky Way and a stationary "lenticular cloud," formed as moist air flows up and over a mountain range, condensing as it cools. Here's an amazing gallery of lenticular clouds.

Thomas Graves

Credit: The Sun, Thomas Graves, 1998

Posted by Frank Roylance at 10:17 AM | | Comments (4)
Categories: Cool pictures

April 16, 2008

"Fine autumn weather"

That's what the folks out in Sterling are calling it - fine "autumn" weather. Clear, dry air beneath a big fat high-pressure system is bringing us sunny days and clear, starry, frosty nights this week. And we can expect it to continue into Saturday before a new low from the east begins to cloud things up and threaten some showers by Sunday.

In the meantime, we're beginning to catch the return, clockwise flow around this high. That will scoop warmer air from the Southeast and send it our way, raising daytime highs to the mid- to upper-70s Thursday and Friday. Getting married Saturday? The good weather should hold long enough to keep things pretty for you and your guests, though clouds will be moving in later in the day. The rain, at least, should hold off.

Nighttime lows will moderate, too. After several frosty mornings this week in the 30s, and even some 20s to the north and west of the urban corridor, we will see the last of the 30s tonight, with overnight lows in the 40s and 50s for later in the week.

One interesting phenomenon to watch in the next two days will be the Chesapeake bay breeze. As the land heats up under strong April sunshine, the air above it will warm, too, and start to rise. As it does, cooler air over the water will be drawn in to replace it. That will hold temperatures down along the Western Shore, in places like Annapolis and Baltimore, while inland communities like Westminster heat up. A similar setup will likely keep the beaches under onshore breezes, keeping them quite cool relative to inland Eastern Shore towns. 



Posted by Frank Roylance at 4:38 PM | | Comments (0)
Categories: Forecasts

April 14, 2008

Noon today is REALLY noon

Dennis Barnes is setting up a beautiful instrument in his garden in Abingdon. It's called an armillary Galileo sundial. He wrote to me yesterday because he is preparing to "set" the sundial today, taking advantage of the fact that today - April 15 - is one of only four days on the annual calendar when solar noon - the moment when the sun is highest overhead - is the same as noon according to "mean solar time," or clock time.

To astronomers, it's the day when the "equation of time" equals zero. At other times of the year, the sun can be as much as 14 minutes "fast" or 16 minutes "slow" relative to clock time.

But of course this is astronomy, so nothing is as simple as we'd like.

Here's Dennis's problem: First, the equation of time (the difference between mean sun time and clock time) is only zero today along the "standard meridian" in each time zone. For us here in Eastern Time, that's 75 degrees west longitude, which runs north and south just off the beaches at Ocean City. So, all of Maryland is actually west of the standard meridian. Solar noon reaches us late as the sun moves across the sky from east to west.

Still with me? Dennis was aware of the problem, but he wasn't sure how far west of 75 degrees he is, or how that would affect his "local solar noon." I took the question to Geoff Chester, at the U.S. Naval Observatory in Washington. He told me that the sun is about 4 minutes "late" for every degree of longitude west of the standard meridian. 

Dennis used Google Earth to determine that his garden is at 76 degrees, 19 minutes and 45 seconds west longitude. So, Geoff did the math and reported that solar noon will reach Abingdon at 5 minutes 19 seconds after 12 noon Eastern Standard Time. But we have to correct for Daylight Time, pushing solar noon over Dennis's sundial to 1:05:19 p.m. EDT

But wait! There's more.

Since this is a Leap Year, the sun on the 15th is actually 5 seconds later than it would be on a non-Leap Year. So solar noon in Dennis's garden will actually occur at 1:05:24 p.m. EDT, according to Geoff's calculations. That's Dennis's new sundial above, photographed at precisely 1:05:24 p.m. Tuesday. You can see the arrow's shadow, smack on the XII.

All of this is, of course, way too fussy for setting a sundial. But it points out the quirks of timekeeping owing to irregularities in the Earth's tilt and orbit that astronomers have noted for thousands of years.

For the record, the equation of time will be "zero" again - bringing sun time on the standard meridians into step with clock time - on June 13, Sept. 1 and Dec. 25.

(Photo by Dennis Barnes, used with permission) 

Posted by Frank Roylance at 5:22 PM | | Comments (3)
Categories: Sky Watching

Sunny days, frosty nights

It was a frosty 32 degrees out on the WeatherDeck this morning. The rear window defroster took care of the glaze in short order, and the windows facing the house and nearby cars were clear. Daytime temperatures will rise as the week progresses, crowding 80 degrees by Friday, if the forecast holds up. Temps will be cooler along the bay, especially as solar heating of the land sets up a bay breeze, drawing cooler air onshore from the Chesapeake.

But the clear skies in the forecast will mean a risk of frost for the next two nights as radiational cooling wipes out warmth accumulated from the sunshine during the day.

The overnight low this morning at BWI was 38 degrees. That's no record. The record low for today's date is 24 degrees, set back in 1950.  Here are some other low readings from around the region this morning.

It may seem like it's been cold this month, but in fact we're running 2.2 degrees above the average so far. We had three straight days in the 70s Thursday through Saturday, reaching 78 at BWI on Friday afternoon. That was 15 degrees above the long-term average for the date, helping to keep the running average fairly high.

Small craft advisories are up on the Maryland portion of the Bay until 4 p.m. today as north winds keep things stirred up. Forecasters are also noting the chance for patchy frost between the I-95 corridor and the mountains tonight and tomorrow night.

Clear skies at night for the rest of the workweek will mean fine stargazing. Unfortunately, the International Space Station will not be making an appearance. But Mars (high in the southwest) and Saturn (high in the southeast) are visible in the evening. And Jupiter shines low in the southeast in the early morning before dawn. The moon makes a straight line with Saturn and Regulus tonight, in Leo. And they form a triangle tomorrow night.

Posted by Frank Roylance at 10:46 AM | | Comments (1)
Categories: Forecasts

April 11, 2008

Gray and drippy. Again.


Hope you enjoyed yesterday's sunny weather, with highs in the 70s, because we're in for yet another long round of gray and drippy weather until early next week. That's us, above, on Thursday - in the clear. But you can see the weather to our west. Not clear. Headed our way. Here's a better look.

We reached a fine 73 degrees in the sunshine yesterday at BWI. Readings from around the region went as high as 79 degrees just east of the DC area. But now we're back in the soup, waiting for the next cold front to drift our way and stall for the weekend. That will leave us with more unsettled weather, with intermittent showers, and maybe an isolated thundershower or two.

Forecasters are watching a flow of warm, moist air moving up from the south ahead of the next cold front. It's coming to us courtesy of that big storm system over the upper Midwest - the source of lots of really bad weather this week - snow, rain, and tornadoes - out on the Plains. It's the counterclockwise flow around that low that's bringing us these mild temperatures and gray skies, and maybe some rain or gusty showers developing from west to east as the day goes by.

As bad as it looks to our west, forecasters in Sterling do not believe this system will bring severe weather this far east. Instead, they say, the system is expected to weaken.

The front is expected to stall to our west on Saturday, leaving us in this mild, gray and breezy limbo until the front pushes past us and out to sea. By Sunday we should be on the cold side of the front. Temperatures are expected to be back in the 50s Sunday, with some sunshine breaking through. Nighttime lows will fall back in to the 30s.

Forecasters think we'll finally break out of the pattern by Tuesday, with seasonable temperatures and sunshine at least until late in the week, when a new storm system may come into view.

Posted by Frank Roylance at 10:44 AM | | Comments (1)
Categories: Forecasts

April 10, 2008

Drought eases on Lower Shore


The new Drought Monitor map is out this morning, and it shows that recent rains - which have been more abundant to our south and east - have eased the severe drought conditions that have prevailed on the Lower Shore for many weeks.

In fact, "severe" drought conditions - which had encompassed more than 17 percent of the state - have entirely disappeared from this week's drought map. It's the first time since November that severe drought conditions have not been noted anywhere in Maryland. The assessments take into consideration rainfall, streamflow, soil moisture and plant health as assessed by satellite monitoring. 

That said, 27 percent of the state - in extreme Southern Maryland and the Lower Shore (tan on the map) - remains in "moderate" drought, including all the territory that had previously been ranked "severe."

And "abnormally dry" conditions (yellow) persist south of Baltimore, on both sides of the Bay.

But as damp as it has seemed, many streams in Maryland continue to run below their averages for this time of year. The fact is, we have not had abundant rainfall. What has fallen as been light - mostly drizzle and showers measured in fractions of an inch.

The forecast promises more of the same. Showers are likely again by late tomorrow, continuing through Saturday and perhaps into the evening. We'll see just a few more fractions of an inch, or more if thunderstorms break out. On the other hand, temperatures will be more springlike, reaching into the 70s today and tomorrow and Saturday before cooler weather returns. We could see temps in the 30s again by Sunday night after a cold front gets by us.

The norms for this time of year at BWI call for highs in the mid-60s, and lows in the low 40s.

Posted by Frank Roylance at 10:35 AM | | Comments (0)
Categories: Drought

April 9, 2008

Big yellow thing appears over B'more

NASA - Spitzer Space Telescope 

It looks vaguely familiar, but somehow odd...  Our familiar gray skies seem to have turned an odd shade of blue this afternoon. And some sort of brilliant orb has appeared - a blinding yellow disk that gives off infrared radiation - heat.

So take cover. Venture outdoors only at your peril. And by all means, do NOT look directly at this freakish apparition. Astronomers assure us it will disappear in time, probably by 7:40 p.m. if not sooner.

Maybe it has something to do with this hole in the clouds over central Maryland. If so, it should pass. The gray will return. Be calm.



Posted by Frank Roylance at 4:06 PM | | Comments (0)
Categories: Sky Watching

Clouds struggle to break up


Easterly winds continue to push cool, damp marine air onto the Atlantic coast and all the way west to the Blue Ridge. You can see where the low clouds run up against the high ridge in the satellite photo above. West of that line, the clouds begin to break up and the sun is shining through.

As the high pressure system that's sweeping all that cool air and clouds off the Atlantic begins to move away, Marylanders east of the mountains should begin to see the clouds thin, and sunshine (!) cut through. Where that happens, temperatures could push into the 60s and 70s.

Unfortunately, those of us along the ocean and the Chesapeake Bay will be the last to see the clouds part. (Where is Charleton Heston when you need him?)

Forecasters out at the NWS Sterling office put it this way: "For locations closer to the bay, including the City of Baltimore, the easterly flow will hang on longer, so we kept low clouds in (the forecast) for the remainder of the day along with patchy fog and drizzle." We'll also likely stick here in the 50s.

As Dan Rodricks likes to say, "Great. Just great."

Tomorrow looks better. After a cold front slips by tonight, they say we should see "partly sunny" skies Thursday. Temperatures could slide into the 70s. Friday now looks a bit cloudier, with rain showers and cooler weather returning for the weekend.

But be thankful you're not living at high elevations at the western end of the state, or in West Virginia. They're looking for snow showers this weekend as lake-effect snows ride in behind the cold front. A cold rain in the valleys.

Sheesh. C'mon Summer!


Posted by Frank Roylance at 10:29 AM | | Comments (0)
Categories: Forecasts

April 8, 2008

A warmup, but clouds linger

NOAA Aqua Earth Observing Satellite 

Looks like this annoying weather will hang on for at least another day. Chilly temperatures in the 50s - that's 10 degrees below normal for this time of year - and clouds in off the Atlantic will remain our dismal fate today. That's us, above, under all those clouds yesterday. (The red circle points out some smokey haze in the Plains.)

The forecast out of Sterling this morning promises more clouds at least until Friday. They're calling it "mostly cloudy," but sparing us the drizzle and spit we've had for the past few days.

The good news is that the temperatures, at least, will be improving as we come under the influence of  counter-clockwise circulation around a low-pressure system to our west, bringing warm air up from the South. They're expecting highs near 70 degrees by Thursday, and 71 by the time we see some significant sunshine again on Friday. But on Friday night the showers move back in along a passing cold front, and temperatures sink back into the 50s during the day by Sunday, and the 40s at night.

Just a hint of warm, balmy weather would be nice about now wouldn't it? A few hours in the sunshine? Surrounded by spring blossoms and the smell of new-mown grass? A chance to wash the car? In shorts? Puleeeze?

But, I digress. The ill winds that have blown this chilly, damp weather off the Atlantic - along with the recent New Moon - have also raised the tides along the Western Shore of the Chesapeake. That link will take you to Tides Online, where you can check the tide gauges around the bay. Minor coastal flooding was predicted. But the Coastal Flood Advisory posted yesterday is due to expire at 11 a.m. this morning. 

Looking deep into the weekend, forecasters are talking about a "potent" storm system developing in the central Plains states. They expect it to move toward Lake Michigan this week, pause, then making a run at the Northeastern states from Saturday into next week. We'd most lilkely see some showers and windy conditions. 

Coming up: Tomorrow, Phil Klotzbach and William Gray, from Colorado State University, will release their spring forecast for the upcoming Atlantic hurricane season, which begins in just seven weeks. They'll deliver it from a tropical weather conference being held in the Bahamas. But could I get my editor to send me down to cover it? Not a chance.

Posted by Frank Roylance at 9:48 AM | | Comments (0)
Categories: Forecasts

April 7, 2008

The word is "dreary"

Taking a lunch break from an all-day computer training session today. So I checked out the forecast, and it looks every bit as dreary as, well, a day-long computer training session.

Blame the ringer spinning out in the Atlantic. There's a big ol' low spinning counterclockwise off the Maryland coast. And to the north of that, over the Gulf of St. Lawrence, there's a big high spinning clockwise. Between them, they're shoving cool, damp, marine air back toward the mid-Atlantic coast. So we get a gloomy deck of gray clouds, and just enough moisture to spit out a few drizzles and showers. And it looks like we're stuck with this mess through Tuesday.

The easterly flow is piling up Chesapeake Bay waters onto the western shore and the tidal Potomac River. That's triggered a Coastal Flood Avisory, with cautions to the usual low-lying spots - Annapolis and Old Town Alexandria among them - to watch out for minor flooding at high tide. The problem is aggravated by last night's New Moon - often a time of exaggerated tides. So the water may rise a foot or two above the predicted levels. You can track the tide gauges here. I've grabbed the mid-day tide graph for you. See below.

Out in the mountains, in the higher elevations, there's fog, thick enough that forecasters have issued  a caution to drivers on I-68 near Frostburg to weatch out for visibilities near zero.

The forecast doesn't offer much to cheer about. Once again, Wednesday offers our best hope for some sunshine as the mess we're in now moves farther off the coast. Highs could approach 70 degrees by Thursday - more if the clouds part and allow more sunshine in. But Friday will see another storm system swinging through the region, with a threat of more showers right through the weekend.

Yes, we need still the rain. But really. This is glum. Am I right?


Posted by Frank Roylance at 12:07 PM | | Comments (0)
Categories: Forecasts

April 4, 2008

Welcome rain; more to come


That's us, under all those clouds, and sure, it's a pain. If you were walking around in it yesterday, the rain and penetrating cold (in the 40s) were unpleasant in the extreme. But farmers, and Marylanders with gardens and wells, should welcome this slow, intermittent rainfall. Forecasters say there's more to come.

We've clocked in 0.60 inch of rain here at The Sun since the rain began yesterday. There was just a little less than that out on the WeatherDeck in Cockeysville. BWI reported 0.70 inch. And here are some other readings from around the region - mostly between a half and three-quarters of an inch.

It's too early in the month to say much about April, but this rain is making a dent in the 1.5-inch deficit we accumulated in March at BWI. Best of all, the heaviest rain this week may fall to our south and east, promising a badly needed boost for soil moisture and ground water down on the lower Eastern Shore - parts of which remain in a severe drought that began late last spring. The NOAA Climate Prediction Center says the Shore can expect improving drought conditions this spring.

The forecasters out at Sterling say a series of low pressure systems will track across the region over the next day or so, bringing total accumulations since Thursday to a couple of inches in some spots. Today, most of the rain will fall to the north and west of the metro areas, with drier weather to our south and east. We're in a sort of transition zone, so we will likely see some rain today, but not a lot. Here's the radar loop.

A cold front slipping by us tonight will trigger more rain - as much as another half-inch tonight and tomorrow - with most of that falling to our south and east. Then, later on Saturday, the whole mess begins to move offshore. That should allow us to enjoy sunny skies on Sunday, with highs  in the 50s.

There's a chance for more drizzle and fog Monday as the high moves away, and - once again - we fall under the influence of its backflow off the ocean. But sunshine returns Tuesday through Thursday, with highs near normal, in the 60s. 

Posted by Frank Roylance at 10:23 AM | | Comments (1)
Categories: Forecasts

April 3, 2008

Rainy days ahead

Hope you enjoyed yesterday's sunshine, because we're headed for two days and nights of rainy weather. Several inches could fall across the region as warm, moist air, and a series of lows, move over and then displace the dome of colder air now in place across Maryland.

If the forecast holds up, we should see the first rain develop after 2 p.m. this afternoon. Folks out in the mountains, at higher elevations, could even see some sleet mixed in with this stuff.

The weather service has issued a Hazardous Weather Outlook message predicting "periods of heavy rain" this afternoon, through Saturday morning. "Rainfall amounts of two to three inches are expected to fall over a relatively long period of time," the message says.

The drawn-out nature of this rain will minimize the danger of small stream flooding, but the creeks will likely rise noticeably.

The rain starts with warm air being swept into the region from the south behind the departing high that brought us that nice weather yesterday. As it rides up over the cold air at the surface, the moisture will condense and fall as rain. Then, a storm center now in the Plains states will move in and intensify over the I-95 corridor late tonight and tomorrow morning, delivering as much as an inch and a quarter of rain in northern Maryland.

Late on Friday, and into Saturday morning, forecasters say we may see yet another round of rainfall - as much as another inch in all - as  a new low pushes through.

Then, it will all track offshore, leaving us with building high pressure and sunnier weather by late Saturday and Sunday. High temperatures for the weekend will be in the low 60s. 

Once again, we welcome the rain. Here's the new Drought Monitor Map, just out this morning. It shows a small increase in the region under the severest drought conditions:


Posted by Frank Roylance at 10:26 AM | | Comments (0)
Categories: Forecasts

April 2, 2008

Midwest snow photographed from orbit

Midwesterners might have wished it were spring, but Monday's snowstorm disabused them of any notion that it actually WAS spring for them. The storm whitened the ground across a broad swath, from Nebraska and South Dakota to the Upper Peninsula of Michigan. When the skies cleared, NASA's Aqua satellite snapped this picture of the results.

That broad brushstroke across the image is snow on the ground. The white patches on the right are clouds. Lake Superior is at upper right.  Here's more.

NASA Aqua 

Posted by Frank Roylance at 4:38 PM | | Comments (0)
Categories: Cool pictures

Only December failed to reach 70 degrees

Yesterday's high of 75 degrees at BWI was no record, but it did close the loop on a year in which only one month - December - failed to reach 70 degrees at the airport.

The mid-afternoon high stopped well short of the record high of 88 degrees for the date, set in 1978. From here on out the daily record highs are all in the 80s or higher. And, truth be told, temperatures in the 60s and 70s are not unheard of at any time of year in Baltimore. The record highs for December, January and February are all in the 60s and 70s.

Still, it seemed like we visited the balmy 70s quite often in this past winter.

Jan. 7:  70 degrees

Jan. 8:  70 degrees

Feb. 6:  72 degrees

Feb. 18:  71 degrees

Mar. 4:  71 degrees

Mar. 28:  70 degrees

December, as forecast, was our coolest month of the winter, never reaching the 70s. In fact, we only touched the 60s once, on Dec. 23, when the mercury at the airport reached 63 degrees.

But, looking back at the records, last winter - 2006-2007 - saw seven days with readings in the 70s, . The high was 75 degrees on Dec. 1. Only February passed without an afternoon in the 70s. It only rose out of the 40s on four dates, making it the coldest February in 30 years. In March last year we enjoyed five dates with highs of 70 or more.

Here is a map showing yesterday's high readings around the region.

Today's forecast promises considerably cooler weather. We'll probably stick in the 50s, but with all this sunshine, it will be delightful. The gusty winds should die down and let that sun keep the edge off.

Until they do, however, we will be on the edge of a wildfire hazard. The National Weather Service has issued a Hazardous Weather Outlook, noting "near critical fire weather conditions." Although recent drizzle has dampened the brush a bit, the stiff breezes and dry air will suck the moisture out of it, making it more easily ignited. So be careful with those smokes.

The clear skies and dry air, if they last into the evening, should make for some nice stargazing. Here's this month's guide to the April night sky, from the Hubble folks.

The fine weather won't last, unfortunately. Or fortunately - we still need rain. Here are some readings from yesterday's drizzle around the region. Pretty skimpy. And here's last week's Drought Monitor map, showing continuing drought conditions in Southern Maryland and the Lower Eastern Shore. 

We'll get some rain as this beautiful high moves offshore and puts us in the return flow off the ocean once again. Another low, or a series of them, will push in from the southwest, bringing us rain in Baltimore beginning Thursday night and continuing with some sort of showers into Saturday. If the forecasters are right, look for it all to clear out later Saturday and Sunday, leaving us with a decent weekend.

Posted by Frank Roylance at 10:18 AM | | Comments (0)
Categories: By the numbers

April 1, 2008

Ice leaving Lake Erie, St Lawrence River

That's spring in my book. Lake Erie is now largely ice-free for the first time in months. And the ice pack has broken up and left the St. Lawrence River at Quebec City.  Satellite data still shows a snow cover in upstate New York, but Pennsylvania looks mostly green (or brown, at least) again.

You can watch the snow retreat on this snow-cover loop for the last month. Time to set up the Tiki bars along the Niagara River (below)!

Niagara River - NY Power Authority


Posted by Frank Roylance at 12:38 PM | | Comments (0)
Categories: Cool pictures

A break in the clouds


Here's why we can't see the sun today - clouds, drizzle and fog. There's a cold front headed this way from the west, with a brief respite from the gloom. We'll likely see a few more showers today, but by late afternoon - maybe during our drive home tonight - we'll start to see some changes.

First, we can look forward to some heavier showers, and maybe even a thunderstorm here and there. Forecasters expect winds around 20 mph, with gusts to 36 mph as the front pushes through. Here's the radar loop;.

Behind all that we should see clearing skies as the barometer turns and high pressure moves in. Forecasters at Sterling promise sunny skies tomorrow, with cooler highs in the upper 50s. We could slip down into the 30s Wednesday night.

But then, on Thursday, we fall back into the return flow from the departing high, which will throw more cool, damp Atlantic air onshore and up against the mountains in what meteorologists call a "cold air damming" event. The wedge of cool, damp air hangs on Thursday and Friday east of the mountains and prevents warmer, drier air from moving in at the surface. That's exactly where we've been for the last couple of days, too. High elevations to our west could even see some sleet Thursday.

From there the computer models begin to disagree. One says the next cold front will clear the region by Saturday, bringing us some April sunshine for the weekend, and highs in the 60s. Another says the rain will hang around until Sunday. Make mine sunshine.

Posted by Frank Roylance at 10:30 AM | | Comments (2)
Categories: Forecasts
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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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