Archive for June, 2007

Heat Gone For Now
June 29, 2007

The latest heat spell has been broken by a cold front but summer has only just begun. The latest shot of heat and humidity produced three consecutive 90 degree days. Wednesday was the hottest with an airport high of 97 and an Inner Harbor high of 99. Wednesday was the hottest day in Baltimore since August 3 last year.

June is almost over and another 90 degree day is not in the cards for the month. This month has recorded seven 90 degree days. In comparison, six 90 degree days are on the books for June of 2006. The similarities with last year end there. This year, June is running about an inch below average on rain and the area looks a little parched because of the heat and spotty nature of the rains that did fall. June of 2006 was very wet due to a late month deluge and the month went down in the record books with a 4.13″ surplus.

The next big summer benchmark is the July Fourth holiday. Temperatures may get close to 90 by then but the biggest concern is any rain that may affect picnics, parades and fireworks. Below are two charts for the GFS computer model for mid week next week.


This long range computer model indicates that a warm front will be in the area on July fourth with a small rain chance. It appears that July fifth would have a higher rain chance when a cold front moves across the area. A lot can happen in the next week to alter this outlook so stay tuned. Enjoy the cooler temperatures and lower humidity levels while they are here.

John Collins

Relief From The Heat Of A Maryland Summer
June 26, 2007

With more heat and humidity headed for the Baltimore area this week everyone will be looking for relief in the form of air-conditioning, a fan or even just a little shade, and it’s weather patterns like this one that remind us why Maryland’s far eastern and western resort towns become so poplular in summer. The dramatic cooling affects of the Atlantic at Ocean City (current surf temp: 67), or the higher elevations around Deep Creek Lake become even more pronounced when the Baltimore area is sweltering under the influence of the Bermuda High off the coast. Four times this month BWI-Marshall has topped 90 degrees and on each of those days the mountains around McHenry, MD were 12-14 degrees cooler! The coast near Ocean City was much more comfortable on two of those hot days. Here’s a look at the high temperature comparisons for the hottest days this month:

June 1: BWI: 91 McHenry: 79 Ocean City: 78
June 8: BWI: 95 McHenry: 81 Ocean City: 91
June 18: BWI: 94 McHenry: 82 Ocean City: 89
June 19: BWI: 92 McHenry: 78 Ocean City: 81

Last week my family had a chance to spend a couple nights with friends at their mountain home situated at 2400′ above sea level overlooking Deep Creek Lake. The days were cool, with highs in the 60s, and the nights actually got chilly, with morning lows of 40-46. Perhaps a bit too chilly for those who like the warmth of June but perfect for those of us who enjoy a break from the long mid-Atlantic summer…including the black bear who arrived without an invitation! (Picture by Doug Miller)

Tom Tasselmyer

Heating Up
June 25, 2007

After five days of ideal weather with pleasant temperatures and low humidity the area will see the other side of a Mid Atlanic summer. Heat & humidity will be returning this week.

Dewpoint temperatures will be rising through the 60s on Monday and hover near 70 on Tuesday and Wednesday. These high dewpoint readings are the hallmark of a tropical airmass and all that goes with it. Hot air temperatures usually accompany these high dewpoints but in this particular situation the actual air temperature will be regulated by the amount of cloud cover. The air mass is expected to be unstable and it won’t take much to generate periods of cloudiness at the peak of the day’s heating potential. Additionally, storms west of the mountains will push eastward and the residual ripples of “energy” that survive the trip across the mountains may be enough to push the instability into scattered storm development east of the mountains. This will be especially true on Monday with more isolated activity likely on Tuesday and Wednesday. By Thursday a cold front will approach and the rain chances go up considerably. It should be more comfortable after the cold front passes.

The area has become a little parched and some rain would be welcome at this time. At BWI-Marshall the rainfall this month stands at 2.00″, .73″ below the 30 year average. It may not seem like much of a shortfall but most of the rain this month has come in small installments. The last good soaker over the whole area was on June 3.

The upshot … be prepared for some heat and humidity and don’t leave the windows open if you are going to leave the house or car for any length of time.

John Collins

Strong Storms For The Start Of Summer
June 21, 2007

An approaching cold front generated some unexpectedly strong storm activity late in the day today. As late as this morning, any rain associated with the approaching front was expected to stay north of the Maryland/Pennsylvania line but the shortwave wound up providing a little extra kick this afternoon, generating severe storms that crossed into Maryland and moved rapidly to the Baltimore area. The squall line that produced the most significant weather moved across the Baltimore area between 5:00 & 6:00pm. By the time the line reached Annapolis it was losing strength but it eventually moved across the Bay and on to a portion of the Eastern Shore.

The storm generated little or no lightning around Baltimore. The cell was moving northwest to southeast at about 45mph. Outflow winds running ahead of the actual rainfall were clocked at 60mph at BWI-Marshall Airport. On TV-Hill the peak wind gust was only 23mph at 5:45pm. The storm was moving rapidly so rainfall was unimpressive despite the brief, heavy downpour. Only .07″ was measured at the airport, .04″ downtown and .02 on TV Hill. Radar estimates showed a narrow band from northern Anne Arundel County northwest across northern Howard County that may have received as much as a half inch of rain.

The approaching cold front will provide a reinforcing shot of dry air that will allow temperatures to run at or a little below average through most of the weekend. A more tropical airmass returns next week though. Highs are expected to run well into the 90s along with high humidity levels. Some spotty rain could provide a little relief by the middle or end of the week.

With the exception of a few bumps and grinds in the first couple of hours, it looks like summer is off to a great start.

John Collins

Summer Starts … Officially
June 21, 2007


Summer officially arrives Thursday afternoon at 2:06pm. and you couldn’t ask for better weather. The passage of Wednesday’s cold front allowed a cooler and much less humid air mass to slip into the region from the northwest. The upper air flow will continue to push the pleasant air our way right into the weekend. Dewpoint temperatures are expected to remain in the 40s and 50s until Monday. At that time, hazy, hot & humid conditions return with dewpoint temperatures juming into the 60s on Monday & Tuesday to around 70 on Wednesday.

The Wednesday cold front generated some thunderstorm activity but the the rain fall was spotty. We could have used more. One severe thunderstorm was reported nearby. Northwest Montgomery County and southern Frederick county received reports of some tree and powerline damage and a small area received rains in excess of one inch by radar estimates. Officially at BWI-Marshall .17″ of rain was recorded, bringing the June rain total to 1.82″, .47″ below the 30 year average. This year the airport has received 16.45″ rain, 3.15″ below average. The storm produced only .03″ at the Science Center and on TV Hill.

We are a little parched but we are not in a drought situation. Officially, north central and western Maryland are “abnormally dry”. Severe drought conditions are evident just to our southwest as shown on the latest drought monitor map.

A little rain wouldn’t hurt but it looks like the first few days of official summer will be dry and pleasant. Enjoy it while we have it.

Update On Tuesday Storm Outlook
June 19, 2007

Just adding to yesterday’s note.

The Storm Forecast Center has added the Baltimore area to the “slight risk” zone for severe storms today. Hot, humid airmass, approaching front, and a wind speed shear at the upper levels of the atmosphere are all adding to the potential for some scattered severe activity during the mid-late afternoon through overnight hours. This appears to be a set-up for mostly a hail/strong wind type of storm scenerio but a random storm cell generating a tornado is never out of the question.

Stay tuned.

John Collins

Early Start For Summer Heat
June 19, 2007

Summer oficially starts at 2:06pm on Thursday (June 21) but the hazy, hot & humid summer type weather has kicked in a few days early. The high at BWI-Marshall was 94, three degress short of the record 97 set in 1957. It hit 96 at the Maryland Science Center. The heat and humidity will be around on Tuesday but the record of 99 set in looks safe. Low to mid 90s are expected.

A cold front will approach the area Tuesday night. Scattered thunderstorms are likely ahead of the front. It looks like the best rain chances will be Tuesday night and Wednesday morning. There is not a good consesus in the weather computer models on the timing of the rain. What storms do develop could border on strong to severe. The jet stream is not really positioned for a major outbreak of severe weather around the Bay but the combination of the hot & humid conditions along with the lifting mechanism of the approaching front and its’ associated atmospheric ripples may be enough to pop some severe storm cells. Hail and straighline winds would be most likely. We could use a little rain. BWI-Marshall is running .42″ short on the month and 3.10″ short on the year.

John Collins

Wednesday Tornado Confirmed
June 16, 2007

The team of meteorologists from the Baltimore/Washington National Weather Service Forecast Office investigated storm damage from Wednesday evening’s round of nasty thunderstorms and determined a weak tornado touched down in northern Baltimore County. Here’s the summary of what they found:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
515 PM EDT THU JUN 14 2007

...NWS STORM SURVEY TEAM CONFIRMS WEDNESDAY JUNE 13 TORNADO IN
BALTIMORE COUNTY MARYLAND...

A NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON WEATHER FORECAST
OFFICE STORM SURVEY TEAM...IN CONJUNCTION WITH THE BALTIMORE COUNTY
OFFICE OF HOMELAND SECURITY AND EMERGENCY MANAGEMENT...SURVEYED
AREAS OF BALTIMORE COUNTY TODAY TO ASSESS STORM DAMAGE THAT OCCURRED
BETWEEN 5:00 AND 6:00 PM ON WEDNESDAY JUNE 13.

THE STORM SURVEY TEAM CONCLUDED THAT A SMALL TORNADO...RATED AT
ENHANCED FUJITA SCALE 0...DID TOUCHDOWN NORTH OF THE TOWN OF BUTLER
IN BALTIMORE COUNTY. THE LENGTH OF DAMAGE THAT THE TORNADO PRODUCED
WAS BETWEEN 1 AND 2 MILES...WITH A WIDTH OF APPROXIMATELY 75 YARDS.
THIS CONCLUSION WAS REACHED BASED ON FALL PATTERNS OF
TREES...BRANCHES...AND THE DEFOLIATION OF DECIDUOUS TREES. NO
STRUCTURAL DAMAGE WAS FOUND...AND NO INJURIES WERE REPORTED TO THE
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON WEATHER FORECAST
OFFICE.

INFORMATION ON THE ENHANCED FUJITA SCALE CAN BE FOUND AT THE
FOLLOWING NATIONAL WEATHER SERVICE STORM PREDICTION CENTER INTERNET
ADDRESS: HTTP://WWW.SPC.NOAA.GOV/EFSCALE (ALL LOWER CASE).

$$

LEE

An interesting twist to this tornado (pun intended) was the fact that it tracked from northeast to southwest, caught up in the general atmospheric flow around low pressure off the New England coast. Most severe, tornadic thunderstorms track from southwest to northeast, but this storm proved that tornadoes can track in any direction. In fact, on the website of NOAA’s Storm Prediction Center (SPC), one of the “frequently asked questions” deals with this idea of unidirectional movement of tornadoes:

Tornadoes can appear from any direction. Most move from southwest to northeast, or west to east. Some tornadoes have changed direction amid path, or even backtracked. [A tornado can double back suddenly, for example, when its bottom is hit by outflow winds from a thunderstorm’s core.] Some areas of the US tend to have more paths from a specific direction, such as northwest in Minnesota or southeast in coastal south Texas. This is because of an increased frequency of certain tornado-producing weather patterns (say, hurricanes in south Texas, or northwest-flow weather systems in the upper Midwest).

For more interesting tidbits about tornadoes, check out the SPC tornado site: http://www.spc.noaa.gov/faq/tornado/

Tom Tasselmyer

Rain On a Few Lawns And Gardens
June 13, 2007

Although they brought some unwelcome wind gusts and hail as well, thunderstorms in the area this evening managed to produce some substantial rain in a few spots. A report from Crumpton on the eastern shore indicated 2.5″ of rain fell in that town. Radar estimates of rainfall at 8:00 p.m. indicated an inch or more of rain fell in many areas south of Crumpton through Queen Anne’s, Talbot and Dorchester Counties. Radar also indicated over an inch of rain in a small area of extreme northern Baltimore County near the Pennsylvania line. Andrew’s Air Force base south of D.C. measured .96″, but here at our weather station in northwest Baltimore we had just .02″ and most of the major National Weather Service reporting stations did not record much rain either:

BWI-Marshall: Trace
Naval Academy, Annapolis: .19″
Reagan National: .14″
Dulles: .18″

We have a chance for more beneficial rains from scattered thunderstorms Wednesday before high pressure settles in with a stretch of mainly dry weather going into the weekend.

Tom Tasselmyer

The Pattern Continues
June 11, 2007



Yesterday I posted a satellite picture showing a large storm circulating off the east coast of the United States. This storm, combined with high pressure over the Great Lakes, is channeling northerly winds over the Mid Atlantic region. The large scale wind flow plus marine moisture from the Atlantic generated today’s clouds and below normal temperatures. A few locations received drizzle or light rain showers.

It looks like we will be stuck between these two weather features for a few more days. On Monday the circulation from the Great Lakes high pressure may be a bit more dominant, resulting in a little more sunshine and a reduced rain chance, although afternoon heating of the atmosphere may pop a few isolated thundershowers. Tuesday it is likely that more marine moisture could drift over the area. That combined with a weak disturbance will increase the chances for scattered thunderstorms. None of this rain looks like it will be particularly significant. The maps at the top are produced by the Hydrometeorological Prediction Center of the National Weather Service. The top map is the Sunday evening surface map showing the high pressure over the Great Lakes and the low pressure center off the U.S. and Canadian coast. The other map is the prediction for precipitation totals through Tuesday evening. It is fairly easy to see the channeling of moisture along the eastern seaboard between the Great Lakes high and the Atlantic low.

In addition to the chances for scattered rains this pattern may produce it looks like temperatures will be held in check and run at or below average for the season for at least the first half of the coming week.

Have a good week.

John Collins