Archive for July, 2011

More Heat!
July 22, 2011

Thursday’s official high temperature in Baltimore recorded at BWI-Marshall Airport was 100°, short of the record 104° set in 1930. The high temperature at the Maryland Science Center at the Inner Harbor was 103°.

100° or higher temperatures are expected again on Friday and possibly Saturday.

The high temperature forecast map for Friday shows the concentration of 100°+ temperatures will be concentrated along the East Coast, central and southern Plains and the desert Southwest. This is an unusually widespread outbreak of extreme temperatures.

Along the eastern seaboard, the high humidity levels make conditions worse.

When humidity levels are taken into account, it will “feel like” temperatures will be in the range of 110° to 120° during the afternoon hours. An Excessive Heat Warning is in Effect. Check wbaltv.com for tips for staying safe during this heat wave.

The following are some interesting statistics compiled by the National Weather Service.

Update Friday evening at 7:48pm edt.

Additional information from the Sterling, VA office of the National Weather Service on Friday high temperatures.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
646 PM EDT FRI JULY 22 2011

...MAXIMUM TEMPERATURE AND HEAT INDEX...

THE FOLLOWING LIST SHOWS PRELIMINARY MAXIMUM TEMPERATURES AND HEAT
INDICES SO FAR FOR SEVERAL LOCATIONS ON FRIDAY JULY 22 2011 UP
THROUGH 6 PM EDT...

                                 MAX        MAX
CITY                            TEMP F  HEAT INDEX F
BALTIMORE MD INNER HARBOR...DMH  108        124
WASHINGTON DC REAGAN NATL...DCA  102        121
ANNAPOLIS MD................NAK  101        119
BALTIMORE MD BWI AIRPORT....BWI  106R       118
DULLES VA AIRPORT...........IAD  105R       117
CHARLOTTESVILLE VA..........CHO  102        112
MARTINSBURG WV..............MRB  103        111
HAGERSTOWN MD...............HGR  100        110

BALTIMORE MD-BWI BROKE A DAILY RECORD HIGH FOR THE DATE.

DULLES AIRPORT VA-BROKE ITS ALL TIME HIGH TEMPERATURE RECORD...ITS
TEMPERATURE RECORDS GO BACK TO NOV 1962.

NOTE...THE NWS DOES NOT KEEP HEAT INDEX RECORDS.

I would add to this that the Friday morning low temperature at
BWI-Marshall Airport was 81 degrees, tying the the
"record high minimum" temperature for the date.

John Collins

Another Hot, Humid Week
July 19, 2011

Heat and humidity are in the headlines again. The extreme conditions extend from the Plains states to the Atlantic coast.

In the Mid Atlantic region, the hottest days will likely be Thursday, Friday and Saturday. High temperatures are forecast to be in the upper 90s and possibly low 100s. Record high temperatures may be broken with Friday and Saturday records the most vulnerable.

The forecast map above outlines expected highs on Friday. The hot spots are the Mid Atlantic region and the central and southern Plains. These areas can expect readings around or 100 degrees or higher.

The dewpoint temperature is an indicator of the amount moisture in the air. Dewpoints in the upper 60s and in the 70s indicate high humidity levels.

The Friday forecast map for dewpoint shows that the eastern half of the country is in a very tropical airmass with dewpoint reading hovering around 70 degrees. Combined with the forecast high temperatures, conditions will be quite uncomfortable, and potentially dangerous. Appropriate precautions are advised when exposed to these extreme conditions.

The Tuesday satellite image is of some interest. The core of the hottest air is still west of the Mid Atlantic region. A weak cool front is pushing into the area and may provide a trigger some isolated or scattered storms across the region.

Storms were west of the Bay Tuesday morning but additional development is possible later in the day. The cool front will wash out over the area in the next 24 hours and the hottest of the air will begin to filter in late Wednesday into Thursday.

Tropical Storm Bret is shown at the bottom of the image. The storm s not expected to reach hurricane strength and is forecast to move to the northeast, remaining well off the southeast coast of the U.S.

John Collins

 

Whew … It’s Hot!!!
July 11, 2011

As of 4:45pm, Monday, July 11, the highest hourly temperature recorded at BWI-Marshall was 92 degrees. A breakdown of the minute-by-minute readings today may add a degree or two for the final word on the Monday high temperature but it will likely fall short of the record of 100 degrees for the date set in 1988. Factoring in the humidity levels, the 92 degree reading feels like 99 degrees.

(NOTE: At 5:28pm the National Weather Service stated that the Monday high reach 93 degrees at 3:38pm.)

The amount of moisture in the air makes these 90+ temperatures exceptionally uncomfortable and potentially dangerous. The dewpoint temperature is and expression of the moisture content of the air and readings in the 70s are very high, similar to a tropical rainforest.

The high temperature forecast for Tuesday will be well into the 90s and the dewpoint temperatures will once again be in the 70s, demonstrated in the maps above and below.

By Thursday, air temperatures and dewpoints will be dropping.

The Thursday dewpoint forecast map above shows readings falling into the 50s and 60s (green shading) for most of the Chesapeake Bay area. Relief is in sight.

Record temperatures are vulnerable on Tuesday.

Source: National Weather Service, Sterling, VA

Air pollution is an issue in these sultry conditions. The maps below display the forecast ozone concentrations over the area for today and Tuesday.

A Code Red Orange Air Quality Alert is in effect for Baltimore.

The late Monday afternoon satellite image shows the scattered clouds and storm free weather over the Mid Atlantic region. Just to the west is a storm complex that hammered the Chicago area with severe weather earlier in the day. Its’ track will stay mostly west of the Chesapeake Bay but it may brush close enough to produce rain or  contribute enough energy to help trigger some mountain storms this evening or overnight.

On Tuesday, a weak disturbance and eventually a weak cool front will increase thunderstorm chances but any activity will most likely be widely scattered. The bottom line is that less humid air will begin to filter into the area Wednesday and temperatures should ease up by Thursday. In the meantime, take it easy.

John Collins

Hot, Humid & Maybe Some Much Needed Rain
July 7, 2011

The Mid Atlantic Region is locked into some hot, humid conditions once again.

The Thursday midday satellite image shows the lack of rain over much of the eastern U.S. A low pressure center in the eastern Gulf will bring stormy weather to Florida though.

The morning weather map shows an essentially stalled front across Pennsylvania. It divides tropical air over the southeast U.S. and drier air centered over the Great Lakes. This front, combined with waves moving along it, will likely be a focal point for thunderstorm development through Friday.

The high temperature forecast map for Thursday shows 90+ readings expected south of the frontal boundary with readings in the 70s and 80s to the north. High humidity levels will prevail in the warmer air as well.

On Friday the front is expected to push slowly southward into Maryland, generating an increase in rain chances across the region.

Because of the proximity of the front, and disturbances moving along it, any thunderstorm activity could reach severe levels.

The Severe Storms Forecast Center has targeted the southern two thirds of Maryland as having a slight risk for severe thunderstorm development.

You can keep track of developing weather on wbaltv.com. You can also watch Tom, Tony and me for the latest weather updates on WBAL TV-11 tonight and Friday.

John Collins