Archive for May, 2008

Hurricane Outlook 2008
May 22, 2008

The National Oceanic and Atmospheric Administration has released their 2008 Atlantic Hurricane Outlook. NOAA says there is a 65% chance of above normal activity for the season that runs from June 1st through November 30th. Keep in mind, however, any long range forecast of weather is extremely difficult and often not very accurate. In fact, over the past 6 seasons these outlooks from NOAA have correctly estimated the number of named storms just 3 times. They have correctly estimated the number of storms that became hurricanes just once in the past 6 seasons and they have accurately estimated the number of major hurricanes only twice since 2002.

Tom Tasselmyer


2nd Wettest May Since 1871
May 22, 2008

With at least a trace of rain on 17 of the 31 days in May 2008, the rainfall total for the month reached 7.77″. That’s 3.88 inches above normal for the month and wet enough to make this the 2nd wettest May in Baltimore since official records began back in 1871. May’s soggy weather has helped to make this a very wet spring. The rainfall total for March, April and May combined is now 14.76″ which is 3.94″ above the normal amount of spring rain.

1. 1989 … 8.71″
2. 2008 … 7.77″
3. 1894 … 7.26″
4. 1960 … 7.10″
5. 1886 … 7.07″

Tom Tasselmyer

Rain Update
May 19, 2008

Just a quick update on the rain so far in May.

An approaching cold front and a little afternoon heating from sun breaking through a cloud deck popped a narrow line of thundershowers across the Baltimore region on Sunday evening. There were gusty winds, a few reports of small hail and briefly heavy rain. Preliminary numbers show BWI-Marshall Airport receiving .08 inches of rain, .12 inches at the Inner Harbor and .15 inches on TV Hill.

As of late Sunday afternoon Baltimore has officially recorded 6.85 inches of rain in May. That is 4.63 inches above the 30 year average. This May is now the sixth wettest on record. The 2008 rain total is 19.11 inches, 3.47 inches above the 30 year average.


As far as water reserves are concerned, the region is much better off now going into the summer months. Baltimore’s reserves are nearly full and water tables in many areas have been at least partially replenished. Just keep your fingers crossed that the weather pattern can provide us with more or less “normal rainfalls” as we move into the hot summer months.

John Collins

Soggy Spring
May 14, 2008

Although the winter did not bring much snow, plentiful spring rains have erased the precipitation deficit that developed in last fall’s dry spell. The 5 day rainy stretch from May 8th through May 12th pushed the spring rainfall total to over 13″ at BWI-Marshall, well above the normal of 8.5″ as of May 13th. More rain may be on the way in the form of scattered showers or thunderstorms Thursday and possibly a period of heavy rain on Friday.

Tom Tasselmyer

Record Cold and Rain
May 12, 2008

As the second strong low pressure system to pass through Maryland in less than a week begins to pull away from the mid Atlantic coast, the record book is being rewritten. Three of the past four days have had record amounts of rain for the date and today’s unseasonably chilly weather set a record for the coldest maximum temperature for May 12th in Baltimore. Here’s a summary of the new records:

May 9th: 1.85″ rain … old record: 1.41″ in 1919
May 11th: 1.49″ rain … old record: 1.28″ in 1924
May 12th: 2.18″ rain … old record: 2.06″ in 1921 (rain as of 6pm)

May 12th: High temperature: 50, lowest maximum temperature for 12th of May … old record: 51 in 1882

Tom Tasselmyer

Rain Keeps Coming
May 12, 2008

A big storm complex is moving across the area early Monday. Rainfall totals have been in the 2 to 4 inch range from Baltimore southwestward to the Virginia suburbs of Washington, DC.

The rainfall will continue all night and localized flooding has become a problem. Flood Warnings are out for the counties surrounding Baltimore and Washington. A Flood Watch covers a larger area north and west of the Bay and will remain in effect through Monday afternoon.

On TV Hill, 1.12 inches of rain has been measured up to 12:45am Monday. Winds have been gusting well into the 20s all evening with a peak gust of 29mph. Winds have been gusting into the 40s on the Eastern Shore. Wind Advisories are out for the western shore of the Bay  and the central DELMARVA Peninsula and a High Wind Warning is in effect for the Southern DELMARVA Peninsula. A Storm Warning has been issued for the waters of the Chesapeake Bay.

The storm center is shifting from Ohio to the Atlantic coast and low pressure is intensifying over the lower Chesapeake Bay. At midnight the barometric pressure had dipped to 29.17 inches at Patuxent River Naval Air Station. Other low readings include Leonardtown, 29.22″; Cambridge, 29.25″; Ocean City, 29.30″; Annapolis, 29.32″; BWI-Marshall Airport, 29.37″.

Winds from the intensifying storm and the soaking rains over the past few days will likely bring down some trees due to the saturated ground. Scattered power outages are likely due to snagged power lines and soaked connections.

Small streams and creeks pose a hazard and will likely be running bankfull or higher Monday morning until the rain eases up.

On a historical note, the record rainfall in Baltimore for May 12 is 2.06 inches in 1921. If the rain keeps up a reasonable pace through the day that record could be threatened.

Be careful out there.

John Collins

More Rain
May 11, 2008

The region has been running at a precipitation deficit since late 2007 and we have finally caught up, at least for the period since January 1, 2008.

Over the past three days, BWI-Marshall Airport has received almost 2.50 inches of rain. Friday’s 1.85 inches of rain was a record for the date. A few areas to the south and east were hit with 3 to 4 inches from the storm and some areas to the north and west received only an inch or less. BWI’s May rainfall totals 2.48 inches as of Saturday, May 10 and is now running 1.30 inches above the 30 year average. For all of 2008, the total is 14.74 inches, a mere .14 inches above the 30 year average.

Yet another storm is brewing and will be moving in late Sunday. Most computer models indicate that some heavy rain is possible. The core of the storm will be passing to the south and the threat of severe weather is diminished around Baltimore. A Flood Watch will go into effect for most of Maryland west of the Bay on Sunday evening. An exceptional outbreak of severe storms over the southeast states could interfere with moisture transport this far north and possibly reduce the amount of rain. We will have to wait and see how all of this plays out Sunday night and Monday morning. Keep the umbrella handy.

John Collins

Snow Season Officially Over
May 10, 2008

May 9, 1923 is one of the signature dates in Baltimore weather lore…it is the latest in the spring that snow has ever been officially observed in Baltimore. As such, we can now say the 2007-2008 snow season is officially over. However, records are made to be broken, and while we are not yet forecasting snow, the storm that is expected to come through the region Monday should bring unseasonably cool temperatures. With the freezing level just a few thousand feet above sea level Monday morning, there is a slim chance that rain could mix with snow over the higher elevations of the Catoctin mountains and points west.

Tom Tasselmyer

Big Rainfall For Some Areas
May 9, 2008

A wet storm system moved across the area in the past 24 hours. The heaviest rains have been south of Baltimore. The two maps below are derived from radar estimates of rainfall up until 11:00am Friday, May 9.

In both views above, the blue shades indicate rainfall up to 1 inch … the light green shades up to 2 inches … the dark green shades 2-4 inches … and the yellow to red shades 4-6 inches. These are, of course, estimates based on computations from the NEXRAD Radar system but seem to verify fairly closely with a few ground based measurements.

The heaviest bands of rain run from Cecil County, southwestward to just south of BWI-Marshall Airport and Washington DC and on into Virginia. This alignment coincides with the path of strong thunderstorm activity which tracked out of Virginia into Anne Arundel County overnight. Numerous flooding reports came out of Virginia. Winds from thunderstorms took down trees in Charles County, put a tree into a house in Ft. Washington in Prince Georges County and produced roof and trailer damage at the foot of the Bay Bridge in Anne Arundel County.

A National Weather Service Storm Survey Team today confirmed an EF-2 tornado near Berea in Stafford County, Virginia. It struck at 10:55pm Thursday. It produced a 4 mile long, 150 yard wide path and damaged numerous structures. An EF-2 tornado generates winds ranging from 86-110 mph.

The Survey Team also confirmed a tornado touchdown in Prince Georges County at Camp Springs. The touchdown was reported at 1:02am Friday around the Town Center subdivision and the Regency Park Townhome subdivision in Suitland. Damage was 100-200 yards wide and sporadic. The preliminary storm rating is EF-0 with winds estimated at 65-85 mph.

As of 3:00pm Friday, the storm has produced 1.68 inches of rain on TV Hill. The biggest rain numbers in Maryland come from Prince Georges County. As of 7:21 am Friday, Ft Washington had received 3.76 inches of rain.

More rain is on the way. A weather disturbance will increase the chances for rain showers on Saturday and a much stronger storm is expected to come in late Sunday. Check out the details with Tom tonight at 5, 6 and 11pm. I’ll be tracking the storms all weekend.

John Collins

May Freeze & Frost
May 5, 2008

It is early May and many are asking if it is safe to put out freeze and frost sensitive plants in the garden. Well, a few statistics are in order.

The latest recorded freeze in Baltimore is May 9 (1923). The next recorded freeze in the books is October 4 (1974) so we are just a few days away from the “statistically freeze free” window.

Frost can occur with temperatures in the mid 30s and the latest recorded dates for readings in that range are May 21-22 (2002).

The latest date in the record books for a temperature to drop into the 30s is May 30 (38 in 1996). The next time a 30 degree reading shows up in the books is September 21 (37 in 1962).

These of course are only statistics and represent the situation in Baltimore. Locations to the north and west tend to be a little colder. Any frost/freeze tender plants put out now may still need a night of protection over the next couple of weeks if temperatures take a tumble but statistically we are almost home free.

Good luck with this year’s garden.

John Collins