Archive for August, 2010

Tuesday Tropical Update
August 31, 2010

Hurricane Earl continues its’ west-northwest track as a category 4 storm with 135mph winds. The trend of edging the forecast track slightly west with each new forecast model continues.

The key to how close Earl comes to the Mid Atlantic coast lies in an upper level disturbance moving in from the Midwest.

The graphic above is one computer model’s upper air forecast for Friday morning. Earl’s position off the mouth of the Chesapeake Bay is obvious. The dip in the “height lines” and the alignment of the wind barbs over Minnesota, Wisconsin, Iowa and Illinois delineates the disturbance. The circulation around the disturbance near the Great Lakes will eventually push Earl eastward but this disturbance is apparently slowing down and that is why forecasts are calling for Earl to move a little closer to the East Coast.

Computer models also forecast what radar echoes will look like at a given time.

This computer radar simulation is for Friday morning. Earl is producing rain along the Mid Atlantic coast. The Midwest disturbance is generating rain in the upper Midwest and Canada. Rainfall related to Fiona is shown from the island of Hispaniola northward.

The late Tuesday morning forecast track for Earl is below.

This track places the core of Earl off the DELMARVA coast. At this point Earls is still forecast to be a major storm with 130 mph winds, gusting to 160 mph. Tropical Storm force winds would most likely be the rule along near the Mid Atlantic coastline if this forecast turns out to be correct. Dangerous surf conditions, gusty winds and perhaps some precipitation from outer rain bands will be the most likely effects from the storm as seen at this time. The storm is still a couple of days away and changes in the forecast track and impact on the Mid Atlantic region are possible.

The image below is the midday Tuesday satellite image.

Hurricane Earl is the large storm north of the Caribbean Island of Hispaniola. Close behind is Tropical Storm Fiona. Farther east is a tropical wave off the East African coast that has some potential for development into a tropical cyclone. On the edge of the image there are two additional disturbances over Africa heading for the Atlantic.

Fiona continues to have a tough time becoming well organized, perhaps because of its’ proximity to Earl.

Computer models forecast Fiona to turn northward  and pass closer to Bermuda as a tropical storm by the end of the weekend. Fiona’s earlier turn north is being influenced by the same Midwest disturbance that will likely prevent Earl from moving inland along the U.S. East Coast.

These storms and any new ones coming off the African continent are traveling in a rich environment for tropical cyclones.

Water temperatures over the central and western Atlantic are very warm. The orange and red shades indicate sea surface temperatures in the low to mid 80s. These temperatures are slow to change so the next few weeks hold a lot of potential for any storms that move over these waters. The other controlling influence is upper level winds and these change from day to day so the guessing game continues.

Check out the latest on the tropics on our web site  http://www.wbaltv.com/hurricanes/index.html

You can also watch Tom, Tony, Sandra and me this week for live updates during WBAL-TV 11 newscasts.

John Collins

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Earl On The Move
August 30, 2010

As of 1:00pm Monday, Hurricane Earl was about 75 miles northeast of St. Thomas in the Virgin Islands with winds topping out at 125 miles per hour. Hurricane force winds extend out 60 miles from the center of the storm.

The early afternoon National Weather Service Radar from Puerto Rico shows the rain bands of the storm radiating from the eye at the upper right edge (northeast quadrant) of the scan.

Over the past few days forecast models have indicated that the storm will turn northward and pass between Bermuda and the East Coast of the U.S. as a major hurricane with winds in excess of 110 mph.

The latest Hurricane Center forecast places the storm off the DELMARVA coast early Friday. Notice that the cone for the potential path of the storm center does include the DELMARVA Peninsula. All computer forecast models so far keep the storm center off shore at the end of the week but this is subject to change and it should be noted that each model run has pushed the storm track slightly farther west. This is a storm to be watched.

At the least, Mid Atlantic Beaches will likely see dangerous surf and breezy conditions. A few outer rain bands of the storm could affect beach areas Thursday night or Friday. At the most the storm could track farther west and be a much bigger problem.

East of Earl, a low pressure system is becoming better organized.

This system stands a very high chance of becoming a tropical depression or tropical storm. The name would be Fiona. This storm would also stand a chance of coming close to or striking the U.S. East Coast. If that were to happen, it would likely be some time next week.

August and September are the peak months for hurricane development. One reason for that is Atlantic water temperatures peak out at this time and warm ocean water is a primary fuel for hurricanes. The graphic below and accompanying text from the NOAA Environmental Vizualization Laboratory demonstrate and explain the process going on right now.

Warm Oceans Intensifying Hurricane Season
On the 5th anniversary of Hurricane Katrina’s landfall along the Gulf Coast (August 29,2005), tropical cyclone activity in the Atlantic is intensifying. Fueled by warm ocean temperatures, a series of consecutive storms have formed in the Intertropical Convergence Zone (the area between Africa and the Caribbean). Hurricanes Danielle and Earl have intensified into major hurricane strength (Category 3+), another system is following in Earl’s wake. The National Hurricane Center estimates a 90% chance that this system will intensify into a tropical storm. If so, it would be #6 of the season, named Fiona. And yet another storm system seems to be just behind.Using Tropical Cyclone Heat Potential data from NOAA/AOML, the amount of heat energy available to fuel hurricane intensification is plotted underneath a GOES-East image from 1445z. Earl is moving over an extremely warm area of ocean water and is expected to intensify as it moves northward along a path similar to Danielle.

You can track these storms any time on the web by  clicking http://www.wbaltv.com/hurricanes/index.html or by checking in with Tom, Tony, Sandra and me all week long on WBAL-TV 11.

John Collins

6 in a row…below 90
August 26, 2010

For the first time since the 25th of May the temperature at BWI-Marshall has remained below 90 for six conesecutive days.  The last 90 degree temperature at Baltimore’s official weather station was recorded last Friday, August 20th when the afternoon high peaked at 91.  However, we not be done with the heat of Summer 2010.  If the forecast holds, it looks like we’ll have a couple more days with highs in the 80s on Friday and Saturday before the heat returns beginning Sunday and continues into the middle of next week.  Here’s the current stretch of cooler high temperatures at BWI-Marshall:

August 21:  87

August 22:  87

August 23:  85

August 24:  74

August 25:  80

August 26:  85

Tom Tasselmyer

Danielle and Earl Early Thursday
August 26, 2010

The peak period of the Atlantic tropical cyclone season is underway and two active storms are churning across the open waters with a new tropical wave coming off the west African coast.

The composite satellite image above shows the situation at 2am(EDT) Thursday. It is still dark in Europe and the US and urban lights are noticeable in the image. Height lines at the 500mb have been added to the image to help delineate the areas of upper atmosphere high and low pressure.

Danielle and Earl are moving westward along the bottom edge of a large area of high pressure that stretches from the western US to north Africa, roughly between the 15th and 30th parallels. Centers of low pressure are over the north Atlantic and Canada with waves referred to as troughs (shorthand “trofs”) extending southward.

Tropical cyclones tend to be pulled toward these low pressure “trofs”. The end result, Danielle is turning northward and is expected to pass to the east of Bermuda. Earl is tracking slightly farther south and should continue a westward track for a while but eventually be drawn north by the “trof” that is now over Canada and the eastern US. Earl, for the moment, is forecast to pass west of Bermuda but well east of the US east coast.

If the next wave or two coming off the African coast strengthen into tropical cyclones at some point, the low pressure wave pattern north of the 30th parallel will likely be different and storms could get closer to the US coast.

The image above is the late morning visible image of Danielle. An impressive eye is developing as wind speed increases.

Check out the WBAL-TV Hurricane Section on the WEB for the latest on the tropics. Click on this link: http://www.wbaltv.com/weather/grid.html#HEARSTWX=http%3A//www.wbaltv.com/weather/19625481/media.html%3Fqs%3D%3Bref%3D/weather/19626622/media.html%3Blongname%3DHurricane

John Collins

Danielle Weakens
August 24, 2010

Danielle weaked to just under hurricane force (74 mph sustained winds) on Tuesday.  Dry air and wind shear to the west of the storm have taken a toll.  The National Hurricane Center still expects the storm to move into favorable environmental conditions regaining hurricane status and strengthening as it approaches Bermuda over the next few days.  A little farther east, satellite images show a strong tropical wave that might develop into tropical storm “Earl” in the next 24 hours.

Tom Tasselmyer

Hurricane Danielle Gaining Strength
August 23, 2010

Danielle has strengthened to category 1 hurricane status with maximum sustained winds of 75 mph.  The National Hurricane Center expects the storm to reach category 3 status with sustained winds of 115 mph before it begins to weaken a bit as it passes east of Bermuda over the weekend.

Tom Tasselmyer

Record Heat?
August 10, 2010

The summer heat of 2010 continues and records are once again vulnerable.

Baltimore Record High Temperatures

Tuesday forecast high temperatures for the area are near 100 degrees and threaten the Baltimore record set in 1900. Forecast highs for Wednesday and Thursday are not quite as hot and the records are less vulnerable.

Rain chances are minimal around the Chesapeake Bay for the next day or two. The main storm track is to the north for the time being and the most favorable conditions for stormy weather are to the west. By Thursday a cold front will be approaching and rain chances will increase.

The Tuesday morning satellite image shows the relatively quiet conditions over the Mid Atlantic region. The third major convective complex this week is moving across the upper Midwest and a disturbance over Florida is drifting into the Gulf of Mexico.

The storms in the Midwest are being fed by moisture from the Gulf of Mexico but that connection is not that obvious in the color satellite image.

The water vapor satellite image above clearly shows the Gulf connection. The image enhances moisture at the middle levels of the atmosphere. A plume of Gulf moisture is feeding right into the storm complex that stretches from eastern South Dakota into northern Illinois. The air is somewhat drier over the northeastern U.S. as indicated by the darker shading.

Stormy weather has been lingering over Florida for the past few days and the disturbance is drifting westward. Hurricane forecasters are monitoring the situation. Another disturbance out in the Atlantic (not pictured) has some potential for strengthening.

John Collins

Lightning Safety
August 4, 2010

An approaching cold front will increase thunderstorm chances over the next two days. Any thunderstorm can produce severe weather. Additionally, the Storm Prediction Center has identified the Mid Atlantic region as under a slight risk for severe storms on Thursday.

Severe or not, the greatest threat from any thunderstorm is lightning. I thought I would pass along some tips on lightning safety from the National Weather Service and the National Environmental Education Foundation.

Source: NOAA/National Weather Service

LIGHTNING SMARTS:

During the summer, thunderstorms occur more frequently due to warm, moist air.  Approximately 1,800 thunderstorms are occurring at any given time.  They usually last about 30 minutes and are typically 15 miles in diameter.  Lightning occurs in all thunderstorms.

Viewer Tip: Lightning strikes the Earth 20 million times per year!  The best place to be during a thunderstorm is indoors. If you do get caught outdoors, these tips can help reduce your risk of being struck by lightning:

  • If you are boating or swimming, get to land immediately.
  • Take shelter in your vehicle, if possible.  Picnic shelters, dugouts and tents are not safe shelters during a storm.
  • If you cannot get to a vehicle, find a low spot away from trees, fences, and poles.  Make sure the place you pick is not subject to flooding.
  • Get off of elevated areas, like hills, peaks or mountain ridges. Do not take shelter under a cliff or rocky overhang.
  • Never lie flat on the ground.

Remember, if you can hear thunder, you are close enough to be struck by lightning!

Learn more about lightning safety from NOAA’s National Weather Service:www.lightningsafety.noaa.gov/index.htm.

John Collins

Active Tropics Again
August 3, 2010

A new tropical storm has taken shape in the Atlantic. Colin is a minimal tropical storm roughly 800 miles east of the Leeward Islands of the Caribbean. The storm is expected to remain at the lower end of the storm strength scale over the next several day and track west-northwest.

The midday Tuesday satellite image shows Colin in the right third of the picture. High altitude winds appear to be interfering with storm organization and will likely hold storm strength in check.

A tropical wave (left of center in the image) is moving westward through the southeast Caribbean. High altitude winds are expected to hold this disturbance in check, at least in the near future.

On Thursday, August 5, NOAA/National Weather Service will release a revised outlook for the 2010 Hurricane season. August is the month when hurricane activity generally increases and outlooks are normally updated at this time.

John Collins

July Review
August 2, 2010

The numbers are in for July and some are impressive. All statistics but the last were recorded at BWI-Marshall Airport.

  • 81.5 degrees     Average Monthly temperature
  • +5 degrees       Average temperature departure from normal
  • 105 degrees     Highest temperature (July 6)
  • 56 degrees       Lowest temperature (July 2)
  • 3                      Record high temperatures(6th7th-25th)
  • 1                       Record high minimum temperature(24th)
  • 20 days            90+ degrees
  • 5 days               100+ degrees
  • #2                    Tied for 2nd warmest avg temperature in July
  • 4.36 inches       Total rainfall
  • +0.51 inches     Rainfall departure from normal
  • 1.25 inches        BWI Greatest 24 hour rainfall
  • 7 inches            Reported rainfall at St Michaels(10th)

John Collins