Monday, November 28, 2011
Tuesday, August 23, 2011
Thursday, July 28, 2011
Sunday, May 29, 2011
Regardless, wind shear will weaken in the tropics over the next few days, so this cluster could become better organized in the next few days. In fact, most of the global computer forecasts show an area of low pressure forming by the end of the upcoming workweek (indicated by the green circle in the western Caribbean).
Tropical systems typically form in the Gulf of Mexico and Caribbean early in June (see map below), so this is a plausible forecast. We will be watching this very closely over the next several days and will have more updates.
Thursday, May 5, 2011
Regardless, the previous record in April was 267 tornadoes which occurred in 1974. The highest number of of tornadoes for any month was May of 2003 (May is typically the most active month), where there were 558 tornado reports. So more than likely April 2011 will shatter all old tornado records.
Here is a map of all the reports:
The top five states were Alabama (144), Mississippi (115), North Carolina (86), Texas (64) and Tennessee (54). Virginia ended up with 35, which is an unusually high amount. You can find the entire list at the following link:
To put things into perspective, here is the map from May of 2003:
You can see that there significantly less tornadoes in the Mid-Atlantic, though it was a terrible month in the Midwest, especially around Kansas City and Springfield Missouri.
Saturday, April 16, 2011
One tornado touched down in Augusta County (EF-1 with max winds 95 mph) and knocked down several trees and destroyed numerous barns.
A tornado is now confirmed in Dinwiddie County with a path around 8 miles long and 300 yards wide. Many homes were damaged along the path of this tornado.
Two more tornadoes were confirmed in Isle Of Wight and Gloucester counties. There was extensive damage in Gloucester with three fatalities. National Weather Service is going to survey the damage more today to see the strength of the tornado.
There was also wind damage in Halifax County where eight homes were destroyed with four minor injuries. National Weather Service will survey the damage today to see if this was from a tornado.
At one point, the Tri-Cities area was under a Tornado Warning, however, with the exception to a few toppled tress, there were no reports of major damage.
There were a few reports of hail in Crewe and Powhatan. We received pictures of quarter to golfball-sized hail.
Here are some maps which show all of the storm reports from today. The "W" represents wind damage, "H" is hail and "T" is tornado. North Carolina was hit hardest today, where there were nearly 100 tornado reports!
Sunday, April 10, 2011
Hurricanes like warm ocean water and low wind shear. Wind shear is typically low during La Nina, which would lead to an active season. However, La Nina is rapidly weakening (see the map below), so the forecast isn't as clear-cut.
Atlantic Water Temperatures
As I stated above, hurricanes strive in warm ocean water. Sea surface temperatures (SST) have been above normal over the past few months, which points towards an active season.
The North Atlantic Oscillation (NAO) has an impact on the Trade Winds. We saw a dramatic shift to a positive NAO during January. This increased the Trade Winds and has consequently cooled the Atlantic waters slightly. If we remain in a positive phase, then ocean temperatures could continue to cool.
Colorado State has already decreased it's initial forecast for this upcoming hurricane season. If La Nina continues to weaken and NAO remains mostly positive, then we might see the number of named storms and hurricanes decrease. We will continue to track this and bring you more updates.
Tuesday, March 29, 2011
We aren't the only ones dealing with dry conditions. You can see on the map below that most of the Southeast is 2 to 8" below normal for rainfall this year.
Not surprisingly, numerous rivers and streams are now running below normal (indicated by the red and orange dots). The rivers to the west are near normal from the heavy rains we saw earlier this month (indicated by green dots).
Right now, moderate drought extends across central and southern Virginia.
Luckily, we will see an active weather pattern over the next several days. In fact, two back-to-back storm systems could bring 1 to 2" of rain from Wednesday into Thursday. This is great news!
Saturday, March 12, 2011
December was the 7th coldest in history (link http://www.erh.noaa.gov/er/akq/climate/special/RIC_AVE_T.pdf). The cold weather persisted into the first half of January, then the overall pattern changed. Temperatures generally remained above normal for the rest of winter. The map below shows that the entire Southeast U.S. experienced temperatures that were 2 to 6 degrees above normal for the month of February.
If you combine all months together, the overall average temperature for this winter was slightly below normal.
There is no doubt about it: this winter was dry. We were roughly 2 to 4" below average across the entire state. Interestingly, we received 10.8" of snow, which is only slightly below the average of 11.9". Most of the snow fell in December and early January before the pattern change. You can see on the map below that we weren't the only ones dealing with dry conditions. It was even worse in Louisiana, Mississippi and Alabama.
Saturday, March 5, 2011
Rain totals should range from around 0.75" to 1.25" (give or take 0.25"). This is great news considering that we are about 2.5" below normal for the year.
Severe Weather Checklist
- Instability (heat and humidity)
Moisture should be high enough to support thunderstorms. Temperatures will be hindered by clouds and rain, especially along and west of I-95. Highs should climb into the mid 60s for central and southeast VA. This should be *just* warm enough for isolated thunderstorms.
- Trigger (something to spark thunderstorm development)
A strong front will pass the area in the afternoon, which is typically ideal for severe storms.
- Wind Shear
We will have strong speed shear (winds increase with height), and minor directional shear (winds change direction with height).
Clouds will prevent any sun for today, which in turn keeps us cooler.
Sunday, February 27, 2011
A line of thunderstorms will race across the area from 3 PM to 10 PM on Monday. The strongest storms will be capable of damaging straight line winds and small hail.
Temperatures will soar into the upper 70s to near 80 on Monday. This heat will provide *just* enough fuel for thunderstorms later in the afternoon and evening.
Storms will initially start west of the Blue Ridge around midday. They should form into a squall line and then race our way. The leading edge of the storms will be moving into western parts of our area around 3 PM.
The atmosphere will only be marginally unstable once the storms arrive, so we could see some weakening of the squall. Nonetheless, any storms that survive the trek across the Blue Ridge will be capable of damaging wind gusts over 70 mph. There could also be some small hail with the strongest storms. Most of the rain will quickly taper after midnight.
Limiting Factors (technical):
Just like last time, we will have a highly sheared environment with only marginal instability. However, upper-level "lift" could overcome this obstacle.
CAPE, or energy in the atmosphere, will be somewhat limited. Here is a plot for tomorrow evening, which shows almost 1000 CAPE west of I-95 (not too impressive). In addition, CAPE is much less in central VA. This could lead to some weakening of storms, especially after sunset. The key will be sunshine...if we see more, then the air could become more unstable.
Shear is going to be very high. The upper level winds will be howling! This will add to the potential of some powerful downbursts. It could also help to maintain the strength of the squall line. On the flip side, it could also rip apart storms as they try to develop. This is something to watch closely tomorrow - shear vs instability.
Sunday, February 20, 2011
La Nina will continue to weaken heading into spring. NAO (North Atlantic Oscillation) will generally remain neutral or positive. Although we will see a brief cool down for the start of March, temperatures will remain roughly near or above average. Precipitation will stay near or below average. The chances for a significant snow (over 6") look slim to none.
Digging into the data (technical):
Meteorological winter is about to end (December through February), so it is now time to look at the overall pattern heading into spring. Earlier this winter, we had a strong La Nina, which typically brings mild and dry weather to our region. However, we experienced a strong -NAO (North Atlantic Oscillation), which is when a strong ridge in the jet stream persists over western Greenland and eastern Canada. This brought us cold and snowy weather for December and early January. This ridge eroded in late January, and we have been mild and dry ever since.
La Nina is starting to quickly weaken. In fact, we could be in neutral conditions by May or June. This is a plot of sea surface temperatures, which shows that Nina still exists, but it isn't as strong as earlier this winter. In addition, what you can't see is the water below, which is starting to warm.
Here is a plot of NAO, which shows negative conditions early in the winter, and then neutral/positive conditions ever since mid January.
There are indications that NAO could turn slightly negative in early March, which would typically get any snow-lover excited. However, the ridge is too far east. I've posted the long range outlook for the upper-level atmosphere (first map), and temperatures for the lower atmosphere (second map). Notice on the first map how the ridge, indicated by the yellow blob, is located east of Greenland. Although this could bring us slightly below average temperatures, it is not in an ideal location for significant snow. Average highs for early March are in the mid 50s and average lows are in the mid 30s. We should generally stay near these numbers for early March. Of course, there will be some fluctuations.
Obviously, there could be some changes to the forecast, however, this isn't looking good for snow-lovers.
Saturday, February 19, 2011
Friday, February 18, 2011
Wednesday, January 26, 2011
Thursday, January 6, 2011
I've named the first scenario "Southern Miss", which represents one computer forecast (00Z ECMWF). In this case, an upper-level storm system will race through the Deep South and into the Carolinas (a storm in the Pacific Northwest lags behind). This track will bring the highest accumulations to Arkansas, Tennessee, and North Carolina. In addition, this type of storm will bring snow into our area earlier...possibly all on Monday. Lastly, accumulations will be minimal in Central VA with higher amounts in southern VA.
I want to point out that the ECMWF ensemble (an average of several different runs of the same computer forecast), shows this storm pulling up the coast instead of shooting into the Atlantic. For this reason, I've put the chances of "Southern Miss" at 40%.
The next scenario I've named "Coastal Carolina" (yes, there is a college theme), which is based on another computer (GFS). This paints a much different picture, which I think is slightly more plausible than "Southern Miss". Notice how the energy in Pacific Northwest moves quicker and merges with the energy in the Deep South. This will allow the storm to deepen and move slower and up the coast of the Carolinas. This would bring a wide swath of heavy snow across Central VA and Western VA. If the track pulls farther off the coast, then the heaviest snow will shift east.
Right now, nothing is etched in stone. This is something we will be watching very carefully over the next few days and will bring you more updates.