Friday, July 29, 2011

Heat Advisory Friday for most of Virginia

A Heat Advisory is in effect Friday for most of the Commonwealth from Noon to 8PM for heat indices ranging 105-110 degrees in the shade. Today's forecast high temperature of 101 degrees in Richmond could tie our record high for this date, July 29th, which was set just a year ago in 2010. This end-of-week heat wave is in response to an expanding upper-level high pressure ridge into our region again, much like a week ago today, with the jet stream remaining well to our north. Southerly flow allowed moisture content to also creep back up high enough to warrant this Heat Advisory:

This isn't our first dangerously hot and humid day of the year, but in case you need the reminders of how to stay safe today, click here for an excellent summary by the American Red Cross. This may be a great page to print off and post for your workplace, home or daycare center!

In addition to the heat and humidity, there is also a Code Orange Air Quality Alert in effect for the Richmond and Petersburg metro areas and surrounding counties in the heart of central Virgina.

A Code Orange means that it is unhealthy for sensitive groups (those with respiratory conditions like asthma, people with heart ailments, older adults, and children) to engage in heavy or prolonged outdoor activity. You can learn more about Air Quality by clicking here.

Stay with CBS6, we'll keep you ahead of the storm.
--Meteorologist Carrie Rose

Thursday, July 28, 2011

Tropical Storm Don is en route to Texas

Our fourth tropical system this year in the Atlantic Basin is tracking slowly through the Gulf of Mexico early Thursday morning after becoming Tropical Storm Don on Wednesday east of the Yucatan Peninsula. As of this update, here are the details on Don:

Although Don is barely at tropical storm strength with winds just faster than 39 mph, it will be moving into a favorable environment for intensification over the next day. Sea surface temperatures in the entire Gulf of Mexico are warmer than 80 degrees Fahrenheit (anything red or darker on the map below), which is precisely what a tropical system requires as fuel for intensification and storm maintenance.

In addition to the low-level fuel, upper-level wind shear should be minimal over the next few days as Don chugs northwestward toward the Texas Gulf Coast. That low wind shear means Don should be able to better organize Thursday and early Friday, and also intensify. The forecast track certainly indicates an increase in wind speeds associated with Don, as shown here:

It does not appear at this time that Don will be able to intensify to hurricane strength (74mph+ winds) before it makes landfall somewhere along the Texas Gulf Coast. A Texas landfall is the most likely of the forecast scenarios, which are shown here in a "spaghetti plot" along with the official forecast track from the National Hurricane Center:

You can learn more about the Saffir-Simpson Hurricane Wind Scale by clicking here. We are now entering what is typically the most active part of the tropical season, from August through October:

Tropical Storm Don should bring much-needed rainfall to a drought-stricken part of the country. The drought in Texas is historic, and may end up being one of the worst, if not the worst, drought on record for them. Here are the latest drought conditions for the Lone Star State:

And just to give you some comparison, here is Virginia's latest Drought Monitor, where our conditions have been steadily improving through the Summer:

The forecast for the drought through the Southern U.S. is varied, but generally the Southern Plains into parts of Arkansas and Louisiana are not expected to improve over the next few months.

This is why Tropical Storm Don may be a most welcome visitor to Texas, because they could sure use the rain, even if it comes with some strong winds.
--Meteorologist Carrie Rose

Saturday, July 23, 2011

Heat & Storms


We hit 100° for the second day in a row across much of the area today. Richmond International Airport officially hit 101°, which was 2 degrees shy of the record. Heat index values during the afternoon ranged from about 100 to 120°.


Strong and a few severe thunderstorms moved through the area between 3 and 7 pm. Thunderstorm wind damage was reported in Amelia, where some trees were down.
The slow-moving storms dropped heavy rainfall in some spots. The heaviest estimates from doppler radar showed some 2-3"+ totals across a large portion of Hanover county.

While the muggy environment provided ample fuel for torrential rainfall, the storms were scattered enough that many locations did not even see one drop of rain.


The thunderstorms also provided a temporary cooling effect. CBS 6's Wayne Covil drove from the James River Bridge to the I-64/Broad St/Parham Rd area just after 5:30pm. He reported that the temperature dropped from 98° to 78° in a span of about 15 minutes as he traveled westward.


We will see just a very minor drop in temperatures for Sunday. Highs should fall just short of 100°. The combination of heat and humidity will produce heat index values between 100-110° -- slightly less than the past few days. For this reason, the excessive heat warning has expired and been replaced with a heat advisory for Sunday.


A cold front will pass through the area Monday night and Tuesday, allowing less humid air to filter into the area. Highs will be just a bit cooler (lower 90s) and humidity levels should drop a bit (dew points dropping from the mid 70s to the low/mid 60s). This will be short-lived, however -- an increase in heat and humidity will return by the end of the week.

Thursday, July 21, 2011

Excessive Heat Warning is in effect through Saturday

An Excessive Heat Warning is now in effect through Saturday for most of the Commonwealth, when late morning through early evening heat index values will commonly range 108 - 115 degrees (in the shade). If you're in the sun, it can feel another 10 to 15 degrees hotter on top of that heat index value because of the added sensory warming from radiation (sunshine) heating on your skin.

If you do have outdoor activities that need to be done into the weekend, please complete your tasks (when possible) before 10AM each day. Even in the evening, the heat index will still be dangerous!
Click here to learn more about the Heat Index and how to remain safe during the next few dangerously hot and humid days.
Stay with CBS6, we'll keep you ahead of the storm.
--Meteorologist Carrie Rose

Wednesday, July 20, 2011

Excessive heat will affect most of Virginia

As expected, the Excessive Heat Watch has been expanded farther into central Virginia, and for a longer time-frame. The Watch now covers most of central, west-central, southeast, and northern Virginia from Thursday through Saturday, when the combination of higher air temperatures and rising humidity levels will lead to common heat index values of 105-110 degrees (in the shade).

We are just one state of many in the nation to be affected by this large upper-level ridge bringing dangerous heat and humidity. Here's a map of every state under some form of Excessive Heat Warning (pink), Excessive Heat Watch (dark red), or Heat Advisory (orange) as of Wednesday morning:

Although we will come close to record high temperatures Friday and Saturday (we are forecasting highs around 100 degrees), it's the record warm low temperatures that are in real danger of falling. This Wednesday morning, we've already cooled below that record warm low temperature for this date (July 20th), so we won't break that record. But the rest of the week, overnight low temperatures will be very close to the records:

You may recall that last week we set our all-time record warmest low temperature in Richmond at 81 degrees on July 12, 2011.
--Meteorologist Carrie Rose (Click "Like" here to join the weather conversation on my Facebook page).
Stay with CBS6, we'll keep you ahead of the storm!

Tuesday, July 19, 2011

Excessive Heat Watch is in effect for Thursday

In anticipation of the dangerous combination of high heat and humidity at the end of this week from a broadening high pressure ridge, an Excessive Heat Watch is in effect for Thursday's expected heat indices (in the shade) of 105-110 degrees. This watch may be expanded into more of central Virginia, but here's the map of affected counties and cities for now:

Heat indices by Friday could be as high as 115 degrees in central Virginia, including the Richmond Metro, and won't return below 100 until next week. Click here to learn more about the Heat Index and how to stay safe through this weekend with the approaching dangerous heat wave. Stay with CBS 6, we'll keep you ahead of the storm!
--Meteorologist Carrie Rose

Severe storms are possible Tuesday

In a hot, humid, unstable air-mass this afternoon and evening, scattered strong to severe storms are possible in Virginia, aided by a surface cool front to our north and a wind shift this afternoon from the northwest. Storms should initiate (develop) around 1-2PM in western Virginia, and track southeast into the rest of central Virginia this afternoon and evening.
Not everyone will get storms, but those of you who do can expect heavy downpours, frequent lightning, gusty winds, and some hail. The severe thunderstorms will be capable of damaging wind gusts in excess of 60 mph and hail larger than an inch in diameter.

We'll be closely monitoring the severe threat this afternoon. If you're on Facebook, be sure to "Like" our Facebook pages for updates (click here for Chief Meteorologist Zach Daniel, click here for Meteorologist Carrie Rose, and click here for the CBS 6 Storm Team Page). Stay with CBS 6, we'll keep you ahead of the storm!

Saturday, July 16, 2011

High Heat & Humidity This Week

A change in the jet stream will allow a dome of very hot air to move from the Plains into our area during the coming week.

Highs will reach the low and mid 90s for the first half of the week, and near 100 for Thursday into next weekend.

Humidity (and dew point) levels will continue to climb over the next few days. After very comfortable levels of humidity the past few days (dew points in the 50s), dew points were around 60 today...and will be in the lower 70s Tuesday through the end of the week.

The combination of heat and humidity will create a heat index near 100 Monday, and then increase to around 110 by the end of the week. Heat advisories will be issued for later in the week. Overnight lows may not dip below the upper 70s Friday and Saturday, which could set new record "warm" lows.

Wednesday, July 13, 2011

Severe Thunderstorm Watch in Effect Until 10 PM

A severe thunderstorm watch is in effect until 10 PM for much of Virginia, including all of the Richmond metro area. Damaging wet microburst winds of over 70 mph and half-dollar sized hail will be possible with the most intense storms. Storms are developing along and ahead of a cold front that will move through Richmond at approximately 8 PM. Much milder and drier air will move into the area behind the front, resulting in very nice weather Thursday and Friday.

New all-time record warm low temperature set Tuesday

We knew Tuesday could be a record-setting hot day in Richmond because of a broad ridge of high pressure advancing east over us. The afternoon high temperature was officially 97 degrees at Richmond International Airport Tuesday, July 12, 2011, which was just one degree shy of the record high for that date of 98 degrees from 1986. However, we did blow out of the water a different temperature record Tuesday. The air temperature during the 24-hour period of July 12th did not fall below 81 degrees! That was our morning low temperature Tuesday, and not only did it break the record-warm low temperature for that date of 76 degrees from 1993, it was also the ALL-TIME record-warmest low temperature since record-keeping began in Richmond in 1897!

And we may not be quite done yet with the records today. So far this Wednesday morning, the low temperature at RIC has only dipped to 78 degrees, which if we don't fall below that before Midnight tonight (which is possible once the cold front passes around 9PM), then we could set another record-warm low for this date, breaking the old record of 76 degrees for July 13th from 2006.

Remember me talking a couple weeks ago about the "new normals" accounting for warmer overnight temperatures as well as gradually warming afternoon high temperatures? Although we can't immediately point to these record-warm low temperatures as further proof of a warmer-shifting temperature baseline, it is certainly worth keeping in mind as we go through our next decade of record-keeping in Richmond.

Stay with CBS 6, we'll keep you ahead of the storm.
--Meteorologist Carrie Rose

Tuesday, July 12, 2011

Dangerous heat threatens Virginia Tuesday and Wednesday

A broad upper ridge of high pressure is advancing east, affecting states from the Southern Plains to the Mid-Atlantic today and tomorrow with dangerous heat and humidity. Heat Index Values in this swath of the country will range 100-115 degrees on average Tuesday:

Here is a closer view of Virginia with our Heat Advisory, which goes into effect at 11AM Tuesday, when the Heat Index should rise above 100 degrees (what it feels like to your body outdoors in the shade...if you're standing in the sun, add another 15 degrees!):

You can see how we determine what the Heat Index is by clicking here to view the Heat Index Chart. Today's actual high temperature in Richmond should reach 100 degrees, which would be our first 100-degree-day of 2011. We've come close to the century mark several times this year at Richmond International Airport. Here are the hottest days so far of 2011:

If it seems "late" in the Summer for us to be having our official first triple-digit-day, it's still not close to the latest first 100-degree-day on record for Richmond:

And even though the Heat Index may feel like 110 degrees at times this afternoon in Richmond, the air temperature should hover around 100 degrees, well shy of our hottest days on record, both of which occurred in 1918.

On dangerously hot and humid days like today and tomorrow, please remember to bring your pets indoors, check on your neighbors (especially the elderly), and closely monitor your kids for signs of heat-related illnesses. Here are a few basic heat safety tips:

Click here for many more ways to protect yourself during the next two days.
As you can see by the chart below, heat was the number one weather-related killer last year in the U.S., so please be safe today and check on others!

With the heat and humidity in central Virginia this afternoon ahead of an approaching upper disturbance, we could see pop-up showers and thunderstorms develop between 3-9PM. A few of those storms could become severe with damaging wind gusts and large hail:

But our primary threat today remains the heat, not the storms.
Stay with CBS6, we'll keep you ahead of the storm!
--Meteorologist Carrie Rose

Monday, July 11, 2011

A dangerous heat wave is marching east

Extreme heat from the country's midsection is moving east with a broad upper ridge of high pressure. High heat combined with rich low-level moisture from the Gulf will produce heat index values today ranging 100-115 (120 in some spots!) in the highlighted areas on this map:

(Heat Advisories are in orange, Extreme Heat Warnings are in pink.)
At the upper levels, that broad ridge will mean increasingly hot and humid weather for us in Virginia through Wednesday:

A low pressure system that has been producing severe weather through northern Plains and Upper Midwest over the past 24 hours (riding along the jet stream) will force a cold front into the Mid-Atlantic late Tuesday.

But ahead of the front, we'll be extremely hot and humid in Virginia, with highs in the upper 90s to around 100 degrees. Heat index values in central Virginia will be 100-105 degrees in most locations during the afternoon hours. The high temperature in Richmond Tuesday could break a record for that date, July 12th, which currently stands at 98 degrees from 1986. The hottest temperature so far in 2011 officially at Richmond International Airport has been 98 degrees (May 31, June 9, June 28), so Tuesday could end up being our hottest day of the year so far, as well as a record-breaker for that date! Even though the surface cold front will pass through by early Wednesday morning, it will take a good 24 hours for that rich low-level moisture to be replaced by drier, more seasonable air. You'll really notice the return to seasonable Summer weather by Thursday. But for the first half of this week, please be heat-safe! Check out my story from earlier this year on important heat safety tips you need to know by clicking here.
Stay with CBS6, we'll keep you ahead of the storm.
--Meteorologist Carrie Rose

Friday was our 2nd wettest day of 2011

Much-needed rain fell in central Virginia Friday, dumping on us for hours! Thankfully, most of these storms did not produce widespread wind damage, but there was frequent lightning (no lightning deaths were reported from this storm system) and torrential downpours. Here are the severe weather reports from Friday:

The blue dots on the map represent wind damage reports in Virginia as trees were downed in those locations from strong wind gusts. But the good news from that storm system came in the form of heavy rainfall (which we still need in parts of Virginia)! Here is the rainfall status update after last week's rain in Richmond:

Friday's rainfall put us above the normal for our month-to-date tally, and it was our second wettest single day of 2011! Currently, the wettest day of this year is May 14th, when 1.74" fell at Richmond International Airport. We came very close to that day on Friday!
And here's some more good news...the latest long-range drought outlook for Virginia shows that our drought conditions will continue to improve through the end of Summer:

--Meteorologist Carrie Rose

Friday, July 8, 2011

Severe weather and flooding is a threat Friday into early Saturday

After rounds of heavy rain and non-severe thunderstorms Friday morning that produced up to 3" in a couple of hours (Williamsburg/James City County area), more heavy rain (1"-3") is expected as a slow-moving cold front slides south through the Commonwealth tonight into early Saturday morning. The atmosphere in Virginia continues to be ripe with rich Atlantic moisture and very warm conditions. As an approaching surface front and associated strong upper-level trough move into the Mid-Atlantic this afternoon and night, widespread strong to severe thunderstorms are expected in the region, with the greatest flooding threat from storms that move along the slowly advancing cold front tonight.
In addition to the flooding threat, some of the most intense storms will be capable of damaging wind gusts in excess of 60 mph, and also large hail. Although there will be minimal wind shear, an isolated, brief, weak tornado cannot be ruled out with any isolated storms that are able to rotate.
Stay with CBS6, we'll keep you ahead of the storm!

Thursday, July 7, 2011

Heavy Rain & Severe Weather Likely Friday

An upper-level trough and associated surface cold front will move slowly through the state Friday into early Saturday. The air mass ahead of the front will be very warm and humid, resulting in widespread thunderstorm development by afternoon and evening. The most intense storms will be capable of large hail and damaging wind gusts, and the entire state is under a slight risk for severe weather during the period.
In addition to the severe weather threat, heavy rain will be likely, with 1 to 3 inches of total rainfall possible across much of the region. Stay With CBS 6, We'll Keep You Ahead of the Storm.

Wednesday, July 6, 2011

Strong to severe storms expected in Virginia Wednesday

Most of the Commonwealth has the Slight Risk for severe thunderstorms today, mainly during the afternoon and early evening hours, capable of damaging wind gusts and large hail. Any storms that develop today, though, will also be capable of heavy downpours and frequent lightning. Our atmosphere in central Virginia continues to be very warm and moist this week. When a weak upper-level disturbance passes overhead today, that could enhance our severe threat with storms that develop.

We'll provide frequent updates on air and online as needed. Stay with CBS6, we'll keep you ahead of the storm!

Monday, July 4, 2011

A Severe T-Storm Watch is in effect until 8PM for part of Virginia

A Severe Thunderstorm Watch is in effect until 8PM for southwest Virginia into Buckingham, Appomattox, and Charlotte Counties. Thunderstorms are already developing in southwest Virginia as of 1PM Monday, and more storms are expected into the rest of central Virginia through the afternoon and evening. As a result, this Watch may be expanded later to include more of the Commonwealth.

The severe storms will be capable of damaging wind gusts up to 70 mph and large hail up to 2.0" in diameter, although wind damage and constant lightning will likely be the main threats. Even if storms do not technically reach severe limits, they will still be capable of locally heavy downpours, gusty winds of 40-50 mph, and prolific lightning. Please move indoors to shelter if a storm threatens your location and wait 30 minutes after hearing the last rumble of thunder before resuming any outdoor activities this 4th of July. We'll continue to provide updates on air and online as necessary. Stay with CBS 6, we'll keep you ahead of the storm!

Severe storms possible on the 4th of July

Nature may provide her own fireworks on the 4th of July in central Virginia as strong to severe thunderstorms are expected to develop this afternoon and evening in the area. The atmosphere in the region will be very warm, moist, and unstable atmosphere during the time-frame of 1PM-10PM Monday. The threats from these storms are expected to be the same as on Sunday: damaging wind gusts in excess of 65 mph and incessant lightning.

Sunday's thunderstorms produced primarily wind and lightning damage in central Virginia, but not much in the way of precipitation totals. At Richmond International Airport on the east side of town, only 0.18" was recorded last night as the severe storm swept through the Metro. However, those storms produced tremendous amounts of lightning, splintering trees and knocking out power. You can check the latest progress on Dominion's power outage restoration by clicking here.

As storms develop and track through the region this afternoon and evening, you can also check today's lightning strikes in Virginia and across the U.S. by clicking here. But the most important safety rule to remember is that if you are outdoors and you can hear thunder, an approaching storm is already close enough to you to produce lightning at your location. Move indoors to safe shelter immediately. If you are outdoors and there is no fully enclosed building to enter, a hard-top vehicle will suffice to protect you from a lightning strike (but soft-top vehicles will not protect you!). I know a lot of you will be outside today celebrating the 4th of July holiday. Please plan now for a safe, indoors back-up plan: somewhere you can quickly move into if a storm threatens your outdoor festivities. To learn more about lightning and how to remain safe from this weather risk, click here.

Although these storms will be scattered across the Commonwealth this afternoon and evening, it appears that Metro Richmond's most likely time-frame to experience thunderstorms will be between 4-8PM.

Stay with CBS 6, we'll keep you ahead of the storm!
--Meteorologist Carrie Rose
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Friday, July 1, 2011

"New Normals" are released publicly today

It's out with the old, and in with the new for weather data across the U.S. to determine what is considered "statistically normal" at about 8000 weather measurement sites. For example, whenever I tell you that our high temperature today is "warmer than average" for a specific date, or that a first freeze is occurring "much earlier than the average first freeze" for Richmond, I'm using 30-year-averaged weather data that is compiled at The National Climatic Data Center (NCDC), the world's largest active archive of weather data. For the past decade, we've been providing you with information ranging from 1971-2000. But every ten years, the NCDC sifts through, verifies, and releases a new 30-year data set that will serve as the "new normals" for which we can relate each day's weather to what the trend has been over the most recent 30 year period. The new range is 1981-2010, dropping the "old" decade of the 1970's.

(Image: NOAA)
Recently at my trip to the American Meteorological Society's 39th Conference on Broadcast Meteorology, I was able to talk with NCDC climate expert Deke Arndt about what these "new normals" mean for the Mid-Atlantic. (Interview on 6-22-11.) Here are his results:

Deke's data shows that the Mid-Atlantic has experienced a warmer shift of "baseline averages" during the time period 1981-2010. Thanks to Deke for taking time to chat with me!

For you pinpoint data junkies, here's the July difference between the newly added decade (2001-2010) and the old decade (1971-1980) that's being dropped, where you can clearly see that the Mid-Atlantic is taking on a warmer data-set than previously used.

NCDC Figure 1

And here's the same thing, but for January mins:

NCDC Figure 2.

Now let's make this a little smoother graphically. Here's a smoothed image of the same information:

(Image Credit: NOAA)

The decade that has been dropped, the 1970's, is considered by most climatologists to be an unusually cold decade for the U.S., whereas we know from data measurements taken globally that 2001-2010 was the warmest decade on record. From the maps above, we can see it's not necessarily the afternoon high temperatures that are warmer, it's the overnight low temperatures that are warmer, and the map above shows a Winter month!

So now let's look at the comparison of individual states' changes in annual "normal" or "average" temperatures. The annual average minimum temperatures are the image on the left, and the annual average maximum temperatures are the image on the right. You can see that with this most recent decade's data included, those temperatures are warmer in the 1981-2010 Climate Normals than in the 1971-2000 version.

(Maps by NOAA.)

Virginia's overnight temperatures are warmer by about 0.5-0.6 degrees Fahrenheit, and our afternoon highs are warmer by about 0.4-0.5 degrees Fahrenheit. That may not sound like much...but if this "new baseline" continues to climb higher over each decade, then we will have seen a significant warming trend in a relatively short time, by Earth's standards. Here's what the temperature trend has looked like since the Industrial Revolution, including an older 30-year-time-frame of 1961-1990 as the 0-line "mean" from which the average temperature deviates above or below the "baseline":

So this shows you that the past decade's data is consistent with a gradual warming trend, especially over the last several decades.

The latest climate data the scientific community as a whole knows of is that as greenhouse gas concentrations have increased (things like methane, water vapor, and carbon dioxide), so has the average global temperature increased about 0.8 degrees Celsius (the international temperature unit) over the past 100 years. Changes in the Earth's energy balance can produce changes in the Earth's climate over time (we've seen this before with volcanic eruptions, for example). But there are uncertainties as we move forward over the next century for potential further rises in that "baseline average," such as expected continued population growth globally, future greenhouse gas emissions (how much and where), and future technology that may change the way the energy business works worldwide. Just as the Industrial Revolution sent a ripple effect of changes in the Earth's energy balance, so may new technology over the next 100 years similarly impact climate, but how? The types of changes that may be seen in the future, both cool and warm variations, will really only be noticeable on a 50-100 year time scale. This isn't something where if we have a major snowstorm one winter or one super hot summer that we can immediately blame the "rising baseline." We're talking about longer-term average changes right now, not weekly forecast time-scales upon which the weather occurs. Weather extremes aren't going anywhere, I assure you. They've been around for ages, and will continue to be.

Back to the "new normals" data...

Here's what the NCDC says about the exact data it's releasing today and soon:
"We currently plan to release NOAA’s official 1981-2010 climate normals in two waves. The main set of normals (station-based monthly and daily normals of temperature, precipitation, snowfall, and degree days) are scheduled to be made available to the public by October 2011, followed by a release of all other climate normal products by April 2012. All the information contained herein is preliminary and subject to change. Final documentation will be made available as NCDC technical reports and/or manuscripts published in peer-reviewed journals."

So in coming months, when you hear me tell you that we are warmer than average on a morning low temperature, I'll be using the "new baseline" data.
--Meteorologist Carrie Rose
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