Over last weekend and the beginning of this week a dangerous flooding situation set up over most of South Carolina.
[map type=”satellite” autofit=”1″ disable_scrollwheel=”1″]
[pin]Gills Creek, South Carolina[/pin]
[pin]Millwood, South Carolina[/pin]
[pin]Kingstree, South Carolina[/pin]
[pin]Sumter, South Carolina[/pin]
[pin]Columbia, South Carolina[/pin]
[/map]
An upper level low which was in place across the southeast CONUS of the United States slowly drifted eastward, but at the same time drew in a tongue tropical moisture into South Carolina where PWATs exceeded 50mm. With much dynamic lift in place provided by the slow moving upper level low, rainfall, which at times very heavy, persisted between October 2nd and the 5th. By the 6th most of the rainfall had finally dissipated and the disturbance had moved out to sea.
A tongue of precipitable water over South Carolina exceeding 50mm Saturday last weekend.
The hardest hit areas comprised of an area along the South Carolina coast extending inland around Charleston and northwest from there. Here, it was common to see storm amounts exceed 500mm. This event broke numerous all time (one, two and three day) rainfall total records including in South Carolina’s capital Columbia which recorded 291mm from the event and a one day, all time, record of 175mm. With all things considered this was a historical event for South Carolina. Unfortunately widespread flash flooding occurred with this heavy rainfall and 17 people perished, it is also expected that this natural disaster will top $1 billion dollars in damages.
Church underwater in South Carolina. (Souce: Sean Rayford via Jeff Master’s blog)
Here are a few more notable amounts from the event (data from NWS):
Gills Creek, SC storm total of 546mm
Seven stations with over 50 years of data had their wettest October on record, only one week into the month (via weather.com)
Millwood, SC storm total 527mm
Kingstree, SC 24-hour total of 399mm, possibly beating the all-time South Carolina 24 hour precipitation record of 376mm from 1999 during Hurricane Floyd (via weather.com).
Sumter, SC storm total of 528mm
This weekend more soggy weather is in place for South Carolina and flood warnings/flash flood watches have already been issued by the NWS. Not as much rain is expected from this system as it is faster moving and PWATs are not quite as high as seen last week. The one bit of good news that has come out of this flooding is that all moderate drought that was in place has been wiped away from the state.
An incredibly abrupt change is in store for Southern Manitoba as a powerful low pressure system is set to blast the near-record warmth out of the region and replace it with unquestionably fall-like weather. As it often is in the shoulder seasons, though, it’s going to be quite the spectacle.
Temperatures have soared into the mid–20’s quickly this morning, rapidly approaching the record high for Winnipeg of 26.1°C set in 1941. A powerful low pressure system to our northwest is approaching, though, and it is going to pack a mean cold front.
Surface analysis valid 12:45PM October 11, 2015
The midday surface analysis shows us three primary features. The first is the frontal wave with warm front across the northern Interlake and cold front draped southwards along the Manitoba/Saskatchewan border. To the southeast of these fronts is the unseasonably warm air mass that is bringing very warm temperatures to the region. The second feature is a low pressure center over central Saskatchewan. The last is a broad cold front that stretches from Central Alberta into Northern Manitoba.
Important to note is that the low pressure centre has occluded[1] and that there is a trowal developing (visible on the satellite image). This lonely low will trundle along for a little bit, until it can re-attach to the cold front slumping down behind it. The temperature gradient along the northern front is actually quite significant, and as the low re-attaches to that frontal wave, it will rapidly intensify. This low will move east-southeast as the steering flow amplifies and digs the upper-level trough.
While we may warm another degree or two, it’s more or less all downhill from here. Wind will continue to pick up out of the west-northwest late this afternoon to around 30km/h as an area of showers blossoms over Southern Manitoba. Widespread shower activity is likely much of the night as strong cooling aloft results in persistent destabilization of the atmosphere. Winds will remain around 30km/h with gustiness on top of that.
The real story will be when the cold front slams through early tomorrow. More rain is likely with the passage of the front, but winds will be the primary issue. As the cold front passes, winds will shift to be out of the northwest and pick up in speed significantly. Sustained winds will likely reach around 55–65km/h, but very strong gusts are possible; it’s highly likely that Winnipeg & the Red River Valley will see wind gusts to 90km/h, however with very strong winds within the conditionally unstable layer and precipitation very likely, it’s possible that wind gusts exceed 100–110km/h. Winds at these speeds can be hazardous when driving and cause damage to buildings (especially roofs) and trees.
NAM forecast sounding for Winnipeg, valid 12Z October 12, 2015
This forecast sounding for Winnipeg from the NAM shows very strong winds near the surface, with up to 60kt present at the top of the low-level instability.
The strongest winds will begin to subside mid-to-late morning, but strong northwesterly winds of 50km/h gusting to 70km/h will likely be in place for the remainder of Monday. The day will start of with a temperature around 9 or 10°C and see it drop to around 4°C by the end of the day. The bulk of the precipitation should taper off with the winds mid-morning, and when all is said and done, this system will likely produce around 5–10mm of rain over the Red River Valley, although for the northern half, there’s a slight chance of seeing more along the lines of 10–15mm.
Environment Canada has issued a wind warning for the Red River Valley regarding this system with the following discussion:
An intense low pressure system will track across central Manitoba tonight and Monday morning. A strong cold front extending southward from this low will sweep across southern Manitoba tonight. Very strong northwest winds will develop in the wake of this cold front with the strongest winds in the Red River Valley as winds will funnel down the valley. Sustained winds of 60 to 70 km/h with gusts over 90 km/h are likely beginning late tonight and lasting until early afternoon on Monday. Winds will gradually subside Monday afternoon from west to east as this system heads off into Ontario.
Damage to buildings, such as to roof shingles and windows, may occur. Loose objects may be tossed by the wind and cause injury or damage. Be prepared to adjust your driving with changing road conditions due to high winds. Avoid wooded areas to prevent injury from falling trees or branches. Campers should move to sturdy shelters.
Be sure to tie up any loose objects and remove fabric canopies from gazeboes. Bring in any objects that could catch the wind, and maybe flip your trampolines over so the wind doesn’t do it for you. It’s going to be a bit of a busy night and a wild Monday morning, so batten down the hatches!
Occlusion is a part of the natural life-cycle of low pressure systems. In simple terms, it means the low has “detached” from the fronts. ↩
Welcome to Weather News This Week, a new feature here on A Weather Moment that will alternate with our existing Elsewhere in Weather News feature. Expect to find a collection of interesting links to writings elsewhere that cover weather events and news as well as advances in the science of meteorology. Let’s get right to it!
Arstechnica took a look at how the language used by climate scientists when talking about climate change differs dramatically from those who oppose them:
[…] language itself is not an indication of the strength of the evidence; it can really only tell us how people are using that evidence to make an argument, and whether they’re doing so tentatively or forcefully. So, looking at how two opposing sides of a scientific argument use language to make their case can tell us something about their thinking.
It can be especially interesting to look at the use of tentative and forceful language in the case of climate change, where the language can be inflammatory. Scientists who describe the likely future path of our habitat often face the accusation of “alarmism.”
Srdan Medimorec and Gordon Pennycook, two graduate school researchers at the University of Waterloo, are interested in how people form beliefs on the basis of argument. They decided to look into the writing of opposing groups—climate scientists and people who refuse to accept the evidence on climate change—to see whether there was a consistent difference in language use.
Over on the Boston Globe, they have a fantastic gallery of images of the historic flooding that occurred in South Carolina.
Flooding around Aberdeen Country Club, on Oct. 6 in Longs. S.C.. (Janet Blackmon Morgan/The Sun News via AP)
The flooding in South Carolina was some of the worst on record and was a result of a quasi-stationary upper-level low anchored over the southeastern U.S. that was able to tap into moisture from Hurricane Joquain. The result was a band of torrential rain and thunderstorms that remained in place for several days, resulting in absolutely smashed rainfall records for many locations which saw more than 20 in (500+ mm) of rain.
On Wednesday, September 30, less than six days from a potential landfall, the ECMWF operational model was consistently keeping Joaquin offshore, even as the GFS and nearly all other models were bringing the hurricane into the U.S. East Coast. From late Wednesday into Thursday, the GFS and other models began to shift toward an offshore track for Joaquin, as the hurricane itself was still diving southwestward into the Bahamas. By Friday, there was virtually unanimous model agreement on the offshore track that proved accurate.
“People are turning to me less and less for what to wear to work and more for an explanation on the more intense and more frequent weather anomalies,” said Wagstaffe, an on-camera meteorologist for the CBC, Canada’s public broadcaster.
“The audience is getting more hungry for knowledge about what’s happening with the weather, and why. The story about climate change is becoming more interesting and what it will mean for our future.”
How Wagstaffe does her job has also changed. There’s more and better satellite and information technology to work with, but the so-called “normal” weather patterns that acted as benchmark have been out of whack in recent years. That includes this summer, when some of the models used to look at the longer-term forecast had to be ignored because of the hot and dry summer in Western Canada and the soggy and cool conditions in Central and Eastern Canada.
Over on the Winnipeg Weather blog, Julien has compiled a few statistics for Summer 2015 in Winnipeg. The whole thing is worth a read, but he especially made some interesting observations about summer humidity in Winnipeg:
In the last 20 years, 9 years saw a top 10 most humid summer since 1953. Summers have become increasingly humid since the 1990’s and this is easily seen in the graph below. The graph shows the top 20 most and least humid summers (red and blue dots) and the 30-year running mean (green line). Whether or not the increasing humidity is a trend that will continue is unknown. With only 63 years of dewpoint records, there simply isn’t enough data to see if there were similar humid periods in the past.
Graph showing a trend of increasingly humid summers in Winnipeg. 1980’s normal summer average dewpoint was about 11.5°C. Today’s normal is now close to 12.8°C.
July and August were particularly humid. With an average dewpoint of 16.1°C in July, it was the second most humid July and month on record since 1953. Only July 2012 was more humid with an average dewpoint of 16.5°C. August tied with 2003 for 14th most humid with an average dewpoint of 13.7°C.
That’s it for this week; we’ll be back in a fortnight with more weather-related reading for you! If you like the idea of this and have any suggestions for format or content, leave us a comment below!
The heat is on for Thanksgiving weekend in Southern Manitoba as a low pressure system tracking across the northern Prairies and draws unseasonably warm air eastwards into the province. Temperatures will soar into the 20’s on the weekend—some 10–15°C above normal for this time of year—with possible record-breaking heat in place for Sunday.
Today will be a fairly cloudy day despite our sunny start, thanks to a large area of cloud spreading eastwards along the leading edge of the warm air. As the cloud moves in, winds will increase out of the south-southeast to 30–40km/h with a bit of gustiness on top. Today’s daytime high will be near 15°C throughout much of the Red River Valley. The cloud cover will thin this evening into the overnight as temperatures dips to the high single digits.
Shown by this forecast of 850mb temperatures, a large area of warm air will be in place over southern Manitoba on Sunday.
Saturday will be a gorgeous day with partly cloudy skies, southwest winds at 20–30km/h and a high temperature around 23°C in the Red River Valley.[1] Temperatures will dip to around the 10°C mark on Saturday night with clear skies.
Sunday will bring mixed skies as a cold front approaches from the northwest. Temperatures will soar into the mid–20’s, giving a run at the record high of 26.1°C set in 1942. It looks like Winnipeg’s temperature will likely end up just short of the record, but it’s something to keep an eye on!
Record Temperatures for Thanksgiving Weekend 2015 in Winnipeg, MB
Date
Record Temperature
Record Year
October 9
27.8°C
1938
October 10
27.8°C
1934
October 11
26.1°C
1942
A cold front will slump through the Red River Valley on Sunday evening, ushering in breezy northwesterly winds up to 40–50km/h and a cooler airmass. The low temperature will settle around 10°C on Sunday night. There will be a chance for some rain on Sunday night into Monday depending on exactly where the wrap-around precipitation of the low passing to our north ends up, but at this point there’s too much uncertainty to make any confident forecast at this point.
Thanksgiving Monday & Beyond
Thanksgiving Monday looks less pleasant than the weekend; there will be plenty of cloud around alongside a chance for rain as a strong low pressure system moves into northern Ontario. Winds will be fairly strong, likely around 40km/h or so. The daytime high will only be in the 10–15°C range, so it will certainly feel significantly cooler than the weekend.
After Monday, things look fairly seasonal with temperatures potentially slightly above normal. No particularly big weather systems appear to be on the horizon, although a slight northwest flow is forecast to develop mid-week, which could increase our chances of some shower activity. All in all, though, a fairly quiet week expected.
Happy Thanksgiving! Enjoy your weekend!
Daytime highs might climb a degree or two higher near the western escarpment of the Red River Valley where southwesterly downslope winds may add a bit of warmth. ↩
