Sunday morning, 21 Oct 2018:
In early October, warm days and cool clear nights are the perfect combination for dew on the grass. One of these nights the temperature of the grass will drop below freezing and the dew will form as frost.
Have you had frost in your neighborhood yet?
Tonight might be the night.
p.s. If the air is below freezing but not humid, the plants freeze without a frost.
(photo by Kate St. John)
9 October 2018
Last week the National Weather Service published an analysis of six of the many tornadoes that hit our area on Tuesday, October 2. There were 14 tornadoes in Pennsylvania that day!
The most damaging tornado hit a nursing home in Conneautville, PA. The most unusual one touched down in the Valley Green Road area of Westmoreland County. NWS Pittsburgh describes what made the Valley Green Road EF1 tornado so interesting:
This tornado was unusual not only for its northward movement in an eastward-moving storm, but especially because it formed on the northern side of the parent thunderstorm, removed from the typical hook echo region.
NWS Damage Surveys for 10/2/2018 tornado event, National Weather Service Pittsburgh
So what is the hook echo region?
According to Wikipedia, “A hook echo is a pendant or hook-shaped weather radar signature as part of some supercell thunderstorms.”
USTornadoes.com describes how it forms: “This “hook-like” feature occurs when the strong counter-clockwise winds circling the mesocyclone (rotating updraft) are strong enough to wrap precipitation around the rain-free updraft area of the storm.”
The annotated radar image below shows the hook at bottom left, curling around the back of the storm with a tornado at the tip.
Tornadoes usually form in the hook echo and they move with the storm. Storm chasers use these facts to find and safely chase tornadoes.
But not at Valley Green Road. That tornado formed on the north edge and traveled north (See region on the annotated example of an Oklahoma tornado below.)
Sneaky tornado! Fortunately it was not very powerful (EF1) and there were only trees in its path.
(photo and hook echo images from Wikimedia Commons. The tornado photo was taken in North Carolina (not in PA); click on the captions to see the originals)
Birds can sense when bad weather is coming. If it’s going to be dangerous and they have some lead time they get out of the way. Hurricane Florence gave them plenty of time to prepare.
Weather radar shows us where it’s raining by detecting objects in the sky. When masses of birds are on the move they show up on radar, though less intense than steady rain. Flocks of birds look green on radar and are only detected when near radar stations. Since most birds migrate at night, that’s when to watch.
This radar image from 5:08am on Saturday September 15 shows the rain bands of Hurricane Florence swirling over the Carolinas. Notice that there’s no rain for miles surrounding the circle of the storm but there are intense green blobs southwest of Florence over the Florida panhandle.
Thousands of birds! They’ve heard the news and they’re leaving the area. Evacuate!
p.s. Read more about birds on radar here and an article about birds escaping storms by flying hundreds of miles out of their way
In case you haven’t heard, it’s been raining here in Pittsburgh. A lot!
This is mostly from the remnant of Tropical Storm Gordon that came ashore in Mississippi on September 4 and arrived here September 8. We were in a drought but now it’s been raining for three days.
Yesterday set a record of 3.73 inches at the National Weather Service in Moon Township but it’s rained even more in the South Hills. Since Friday morning 7.5 inches have fallen at the Allegheny County Airport in West Mifflin (as of 10 Sept 2018, 7:53a). And it’s still raining!
Basements are flooded and roads are closed. Two screenshots from PennDOT traffic cameras show:
And the rivers are rising. Here’s the National Weather Service’s Ohio River prediction for Pittsburgh. Uh oh!
Fortunately our house and street are fine (photo at top) but I feel bad for those who live in the valleys.
Rain, Rain Go Away!
(photo by Kate St. John, PennDOT traffic camera screenshots, Ohio River gauge from the NWS Advanced Hydrological Prediction Service)
Pittsburgh’s weather had a tropical flavor this month with a chance of thunderstorms predicted every afternoon.
On clear days I could see individual thunderheads form and sometimes hear them rumble in the distance. This late morning cloud on August 13 had some interesting features. Was it going to rain or thunder?
It was already a two-part cloud: Cumulus is the bright white top, nimbus is the darker lower section.
While I watched, two updrafts rapidly pushed moisture higher in the sky. If I’d made a video you would see both columns expanding upward and growing fast. The small cloud on the left dissolved moments after I took this photo. The big one kept growing.
The nimbus section looked threatening with dark lumpy areas (photo retouched to add contrast). I’m not sure what the lumps mean but they probably weren’t good.
I watched this cloud as I walked home and, sure enough, it thundered after I took the photo. Fortunately I was indoors before it rained.
(photos by Kate St. John)
Feeling sweaty this month?
It’s not the heat and it’s not the relative humidity.
On Throw Back Thursday, learn about the number that predicts we’ll have a sweaty day in this vintage post: Feeling Dewy
(photo from Wikimedia Commons. Click on the caption to see the original)
What happens when a hurricane hits Newfoundland? I found out last week when Hurricane Chris came to eastern Newfoundland while I was there on a birding trip.
The cold waters of the North Atlantic usually take the fangs out of hurricanes before they hit Atlantic Canada and so it was with Hurricane Chris. Before the storm we asked some Newfoundlanders about it and they said it wouldn’t be bad. “We won’t even take in the lawn furniture for this one.”
By Thursday morning, 12 July 2018, Chris was downgraded from hurricane strength to a post-tropical cyclone — from winds greater than 74 mph (119 kph) to winds less than 40 mph (64 kph).
Nonetheless, it was forecast to hit Cape Race around 8pm on Thursday with sustained winds of 35 mph (56 kph) while dumping 3-4 inches of rain (75-100 mm) near Terra Nova National Park. The map below shows both locations with purple pins: “Cape Race, Day 4” on the south shore and “Terra Nova, Day 6” in the north.
Our birding schedule meshed perfectly with the hurricane’s timing. We left Trepassey near Cape Race on Thursday morning and were sleeping in Clarenville by the time bad weather hit the Avalon Peninsula Thursday night.
Along the way we experienced the calm before the storm — hot and windless. On the Maine coast I’ve heard this called The Hurricane’s Breath because it is so unusual.
When the post-tropical cyclone crossed Cape Race Thursday night its maximum sustained winds were 40 miles per hour (67 km/h) with gusts up to 54 mph (87 km/h). Meanwhile about 3 inches (76 mm) of rain fell near Terra Nova.
So what did it look like on the south coast of Newfoundland when the storm was at its peak? Chris Mooney, a park interpretation technician at Cape St. Mary’s Ecological Reserve, took these videos from his home in Branch, NL on Thursday evening.
Posted by Chris Mooney from the town of Branch, 7/12/2018 at 9:02pm. (Click the speaker icon to turn on the sound.)
… and posted at 9:24pm
Chris remarked that salt spray had already coated his windows so much that he couldn’t see out of them.
And what about the nesting birds on the rock? “We’ll lose a few chicks for sure.”
Fortunately the remnant of Hurricane Chris was a relatively mild storm. When a real hurricane hits Newfoundland it’s devastating. Click here to read about Hurricane Igor in September 2010, the strongest hurricane ever to hit the island.
(videos and screenshot by Chris Mooney via Facebook)
1 June 2018
Saturday is the 20th anniversary of the 2 June 1998 tornado that hit the City of Pittsburgh. Before that event many of us thought it was impossible for a tornado to touch down in the city limits. Hah!
Everyone who saw it has a story.
That day I was still at my desk around 6pm, gazing out the window as I talked on the phone with someone in Indianapolis. Though my office was more than three miles from the tornado I could see the storm’s approach as the sky got dark and the wind increased. I saw a crow fly into the wind but as hard as he flapped he went backwards. Uh oh!
I told the person on the phone, “I think a tornado is coming.” He said, “Don’t tell me about it. We have too many of those,” and he kept talking. Since the City of Pittsburgh had never had a tornado I figured it was OK to stay in my office but I dragged myself and the phone under my desk to continue the conversation away from the window.
Meanwhile, bad things were happening on Mt. Washington as Chuck and Joan Tague drove home across the Liberty Bridge. The worst of the storm missed their Chatham Village neighborhood but the roads were so blocked with fallen trees that they parked far away and walked home. The power was out for a very long time.
Chuck’s story is impressive! Click here or his photo below to read it.
We think of it as “the Mt. Washington tornado” but it also touched down in Carnegie and Hazelwood and traveled 32 miles before it dissipated. It was one of nine(*) tornadoes that hit our region that evening.
Read more about the Tornado Outbreak of June 2, 1998 here on the National Weather Service website, and in the Post-Gazette When Tornadoes Tormented the Pittsburgh Region. (* NWS confirmed 9 tornadoes; the P-G says there were 14!)
Do you have a memory from that day? Leave a comment with your story.
(small photos from the National Weather Service report on the June 2, 1998 tornado outbreak. Photo of tornado-downed tree in Chatham Village by Chuck Tague)
6 May 2018:
How to predict a great birding day in early May? Find out last night’s weather.
At this time of year migrating songbirds spend the day eating and resting, then fly north overnight. Their decision to move depends on the weather. Here’s what they like best:
Weather radar is sensitive enough to show rain and snow. Did you know it also shows migrating birds?
The screenshot above shows the central Great Lakes weather radar at 4am, 6 May 2018. Yellow, orange and red indicate rain of increasing intensity. Green and blue are either light precipitation or birds. Green circles with blue edges are birds. Birds show up as circles because the detection limit of each radar installation is circular.
So what does this radar plot mean for Pittsburgh? Here’s a marked up version.
The red circle shows an area of bad weather. (Heavier rain is yellow and a hint of orange.) The red line marks the northern limit of the bad weather. Notice that there are no green circles north of the red areas. The birds stopped south of there.
Bad weather stopped the birds last night. Will we see the same birds in Pittsburgh today as we did yesterday? And in the same places?
Let me know what you find out.
p.s. Click on the radar images above to see the current Central Great Lakes radar map at weather.gov.
(screenshots of Central Great Lakes weather radar, 6 May 2018, 3:58 EDT from weather.gov)
For more than a century Pittsburgh was The Smoky City with air so bad we were called hell with the lid off. After World War II we transformed ourselves with clean air laws enforced by the Allegheny County Health Department. The smoke is gone and we’re looking good, but Pittsburgh is still one of the top 10 most polluted places in the U.S.
You can’t see our bad air anymore but some days you can smell it. Yesterday was one of those days.
The Smell PGH map above (May 2) has a colored triangle for every air quality report made on the crowd-sourced app. The darker red the triangle, the worse the air smelled to the person who made the report to the Allegheny County Health Department. At the bottom right, May 2 has a black square above it (bad air!). So do May 1 and April 27. You can see our smelly days.
The reports are easy to make. I downloaded the app and followed the directions at the Smell PGH website:
As soon as you press [Smell Report] your colored triangle sends a message to the Allegheny County Health Department and the app shows you the current map. Don’t forget to enter your name and email address under Settings for more impact.
I used to think I was alone when I noticed bad air days. The app has changed my outlook. Find out more at the Smell PGH website.
p.s. The weather changed. Today, May 3, 2018, is much better.
(screenshots from the Smell PGH website)
