Welcome to City-Data.com Forum!
U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Weather
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
Reply Start New Thread
 
Old 12-20-2014, 05:46 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619

Advertisements

Saw this awesome post by Tom Nizol.



Then saw this discussion by NWS NY. See Bolded.

NATIONAL WEATHER SERVICE NEW YORK NY
710 PM EST SAT DEC 20 2014

CLOUD COVER AND A NLY FLOW TODAY KEPT TEMPS IN CHECK WITH
AFTERNOON HIGHS ONLY IN THE UPPER 20S TO THE LOWER 30S. THE LAST
DAY OF AUTUMN WILL FINISH AS ONE OF THE COLDEST. WINTER SOLSTICE
IS 603 PM SUNDAY EVENING.

COLD HIGH PRESSURE SETTLES OVER THE SAINT LAWRENCE RIVER VALLEY
THIS EVENING. THIS WILL MAINTAIN THE COLD AIR SUPPLY WITH LIGHT
NLY WINDS. LOW-LEVEL MOISTURE WILL ALSO REMAIN TRAPPED BENEATH A
STRONG INVERSION AT APPROXIMATELY 900 MB. THUS...LOOKING AT
CONTINUED CLOUDY SKIES TONIGHT. THIS WILL KEEP TEMPS FROM DROPPING
TOO FAST WITH LOWS RANGING FROM THE LOWER 20S WELL INLAND TO AROUND
30 AT THE COAST.

A SHORT WAVE TROF OVER THE OHIO VALLEY THIS EVENING WILL MOVE
ACROSS THE AREA LATE TONIGHT. THIS COUPLED WITH THE LOW-LEVEL
MOISTURE MAY PROVIDE JUST ENOUGH LIFT FOR SNOW FLURRIES OR VERY
LIGHT SNOW...WITH THE BEST CHANCE BEING ACROSS EASTERN LI AND SE
CT. LITTLE OR NO SNOW ACCUMULATION IS FORECAST. THERE COULD ALSO
BE SOME RAIN MIXED IN AND/OR FREEZING RAIN WITH LACK A ICE
CRYSTALS IN THE CLOUD BEARING LAYER. OFTEN THOUGH ALONG THE
COAST...SEA SALT CAN LOWER THE ACTIVATION TEMP OF ICE NUCLEI.
Reply With Quote Quick reply to this message

 
Old 01-04-2015, 06:21 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
Basics.

Reply With Quote Quick reply to this message
 
Old 01-05-2015, 08:49 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
Figure I put this here too to get an idea how the cold air masses move into the U.S

It's a 10 day loop of the projected 850mb temps from the latest GFS6z. Jan 5th - Jan 15th

First you'll notice 2 split Polar Vortex's.

Next You'll see the coldest core pocket of air pivot and rotate into the Mid West and New England this week, another one breaks off for this weekend and rotates into us, and watch towards the end of the run yet another from the Arctic breaks off and dives down.

Watch the Atlantic ridge shift East towards Europe with temps aloft +10C to France and Italy.

-10C (pinks) stay focused over North America and Asia.



https://www.youtube.com/watch?v=k8oZbfPkEIc&feature=youtu.be
Reply With Quote Quick reply to this message
 
Old 01-11-2015, 03:49 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
3 Maps. Regarding the tricky situation

It's easy to keep track.. Here's what I'm looking at. There's 3 levels we have to watch tomorrow. Surface temps, 2000 foot temps, and 4500 foot level temps.

Here is the 925mb & 850mb temps. Currently below freezing on both levels north of Atlantic City.

So basically if precip fell now it would be snow. If you don't want ice, then you don't want to be above the freezing line (0C) at 850mb and below freezing at the surface.

Links update every 15 minutes.

Look at those wind barbs. South & west winds pushing the warm air up.

For instance... look at central Indiana. Left image 2000 feet its below freezing. Right image 4500 feet its above freezing. There is precip there and it's ice and sleet



You all know how to get the surface temps aside from your own thermometer. Just keep an eye on the radar and these 2 levels as well.

----------------------

Here's another easier look. Numbers are the surface temps. 32 in Indianapolis.

Shaded colors are the crucial 4500mb temps. It's above freezing at 4500 feet above Indianapolis, hence the ice.

You can see the freezing line already pushing up. You don't want that level to be above freezing when your temps are at or below freezing.

We'll see where it is in the morning. I might not have time to post maps. :-(




Current Watches. Ice Storm Warning in Indiana.

Reply With Quote Quick reply to this message
 
Old 01-19-2015, 06:46 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
As I said many times, a lot of times you can learn a lot from reading NWS Discussions.

For instance... We have a Clipper coming down mid week, but... here's what NWS Philly says for the day before the impact.

"THERE IS A PRE CLIPPER CLIPPER ON TUESDAY THAT THE MODELS ARE PREDICTING TO GET SHREDDED BY THE CONFLUENT FLOW OVER THE NORTHEAST"


So that first clipper is getting shredded. Not sure what confluent flow is? Do a search. Great way to learn.

Then....... it's not so much the Alberta clipper which is causing the snows here Wednesday..


"WHILE WEDNESDAY WE ARE GIVING CREDIT TO THE CLIPPER LOW FOR PRECIPITATION CHANCES. IN REALITY MOST OF THE TRIGGERING/LIFT IS COMING FROM A STRONG SHORT WAVE ROUNDING THE BASE OF THE 500MB TROF"

So it's a shortwave rounding the base of the trough which is triggering lift in the atmosphere.. TONS of info on this with this link.

And....

"IN ADDITION, UNLIKE THE PREVIOUS CLIPPER, BECAUSE OF THE SHORT WAVE AND BETTER JET LOCATION, OMEGA WITHIN THE SNOW GROWTH AREA IS PREDICTED. OF COURSE THE RUB REMAINS A SHORT WAVE ABOUT 66HRS AWAY AND STILL IN THE PACIFIC OCEAN IS DIFFICULT TO PIN-POINT"


So the Jet is in better position this time AND some energy with this system is still in the Pacific so details are tough!
Reply With Quote Quick reply to this message
 
Old 01-21-2015, 04:12 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
You can always learn from the NWS Discussions and videos from Meterologists. Bernie is one of my favorites. Doesn't hype things and gets technical at times.

Have a watch and listen, hopefully you enjoy it and gain some knowledge from it like I do.
Reply With Quote Quick reply to this message
 
Old 01-21-2015, 04:30 PM
 
Location: New Jersey
15,318 posts, read 17,214,623 times
Reputation: 6959
Quote:
Originally Posted by Cambium View Post
As I said many times, a lot of times you can learn a lot from reading NWS Discussions.

For instance... We have a Clipper coming down mid week, but... here's what NWS Philly says for the day before the impact.

"THERE IS A PRE CLIPPER CLIPPER ON TUESDAY THAT THE MODELS ARE PREDICTING TO GET SHREDDED BY THE CONFLUENT FLOW OVER THE NORTHEAST"


So that first clipper is getting shredded. Not sure what confluent flow is? Do a search. Great way to learn.

Then....... it's not so much the Alberta clipper which is causing the snows here Wednesday..


"WHILE WEDNESDAY WE ARE GIVING CREDIT TO THE CLIPPER LOW FOR PRECIPITATION CHANCES. IN REALITY MOST OF THE TRIGGERING/LIFT IS COMING FROM A STRONG SHORT WAVE ROUNDING THE BASE OF THE 500MB TROF"

So it's a shortwave rounding the base of the trough which is triggering lift in the atmosphere.. TONS of info on this with this link.

And....

"IN ADDITION, UNLIKE THE PREVIOUS CLIPPER, BECAUSE OF THE SHORT WAVE AND BETTER JET LOCATION, OMEGA WITHIN THE SNOW GROWTH AREA IS PREDICTED. OF COURSE THE RUB REMAINS A SHORT WAVE ABOUT 66HRS AWAY AND STILL IN THE PACIFIC OCEAN IS DIFFICULT TO PIN-POINT"


So the Jet is in better position this time AND some energy with this system is still in the Pacific so details are tough!
I didn't realize NOAA had a glossary. Very cool.

Confluence
A pattern of wind flow in which air flows inward toward an axis oriented parallel to the general direction of flow. It is the opposite of difluence. Confluence is not the same as convergence. Winds often accelerate as they enter a confluent zone, resulting in speed divergence which offsets the (apparent) converging effect of the confluent flow.

Difluence
(or diffluence) - A pattern of wind flow in which air moves outward (in a "fan-out" pattern) away from a central axis that is oriented parallel to the general direction of the flow. It is the opposite of confluence.

Difluence in an upper level wind field is considered a favorable condition for severe thunderstorm development (if other parameters are also favorable). But difluence is not the same as divergence. In a difluent flow, winds normally decelerate as they move through the region of difluence, resulting in speed convergence which offsets the apparent diverging effect of the difluent flow.

Still kind of confusing.
Reply With Quote Quick reply to this message
 
Old 01-21-2015, 05:20 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
Quote:
Originally Posted by ilovemycomputer90 View Post
I didn't realize NOAA had a glossary. Very cool.

Confluence
A pattern of wind flow in which air flows inward toward an axis oriented parallel to the general direction of flow. It is the opposite of difluence. Confluence is not the same as convergence. Winds often accelerate as they enter a confluent zone, resulting in speed divergence which offsets the (apparent) converging effect of the confluent flow.

Difluence
(or diffluence) - A pattern of wind flow in which air moves outward (in a "fan-out" pattern) away from a central axis that is oriented parallel to the general direction of the flow. It is the opposite of confluence.

Difluence in an upper level wind field is considered a favorable condition for severe thunderstorm development (if other parameters are also favorable). But difluence is not the same as divergence. In a difluent flow, winds normally decelerate as they move through the region of difluence, resulting in speed convergence which offsets the apparent diverging effect of the difluent flow.

Still kind of confusing.
Would be nice if they put images next to their descriptions. I don't have an example to show with the current 500mb map yet. Here's another good link. I like their car movement analogy. One is winds pointing inwards, one is out.
THE SURFACE CHART

Good reminder when air rises it creates instability and storms. When air sinks it tends to lead to good weather. High Pressures spinning clockwise makes air sink, hence the clear weather. Convergence and Divergence | Climate Education Modules for K-12



Reply With Quote Quick reply to this message
 
Old 02-11-2015, 01:21 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
I'm hoping everyone in the "weather" thread is watching Bernie's videos. Even if you know the stuff, it's always good to see and hear it again. Good stuff! No hype, lots of technical talk and well spoken!


https://www.youtube.com/watch?v=XmpJ...ature=youtu.be
Reply With Quote Quick reply to this message
 
Old 02-28-2015, 10:55 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
Which direction is this moisture heading ? Current radar



You can typically look at the general upper flow to see the direction. 500mb Heights to see. Doesn't always work for coastal areas with onshore flow or Thunderstorms with a spin. But to get the general direction look at the 500mb heights.



Future radar loop shows it in motion. SW to NE

Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply

Quick Reply
Message:


Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Weather

All times are GMT -6.

© 2005-2024, Advameg, Inc. · Please obey Forum Rules · Terms of Use and Privacy Policy · Bug Bounty

City-Data.com - Contact Us - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 - Top