Thursday, December 29, 2011

Coldest Air of the Season Coming Soon...

So far, the lowest temperature this young winter season has been 20 at Louisville Int'l and 17 at Lexington. At this time, all models are in agreement that a shot of Arctic air is poised to plague the region resulting in perhaps the coldest air of the season. Daytime highs look to struggle to reach the freezing mark.

You would think snow chances would rate very high during this time frame. True, we may see a fetch of moisture off of the Great Lakes, but what we need is a storm system that gets its act together to produce a decent snow event here while the window of opportunity is open.

Most likely, this cold snap won't last long unless we get a strengthening block to our northeast, which models do hint at some blocking. We'll have to wait and see on that one.

Till then, enjoy the mild air. I think I may end up going hiking...

MS

Tuesday, December 27, 2011

Cold Front Pushing Through (9:45am UPDATE)

As I'm typing this, the cold front is literally over top of my location here just outside of Louisville. Winds have just shifted around to the west from the south.

This is verified by the SPC Mesoanalysis page looking at the 850mb sounding for 9am. The 'zero' line resided just west of Louisville and extended to Bowling Green, where their temps were in the mid 40's.

Moderate snow falling at Paducah, while light snow is falling at Indianapolis. Only rain being reported at Evansville but should have changeover by next hour.



Newburgh IN above

Here's a cool link to Vincennes IN live streaming webcam where snow has fallen this morning and produced a nice coating.

http://www.webcamvue.com/default.asp?webcam=hyObihvBIehN

More updates later...

MS

Monday, December 26, 2011

Running With the NAM 12/27

The latest 06z run of the NAM is painting a clearer picture about what to expect from this next storm system, impacting the region mostly overnight and into the day on Tuesday.

Although I would like to review the next run (12z) of the NAM, I've seen enough trends from run to run that convinces me that this system will produce a rain and rain/snow event for the region.

However, for most, if not all of us, don't expect anything significant. Of course, we love surprises, though. This will be one of those instances where dynamic cooling can deal an interesting hand. There will be factors in play that could lend credence to this possibility...

1) Low pressure strengthening to our south
2) Freezing levels above ground level dropping throughout the day
3) Precipitation will still be in the region as the above factors play out.

In addition, a possible deformation zone could set up on the back side of the low thus producing an enhancement of rain/snow or whatever is falling at the time. If this should occur, it would most likely take place east and south of Louisville. Again, though, I like surprises.

Still, don't get too excited about this one as surface temps and wet grounds are not expected to support a nice, heavy wet snowfall. Please, surprise me.

MS

Sunday, December 25, 2011

GFS Model On A Roll

I have followed the GFS forecast model for the past two significant weather systems. Even though there were obvious flaws in presentation and consistency from run to run, its basic thought outclassed its 'foreign' competitors, the GEM and ECMWF, in the medium range forecasts.

There is another storm system lurking that should bring us precipitation during the day Tuesday, with changeover from rain to at least a mix of rain/snow quite possible by evening. Both the GFS and GEM are showing residual snow in the area Tuesday evening, primarily east of Louisville, that may include light accumulation. Considering a wet ground, any significant accumulation does not look likely unless any heavier bursts of snow that may develop cause deteriorating circumstances briefly.

However, the storm system looks to make a quick exit. There is no definitive TREND  toward a colder pattern, based on my observations of the current NAO forecast. So far, the GFS forecast model and the NAO have provided me with the correct assumptions so far. Therefore, I'm sticking with them on this next system, as it has similar characteristics to previous systems.

So, expect rain with a good chance for at least mixed precipitation, possibly all snow toward the end of the storm system's influence on our region. Light accumulations are possible. Again, don't get too excited as the ground should be too wet and 'warm' for any decent, long-lasting sticking snows.

Of interest to me at present, is the NAM's forecast guidance. Look for their forecast at about 36 hours out to see the best scenario for our weather.

MS

Tuesday, December 20, 2011

12zGFS and Euro UPDATE

The latest GFS is out and its complete suite of data for this upcoming weekend, or should I say early next week?

While it seems the GFS has taken a verbal assault as of late, because of its crack-like mood swings, I thought the GFS was the first one to suggest a warmer solution to this week's storm system (the current storm system). And this was several days out. I have the maps to prove it. While not consistent in its presentation, the main thought was rain, not snow.

Can 'lightning strike twice in the same place'? Well, let's see what the latest run suggests. As you'll notice, the presentation of its solution is a bit later than the GEM or the latest Euro that I'll show you in a bit.





















Looks like a light precipitation event according to this run. However, I would start paying more attention to this model in another 24 hours as the GFS should start figuring this one out, at least the idea, by then.
Again, here's the precip type below...showing mostly rain, as expected.





















And of course, those critical temperatures...





















As in my previous post, the temperature map shows Celsius readings, but we are solidly in the shading that denotes above freezing temperatures during the storm event thus rain.

Last, the Euro shows a more wintry setup. However, even this model suggests a rain event primarily. With rain changing over to snow eventually, or possibly, could be interesting to see if the cold air can catch up with the moisture in eastern KY and wring out a couple of inches or not.























Therefore, I'm still not impressed by any of the models yet but do feel confident that these models will start coming to some type of agreement within the next 24 hours or so.

MS

12zGEM UPDATE for Christmas Weekend

The complete suite of data is out for the latest GEM forecast model as it pertains to this weekend. I'm going to present the GFS(12z) and its complete suite as it becomes available. Be looking for it in a future post later this afternoon.

Here's the latest...





















The latest GEM presents a solution on Christmas day that shows precipitation breaking out across the region, especially the central and eastern parts of the state. The location of the low looks favorable for wintry precipitation, but...





















The precip type map above shows mostly rain, albeit a cold rain, for the entire region. Now, as the low shifts off to the east and northeast, the colder air will wrap around into the region with any leftover precipitation changing to a period of lt snow or flurries.

The 2m Temperature profile shows why we could expect mostly rain for the region initially...





















Temperatures above are presented in Celsius, but you can tell by the color shadings that the nearest blue (or freezing) line would be back in Illinois, moving quickly behind the low that could be traversing the Smokies by this time on Christmas day.

Next up on board is the GFS (12z)

MS

Monday, December 19, 2011

White Christmas???

All eyes are glued to the forecast models. There are some indications for a colder period of weather that may finally include the 'S' word by later this week into the holiday weekend. Of course, timing issues will ultimately decide who gets a possible white Christmas.

I've been looking at the GFS Ensembles Mean 2-m level temperatures for the week.
This is for December 25, still several days away so things can change...


















A unanimous trend for above normal readings by Christmas day. However, these same ensembles do show below normal readings shortly after December 25. More likely, this appears to be the best time for any significant wintry weather to occur here, according to this most recent run of the ensembles.

Now, let's take a look at the models...

The 0z runs from the Canadian GEM shows this particular setup...




















According to the precip type map above, the GEM wants to show a possible mix/ice setup on Christmas morning. Now, that wouldn't be nice.

The GFS shows a slower solution with affected areas more east than the GEM.
This is for the day after Christmas...




















The Euro wants to show a nor'easter, where barometric pressure readings drop from 1009mb to 990 mb in 24 hours. This is forecast around Christmas day according to its latest run.

I will be interested in seeing how the 12z runs pan out. Expect many changes both in time and substance as these models try to figure out what may happen.

MS

Sunday, December 18, 2011

Do You Like Science? Wind Chill Calculation
















Thanks to the calculation above, it's quite easy to figure out a wind chill reading for temperatures between -45 degrees and 45 degrees Fahrenheit and wind speeds between 3 and 60 mph.

Here's a snapshot of my EXCEL page...
           A                        B                       C
Temperature(F)
Wind Speed(mph)
Wind Chill(F)
33
18
21.88
 
In cell C2, here's the formula as copied from the chart above:
=35.74+0.6215*A2-35.75*(B2^0.16)+0.4275*A2*(B2^0.16)

To use the NWS wind chill calculator, use the formula above or refer to the site below...

Also, review the .pdf format for the Wind Chill Chart that you see above. Something you'll notice on the chart that was not on previous charts is a frostbite indicator with exposure times.

MS

 
 
                     
 
 


 

Friday, December 16, 2011

Model Wars - Early Next Week and Pre-Christmas

Well, I decided not to post any graphics for this upcoming storm system early next week. All of the models indicate an all liquid event. But, some residual precipitation may become a mix toward the end of the event according to a couple of models.

Next on board is a storm system that may take shape just before Christmas and the preceding day. By next Friday, the GFS leads the way, again supporting an idea that the teleconnections continue to show, a mild solution with all rain developing from a southern storm system.






Next, the GEM wants to show an all rain event but does support an idea of really cold air filtering in behind this storm system, while tracking eastward and becoming a formidable storm system along the east coast cranking up to deliver possible snows for the eastern part of the state.



The next graphic shows the southern storm now feeding off the Atlantic and produces an east coast storm that could bring accumulating snows to parts of the region as indicated by the precip type map below.



The teleconnection signals continue to favor the GFS in this circumstance. However, the NAO forecast ensembles does show a more negative read by the end of the month. Perhaps by then, the cold air will become established to support a more wintry storm system.

Perhaps, the GEM is trying to pick up on this a little earlier than the GFS. We'll see how the other models try to figure this one out. However, chances for a White Christmas are looking a little less likely. Originally, I had projected a 40% chance for a White Christmas during my winter weather forecast 2011/2012.

MS


Tuesday, December 13, 2011

Model Wars UPDATE 12/13 GEM vs GFS

Yesterday's 0z runs of the GEM and GFS showed two different scenarios for a storm system poised to develop early next week. The GFS showed a progressive solution while the GEM showed a slower solution with a low tracking to our south, providing the region with a possible wintry mix.

Today's 12z runs show the two models combining forces for a slower solution and a storm track to our west. At this time, both are indicating a rain event for the early next week time period. There's just a slight timing difference between the two. The GFS does hint that there could be some wraparound moisture. If cold enough, have to watch for some flakes then.

The 12z ECMWF has also trended northward and westward. Looks like a clean sweep for rain according to the latest trends.

This does correspond with the general atmospheric consensus. NAO to remain positive for the near term.

Just not enough cold air to tap into just yet. However, some of these stronger lows that will be tracking far north of us may bring down chunks of colder air to parts of the U.S. within the next 10-14 days. Perhaps a pattern change then? We'll just have to see.

MS

Monday, December 12, 2011

Model Wars - GFS vs GEM

I found a potential weather system that could be impacting our region by the beginning of next week. In this specific series, I want to follow these two, what I call, medium to long-range model forecasts and their interpretation of the existing data. As an extra bonus, I decided to throw in the ECMWF at the end of this discussion.

A brief introduction is necessary along with the 'cast' that may be playing a role in this potential system.

The maps I'm about to show you are from the GFS and the Canadian GEM-GLB models. Both models are on board that a southern storm system could develop along a strong cold front that may impact our weather here in the next 7 days or so.

Here's the cast of main characters to look for:

1) Cold front in mid-section
2) Developing Low along Texas coast
3) Strong SE ridge of high pressure

First, the GFS model, initialized Sunday evening December 11, for the period of December 20-21



Primarily a rain event for the area as the SE ridge pumps warm air into the area but shows signs of breaking down and moving on.


GFS moves the system on outta here with colder air coming in behind the system.

Next, the GEM for the same time period initialized at the same time as the GFS.


The SE ridge pumps moisture from the south, creating an all-rain event at the outset. Again, ridge breaks down and moves on...colder air filters in behind the front.

Ah, an ominous southern track that could create wintry problems around here according to this model run. With cold air in place, low rides along the front, creating a potential wintry mess.

Here's a look at precip types according to the GEM for the same time period (Dec 20-21)


Again, all rain along the front...notice a low taking shape down south.

Rain, sleet, and snow setting up, where else, across the battle zone of winter to be or not to be, an all-too familiar scene.

Now, you know these models will change over the coming days. But I posted this so we can see who has the better idea on this system this far out.

Coincidentally, the ECMWF has maps out that go this far out. It too shows a Low from the south, riding up the front that basically slices Kentucky in half, diagonally with rain to the south and southeast and a snow/mix north and northwest.

In another day or so, I'm going to present more models and their thoughts about this potential storm system, including an update on the two that I featured here, the GFS and the GEM.

MS

Sunday, December 11, 2011

Model Wars INTRO

It seems so many weather professionals and enthusiasts rely on the long-term model runs nowadays. You know, I think they're great for giving us an idea about an impending 'large' storm system.

However, and even the professionals will tell you this, so it's not just me, these medium to long-range model runs should not be relied upon to tell you exactly what you're going to get 6-10 days out. Each model run normally adjusts, sometimes wildly, in order to ascertain the best scenario for how the weather will unfold over the coming days. That's normal.

Yet, so many people, often weather enthusiasts like myself, figuratively live and die by each model run of a storm system that hasn't even come into existence.

What I like to do is check out the medium to long-range models and try to take note of any TRENDS, hopefully consistent trends about a particular setup that could lead to significant weather affecting our region. I know that the models are going to flip, waffle, swing, sizzle, and fizzle. That's OK. I expect that to happen because the models are trying to interpret data that is constantly changing. Therefore, I, for one, try not to get too excited about each and every model run from so far out in the future.

But, you may wonder, which of the medium to long-range models are most reliable or most accurate? Good question. I've heard people praise the European model, some the Canadian, and others the GFS. Although each has their strong side, each also has their weak side. Some may be good at showing a future Arctic outbreak but cannot determine how to develop a southern storm system based on energy ejecting out of the southwest. Other models may be able to show a Great Lakes cutter but cannot 'time' a system consistently or accurately.

Well, just for fun, let's try and keep up with some of the more popular medium to long-range models anytime a possible 'big' storm system looms on the horizon and determine which one is best. To be fair, though, I'm going to go out about 6 days so that all of these models will have a chance.

Remember, though, each storm system should be different. I believe that we'll discover some of these models are actually better than others when handling a particular storm system.

Therefore, be looking for it. I'll be posting the first Model Wars soon. I've looked at a few of the models so far, but nothing that important for our weather by next Saturday yet. However, there is a west coast storm to look at and a developing southern storm that is on the grids by then. But, I'm really interested in a possible Pacific storm system that may follow the upcoming one.

MS

Friday, December 9, 2011

Total Lunar Eclipse For the West

Sacramento CA is in line for a nice early morning treat, a total lunar eclipse. The treat is that the eclipse will be toward moonset, when the moon takes on an 'enlarged' appearance, as the atmospheric effects help distort the moon's size.

Colorful hues of copper and orange are expected during the total lunar eclipse.

Next total lunar eclipse on April 15, 2014. We'll be able to see that one, weather permitting.

Read more about the early morning Saturday event here.

MS

Coldest Air of the Season

The coldest air of the season is on the move. Follow the temps here...
Click on the map above...

Just before 2:00pm, clouds are rapidly increasing throughout north-central Kentucky. Radar echoes of sprinkles/flurries are occurring over parts of central and southern Indiana. Temps are crashing behind the front. Last hour, Indianapolis was at 34 degrees and flurries.

Forecast temperatures overnight suggest teens in areas around Louisville. The city itself has a projected low of 24 but would not be surprised if that value is adjust downward.

MS

Teleconnections - Something To Go By

Several days ago, I noticed a trend from the teleconnectors, NAO, AO, and the PNA that did not favor much in the way of big storm systems producing a hefty snow for our region. So far, these teleconnectors have been right.

What kind of future signals are these teleconnectors pointing to at present?

First, let me share with you today's graphs of the NAO, AO, and the PNA respectively.

North Atlantic Oscillation (NAO)


Please enlarge the graph above, as of today, December 9, the trend for the NAO going forward is positive, with some vascillation between neutral and positive. Although the 7-day forecast confidence level remains quite high, afterward, confidence values decrease. In fact, the 10-day forecast drops below 50 yet continues to show mostly a positive trend.

Not good for big snows around here unless the signals show something different in the coming days.

Next, the Arctic Oscillation (AO)


Unfortunately, the AO is forecast to remain positive, and the forecast values going forward are pretty confident for the next 10 days with some expected fluctuations between positive and neutral.

Last, the Pacific North American (PNA) pattern...


After a brief dip, the PNA is expected to turn neutral, perhaps slightly positive. PNA values that are negative allow for colder air to stay out west. However, this time, PNA values could go slightly positive in the days ahead. This would warm up the west and provide the midwest some cold air dropping in from Canada. However, as the NAO should remain positive, any cold air should not last too long.

This certainly sounds frustrating, as my winter forecast for 2011/2012 indicates a turn to a long-lasting colder air pattern, especially by the end of the month. Remember, though, it's still early. I'm still expecting the effects of La Nina to begin intensifying here by the end of the month. But, we do need the NAO to begin its trend toward negative, if we are going to see any threat of a big snow system.

Hopefully, in the days ahead, the trend will become our friend and begin pointing toward a colder, more typical wintry pattern for late December.

MS

Wednesday, December 7, 2011

NOWCAST 12/7/11 and Webcams

1:00pm UPDATE
Flakes are mixing in at this time over parts of the state. Look for a transition to all snow by dark or a little after. However, don't expect temperatures to cooperate much for a lot of accumulation.

After dark, accumulations should occur, primarily on grassy surfaces adn again in those areas highlighted yesterday in far e/se Kentucky. I'm still expecting 1-2" in lower elevations and 3-4".

Snowshoe WV
Snowshoe Mountain Web Cam

Pikeville KY
Pikeville, Kentucky - Pikeville Park 1 Webcam

MS

Tuesday, December 6, 2011

Now Is The Time - NAM 24-36 Hrs Out

It's a good time for me to think about snow amounts for portions of east/se Kentucky. The NAM has been very consistent over the past several runs about a possible snow event.

I want to show you a 850mb map from the NAM for tomorrow (Wednesday morning).


Feel free to enlarge the map above by clicking on it. Take note where the zero line is (the solid dark line). For me, it's not so much that the zero line says snow at the surface. I like to see those values around -4 or -6 to see mostly snow at the surface.

Depending on when the precipitation starts, it appears from this run that temperatures above will be warm enough to support mainly rain or a rain/snow mix for the east/southeast during the daylight hours.

However, note what happens by nightfall...



This time, I would like you to click on the map above. Note that the zero line is far east of the region by Wednesday evening. More importantly, notice that temperatures at the 850 mb level will be cold enough to support snow (at least -4). Also, examine that humidity levels will be quite high as indicated by the green shading thus supporting that flakes should still be flying by then in far east and southeast Kentucky.

The latest NAM model run (12z) shows precip breaking out during the morning hours tomorrow. Should be all liquid then. As the day progresses, expect rain transitioning to a mix, and then by nightfall, should become all snow with up to a couple of inches for those areas I highlighted in an earlier post, from Pineville to Pikeville. Most accumulations should be confined to grassy surfaces. However, some slick spots could develop as wet roadways could freeze during the overnight. May even be slushy accumulations in some of the higher elevations on the roadways.


Note the 2 meter temperature profile for overnight late Wednesday/after midnight Thursday, still shows temps near or above freezing. Most precip should be winding down by then.

Therefore, I still think WWAdvisory could go up during the evening and overnight hours for those locations mentioned above as temps could fall below freezing the rest of the night. Really depends on the temperature of the pavement, as well.

Summary:
From Pineville to Pikeville, 1-2", mainly grassy surfaces; up to 3 or 4" in highest elevations of far southeast Kentucky.
Isolated slick spots after dark.

MS

Monday, December 5, 2011

Snow Watch Monday Evening UPDATE

The NAM is still wanting a snow event. The latest 18zNAM continues to paint an accumulating snow for east/southeast Kentucky. Could still be looking at potential 2-4" for most locations of southeast Kentucky.

If the NAM can hold steady on this trend (of a snow event for east/southeast KY), we may be talking about winter weather advisories at the very least. Far east/southeast KY may go under Winter Storm watch as early as tomorrow.

Let's just see how the other models want to negotiate the upcoming storm and see if the leading NAM model will fold or not.

So far, it looks good...

MS

Updated Rain Totals and Flooding Issues

RAIN TOTALS THRU 4:00pm est

Evansville 3.36"
Louisville 2.61"
Paducah 5.02"

Several high water issues around the Commonwealth. Locally, watch out for ponding of water. Poor drainage issues as a result of debris and saturated grounds. Keep those storm drains clear! It does help some.

I'll be talking about possible snows across the state...coming up.

MS

Louisville's All-Time Wettest Year - 2011 (Also Paducah and Evansville)

As of this post, Louisville has just recorded its wettest year ever, exceeding 2004's total of 64.60".

Paducah has also set its all-time wettest year ever, surpassing 1950's total of 70.58" during the morning hours today.

Evansville set its all-time wettest year ever, beating out 2006's total of 66.18" not too long after midnight.

MS

Rain Totals and Snow Watch Update

As of 5:00 am est...

Louisville 1.08"
Evansville 2.40"
Paducah 3.66"

Louisville, your rain is about to become steadier and heavier during rush hour; therefore, take it slow.

Snow Watch continues...

The most recent run of the 06zNAM still shows a decent accumulation of snow for parts of Kentucky. However, the overall focus appears to be centered across east Kentucky, east of I-75. The NAM shifts east a little bit during this run. Let's keep an eye on the trend. Amounts of 2-4" possible, with locally higher amounts by Thr/Fri time frame. Perhaps lt snow/flurries across central Kentucky, up to an inch in places.

GFS trying to compromise, adjusts for possible snow amounts for east Kentucky.
Awaiting the 12zGEM model run early afternoon.

NWS office in Louisville, in its early morning AFD, downplaying snow system, saying SE parts of its county warning area could be clipped...

"The Euro and GFS scoot the upper trough
eastward too quickly, barely clipping our southeast CWA with light
rain Wednesday afternoon/light snow Wednesday night. This latter
solution is the favored result, and really think that most
precipitation will remain southeast of our
CWA given the fast
movement of the upper-level
shortwave. "

Also, NWS office in Jackson, in its most recent AFD, discusses the possibility of accumulating snow this week...

"ABOUT HALF
OF THE 00Z
GFS ENSEMBLE MEMBERS SHOW PRECIP OVER THE FORECAST AREA.
WILL INCLUDE PEAK
POPS IN THE CHANCE CATEGORY FOR ALL BUT THE FAR NW
PART OF THE FORECAST AREA WHERE
SLIGHT CHANCE WILL BE USED...AND
WILL NEED TO WAIT FOR MORE CONSISTENCY IN THE MODELS TO EITHER RAISE
OR LOWER THE
POPS. SHOULD THINGS COME TOGETHER JUST RIGHT...THERE IS
SOME POTENTIAL FOR ACCUMULATING SNOW
."

MS

Snow Watch

The snow addict in me is telling me that this could be our first snow of the season of any significance. The latest NAM offered some hope for a burst of snow coming in here behind some really cold air.

One of the analog years that came up is one that I featured in my winter forecast, winter of 2000/01. The analog I saw corresponded with a Jan 2001 setup that put down widespread 2-4" amounts for central and east Kentucky. Some locations had well over 4" during the week.

Although it's still premature to say this is a definite snow setup, I'm getting excited. As I said in a past post, the Dec 7-9 time frame bore watching.

Let's see what the next couple of runs suggest. Pay attention to the NAM. If this is a true snow setup, the NAM will offer the best solution in time.

MS

Sunday, December 4, 2011

Weather Terminology Unmasked

At the NWS office in Louisville, I noticed their overnight Area Forecast Discussion included the term, isentropic lift. Often, I see this term used in their discussions. While I had no idea about an exact definition of the term, isentropic, I knew it was related to precipitation.

First, here's a brief excerpt from the discussion I'm talking about...

"As a weak shortwave ejects from the longwave western trough late
tonight, increasing
isentropic lift associated with the rightentrance region of a strengthening jet will bring in a second round
of widespread rain which will overspread our entire forecast area by
the
dawn Monday morning."

Thankfully, the NWS provides a glossary for these terms that are underlined. In fact, by clicking on the term, isentropic lift, here is the official definition...

"Lifting of air that is traveling along an upward-sloping isentropic surface.

Isentropic lift often is referred to erroneously as overrunning, but more accurately describes the physical process by which the lifting occurs. Situations involving isentropic lift often are characterized by widespread stratiform clouds and precipitation, but may include elevated convection in the form of embedded thunderstorms
."

That's a nice way to explain away the process in general terms. However, isentropic??? Me and my inquiring mind needed to know.

The word itself, isentropic, needed a little bit more explanation. Well, if the term would have been called isoentropic (iso+entropic), I could have figured out a partial explanation. Just as isobars mean lines of equal barometric pressure, isoentropic would mean equal entropy.

And what is entropy? A quantitative measure of disorder, chaos, in a system or process. Sounds a lot like our weather. It's a significant player in the law of thermodynamics that involves heat transfer.

Well, I found an excellent read about the isentropic lifting process HERE.

Here is a partial explanation from the site I just linked you guys to...

"NWS refer to isentropic lift or isentropic upglide simply as the word, "overrunning" in that it is an event defined as relatively warmer, moister air that rides up and over a thin, relatively cooler, drier shallow layer at the surface over a particular region. Such air that is forced to rise upwards when it is moist or when it becomes moist, forces the air to cool and condense into clouds and then water droplets which finally fall as rain, if the isentropic lift is strong enough to bring this about."

However, he describes the process nicely afterward. Give it a read. You might learn something.

MS

Saturday, December 3, 2011

Flood Potential UPDATE

Well, the late evening HPC numbers are in, a little less QPF than previous runs. However, with a solid 2-4" expected statewide, Flood WATCHES are up for much of central and west Kentucky.

The 12zGEM and 18zGFS have pretty much flip-flopped on rain totals since yesterday. Now, the GEM is calling for about 2.07", while the GFS is calling for 1.87" for the period here in Louisville.

Nevertheless, rain totals that approach 2" will cause river levels to rise, possibly nearing flood stage along the Ohio river gauges. If more than 2" occurs, expect minor to moderate flooding throughout the region, including tributaries that flow into the Ohio river.

Personally, I'm expecting about 2.5", good enough to make this the wettest year on record. Even 2" will do it. Man, what a year!

MS

Friday, December 2, 2011

Flooding - A Possibility Next Week

The HPC is going gangbusters here on this early Friday afternoon regarding expected precipitation amounts for next week. 5-day QPF amounts of 3-5" for much of the state is forecast. Sounds a little excessive, but the amounts have trended higher over the past couple of runs. In fact, some in the range of 5-6" downstate could be realized.

The 12zGFS is still showing over 2" for Louisville and the 12zGEM about 1.75". I don't quite have the numbers for the NAM yet, but I don't rely on this model very much for rainfall amounts.

Nevertheless, most models are pointing toward another heavy rain maker, which should lead to river rises that may involve minor to moderate flooding in parts of the state by mid to late next week.

Ohio River at McAlpine Lock and Dam

According to the Advanced Hydrologic Prediction Service, the Ohio River LG is forecast to fall slowly to around 40 feet by Monday. With expected heavy rains not yet factored in, expect rapid river rise that looks to exceed flood stage of 55 feet if more than 2" should occur.

The Ohio River UG, where downtown Louisville is located, should fall slowly to a little over 17 feet by Monday. Again, expect the river to rise throughout the week, possibly exceeding flood stage of 23 feet next week if the heavy rains verify.

Stay tuned...

MS

My Forecast Snow Amounts For This Winter 2011/2012

In my winter forecast for 2011/12, I did not include my thoughts about how much snow will fall at any one location for the upcoming winter because, realistically, one cannot know this. There are just too many 'what-ifs' to figure out, and the storm tracks are extremely pivotal in determining who gets a lot and who gets a little or nothing.

But, I have been working on a probability table for some locations with an estimate of how much snow could accumulate for this winter at random locations. Due to timing differences, the snowfall estimates may run over into March.

Louisville:
The heat island effect may play a minor part in our snow amounts at the 'official' location. In my winter forecast, I have Louisville on the edge of heavy snow accumulations. However, I'm still expecting above normal snowfal. I'd rather see snow amounts measured at the National Weather Service on Theiler Lane, away from all of the concrete, though

However, we will stick with the airport readings for this forecast. In order not to bore you with my methodology, I will present only a partial table of probable snow amounts compared to normal.

Dec-Feb Average Snow Amounts = 10.8" (based on 1981-2010 norms)

Probability scale of 1-10 and suggested snow amounts

3  - 14"
4 -  15-16"
5 -  17"
6 -  18-19"
7 -  20-21"
8 -  22-24"
7 -  25-26"
6  - 27"
5 -  28"

Therefore, for Louisville, the highest probabilities of 7 and 8 out of 10 suggest snow amounts in a range of 20-26", probably closer to 22".
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Lexington:
In my winter forecast, I have Lexington in an area where heavy snow could certainly accumulate. Even if this should not verify, I'm still expecting above normal snowfall.

Dec-Feb Average Snow Amounts = 11.0"

Probability Scale of 1-10 and suggested snow amounts:

4 -  14"
5 -  15-16"
6 -  17-19"
7 -  20-23"
8 -  24-27"
7 -  28-29"
6 -  30"

As you can tell, there is a wide spread in probable amounts, anywhere from 20-29". I think Lexington will be in the middle of that range, 26-27".

In a future post, I'll try and include a couple of other locations. Nevertheless, expect higher snowfall amounts as one travels from west to east across the state.

You can access my thoughts about the upcoming winter on this blog in the Miks Piks section.

MS

How About One More Winter Forecast for Kentucky

This one is from one of my favorite meteorologists in the Louisville area. A multi-year Best of Louisville award winner and everyone's go-to winter weather enthusiast, John Belski.

Click Belski's Winter Forecast 2011/2012

Briefly, he is forecasting 20-25 inches of the white stuff, just slightly below my expectations for the coming winter.

Although I don't believe in forecasting snow amounts so far out, I will be posting the highest probabilities with an estimate of what could accumulate during the Dec-Feb time frame for selected locations.

MS

Thursday, December 1, 2011

Snapshot of December

Average highs really take on a wintertime look.
For Louisville...
Dec 1 - Avg High = 51; Avg Low = 34
Dec 31 - Avg High = 43; Avg Low = 27

From the Climate Prediction Center...
Temperatures:
Precipitation:

According to the CPC, they are forecasting that the period from December 6-10 will average near normal for temperatures while precipitation is forecast to be above normal.

In addition, for the period from the 8th thru the 14th, above normal temperatures and precipitation are expected.

It could be possible that the CPC is forecasting this scenario based on recent, ongoing teleconnection signals involving the NAO/AO, whose values are expected to be neutral to positive over the coming several days, while the PNA is expected to be negative.

This has been a concern to me, as I noted this trend a few days ago. Serious cold air will be lurking not too far away from our region for the next couple of weeks. In fact, during the first week of December, we should get a taste of what a Polar Pop is like. However, after this period, temperatures are expected to be milder, either supporting all liquid or possible icing, if we get into a shallow layer of Arctic air near the surface while 850mb temperatures may be warm enough to support rain. This would be during the 7-9 period, primarily. Something to keep an eye on.

Personally, I'd rather have the snow. Things always change. Let's hope so.

MS

MikJournal Monday 07/16/2018 Seasonal Update

Good morning. Yes, I'm still here. It's been a while since my last post. Gardening, chores, vacation, and other outdoor activities h...