Re: Official Long Range Thread 6.0

[Snow88]

GFS is really active with 3 storm chances moving forward

[rb924119]

Something I just noticed, and I'm sure it's already been said, but another reason that this storm is currently being progged to remain on more of a southern route versus a northern one (for now) is that the clipper from Friday actually helps to create a temporary east-based block. This allows the upstream flow to be slightly more zonal than meridional, and steer the storm more from westerly versus southerly or south-southwesterly. It also helps to promote that confluent region that was also stated. In my opinion, this will be the key to the evolution of the system. Our PNA will be strongly positive regardless, thanks to a beautiful omega block being created by Rossby wave train re-development from a rapidly intensifying system east of the Asian continent. This will also help to set up our Aleutian trough. Just my thoughts. Surprisingly, I'm feeling REALLY confident about this storm producing right now. I have always been a fan of Miller-A type storms, but SWFE can "drop a lot in a little" purely through warm advection processes. Combining these two I think can set up for a surprise "fast and furious" type event. Again, just my opinion.

[Frank_Wx]

Yea RB, I mentioned that last night. Friday clipper will act as a block / 50-50 confluence

[rb924119]

Yea RB, I mentioned that last night. Friday clipper will act as a block / 50-50 confluence

My bad, Frank, I didn't read through all of the pages lol Btw, have you ever used Isentropic analysis before? Jc

[chief7]

I just looked at the Tele connections the and nao looks a little negative like .05 The PNA A little positive maybe .05 The ao looks -1.5 this is all for the possible storm on Sunday /Monday

[Snow88]

GFS. Way further south and less phasing than 6z. Laugable difference.

[jimv45]

Try not to look at that until the clipper gets out of the way it will flip back and forth I feel good about that storm will see!

[skinsfan1177]

So this storm looks like temps will be marginal for my area . I know if its west itty puts me on warm side so best track would be BM. I know it's EARLY but I thought cold would be locked in . Great write ups guys

[RJB8525]

i don't wanna start this war crap but TWC just has Rain/snow mix for Monday doesn't sound like they will change it they seem firm on it

[Frank_Wx]

Try not to look at that until the clipper gets out of the way it will flip back and forth I feel good about that storm will see!

Great point.

[amugs]

Feb 1-2 storm GFS OP is south



As is GEFS



Feb 5th system - 12Z GFS

[Analog96]

Try not to look at that until the clipper gets out of the way it will flip back and forth I feel good about that storm will see!

Yeah, we'll have a better idea probably Friday 12Z.

[amugs]

Try not to look at that until the clipper gets out of the way it will flip back and forth I feel good about that storm will see!

Yeah, we'll have a better idea probably Friday 12Z.

Greg,

Absolutely, but need that PNA ridge not to collapse - the Atlantic is finally coming around and well we'll see.

[amugs]

Ohm did you see the temps for Tuesday morning lows - yikes!!! Holy Mother of COLD!!

Forgot can't post SV NA Maps - reading -10's for NWNJ,EPA, NNJ and LHV 2M temps. Could be if we keep snowpack - that is one brutally cold air mass fro next week.

[Frank_Wx]

Yea RB, I mentioned that last night. Friday clipper will act as a block / 50-50 confluence

My bad, Frank, I didn't read through all of the pages lol Btw, have you ever used Isentropic analysis before? Jc

Do tell, sounds interesting.

[amugs]

Greg and Jim - NWS heard you

.GUIDANCE/UNCERTAINTY EVALUATION AND PREFERENCES...

THERE CONTINUE TO BE VARIOUS SOURCES OF UNCERTAINTY FOR THE SYSTEM
EXPECTED TO AFFECT THE CNTRL-ERN STATES FROM THE WEEKEND INTO THE
START OF NEXT WEEK. SUPPORTING ENERGY AMPLIFYING INTO THE PLAINS
DURING THE WEEKEND ORIGINATES FROM A COMBINATION OF FLAT FLOW
HEADING INTO BC AND SHEARED ENERGY OVER ALASKA IN THE SHORT RANGE.
THESE IMPULSES DO NOT REACH WRN CANADA UNTIL LATE FRI SO IT MAY
TAKE UNTIL AT LEAST THEN TO GET A REASONABLE ANALYSIS OF THIS
ENERGY. BEYOND THIS ISSUE IS THE QUESTION OF NRN STREAM TROUGH
AMPLITUDE OVER THE CONUS AND HOW MUCH INTERACTION THERE IS WITH
THE TROUGH OVER THE SWRN CONUS/NRN MEXICO. GREATER NRN STREAM
AMPLITUDE/MORE INTERACTION AS PER 00Z GFS/CMC RUNS LEAD TO A
SLOWER/NWWD SFC SYSTEM IN CONTRAST TO THE FLAT NRN STREAM
SHRTWV/WEAK AND FAST SFC WAVE OF THE 00Z UKMET. THE UKMET/CMC
HAVE ESSENTIALLY SWITCHED PLACES RELATIVE TO THE SOLN ENVELOPE
COMPARED TO 24 HRS AGO. MEANWHILE THE FULL ARRAY OF ENSEMBLE SFC
LOWS BY LATE SUN ONWARD IS QUITE BROAD WITH LITTLE CLUSTERING
ASIDE FROM SUGGESTING THE BEST PROBABILITY WOULD BE FOR THE SYSTEM
TO BE JUST OFF THE NERN COAST BY 00Z TUE. ON THE POSITIVE SIDE...
TAKEN AS A WHOLE THE PAST 24 HRS OR SO OF GUIDANCE HAS STABILIZED
ON A SLOWER/STRONGER EVOLUTION THAN SEEN IN EARLIER CONSENSUS.
FOR THIS UPDATE ULTIMATELY PREFER TO EMPHASIZE A BLEND OF THE 06Z
GFS/00Z ECMWF/00Z GEFS MEAN WITH LESS WEIGHTING ON THE FLATTER 00Z
ECMWF MEAN. THIS SOLN YIELDS A GOOD INTERMEDIATE SFC TRACK WHICH
COMPARES WELL WITH LAGGED AVG FCSTS INCORPORATING RECENT GFS/ECMWF
RUNS... FROM THE OH VLY 00Z MON TO THE DELMARVA/SERN PA 12Z MON TO
JUST OFF THE NRN NEW ENGLAND COAST 00Z TUE. THE FAVORED BLEND
REPRESENTS CONSENSUS WELL OVER THE WRN STATES WHERE RIDGING ALOFT
WILL FLATTEN AS WEAK ENERGY ALOFT COMES INLAND.

[Guest]

YE ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO AFFECT THE REGION
SUNDAY NIGHT INTO MONDAY. UNCERTAINTY IN THE FORECAST TRACK FOR
THIS SYSTEM IS HIGH AT THIS TIME. IT APPEARS THE MOST LIKELY TRACK
FOR THE LOW IS TO THE SOUTH OF THE REGION. THIS WOULD RESULT IN
MOSTLY SNOW FOR OUR AREA. IF THIS IS THE CASE...THERE IS THE
POTENTIAL FOR 6 INCHES OR MORE OF SNOW. SINCE THIS IS A
PROGRESSIVE SYSTEM...MAXIMUM AMOUNTS WOULD BE MODERATE - LESS THAN
A FOOT.

HOWEVER...THERE IS A POSSIBLY THAT THE SYSTEM TRACKS TO OUR
NORTHWEST. THIS WOULD RESULT IN MOSTLY RAIN AND POSSIBLY 1-2
INCHES OF LIQUID. THIS...COMBINED WITH MELTING SNOW...COULD
RESULT IN FLOODING.

So basically I'll translate. WE'RE STILL REALLY EMBARRASSED OVER OUR FAILURE FROM THE "BLIZZARD" FORECAST SO GOING FORWARD IT WILL EITHER RAIN OR SNOW WE DON'T KNOW YET!

[skinsfan1177]

Now couldn't the storm be slowed down by the clipper on Friday acting as a block slowing down the progressive

[CPcantmeasuresnow]

18Z GFS pretty much a non event for Monday, which doesn't mean a thing yet.

[rb924119]

Yea RB, I mentioned that last night. Friday clipper will act as a block / 50-50 confluence

My bad, Frank, I didn't read through all of the pages lol Btw, have you ever used Isentropic analysis before? Jc

Do tell, sounds interesting.

Isentropic analysis is incredibly useful for deciphering vertical motion based on upglide. Basically, you know how we typically look at heights on a map of constant pressure (i.e. the 500 hPa level, but heights go from 540-572 decameters)? On isentropic maps, you are looking at pressures (and winds) on a constant TEMPERATURE surface, or potential temperature surface (i.e. 289K surface). When you plot these, you can almost instantly pick out where your strongest ascent and descent will be based upon how the winds appear relative to the pressure contours, in addition to almost every frontal feature I can think of. If they parallel the contours, you have no vertical motion; but if they are perpendicular to the contours, then the stronger the winds, the stronger your vertical motion.

For example, take a look at the following link (you may have to select the "Pressure" and "Wind" boxes in the top left):
http://www.wxcaster.com/isentropic_chart.php3?model=GFS&level=289&fcsthr=24

Once it opens, look at the Midwest. You can see 30-45 knot winds crossing the pressure lines perpendicularly from lower to higher. If they are increasing in pressure, they must be headed toward the surface......descent. Now, if you go to a normal weather map, you can see how nicely this region of descent matches up to the 1036 hPa high that is progged to be there at the same time. Likewise, if you look from Louisiana to the Northeast, you will notice two things. The first is that the pressure contours sort of "spike" northeastward. Because this is on a potential temperature surface, you are actually looking at the cold front associated with the clipper (note the descent behind it in the Plains, as discussed earlier). If you look to the east of the front, there is cross-contour flow ascending from higher pressures to lower ones. Also observe, however, that as you move towards the Northeast, the winds crossing the contours become substantially weaker and change direction to a more neutral flow. Further south, though, the flow is stronger, and if I were to make a forecast solely based on this one map, I'd say a weak line of showers and possibly a few thunderstorms is soon to develop in the Mid-South along or just ahead of the cold front itself, while the Northeast is beginning to cloud over ahead of the clipper.

If you were to fast-forward to another possible snowstorm, this would be very useful in determining where a quasi-stationary band, bands of precipitation, or strong WAA snows might develop. I guarantee if you look at that band that sat over Long Island/NYC for a few hours during this last event, you would find that it could probably be easily identified using one of these maps. Yet another tool that I forgot to look at for this last storm lol Idk, I've used them a couple of times in forecasting and have found it to be really, really useful in finding any areas of WAA and large-scale ascent, even if weak. If you, or anybody else has further questions, please ask. It's kind of an abstract thing to look at, at first, but once you understand what it's showing you, it's just like looking at a normal weather map.

[Frank_Wx]

Rb, that is a fantastic tool. Just bookmarked it. Thank you for teaching myself and other about Isentropic analysis. Highly appreciated

[Frank_Wx]

The GEFS and ECMF agree on an MJO pulse into phase 7 around Day 9-11.







Hopefully the Sunday into Monday storm is able to come to fruition. It has a weak signal for some blocking with positive heights extending into Greenland and confluence setting up from the deepening clipper system. After that, it does not look like we will have much in the way of blocking, not even east-based. The low heights are retreating back to the pole it looks like. Here are the GEFS



The large Pacific trough matches the MJO composite nicely, which is able to spike the PNA, but it remains to be seen if that ridge rolls east or we're able to stay under a trough. This is around February 9th-10th. Until then, we should remain in a below normal temp. regime with 1-2 storm chances.

[skinsfan1177]

Geez Frank that's not great was hoping for blocking to occur and lock pattern in. We still can produce snow storms without the block

[sroc4]

Yea RB, I mentioned that last night. Friday clipper will act as a block / 50-50 confluence

My bad, Frank, I didn't read through all of the pages lol Btw, have you ever used Isentropic analysis before? Jc

Do tell, sounds interesting.

Isentropic analysis is incredibly useful for deciphering vertical motion based on upglide. Basically, you know how we typically look at heights on a map of constant pressure (i.e. the 500 hPa level, but heights go from 540-572 decameters)? On isentropic maps, you are looking at pressures (and winds) on a constant TEMPERATURE surface, or potential temperature surface (i.e. 289K surface). When you plot these, you can almost instantly pick out where your strongest ascent and descent will be based upon how the winds appear relative to the pressure contours, in addition to almost every frontal feature I can think of. If they parallel the contours, you have no vertical motion; but if they are perpendicular to the contours, then the stronger the winds, the stronger your vertical motion.

For example, take a look at the following link (you may have to select the "Pressure" and "Wind" boxes in the top left):
http://www.wxcaster.com/isentropic_chart.php3?model=GFS&level=289&fcsthr=24

Once it opens, look at the Midwest. You can see 30-45 knot winds crossing the pressure lines perpendicularly from lower to higher. If they are increasing in pressure, they must be headed toward the surface......descent. Now, if you go to a normal weather map, you can see how nicely this region of descent matches up to the 1036 hPa high that is progged to be there at the same time. Likewise, if you look from Louisiana to the Northeast, you will notice two things. The first is that the pressure contours sort of "spike" northeastward. Because this is on a potential temperature surface, you are actually looking at the cold front associated with the clipper (note the descent behind it in the Plains, as discussed earlier). If you look to the east of the front, there is cross-contour flow ascending from higher pressures to lower ones. Also observe, however, that as you move towards the Northeast, the winds crossing the contours become substantially weaker and change direction to a more neutral flow. Further south, though, the flow is stronger, and if I were to make a forecast solely based on this one map, I'd say a weak line of showers and possibly a few thunderstorms is soon to develop in the Mid-South along or just ahead of the cold front itself, while the Northeast is beginning to cloud over ahead of the clipper.

If you were to fast-forward to another possible snowstorm, this would be very useful in determining where a quasi-stationary band, bands of precipitation, or strong WAA snows might develop. I guarantee if you look at that band that sat over Long Island/NYC for a few hours during this last event, you would find that it could probably be easily identified using one of these maps. Yet another tool that I forgot to look at for this last storm lol Idk, I've used them a couple of times in forecasting and have found it to be really, really useful in finding any areas of WAA and large-scale ascent, even if weak. If you, or anybody else has further questions, please ask. It's kind of an abstract thing to look at, at first, but once you understand what it's showing you, it's just like looking at a normal weather map.

This is pretty cool.  I have something knew to get my learn on about.  Thanks rb. I notice that is the GFS 24hr forecast. Is ther any way to see other models, and or toggle through other times?

[sroc4]

BTW anyone have a site that has the key to the wind speed symbols for wind analysis charts?

[rb924119]

No worries, Sroc and Frank!! I always love sharing knowledge and tools with fellow forecasters! Here's the only site that I currently know of that gives you a couple options for the model you look at.

http://www.wxcaster.com/isentropic.htm

As for the wind speed symbols, each barb (appendage coming off of the main stem) is equal to 10 knots (where 1 knot is approximately equal to 1.2 m/h). A half barb is equal to 5 knots, and a filled in triangle is equal to 50 knots. So, a 150 knot jet (or wind, regardless of height) would have three filled in triangles branching off of the main stem. A 75 knot wind would have a filled in triangle, two full barbs and a half-barb. Make sense? If I can find a decent image, I'll post that too.

[rb924119]

http://ngwww.ucar.edu/supplements/wmap/wmex09.gif

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