HPC Medium Range Discussion...Low Model Confidence

[MWatkins]

WeatherEmporer, no that was true a few days ago, a real ridge is forecasted to build off the east coast of the US within a couple of days that will steer it west...nothing to do with intensity..

boca-chris even the NHC mentioned this in their discussion. As per their 11am discussion that very same ridge you are mentioning is forecast to have a weakness in it and move towards the east allowing Irene to go more northward. The facts are the facts regardless of what my opinion is or what yours are. But you could be right afterall. Thats why once again the waiting game continues until......the 00Z models come out.... And it has alot to do with intensity because the pro-mets here even agreed with me that had Irene REALLY intensified like it was forecast to do so, it would have gone fishing long time ago.

<RICKY>

Quick comment on that idea…

A few days ago there was a weakness in the mean-layer (500MB) that would have tugged Irene NW if it was being steered in that layer…but since it was caught in the low-level flow it did not respond.

However…the mean layer flow is now oriented more E/W so that the poleward movement will be less if/when Irene gets strong enough to get back into the mean layer steering flow. Also…given the GFS’s latest solution with more ridging…which was not accounted for in the latest forecast discussion…the confidence in the models right now is shot.

Note the existing flow pattern analysis for a storm down in the 990mb to 999mb range (moderate tropical storm):

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm2.html

For a stronger hurricane…the flow is even more E/W:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm4.html

Actually for a weak storm there is more NW flow in the low levels than anyplace right now:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm1.html

So in this case…given the CURRENT pattern (this will change) the low levels would produce more northerly component than the mean layer…which is a flip from how it usually works.

MW

[gatorcane]

its mid-August so I favor the ridge to win out over a trough approaching from the NW.

[WeatherEmperor]

WeatherEmporer, no that was true a few days ago, a real ridge is forecasted to build off the east coast of the US within a couple of days that will steer it west...nothing to do with intensity..

boca-chris even the NHC mentioned this in their discussion. As per their 11am discussion that very same ridge you are mentioning is forecast to have a weakness in it and move towards the east allowing Irene to go more northward. The facts are the facts regardless of what my opinion is or what yours are. But you could be right afterall. Thats why once again the waiting game continues until......the 00Z models come out.... And it has alot to do with intensity because the pro-mets here even agreed with me that had Irene REALLY intensified like it was forecast to do so, it would have gone fishing long time ago.

<RICKY>

Quick comment on that idea…

A few days ago there was a weakness in the mean-layer (500MB) that would have tugged Irene NW if it was being steered in that layer…but since it was caught in the low-level flow it did not respond.

However…the mean layer flow is now oriented more E/W so that the poleward movement will be less if/when Irene gets strong enough to get back into the mean layer steering flow. Also…given the GFS’s latest solution with more ridging…which was not accounted for in the latest forecast discussion…the confidence in the models right now is shot.

Note the existing flow pattern analysis for a storm down in the 990mb to 999mb range (moderate tropical storm):

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm2.html

For a stronger hurricane…the flow is even more E/W:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm4.html

Actually for a weak storm there is more NW flow in the low levels than anyplace right now:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm1.html

So in this case…given the CURRENT pattern (this will change) the low levels would produce more northerly component than the mean layer…which is a flip from how it usually works.

MW

wow Mike. Thanks for puttin me straight. Thats why your one of the best

<RICKY>

[Aquawind]

Awesome thread MW...

Paul

[jabber]

WeatherEmporer, no that was true a few days ago, a real ridge is forecasted to build off the east coast of the US within a couple of days that will steer it west...nothing to do with intensity..

boca-chris even the NHC mentioned this in their discussion. As per their 11am discussion that very same ridge you are mentioning is forecast to have a weakness in it and move towards the east allowing Irene to go more northward. The facts are the facts regardless of what my opinion is or what yours are. But you could be right afterall. Thats why once again the waiting game continues until......the 00Z models come out.... And it has alot to do with intensity because the pro-mets here even agreed with me that had Irene REALLY intensified like it was forecast to do so, it would have gone fishing long time ago.

<RICKY>

Quick comment on that idea…

A few days ago there was a weakness in the mean-layer (500MB) that would have tugged Irene NW if it was being steered in that layer…but since it was caught in the low-level flow it did not respond.

However…the mean layer flow is now oriented more E/W so that the poleward movement will be less if/when Irene gets strong enough to get back into the mean layer steering flow. Also…given the GFS’s latest solution with more ridging…which was not accounted for in the latest forecast discussion…the confidence in the models right now is shot.

Note the existing flow pattern analysis for a storm down in the 990mb to 999mb range (moderate tropical storm):

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm2.html

For a stronger hurricane…the flow is even more E/W:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm4.html

Actually for a weak storm there is more NW flow in the low levels than anyplace right now:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm1.html

So in this case…given the CURRENT pattern (this will change) the low levels would produce more northerly component than the mean layer…which is a flip from how it usually works.

MW

Mike,

If I am reading the flows correctly, it appears that she (Irene) should have even a more left shift then the models are 'forecasting'. How accurate are these flows. Is this model data or actual observable?

Thanks

[MWatkins]

WeatherEmporer, no that was true a few days ago, a real ridge is forecasted to build off the east coast of the US within a couple of days that will steer it west...nothing to do with intensity..

boca-chris even the NHC mentioned this in their discussion. As per their 11am discussion that very same ridge you are mentioning is forecast to have a weakness in it and move towards the east allowing Irene to go more northward. The facts are the facts regardless of what my opinion is or what yours are. But you could be right afterall. Thats why once again the waiting game continues until......the 00Z models come out.... And it has alot to do with intensity because the pro-mets here even agreed with me that had Irene REALLY intensified like it was forecast to do so, it would have gone fishing long time ago.

<RICKY>

Quick comment on that idea…

A few days ago there was a weakness in the mean-layer (500MB) that would have tugged Irene NW if it was being steered in that layer…but since it was caught in the low-level flow it did not respond.

However…the mean layer flow is now oriented more E/W so that the poleward movement will be less if/when Irene gets strong enough to get back into the mean layer steering flow. Also…given the GFS’s latest solution with more ridging…which was not accounted for in the latest forecast discussion…the confidence in the models right now is shot.

Note the existing flow pattern analysis for a storm down in the 990mb to 999mb range (moderate tropical storm):

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm2.html

For a stronger hurricane…the flow is even more E/W:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm4.html

Actually for a weak storm there is more NW flow in the low levels than anyplace right now:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm1.html

So in this case…given the CURRENT pattern (this will change) the low levels would produce more northerly component than the mean layer…which is a flip from how it usually works.

MW

Mike,

If I am reading the flows correctly, it appears that she (Irene) should have even a more left shift then the models are 'forecasting'. How accurate are these flows. Is this model data or actual observable?

Thanks

I am not 100%sure if the folks at CIMMS use the models to help with the analysis at all or if they have some sort of program to integrate model data with real-time winds. I am pretty sure a good deal of this is human-analysis but I don't know how much of it is done using sat images vs. maps...it's good directional information but there is so much information that has to be filled in from analysis that it isn't absolute....but it's a pretty good guide.

MW

[jabber]

I am not 100%sure if the folks at CIMMS use the models to help with the analysis at all or if they have some sort of program to integrate model data with real-time winds. I am pretty sure a good deal of this is human-analysis but I don't know how much of it is done using sat images vs. maps...it's good directional information but there is so much information that has to be filled in from analysis that it isn't absolute....but it's a pretty good guide.

MW

Mike,

Thanks for the info. I looked at these flows for quite a while a still cannot understand the track selected. I guess much more then these flows are taken in account. I still do not see what will take this so far up.

[sma10]

Here’s a quick note about the most recent medium range discussion from the HPC…the agency which handles the extended range forecasting beyond the 5 day responsibility of the TPC. For folks who are big model fans who want to figure out which models are handling the synoptic set-up the best…I would strongly recommend reading this outlook every day.

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

First…take a look at the coordinated positions of Irene on days 5 and 7:

Day 5:
http://www.hpc.ncep.noaa.gov/medr/day5nav_color.html

Day 7:
http://www.hpc.ncep.noaa.gov/medr/day7nav_color.html

HPC doesn’t make their own forecast…they coordinate with the TPC on the day 6 and 7 positions. Note their comment on the final discussion updated this afternoon:

FINAL MEDIUM RANGE DISCUSSION...

CONFIDENCE IS MARGINAL AT BEST...BUT THE 12Z NCEP ENS MEAN IS
REASONABLY SIMILAR TO THE PREFERRED 06Z GFS SOLN...SO ONLY MINOR ADJUSTMENTS WERE MADE TOWARD THE 12Z NCEP MEAN FOR THE AFTN PACKAGE. PSNS FOR IRENE WERE BASED ON COORD WITH TPC. HOWEVER...WITH THE 12Z GFS NOW KEEPING MORE RIDGING TO THE N OF IRENE AND STEERING IT ON A MORE SLY TRACK...CONFIDENCE IS INCREASINGLY DIMINISHING ON THE SYS TURNING NWD TO THE DEGREE THAT THE COORD TRACK IMPLIES.

Now…what that means…exactly…is still open for discussion. I personally believe the Carolinas are in for a bit of trouble…but I would not let my guard down any place south of there yet. For example, lets take a look at every single model from 18Z yesterday and compare the 24 hour forecast plot to the actual, 22.5N 58.0W at 2PM today:

Code: Select all

 
Forecast Model Positions from 8/9/05 at 18Z verification for 8/10/05 18Z
A90E    23.0N     57.1W
 A98E    23.0N     57.0W
 AVNI    24.9N     57.5W
 BAMD    23.2N     57.5W
 BAMM    23.1N     58.1W
 BAMS    24.0N     58.4W
 CLIP    23.0N     56.6W
 CLP5    23.2N     56.5W
 CONU    24.7N     58.0W
 DRCL    23.4N     57.7W
 DSHP    24.3N     58.8W
 DSNS    24.3N     58.8W
 GFDI    25.1N     58.0W
 GFDL    24.9N     58.6W
 GFDT    24.6N     58.3W
 GFTI    24.8N     58.2W
 LBAR    23.1N     57.3W
 MRCL    23.4N     57.7W
 NGPS    24.1N     59.8W
 NGXI    23.9N     58.7W
 OFCI    24.3N     58.7W
 OFCL    23.4N     57.7W
 SHIP    24.3N     58.8W
 SHNS    24.3N     58.8W
 XTRP    22.7N     55.8W
 GFDN    24.4N     60.1W
 OOPC    24.2N     59.0W


This storm is generating a ton of along-track forecast errors...

MW

Wow...that is something to have a full collection of models ALL be that far off at 24 hrs.

But we would be remiss if we didn't give it up for XTRP and its very respectable performance That would turn out really sad if the extrapolated motion ends up being the top performer with this storm