Global model runs discussion

[cycloneye]

GFS will be upgraded on September 5th

This is another upgrade as the last one was in May.

Technical Implementation Notice 12-42
National Weather Service Headquarters Washington DC
330 PM EDT Tue Sep 4 2012

To: Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
-NOAAPORT
-Other NWS Partners, Users and Employees

From: Tim McClung
Science Plans Branch Chief
Office of Science and Technology

Subject: Change in Land Surface Model in Global Forecast
System and Associated Cool and Moist Bias in Near
Surface Temperature and Moisture Fields

Beginning with the 1200 Coordinated Universal Time (UTC) model
run on Wednesday, September 5, 2012, the National Centers for
Environmental Prediction (NCEP) Central Operations will implement
a fix to the Land Surface Model used to drive the Global Forecast
System (GFS). This correction is expected to improve the cool
and moist bias in the near surface air temperature and moisture
fields during the warm season.

Starting in mid-June 2012, NCEP confirmed a problem with the GFS
near-surface temperature and moisture simulations. The model was
not verifying in the late afternoon over the central United
States when drought conditions existed. Specifically, users noted
a significant 2m cold and wet bias in both the MOS and GFS
gridded products. The NCEP Environmental Modeling Center (EMC)
traced the problem to a look-up table used in the land surface
scheme that modulates evapotranspiration based on vegetation type
and root zone depth. Current settings allowed for excessive
transpiration and plant-extraction of soil moisture from deeper
soil layers, which caused the lower atmospheric boundary layer to
become too moist and cool.

http://www.nws.noaa.gov/os/notification ... _model.txt

[HURRICANELONNY]

I don't know if GFS is going to be right with the NWS Miami stating a cold front will pass through S.Fl next weekend. That wouold be pretty early and would have to be watched for something developing on it if it did.
9/4/12
The latest long range models are also showing a cold front moving
through South Florida early next week from the north. This will
bring in drier and cooler weather to the area. So at this
time...will keep a slight chance of probability of precipitation over the County Warning Area for early
next week. But the probability of precipitation might have be lower or even remove from
the zones for early next week if the long range model trends
continue to show the cold front moving through the area.

[CourierPR]

If a cold front moves through SFL, then the NW Caribbean will need to be monitored for possible development.

[Cyclenall]

Some of these model trends are very interesting, I didn't expect another Ivan revival with Isaac with even some consensus for that!! That only happened once in the records but suggestion of it happening just 8 years later with Isaac is nuts. They are also both "I" names. Some of those patterns in the fantasy long range of 384 hours are also pretty unique, wouldn't mind seeing some of those ridging patterns over NA.

So the GFS is getting another upgrade huh? That's good, the largest problem it had was the cold and wet bias for surface temperatures on landmass so this was very needed but its a little late for this summer . I didn't even monitor the GFS model for that reason when it came to temperatures.

[rainstorm]

18z brings the season to an early end. just a few very weak tiny lows. hopefully the 2nd half of the season isnt stormless.

[Hurricane Alexis]

18z brings the season to an early end. just a few very weak tiny lows. hopefully the 2nd half of the season isnt stormless.

It does develop 2 weak tropical storms.

[SoupBone]

18z brings the season to an early end. just a few very weak tiny lows. hopefully the 2nd half of the season isnt stormless.

Hopefully the 2nd half of the season IS stormless or sends every one out to see long before it reaches the islands. Time for Fall and Winter!

[gatorcane]

18z brings the season to an early end. just a few very weak tiny lows. hopefully the 2nd half of the season isnt stormless.

Why do you see that as an early season end? We are expecting the first couple of weeks in September to be slow in the MDR and Caribbean due to dry sinking air across much of the Atlantic during this time period. Plus October has a secondary peak where storms like to form in the Caribbean in particular (especially along stalled frontal boundaries in the Western Caribbean as Courier mentions). The long-range GFS has been flirting with the idea of a system impacting the Leewards/Puerto Rico and then perhaps the Bahamas and SE CONUS after that.

[ConvergenceZone]

18z brings the season to an early end. just a few very weak tiny lows. hopefully the 2nd half of the season isnt stormless.

Why do you see that as an early season end? We are expecting the first couple of weeks in September to be slow in the MDR and Caribbean due to dry sinking air across much of the Atlantic during this time period. Plus October has a secondary peak where storms like to form in the Caribbean in particular (especially along stalled frontal boundaries in the Western Caribbean as Courier mentions). The long-range GFS has been flirting with the idea of a system impacting the Leewards/Puerto Rico and then perhaps the Bahamas and SE CONUS after that.

Like many people, rainstorm is probably in a "I'll believe it when I see it" mode, and I'm the same way.....
Storms STILL continue to have a hard time getting going...I mean, how long has Leslie been a tropical storm now?? I said it a month ago and I'll say it again, storms are just having a hard time developing this year. I honestly thought with Leslie we'd have a buzzsaw cat 3 hurricane that we could follow as it recurves out to sea, but by the time it even hits a cat 2(if it even gets there, it will flying off the map carried by the jetstream).

Nothing has even given the hint that it can sustain in the carib....If it's not dry air, then it's shear, if it's not shear, then it's an ULL nearby....Not complaining, just stating how it's been this year, so that you'll know why we are in a "I'll believe it when I see it" mode.... It very well COULD die off early. it's happened in previous years before...

[rainstorm]

0z brings back a leslie redo, ugh

[tolakram]

0z brings back a leslie redo, ugh

This thread is rather useless without links or thoughtful discussion of model runs. I'm not sure what 'Leslie redo, ugh' means.

[cycloneye]

I think what she refers to is this. CV Wave develops, clip the Leeward islands,BVI,VI and PR and ends in this position.

[rainstorm]

the 06z seems to bring the possible hurricane a bit further west.

[Hybridstorm_November2001]

@ Cycloneye it could happen there have been years, 1869 & 1954 for example, in which this region has had twins (as I call them).

Though I'd much rather be in the hit zone this far out, than in say 72hr out.

[cycloneye]

Very different GFS run at 12z from the past ones as it makes a big recurving in the Central Atlantic.

12z Loop

[blp]

Very different GFS run at 12z from the past ones as it makes a big recurving in the Central Atlantic.

12z Loop

I saw that. Looks like the ridge is much weaker and the system is stronger on this run. Let's see what the Euro shows.

[rainstorm]

thats a buzzkill. heart of the season and nothing exciting. looks like it doesnt do much og anything in the gom either.

[chaser1]

thats a buzzkill. heart of the season and nothing exciting. looks like it doesnt do much og anything in the gom either.

Well, I thought of a couple interesting points regarding the 12Z GFS run and prior runs that might make an argument that the 12Z was somehow a "bad run"....., but then I took a look at the Euro and decided to just not bother

[cycloneye]

12z Euro goes like GFS on a recurve in Central Atlantic. I wonder if we are not going to get anymore threats in the Eastern Caribbean as the CV season goes down.

[rainstorm]

it still looks like the season is going to end early. i suppose something odd could pop up not shown on any models