Global model runs discussion

[SFLcane]

Looks like another escape route there luis...

[cycloneye]

Levi Cowan tweeted this afternoon about GFS and CMC showing the same at 240 hours.

Levi Cowan ‏@TropicalTidbits 5h
Today at 12z is the first time the GFS and CMC have agreed on a strong African wave. This tells us to watch for it.



https://twitter.com/tropicaltidbits

[SouthFloridawx]

It's four runs in a row for the GFS.

7/15 00Z - 384 Hour


7/15 06Z - 384 Hour


7/15 12Z - 384 Hour - Weak Surface Reflection


7/15 12Z - 360 Hour - Just to prove it


7/15 18Z - 384 Hour

[WeatherEmperor]

Also notice from the post above, that the 00z and 12z models show a weaker system whereas the 06z and 18z runs show a stronger system. I dont know how much emphasis should be placed on this...but generally speaking arent the 00z and 12z the more reliable runs?

Sent from my HTC EVO 4G LTE

[cycloneye]

Also notice from the post above, that the 00z and 12z models show a weaker system whereas the 06z and 18z runs show a stronger system. I dont know how much emphasis should be placed on this...but generally speaking arent the 00z and 12z the more reliable runs?

Sent from my HTC EVO 4G LTE

Normally the 12z and 00z runs are the most reliable as those have more data than the 06z and 18z ones.

[Alyono]

Also notice from the post above, that the 00z and 12z models show a weaker system whereas the 06z and 18z runs show a stronger system. I dont know how much emphasis should be placed on this...but generally speaking arent the 00z and 12z the more reliable runs?

Sent from my HTC EVO 4G LTE

Normally the 12z and 00z runs are the most reliable as those have more data than the 06z and 18z ones.

The 6 and 18Z runs now have nearly as such data as do the 0 and 12. 99% of data assimilated into the models these days is satellite and radar. Thus, your statement is not really that accurate

[SouthFloridawx]

Does it have more to do with the when the Earth naturally has increased convection? Like at night the thunderstorms tend to fire up over the water more than the land...

Also notice from the post above, that the 00z and 12z models show a weaker system whereas the 06z and 18z runs show a stronger system. I dont know how much emphasis should be placed on this...but generally speaking arent the 00z and 12z the more reliable runs?
Sent from my HTC EVO 4G LTE

Normally the 12z and 00z runs are the most reliable as those have more data than the 06z and 18z ones.

The 6 and 18Z runs now have nearly as such data as do the 0 and 12. 99% of data assimilated into the models these days is satellite and radar. Thus, your statement is not really that accurate

[SouthFloridawx]

I meant over the water at night.

[cycloneye]

Also notice from the post above, that the 00z and 12z models show a weaker system whereas the 06z and 18z runs show a stronger system. I dont know how much emphasis should be placed on this...but generally speaking arent the 00z and 12z the more reliable runs?

Sent from my HTC EVO 4G LTE

Normally the 12z and 00z runs are the most reliable as those have more data than the 06z and 18z ones.

The 6 and 18Z runs now have nearly as such data as do the 0 and 12. 99% of data assimilated into the models these days is satellite and radar. Thus, your statement is not really that accurate

Thanks for clearing this up.

[SouthFloridawx]

Okay, so I'm going to rephrase my question so that it makes more sense. I'm just wondering if the model inertly have within them, when convection is more favorable during different times of the day. I can't remember what the technical terms are now. I think one of them is dinural. Could this have an effect on the model out-put?

[USTropics]

Okay, so I'm going to rephrase my question so that it makes more sense. I'm just wondering if the model inertly have within them, when convection is more favorable during different times of the day. I can't remember what the technical terms are now. I think one of them is dinural. Could this have an effect on the model out-put?

I think you're referring to diurnal maximum and diurnal minimum. I don't see it having any direct impact on the output for different model run variants during the day (00z, 12z, etc) as it is a daily, cyclical pattern.

To answer your question, I'll try and explain diurnal maximum and its effects. The earth's crust has a high heat capacity, allowing it to absorb solar radiation throughout the day. Through conduction, the earths crust begins to heat up the air directly above it, which heats up the cool air column directly above that. While the sun is at its highest point at noon (and thus solar radiation at its most concentrated strength), maximum solar heat lags behind by several hours, as the ground and air layer must first absorb heat before it can begin to radiate heat. When the amount of incoming solar radiation equals the amount of outgoing radiation (around 3-5pm), we reach our daily high temperature.

CAPE (Convective Available Potential Energy) is at a maximum during the day due to this daytime heating, which is why we see a convective maximum late in the afternoon over land (afternoon thunderstorms you can set your clock to in Florida). However, this mechanism has no inherent effect on tropical convection.

There is another mechanism in play that aides in tropical moisture though. During the overnight and early morning hours, the earth is no longer absorbing solar radiation, and is therefore radiating heat back to space at its maximum potential, which is why temperatures decrease overnight. The warm surface continues to mix convectively upward at night, being replaced by cooler air towards the surface. This creates a more moist atmospheric profile, and given sufficient forcing for rising motion (in the tropics, converging winds at the low levels such as those associated with the ITCZ or a tropical wave/cyclone), convection is most likely to be at its maximum just before the sun rises in the tropics.

[cycloneye]

The ups and downs by GFS continue as 00z didn't have anything developing but 06z did.

[Alyono]

the differences may simply be due to the fact that we are dealing with numerical APPROXIMATIONS. They are going to have error and very slight changes to the initial produce completely different forecasts

As for satellite data, remember, that if one took out the sat data from the GFS in Sandy, it would have indicated an out to sea track until 24 hours before landfall.

[weatherwindow]

The ups and downs by GFS continue as 00z didn't have anything developing but 06z did.

Good morning, Luis
The Sun 7/14 00Z CFS may be picking up on that same wave beginning at the 396hr mark(the beginning of the run) and appears to loses it at the 468hr mark. However, it is picking up on the next?? wave with some stuttering moves it to and thru the Leewards and PR, on 8/8 as a weak closed low. This low is moved WNW north of Hispaniola and thru the Fla Straits on 8/11, still a weak closed low. Little development is noted in the GOM thru 8/14 and it is lost without landfall...Greeting from KW, Rich

http://www.weatheronline.co.uk/cgi-bin/ ... RES=0&WMO=

Use model data with caution. Longer range models are notoriously inaccurate and may only be useful for discerning trends. They do , however, provide an opportunity for discussion

[SouthFloridawx]

Okay, so I'm going to rephrase my question so that it makes more sense. I'm just wondering if the model inertly have within them, when convection is more favorable during different times of the day. I can't remember what the technical terms are now. I think one of them is dinural. Could this have an effect on the model out-put?

I think you're referring to diurnal maximum and diurnal minimum. I don't see it having any direct impact on the output for different model run variants during the day (00z, 12z, etc) as it is a daily, cyclical pattern.

To answer your question, I'll try and explain diurnal maximum and its effects. The earth's crust has a high heat capacity, allowing it to absorb solar radiation throughout the day. Through conduction, the earths crust begins to heat up the air directly above it, which heats up the cool air column directly above that. While the sun is at its highest point at noon (and thus solar radiation at its most concentrated strength), maximum solar heat lags behind by several hours, as the ground and air layer must first absorb heat before it can begin to radiate heat. When the amount of incoming solar radiation equals the amount of outgoing radiation (around 3-5pm), we reach our daily high temperature.

CAPE (Convective Available Potential Energy) is at a maximum during the day due to this daytime heating, which is why we see a convective maximum late in the afternoon over land (afternoon thunderstorms you can set your clock to in Florida). However, this mechanism has no inherent effect on tropical convection.

There is another mechanism in play that aides in tropical moisture though. During the overnight and early morning hours, the earth is no longer absorbing solar radiation, and is therefore radiating heat back to space at its maximum potential, which is why temperatures decrease overnight. The warm surface continues to mix convectively upward at night, being replaced by cooler air towards the surface. This creates a more moist atmospheric profile, and given sufficient forcing for rising motion (in the tropics, converging winds at the low levels such as those associated with the ITCZ or a tropical wave/cyclone), convection is most likely to be at its maximum just before the sun rises in the tropics.

Thank you for explaining that. I have a better understanding of the topic now. I was always wondering about it.

[Blown Away]

12z GFS still shows our low and it rakes the NE Caribbean, PR, and DR. Appears like a big classic CV type low...

[cycloneye]

http://img163.imageshack.us/img163/796/1q1j.jpg
12z GFS still shows our low and it rakes the NE Caribbean, PR, and DR. Appears like a big classic CV type low...

Another view of this 12z run looking at the MSLP.

[cycloneye]

18z GFS failed to develop CV Wave. Why the model is so inconsistent?

[Hurricaneman]

18z GFS failed to develop CV Wave. Why the model is so inconsistent?

Because its long range is my best guess

[SouthFloridawx]

It's back

12Z