Upper low is TOO WEAK IN GFS

[Derek Ortt]

http://www.nwhhc.com/dean300mb.gif

I posted this in its own thread so that it can be quickly highlighted

The 300mb heights are too high in the 0Z GFS and I would not expect them to be better in the 6Z

the weakness is a little more pronounced than the models are analyzing

[HouTXmetro]

What about the Remants of Erin, they are going nowhere fast.
Any effect on the future track of Dean?

http://www.weather.gov/sat_loop.php?image=wv&hours=24

[cheezyWXguy]

what does this mean in terms of a posssible northward turn into GOM by Dean?

[Derek Ortt]

UKMET is good in its initialization and keeps the storm a little south of the US/Mexican border

but it shows again that the good old GFS butchered an initialization.

This probably means that the GFS should have been north, had it had a realistic upper pattern

[MWatkins]

This mornings runs (GFS Etc) are going to be very intresting. That upper low was right over the peninsula at 12Z which means the TBY, MFL, MLB etc sounds should shoot right through it.

Will be VERY interesting to see how this shows up in the models in a few hours. This is going to be the best look at it we're going to get probably...

MW

[Derek Ortt]

I wish I had the confidence that you had Mike

The UKMET already had the proper heights at 0Z while the GFS lagged

I wonder if the GFS data assimilation is just disregarding the obs

[HouTXmetro]

This mornings runs (GFS Etc) are going to be very intresting. That upper low was right over the peninsula at 12Z which means the TBY, MFL, MLB etc sounds should shoot right through it.

Will be VERY interesting to see how this shows up in the models in a few hours. This is going to be the best look at it we're going to get probably...

MW

In Laymens terms?

[MWatkins]

This mornings runs (GFS Etc) are going to be very intresting. That upper low was right over the peninsula at 12Z which means the TBY, MFL, MLB etc sounds should shoot right through it.

Will be VERY interesting to see how this shows up in the models in a few hours. This is going to be the best look at it we're going to get probably...

MW

In Laymens terms?

2 times a day stations all over the world launch soundings...essentially weather balloons that measure temperature, wind vectors, speeds and pressure throughout the atmosphere. This information (at least in theory for the GFS - see Derek's reply ) is used to calculate the strength of various weather features and the upper flow pattern etc.

Many soundings will go right through the upper low this morning, giving the models a lot of information to work with.

MW

[HouTXmetro]

This mornings runs (GFS Etc) are going to be very intresting. That upper low was right over the peninsula at 12Z which means the TBY, MFL, MLB etc sounds should shoot right through it.

Will be VERY interesting to see how this shows up in the models in a few hours. This is going to be the best look at it we're going to get probably...

MW

In Laymens terms?

2 times a day stations all over the world launch soundings...essentially weather balloons that measure temperature, wind vectors, speeds and pressure throughout the atmosphere. This information (at least in theory for the GFS - see Derek's reply ) is used to calculate the strength of various weather features and the upper flow pattern etc.

Many soundings will go right through the upper low this morning, giving the models a lot of information to work with.

MW

Thanks, learn something new everyday.

[flwxwatcher]

Is NOAA planning a Gulf stream Flight anytime soon.

[Derek Ortt]

tonight, but if the GFS canot even use the rawindsondes properly, the G-IV may not do it a whole lot of good

[Janie2006]

The new model runs could end up surprising quite a few people.

[HollynLA]

tonight, but if the GFS canot even use the rawindsondes properly, the G-IV may not do it a whole lot of good

Derek, I'm assuming you're thinking that this could possibly cause the track to trend more north than the models are currently showing?

[ronjon]

Based on the Miami sounding, the ULL may be stronger than previously thought. Those are pretty darn cold temps for the tropics.

From NWS Miaimi Disc:

PREV DISCUSSION... /ISSUED 800 AM EDT SAT AUG 18 2007/

UPDATE...INCREASED THE RISK FOR A FEW SEVERE STORMS IN THE HWO THIS MORNING. MID/UPPER LOW IS OVER THE SOUTHERN PENINSULA RIGHT NOW.
ACARS DATA SHOWS EXTREMELY COLD AIR ALOFT OVER THE AREA...AROUND -12C! THIS WILL RESULT IN A VERY UNSTABLE AIRMASS WITH LARGE HAIL/GUSTY WINDS POSSIBLE IN STORMS TODAY. AS THE MID/UPPER LOW MOVES WEST...WARMING WILL TAKE PLACE ACROSS THE ATLANTIC COAST...BUT IT WILL CONTINUE VERY COLD ALOFT OVER THE NAPLES AREA DURING THE TIME OF MAX HEATING...WHICH COULD SET THE STAGE FOR A VERY ACTIVE TSTORM DAY ESPECIALLY GULF COASTAL LOCATIONS THIS AFTERNOON.
/GREGORIA

[Extremeweatherguy]

not only is the upper low too weak..but Dean is too. The 12z run initialized him at around 1002mb, when in fact he is actually a sub-930mb storm.

[Sanibel]

Derek was the first to shout out about the High sending Katrina towards New Orleans instead of the panhandle. I'd pay attention.

[cpdaman]

if the ULL moves more Sw will that increase the weakness or decrease the weakness ( by allowing heights to build to the north) providing a more east-west steering?

Derek?

[WindRunner]

Umm, Derek, the data stamp says it's last Sunday's GFS, and I think that's right because absolutely none of the obs match the model initialization . . .

[Sanibel]

Think Windrunner is right. Time-stamp says it's a 144 hour observation from Sunday August 12th.

[WxGuy1]

not only is the upper low too weak..but Dean is too. The 12z run initialized him at around 1002mb, when in fact he is actually a sub-930mb storm.

A global model is not typically going to initialize a hurricane to <930mb. The resolution is too coarse to capture that. As Wthrman noted in another thread, the global models do a pretty good job of forecasting steering currents (dictated by large-scale synoptic "features"). The GFS may be a bit week w/ the ULL, but it's not like this will cause Dean to throw on the breaks, take a 90d turn, and end up hitting Orlando. We're mainly talking about potentially-increased chances of a Texas landfall. I still think the most likely outcome is a hit to mainland Mexico.