GOM trough digs in -- pushing east?....

[APRS-CW0262]

What's strange is here on the east coast of Florida pres. has not risen in the last 24hrs.

[Air Force Met]

So in other words what effects will this have on the track and strength of Ivan?

First of all...I think Ivan will slow down. They always slow down when there is a COL approaching from the NW. Plus...go to this loop (short term RUC)...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml

Look what happens to the flow north of Ivan over the next 12 hours...don't pay much attention to where the RUC has Ivan...just look at the steering flow.

1) The trough continues to pull out and the southerly flow over N Florida becomes more easterly.

2) The high over e tx moves eastward and joins the ridge. This shouls slow Ivan down even more in the short term.

After Ivan slows...he should resume a more NW track...probably from 300-310...maybe 315.

Now...synoptically...that is what SHOULD happen. He SHOULD slow and then SHOULD gain more of a westerly component.

That being said...many times hurricanes don't do what they should

Meteorologically, however, that is what he should do given the steering flow shifting more to the east north of him and the high moving north of him. In 24 hours...the e tx hi is forecast to be due north of him and then shifts east.

If he doesn't do it...don't ask me why he didn't because I won' be able to say...but I still think landfall is b/w Mobile and N.O....closer to mobile or Biloxi.

Intensity: I think he will be a cat 3. There will still be some dry air in the northern GOM and the approaching SWT from the west should give some SW shear.

[CYCLONE MIKE]

Thank You Air Force Met! Thank is the best explanation of what could/should happen that I have read. I appreciate it.

[PurdueWx80]

Air Force - we are in perfect agreement then. There is just too good a chance that enough of a ridge will bulk up north of Ivan to assume he is going further east. The "trough" this thread mentions to the NW or N of Ivan only appears to be in a very thin layer of the atmosphere..as you can see in a close up WV loop that ridging dominates. Cat 3 is an excellent estimate as well, given the warm pool Ivan will be traveling over. All that dry air will likely impede rapid development again.

[Brent]

Give it up Dixie... it's not headed for you.

J/K

[HouTXmetro]

The scenario Airforce met explained is exactly what the local Houston mets were talking about last night. We shall see.

[tronbunny]

Give it up Dixie... it's not headed for you.

J/K

I'm going to defend Dixie, here...

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE 14 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC OCEAN TO THE AFRICAN
COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1145 UTC.

...SPECIAL FEATURE...
<snip>
IN THE UPPER LEVELS...IVAN IS FLANKED BY A SHORTWAVE TROUGH TO THE WEST THAT IS DIGGING FURTHER S AND ADVECTION MODERATE SUBSIDENCE/DRY AIR N OF 21N FROM 90W-94W. STRONG MID/UPPER LEVEL RIDGING IS TO THE EAST OF IVAN. THE OUTFLOW IS GOOD IN ALL BUT THE SW QUADRANT WHERE SOME DRY AIR IS BEING ADVECTED INTO THE SYSTEM.

Anybody feel foolish?

[Josephine96]

LOL.. Good 1..

[dixiebreeze]

Thanks Tronbunny.

And Brent, you better hope Ivan doesn't visit you in 'Bama. You're a few cards short of a deck if you think any of us in Florida want Ivan here!

[Air Force Met]

IN THE UPPER LEVELS...IVAN IS FLANKED BY A SHORTWAVE TROUGH TO THE WEST THAT IS DIGGING FURTHER S AND ADVECTION MODERATE SUBSIDENCE/DRY AIR N OF 21N FROM 90W-94W. STRONG MID/UPPER LEVEL RIDGING IS TO THE EAST OF IVAN. THE OUTFLOW IS GOOD IN ALL BUT THE SW QUADRANT WHERE SOME DRY AIR IS BEING ADVECTED INTO THE SYSTEM.

Anybody feel foolish?

Nope...don't feel foolish at all. That is a wrong analysis. Sorry. Take a look at the links I posted and you will clearly see the trough is to the north of Ivan and that there is a col west of Ivan with the approaching ridge. Whoever wrote that discussion doesn't know how to analyze a water vapor and initialize it. It is very clear on the sat. derived winds AND the upper air analysis that the trough is north of the system and the dry air on the wv image is being caused by the approaching ridge. Go look at the current upper level winds ay 90W. THERE IS ANTICYCLONIC TURNING at 90W.

Look at this 00HR chart...not a forecast but what was actually happening when the writer of the discussion said there was a trough...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_000m.gif


Do you see a trough at 90W? No...there is a ridge and a high sitting over eastern LA. The trough is now sitting a little NNE of Ivan and has lifted out. Again...look at the links I posted and tell me where that is wrong? Look at the one I just posted. There is no trough there. How can there be a "digging trough" in anticyclonic flow?

Again...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_000m.gif

So...do I feel foolish? Nope. However wrote that discussion ought to though. Don't take my word for it...here is what the NHC said about it:

A SECOND MID-LEVEL HIGH IS
CENTERED OVER LOUISIANA WITH A RIDGE EXTENDING SOUTHWARD INTO THE
WESTERN GULF OF MEXICO. 12Z RAOBS AND JET DATA INDICATE THAT THIS
LATTER RIDGE IS A LITTLE STRONGER THAN FORECAST BY THE 6Z GFS RUN.

Compair that to what the writer of the discussion wrote AND the data. Who do YOU think is right? The NHC or the lone individual who is bucking the NHC and the data?

So...NO!! don't feel foolish at all. Actually, I feel very right about my analysis on the RIDGE located over LA (See the NHC 11 am discussion...if there was a trough west of Ivan and digging south...they would have mentioned it!...They don't...they only talk about the ridge that I said was there).

Why do I feel right? Because the 12z analysis (not some model...the actual plots)...backs it up.

[Lindaloo]

Awesome AFM!! Thanks! Now, did someone mention foolish? LOL!!

[Air Force Met]

Awesome AFM!! Thanks! Now, did someone mention foolish? LOL!!

Whoever wrote that discussion probably knows how to analyze water vapor...matter of fact...I' sure they do. However, when looking at the east side of ridges...especially when a trough WAS there...you have to not only look at the water vapor...you have to match it up with data.

Just looking at the WV loop...and nothing else...I would have said "possible trough digging down." But...I've also been doing this for 17 years and I know that an approaching ridge and col...combined with subsidence also produces that kind of image. So...I always initialize my analysis with the upper air obs.

Matter of fact...go here and you will see that actual plots...

http://weather.noaa.gov/pub/fax/QHTA11.TIF

or here (choose 4.b) http://weather.noaa.gov/fax/barotrop.shtml#mb500

See the anticyclonic turning where the trof is "diggin"? How can there be anticyclonic turning where a diggin trough is? Not there. The analysis has a high...the NHC says there is a high...the sat. derived winds say there is a high. If someone sees a diggin shortwave on that chart...to the west of Ivan near 90-94...please show me. All I see is ridging.

[kevin]

Bravo AFM!

[Lindaloo]

LOL AFM!! You are da man!

[Air Force Met]

Bravo AFM!

Thanks. It's not that hard though. I am an ok forecaster...but analysis has always been my joy and what I am best at. In school, my instructors drummed into me that a good forecast has to start with a near perfect analysis and a initializing of the models. So...I forced myself to learn how to analyze. In a world of computer generated graphics and model output...I am STILL hand analyzing charts (the difax from the NWS)...and re-analyzing those charts...with pencil and markers in hand...just like I did 17 years ago when I first started. Matter of fact...I still make my jr. forecasters hand-analyze charts...when all around us depend on someone else to do them or just look at what the models say (we call them model-readers...not forecasters).

Our primary job is to forecast bombs on targets...and to aid FEMA with natural disasters (we have a duel mission) in the 5th Army region (all states west of Mississippi). And our forecasters out perform other forecasters...I think...because they have a great handle on the analysis...and when model shows a shortwave ridge or trof...out forecasters know fromthe analysis whether it is too strong or too weak.

Some call me a disnosaur because I still hand analyze...but I find it a nice releiver of stress

[Brent]

And Brent, you better hope Ivan doesn't visit you in 'Bama. You're a few cards short of a deck if you think any of us in Florida want Ivan here!

LOL, it was a joke. You do act like you want it though. It's just an impression I get.

Ivan is headed here too. I'm well inland, but we're still expecting tropical storm force winds with some gusts possibly to hurricane force and lots of rain.

[PurdueWx80]

AFM - I agree whole-heartedly w/ you on the hand analysis. They still teach these methods at Purdue - and I'd like to think of myself as an equally excellent analyzer because of this. Computer algorithms that do all of the analysis for you aren't perfect, and sometimes a subjective look is much better than the rules a computer follows. Don't be ashamed!!!! Dinosaurs are cool!

[dixiebreeze]

And Brent, you better hope Ivan doesn't visit you in 'Bama. You're a few cards short of a deck if you think any of us in Florida want Ivan here!

LOL, it was a joke. You do act like you want it though. It's just an impression I get.

Ivan is headed here too. I'm well inland, but we're still expecting tropical storm force winds with some gusts possibly to hurricane force and lots of rain.

Brent, having been without power for a week and a yardfull of debris, plus eye surgery in the middle of Frances, I can tell you clearly "I DON'T WANT IVAN!"

And I hope he spares you, too.

[Josephine96]

We're all just nervous/excited about this monster being so close..

[kevin]

Well you know what happened to the dinosaurs don't you? They became penguins.