ATL: TROPICAL DEPRESSION ALEX - DISCUSSION

[MWatkins]

There's a lot going on in this thread...but I am suprised that the pressure is so low (958) with such a relatively weak wind from the aircraft.

This reminds me a LOT of 2005...when we had hurricanes in the low 900's pressure wise with category 4 winds. Seemed hard to believe at the time, but that's what happens with such low background pressures.

I have a feeling the winds will somewhat catch up to the pressure as the day progresses.

MW

[HURAKAN]

Quite impressive system

[thetruesms]

Oh, I forgot to mention that this thread has been chock full of one of my pet peeves. There is no physical relationship between a storm's minimum pressure and wind speeds! The relationship is between pressure gradient and wind velocity. To sustain a larger wind field, you need a lower minimum pressure.

As with surge potentials, I'm going to place this one entirely on the old Saffir-Simpson scale. Finally it refers to winds only, but I'm afraid the damage has been done.

[linkerweather]

There has been a lot of discussion about the low pressure and the not so high wind speed. Although this seems to be on the edge of the spectrum, remember with a larger circulation the pressure gradient is looser heading toward the center than if it were a small circulation. With a looser pressure gradient the wind won't be a strong.

[NEXRAD]

Full details are in my write-up in the "Tropical Analysis" forum, but some thoughts this AM...

1) Alex's core has a really good appearance on the early morning 85GHz imagery. With the dry-air filtering through the storm's NE quadrant being replaced, I only expect that the storm's core has continued to improve. The 85GHz imagery suggested Alex as having a very compact eye with potent convection wrapped around with perhaps some weakness in the Wrn eyewall. Such a small core makes Alex more prone to quick swings in intensity from my experience over the past decade.

2) The hurricane's outflow is excellent and dual-channel poleward. This type of outflow is particularly conducive for a storm's intensification.

3) The ridging over the Great Plains will be gradually moved Eward thanks to energy aloft. This should set-up at least the lower level (950mb and 850mb) ridging due N if not NNE of Alex late today. Net influence here should keep Alex a bit right of the guidance envelope.

(Note: This information is not official per the NWS, NOAA, TPC/NHC. As always, rely on information from official sources for your decision making and preparedness.)

- Jay
South Florida

[KWT]

I think the eventual landfall will still be in Mexico but a little closer to Brownsville then was expected

Indeed, radar looks like its bent back a little bit again to the NW but it still looks like its coming in north of the forecast point unless it bends back due west more or less right now...looks like the system is going to come closer to the border then wasa perhaps expected and with those double/triple wind Maxima occuring we will probably see hurricane force winds extend much further out soon.

[Evil Jeremy]

Alex is looking healthy this morning. It won't be long before those winds wake up and smell the coffee that is the low pressure and realize.... ok, that wasnt working, but you all know what I meant.

Anyways, Alex's short term motion is key here. How much further north it tracks before bending back to the west can make a big difference for South Texas.

[KWT]

Full details are in my write-up in the "Tropical Analysis" forum, but some thoughts this AM...

The 85GHz imagery suggested Alex as having a very compact eye with potent convection wrapped around with perhaps some weakness in the Wrn eyewall. Such a small core makes Alex more prone to quick swings in intensity from my experience over the past decade.
- Jay
South Florida

The problem is as I think has been pointed out, recon shows 3 distinct wind Maxima with Alex, each one more or less between 80-85kts at FL (the inner eyewall is a touch higher generally between 85-88kts) and so that probably goes some way to explaining why the wind isn't matching the pressure, its forming Concentric eyewalls instead.

[CrazyC83]

I think the storm surge could be much higher than expected for a Cat 1 as well, and the winds could spread an extremely large area for a long time.

I wonder what the IKE is?

[NEXRAD]

KWT - Good point. The 06Z 85GHz imagery didn't show much evidence of such structure, but I just got some fresh imagery in. Alex strangely does seem to be forming a dual eye-wall, or at least some sort of dual deep convective structure. If the outer wall merges and breaks down, though, we could see some quick jumps in intensity. I suspect the structure is presently due to yesterday's dry-air entrainment, which is now diminishing per what I've seen in IRWV.

- Jay
South Florida

[Nederlander]

I think the storm surge could be much higher than expected for a Cat 1 as well, and the winds could spread an extremely large area for a long time.

I wonder what the IKE is?

Integrated Kinetic Energy ...

edit: sorry, i may have misread that.. you were probably asking for the number..

[KWT]

Indeed Jay, the only problem is I feel once you get that set-up and it becomes established (those outer maxes are deffo higher in relation to the inner eyewalls winds than last night) as Ike proved it becomes nearly impossible to shed it, esp in the time Alex has got left.

Still we'll have to wait and see.

Radar watching really does begin from now on!

ps, current motion will take it rather too close to Brownsville for comfort...

[CrazyC83]

Even with the pressure so low, with such a wide and spread out wind field it will be hard for the winds to catch up. That explains why Ike never became more than a Cat 2 in the Gulf. Also the structure is fairly similar to that of 1957's Hurricane Audrey.

[Over my head]

I think the storm surge could be much higher than expected for a Cat 1 as well, and the winds could spread an extremely large area for a long time.

I wonder what the IKE is?

Integrated Kinetic Energy ...

edit: sorry, i may have misread that.. you were probably asking for the number..

My mind wasn't even if Crazy's was...you answered My question. Thanks

[TeamPlayersBlue]

I.K.E. is more important in a storm in my opinion. Wasn't IKE the highest recorded? Dont quote me on that this but i read somewhere it's IKE was much higher than Katrinas.

As far as Alex, Brownsville better keep their eyes on this. It is headed basically just south of the now if it continues on this course

[Evil Jeremy]

Recon just about to make another center pass, lets see if it can find a lower pressure, higher winds, and more information on its current movement.

[MWatkins]

Even with the pressure so low, with such a wide and spread out wind field it will be hard for the winds to catch up. That explains why Ike never became more than a Cat 2 in the Gulf. Also the structure is fairly similar to that of 1957's Hurricane Audrey.

Ike had a lot of other problems aside from a large pressure field.

The eye had structual challenges and got really big just hours before landfall. If I remember correctly it had ingested some dry air, and never fully recovered from having it's windfield spread out after travelling over Cuba.

Interestingly, with a 5 meter wind tower at Galveston College only a few blocks inland, we didn't record wind speeds over 76 mph...

MW

[Evil Jeremy]

958.3 mb pressure at 23.8N and 95.4W

[TeamPlayersBlue]

Center seems to have tracked a bit more northerly than the recon flights last pass through

[Evil Jeremy]

So according to recon, Alex has moved approximately .4 north and .1 west from the intermediate advisory position.