ATL: TROPICAL DEPRESSION ALEX - DISCUSSION

[KWT]

New convection is firing all around Alex's core convection. The leading edge of moist, tropical air is surging W and NW ahead of the system and new convective activity is persistently firing behind this leading edge. I suspect Alex's dry air problems may be quickly diminishing. The storm seems to have a very well-defined center and core on visible imagery.

- Jay
South Florida

Will be interesting to see if it continues as it heads towards Mexico and its circulation brings ever more dry air into the circulation though, may well have a small window where with its better structure it can make the most of it, but I'd have to think it'd level off to a point.

Still think its going to be a close run thing as to whether this gets to category-2, the presnetation is better, just needs filling out a bit. Probably got about 18-21hrs or so left.

[Waterdrop]

can one assume the waves will be brilliant tomorrow in the galveston area??????????

Maybe not brilliant on Wednesday, but maybe Thursday and Friday you'll get some clean swell.

thank you for answering my question. i'll def delay a day.

[AJC3]

It actually looks more like a storm trying to become extratropical...

What it actually looks like is one of those deep wintertime "pinwheel" type occluded lows that you often see in the north Atlantic. Of course, what it really is, IMO, is an artifact of dry air intrusion, particularly at outflow level. That's why you don't see a dense cirro-stratus canopy from the convection. If you look closely, the CS from the TS tops has tended to dissipate fairly rapidly, compared to normal. I think this may be an artifact of some dry U/L leftover from the base of the upper trough that was there a day or two ago.

It's not unlike what you would see if you were to slice off the top 50MB of most bordeline TS/cat 1 hurricanes.

[Aric Dunn]

It actually looks more like a storm trying to become extratropical...

What it actually looks like is one of those deep wintertime "pinwheel" type occluded lows that you often see in the north Atlantic. Of course, what it really is, IMO, is an artifact of dry air intrusion, particularly at outflow level. That's why you don't see a dense cirro-stratus canopy from the convection. If you look closely, the CS from the TS tops has tended to disipate fairly rapidly, compared to normal. I think this may be an artifact of some dry U/L leftover from the base of the upper trough that was there a day or two ago.

sounds like a likely possibility.. makes sense though convection does not seem to have a problem developing just wont maintain ..

[Hurricanewatcher2007]

New convection is firing all around Alex's core convection. The leading edge of moist, tropical air is surging W and NW ahead of the system and new convective activity is persistently firing behind this leading edge. I suspect Alex's dry air problems may be quickly diminishing. The storm seems to have a very well-defined center and core on visible imagery.

- Jay
South Florida

Will be interesting to see if it continues as it heads towards Mexico and its circulation brings ever more dry air into the circulation though, may well have a small window where with its better structure it can make the most of it, but I'd have to think it'd level off to a point.

Still think its going to be a close run thing as to whether this gets to category-2, the presnetation is better, just needs filling out a bit. Probably got about 18-21hrs or so left.

NHC is forecasting it to strengthen right up until landfall and I see no reason to go against that forecast. It's pretty quickly right now dealing with the dry air and it will have one more Dmax to do whatever it is going to do.

[lebron23]

I wouldnt be shocked to see a special advisory to say its a hurricane

[Aric Dunn]

I wouldnt be shocked to see a special advisory to say its a hurricane

wont need to .. the recon plane is in route and should make first pass for the 8pm advisory

[HouTXmetro]

Question, Alex is going to keep it moving west once it gets inland right? Or are we looking at a inland stall after landfall? I know some of the models were predicting weak steering in a few days and perhaps a coastal runner.

[KWT]

NHC is forecasting it to strengthen right up until landfall and I see no reason to go against that forecast. It's pretty quickly right now dealing with the dry air and it will have one more Dmax to do whatever it is going to do.

They don't call for strengthening till landfall they call for it to reach 75kts then hold steady to landfall, that seems reasonable enough for it to hold but as we've seen in so many countless large storms they do tend to swallow down a lot of dry air once they get close to landfall.

[Hurricanewatcher2007]

NHC is forecasting it to strengthen right up until landfall and I see no reason to go against that forecast. It's pretty quickly right now dealing with the dry air and it will have one more Dmax to do whatever it is going to do.

They don't call for strengthening till landfall they call for it to reach 75kts then hold steady to landfall, that seems reasonable enough for it to hold but as we've seen in so many countless large storms they do tend to swallow down a lot of dry air once they get close to landfall.

You must not have read the discussion closely enough!

WHILE NOT EXPLICITLY IN THE
FORECAST... IT IS LIKELY THAT ALEX WILL REACH A PEAK INTENSITY OF
80-85 KT BEFORE IT MAKES LANDFALL BETWEEN THE 24 AND 36 HR FORECAST
POINTS.

[lebron23]

Dr Neil Frank thinks its a hurricane

[KWT]

Ah fair enough then, well 80-85kts would be reasonable as a peak...of course doesn't say it will make landfall at that strength does it...

Its just common sense really that dry air comes into the circulation as the system gets closer really, it happens more often then not in these big systems...I've seen it countless times, all depends how well the center can keep itself bursting towards the final push.

FWIW I actually agree on a 80-85kts peak, no reason why it can't make category-2 if the systems cetner can keep away from the dry air circulating round, I'm still going as high as 85-90kts but with some slight weakening before landfall...If the system runs WSW could see a brief burst of RI even.

ps, thats not a forecast BTW...a slight difference between saying its likely and actually forecasting it

[micktooth]

It actually looks more like a storm trying to become extratropical...

What it actually looks like is one of those deep wintertime "pinwheel" type occluded lows that you often see in the north Atlantic. Of course, what it really is, IMO, is an artifact of dry air intrusion, particularly at outflow level. That's why you don't see a dense cirro-stratus canopy from the convection. If you look closely, the CS from the TS tops has tended to dissipate fairly rapidly, compared to normal. I think this may be an artifact of some dry U/L leftover from the base of the upper trough that was there a day or two ago.

It's not unlike what you would see if you were to slice off the top 50MB of most bordeline TS/cat 1 hurricanes.

Thank you for the great analysis it was very insightful. A lot of us on this board are NOT very technical and I enjoy your explanations.

[ndale]

One of the tv mets here in Austin just mentioned the remnants of Alex may drift north after landfall causing us more rain here. The forecast track looks like it going further south into Mexico so I don't know where he gets his info for that statement. Does anyone have ideas on this-is the ridge going to remain strong enough to keep it south or will the ridge weaken by the weekend?

[Tireman4]

Dr Neil Frank thinks its a hurricane

He is the man. When the rubber hits the road during tropical system season, I do trust him.

[funster]

One of the tv mets here in Austin just mentioned the remnants of Alex may drift north after landfall causing us more rain here. The forecast track looks like it going further south into Mexico so I don't know where he gets his info for that statement. Does anyone have ideas on this-is the ridge going to remain strong enough to keep it south or will the ridge weaken by the weekend?

NHC TRACKS ALEX INTO THE NORTHERN COAST OF MEXICO JUST SOUTH OF BROWNSVILLE
TOMORROW NIGHT WITH THE GULF WIDE OPEN FOR CONTINUED GOOD-LIKELY
CHANCES FOR SHOWERS AND THUNDERSTORMS MAINLY OVER THE SOUTHERN
TIER OF THE REGION. WIDESPREAD SHOWERS AND THUNDERSTORMS THURSDAY
IN A WIDE OPEN TROPICAL GULF FLOW REGIME AS ALEX WEAKENS OVER
NORTHERN MEXICO. A CONTINUED OPEN GULF FRIDAY WILL RESULT IN
SIMILAR CONDITIONS WITH A GOOD CHANCE OF SHOWERS AND STORMS. RAIN
AMOUNTS FROM ALEX WEDNESDAY THROUGH FRIDAY COULD RANGE AS HIGH AS
4 TO 6 INCHES ACROSS THE SOUTHERN TIER TO ONE TO THREE INCHES
ACROSS THE NORTHEAST CORRIDOR.

- from the Austin/San Antonio discussion here: http://www.weather.gov/view/prodsByStat ... discussion

[KWT]

Should see just where this system is at soon enough, recon should be there in about an hours time and ready to make its first pass.

[lrak]

Yay, the NASA satellite page is working again!

[txagwxman]

Alex has one of the large anti-cyclones aloft I can remember....The outflow channel goes from Jamaica into South America.

[lrak]

FYI - the NHC ftp server has some storm surge graphics for Alex up. There's a height above MSL (realy MLW) and an inundation static image and loop:

ftp://ftp.nhc.noaa.gov/surge/Latest/

Height above MSL animation:
ftp://ftp.nhc.noaa.gov/surge/Latest/al7_br2.gif

Inundation animation:
ftp://ftp.nhc.noaa.gov/surge/Latest/al7 ... dation.gif

Both graphics are what is called deterministic forecasts, based on the actual track not just SLOSH basin displays. They're based on a projceted average-sized Cat 2 at landfall.

VERY COOL wxman57, thanks for the cool graphics!