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WxWatcher007

Hurricane Hanna

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16 minutes ago, hawkeye_wx said:

At first glance, it appears Hanna is blowing up.  However, as the NHC says, the very intense burst of convection is south and east of the center, not over it.  If it's not over the center, it's not doing much good.

Yeah I’m not really sure what to think yet. I do think this has a higher ceiling now as organization continues.

Recon should be flying in the next 2.5-3 hours so that should help. The last few IR frames look particularly interesting with a very impressive burst but like you said, it needs to be squarely over the center. 
 

31332759.gif?0.9445385078309881

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At first glance, it appears Hanna is blowing up.  However, as the NHC says, the very intense burst of convection is south and east of the center, not over it.  If it's not over the center, it's not doing much good.

The center vortex wasn't exactly gang busters on the last recon pass. The persistent intense MCS looks to have acquired mid-level rotation already on its own, and it wouldn't surprise me if strong convergence into those intense cells doesn't force a new surface vortex under it. LLC reformation / relocation isn't necessarily unusual in weak or newly evolving systems with such intense convection versus a weak LLC. Yeah, we'll know what's up when recon gets there. 25e6f8c7770c87ee3f7bc4dc6db63131.gif&key=91b28bc82db6efdf99f12d911bd2d3d7bc19275da100d605f026d34b816a77d7

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This is probably the best burst yet. If it persists I have no reason to think a bit of a reformation or tuck isn’t possible. That’s what happened yesterday afternoon during a recon flight. A strong convective burst popped a strong mid level rotation, and the relatively weaker LLC shifted SE to better align.

Thing here is if there is a misalignment, it doesn’t look like it’s off by much. Idk.

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Even if you took these loops at face value, the “core” is open to the west. That has to close before any real uptick from the gradual intensification we’ve been seeing can commence.

31332759.gif?0.8667011386361807

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11 minutes ago, jbenedet said:

This looks like a step-wise jump in intensity should this be the formation of a sustained CDO, which appears to be the case. 

I agree. I don’t see a core really closing off yet via WV and IR, so I’m not expecting anything too dramatic right now. Western side still looks like it’s lacking a bit. Definitely better than yesterday. 

Looks like recon is starting their descent.

Edit: let me just add, I think it’s unlikely, but I wouldn’t be surprised if recon found the beginnings of an eyewall during their flight. The curved structure and hints of more intense curved convection inside the deep echoes are intriguing.

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Recon is in the storm now and shouldn’t be too far from the center. FL winds are definitely up a bit early on. One unflagged SFMR of 41kts but everything else is 34kt or below. Again just early data. 

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Recon just found the center at the northern tip of the cloud shield.  The core is still weak with a pressure over 1000 mb.  All that very intense convection to the south didn't help a bit.

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1 minute ago, hawkeye_wx said:

Recon just found the center at the northern tip of the cloud shield.  The core is still weak with a pressure over 1000 mb.  All that very intense convection to the south didn't help a bit.

Yup. All kinds of misaligned. 1000.5mb extrapolated.

I wonder what they’ll find further south. Winds are up in parts of the convection but organization is still clearly lacking. <shrug> 

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Here’s the first vortex message 

Product: NOAA Vortex Message (URNT12 KWBC)
Transmitted: 24th day of the month at 12:09Z
Agency: National Oceanic and Atmospheric Administration (NOAA) 
Aircraft: Lockheed WP-3D Orion (Reg. Num. N43RF) 
Storm Number & Year: 08 in 2020
Storm Name: Hanna (flight in the North Atlantic basin)
Mission Number: 4
Observation Number: 04

A. Time of Center Fix: 24th day of the month at 11:37:53Z
B. Center Fix Coordinates: 27.13N 92.75W
B. Center Fix Location: 215 statute miles (346 km) to the S (173°) from Lake Charles, LA, USA.
C. Minimum Height at Standard Level: 697m (2,287ft) at 925mb
D. Minimum Sea Level Pressure: 1001mb (29.56 inHg) - Extrapolated
E. Dropsonde Surface Wind at Center (Undecoded): NA
F. Eye Character: Not Available
G. Eye Shape: Not Available
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 47kts (54.1mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 54 nautical miles (62 statute miles) to the SSE (150°) of center fix at 11:21:09Z
J. Maximum Flight Level Wind Inbound: From 197° at 45kts (From the SSW at 51.8mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 64 nautical miles (74 statute miles) to the SE (137°) of center fix at 11:16:19Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 26kts (29.9mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 3 nautical miles to the N (360°) of center fix at 11:38:48Z
N. Maximum Flight Level Wind Outbound: From 5° at 24kts (From the N at 27.6mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 70 nautical miles (81 statute miles) to the W (271°) of center fix at 11:57:31Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 22°C (72°F) at a pressure alt. of 772m (2,533ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 24°C (75°F) at a pressure alt. of 783m (2,569ft)
R. Dewpoint Temp (collected at same location as temp inside eye): 23°C (73°F)
R. Sea Surface Temp (collected at same location as temp inside eye): Not Available
S. Fix Determined By: Penetration, Radar, Wind and Pressure
S. Fix Level: 925mb
T. Navigational Fix Accuracy: 0.01 nautical miles
T. Meteorological Accuracy: 2 nautical miles

Remarks Section:
 

Sea Level Pressure Extrapolation From: 925mb
Maximum Flight Level Wind: 45kts (~ 51.8mph) which was observed 65 nautical miles (75 statute miles) to the SE (137°) from the flight level center at 11:16:20Z
Maximum Flight Level Temp: 26°C (79°F) which was observed 7 nautical miles to the NW (324°) from the flight level center

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1 minute ago, hawkeye_wx said:

The morning visible loop does not look very healthy.  As recon showed, there is a weak core with convection displaced to the south.

Hopefully things stay that way.  I absolutely do not want to see a significant storm impact the Texas coast, especially with the state of the pandemic across Texas.  But this hurricane season is only getting started (and looks to be a potentially-significant one), so there is always the possibility.

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The morning visible loop does not look very healthy.  As recon showed, there is a weak core with convection displaced to the south.

Yeah, so far, no sign of alignment with stronger MCS feature to the south or relocation of surface vort max underneath. There doesn't appear to be any shear. Just one of those quirky situations where a surface convergent boundary/band is dominating to the south and starving the actual surface low of sustainable convection. The stubborn persistence of this structure is taking valuable time away from Hanna becoming a formidable hurricane versus weak one and likely will verify the official forecast of a strong TS. That we are closing in on 24 hrs from landfall and Hanna is still struggling to organize its core vortex is a big deal. I thought it was working out these structural issues over night; and due to the great upper environment, would already be intensifying right now, leading into rapid intensification by this afternoon. That is not looking like a good call at all on my part. Alas, even when all the ingredients are there, TCs have to overcome their own convective structure and evolution as well.

 

The NHC have been wise to stay rather conservative with this one.94bfa10e82b8c0295f20bfa36470055c.gif&key=12b587f9220c3829014f8b3e298c4818055985a244526b8a7ff3d4205fc34763

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I’m not as bearish. Obviously the center is tilted or misaligned, but this system is still gradually intensifying IMO. Fortunately for the people of Texas, the longer it takes to align the less likely any type of rapid intensification occurs. 

Hanna has just had a hard time getting convection upshear to promote vertical alignment. It has tried, but failed twice so far. 

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I’m not as bearish. Obviously the center is tilted or misaligned, but this system is still gradually intensifying IMO. Fortunately for the people of Texas, the longer it takes to align the less likely any type of rapid intensification occurs.  Hanna has just had a hard time getting convection upshear to promote vertical alignment. It has tried, but failed twice so far.  

 

Not to say it isn't intensifying. It's just at a slow rate with this lopsided structure. Also not downplaying as it is still a dangerous situation. There are still uncertainties and we have seen TCs do some crazy RI in a very short lead time. But realistically it still takes time for even RI to get a core RMW up into well-developed hurricane territory. Also clearly there is the significant flood threat for S TEXAS regardless of wind potential.

 

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1 minute ago, Windspeed said:

Not to say it isn't intensifying. It's just at a slow rate with this lopsided structure. Also not downplaying as it is still a dangerous situation. There are still uncertainties and we have seen TCs do some crazy RI in a very short lead time. But realistically it still takes time for even RI to get a core RMW up into well-developed hurricane territory. Also clearly there is the significant flood threat for S TEXAS regardless of wind potential.

 

Yeah, not saying you or anyone here is downplaying. I love our discussion. I really thought we had something going a few hours ago when the first big convective bursts started going up. Both Gonzalo and Hanna have been interesting in that regard. Gonzalo had a more hostile environment for sure, but had its chances to get over the hump.

Hanna is in an even better environment, but can’t quite get right. That said, the globals and HWRF show that the biggest window for intensification is right before landfall. If Hanna ends up ahead of schedule in any way it could surprise.

I think category two is probably the ceiling if everything goes “right”, but I currently lean toward a 60-70kt landfall late tomorrow morning.

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Yeah, not saying you or anyone here is downplaying. I love our discussion. I really thought we had something going a few hours ago when the first big convective bursts started going up. Both Gonzalo and Hanna have been interesting in that regard. Gonzalo had a more hostile environment for sure, but had its chances to get over the hump. Hanna is in an even better environment, but can’t quite get right. That said, the globals and HWRF show that the biggest window for intensification is right before landfall. If Hanna ends up ahead of schedule in any way it could surprise. I think category two is probably the ceiling if everything goes “right”, but I currently lean toward a 60-70kt landfall late tomorrow morning.

It's really odd. You mentioned Hanna's difficulty establishing convection upshear. There is some weak shear. But Hanna's vector and speed of motion is only dealing within ~10 kts over the center. So yes, there is some, but wouldn't appear to be enough to prevent expansion NW. The shear map even shows the shear axis is weakest over Hanna's center? I really think there is just better dynamics in play south of the present location of the LLC. The band that setup there due to robust convection needs to move north and wrap the low level vort or convection needs to wane there killing that inflow boundary. Also, Hanna is spitting out outflow boundaries to the north of the deep cloud canopy. Perhaps there is some stable air mass hanging out there. Something is amiss for now.53823887e8994ff1f3660b3aa8ead072.jpg&key=b4b354aae24b3a05e7570a73708bff14dbffc8d3a2c3e32cacb5c6190e7cecd5d83410f4806b1547e04398ab34d6ac8f.jpg&key=e7d4eba55f5f33f6fbbfdc14be27f3b64ba4a4f3e54f9078025938c36eeba9be
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There's not much wind in the core, and there won't be until robust convection refocuses over the center.

Regarding the discussion a couple posts above, I was wonder if there might be some sinking air or something suppressing the north and west sides.

I think the last few HWRF runs had Hanna finally getting its act together and ramping up beginning this afternoon/evening, so we'll see if that's right.

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Tropical Storm Hanna Discussion Number   7
NWS National Hurricane Center Miami FL       AL082020
1000 AM CDT Fri Jul 24 2020

Reports from a NOAA reconnaissance aircraft this morning and nearby 
ship D5DY4 indicate that Hanna has strengthened a little. However, 
the aircraft data also showed that Hanna's center had moved or 
reformed a little farther north near the northern edge of the 
convective cloud mass. A partial SSMI/S pass around 1231Z suggested 
that a mid-level eye feature could be forming, but it also possible 
that a dry slot may be intruding into the cloud shield from the 
northwest and west. The initial intensity of 40 kt is based on 
aircraft SFMR surface winds of 38-40 kt, and the 1200Z D5DY5 ship 
report of 48 kt at 89 meters elevation, which reduces to a 38-kt 
10-meter wind speed.

Even with the earlier northwestward jump in the center position, 
reconnaissance and microwave satellite data indicate that Hanna's 
motion is still west-northwestward or 285/08 kt. There remains no 
significant change to the previous official track forecast or 
reasonings over the past couple of days. The latest NHC model 
guidance remains in good agreement that mid-level ridge will build 
to the north and northwest of Hanna over the next couple of days, 
resulting in the cyclone turning westward by tonight and on 
Saturday. It should then turn west-southwestward Saturday night and 
Sunday. The new NHC forecast track continues to show the center 
making landfall along the south-central coast of Texas within the 
tropical storm warning area Saturday afternoon or evening, which is 
in good agreement with the various consensus models.

Hanna's convective cloud shield remains very asymmetrical with the 
bulk of the convection confined to the southern semicircle despite 
the otherwise symmetrical and expanding upper-level outflow pattern. 
More recently, some deep convection has developed near the center 
and the aforementioned possible mid-level eye feature. Hanna is 
forecast to remain in relatively low vertical wind shear regime and 
over SSTs of 30C or more, a combination that typically favors 
significant intensification. However, nearby dry mid-level air noted 
in 1200Z soundings from Corpus Christi and Brownsville has been 
eroding and preventing convection from developing in the northwest 
quadrant and near the center, which has inhibited strengthening over 
the past couple of days despite the low shear conditions. The latest 
global model guidance shows the dry air mixing out in about 24 h 
just prior to landfall, which should allow for at least gradual 
strengthening until landfall occurs in about 30 h or so. However, if 
an eyewall forms during the next 12 h, then it is possible that 
Hanna could be near 60 kt when it makes landfall. The new NHC 
intensity forecast is similar to the previous advisory, and is a 
blend of the IVCN and HCCA consensus intensity forecasts.


Key Messages

1. Hanna is forecast to strengthen and it is expected to
bring tropical-storm-force winds to portions of the Texas coast,
where a tropical storm warning is in effect.

2. Hanna is expected to produce heavy rains across portions of
southern Texas.  These rains could result in flash flooding and
isolated minor to moderate river flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 27.2N  93.2W   40 KT  45 MPH
 12H  25/0000Z 27.5N  94.6W   45 KT  50 MPH
 24H  25/1200Z 27.4N  96.2W   55 KT  65 MPH
 36H  26/0000Z 27.3N  97.6W   50 KT  60 MPH...INLAND
 48H  26/1200Z 27.0N  99.0W   35 KT  40 MPH...INLAND
 60H  27/0000Z 26.3N 100.4W   25 KT  30 MPH...INLAND
 72H  27/1200Z 25.7N 101.6W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  28/1200Z...DISSIPATED

$$
Forecaster Stewart

 

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There's not much wind in the core, and there won't be until robust convection refocuses over the center. Regarding the discussion a couple posts above, I was wonder if there might be some sinking air or something suppressing the north and west sides. I think the last few HWRF runs had Hanna finally getting its act together and ramping up beginning this afternoon/evening, so we'll see if that's right. 

 

That may very well be a byproduct of the vigorous lift associated with the persistent convection to the south. Intense convection not associated with the actual center is creating subsidence near to the LLC and MLC and all locations north of the system. Then again, not being fooled by the 300-200 hPa directional upper outflow, which should be very favorable, the 500-400 hPa flow may be forcing that area of subsidence / stable air and undercutting into the mid level vort of the present center of circulation. I suppose we'll just have to wait and see how this evolves this afternoon. The HWRF still wants to crank this vortex up in short order by this evening.

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The 6z GFS depiction of Hannah at this hr is uhm “off”. Not expecting globals to resolve canes well but it basically looks like an open wave at this hr on the 6z run. Looks like a completely different system. Sell the GFS and buy the cane models until initializations start to match what’s happening at/around T_0.  

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The core convection is still modest, but it's trying to wrap around the north side, and the cirrus shield is expanding north and west from the center.  It's a start.

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Yea that big convective burst overnight didn’t do as much for it as I thought it would. Figured realignment would be quick and easy with the low shear, guess not.

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Interesting feature probably of little importance. 

Some sort of a wave is moving west through the 91W contour. It is staying in line despite Hannah's circulation. 

DHskp2G.gif

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