ATL: HANNA - Remnants - Discussion

[Chemmers]

https://www.tropicaltidbits.com/sat/sat ... =ir-dvorak

Is it me or is this trying to become a hurricane as well

[GCANE]

A couple close-in towers firing with lightning.
One to the SW of the CoC, other to the east.

[GCANE]

That was a weird turn.. definitely defined circ.. why they are avoiding it.. idk lol

https://i.ibb.co/0YRFf2T/Capture.png

About two minutes ago, I was just thinking about the infamous "Back Up, Back Up" from Reed Timmer.

LLLLOOOOLLLL!!!!

It was a "Back Up, Back Up" after all

 https://twitter.com/JeremyDeHart53d/status/1286133293096808448





https://www.youtube.com/watch?v=ndngCGWrM-A

Apparently they had to switch planes which delayed recon.
If they went earlier as scheduled, likely this wouldn't have been tagged a TD then.

[GCANE]

X marks the CoC
ULL over the BoC and over FL.
Big TUTT NE of the Bahamas.
Afternoon popup thunderstorms over FL could erode the ULL over the state.
Would open the door for the TUTT to kick in a poleward outflow channel.
Stay tuned later today.

[xironman]

Very low shear, moist environment and warm water. If it organizes it ramp up pretty quickly, and it already looks much better this morning.

[GCANE]

Final Analysis from last night's recon.
Likely NHC waited for the analysis to complete and then tagged it a TD.
Subjectivity is taken out of the equation - smart.







The plots above were calculated using the plot below.





Aircraft-based Tropical Cyclone Surface Wind Analysis

This product, high resolution (top) and lower-resolution (middle), seeks to create a real-time and fully automated surface wind analysis system by combining the existing satellite-based six-hourly multi-platform tropical cyclone surface wind analysis (MTCSWA operational version) and aircraft reconnaissance data. This product applies an automated quality control procedure and variational analysis techniques developed for use in the MTCSWA and previous studies that make use of flight-level wind observations to produce analyses. The operational version of MTCSWA is used as a first guess field for aircraft reconnaissance wind data (flight-level and SFMR) that are be composited over a maximum of a 9-hour period of time and analyzed using data weights and smoothness constraints that are found to create an optimal analysis using those inputs. The center location will be determined using a combination of operational best track and aircraft-based center positions and detailed positions are determined by a tensioned cubic spline. Flight-level to surface wind reductions follow the operational rules developed by NHC following Franklin et al (2003) and as interpreted in Table 1 of Knaff et al. (2015) and the inflow angles are calculated using the parameterization developed in (Zhang and Uhlhorn 2012). Also following the findings of Franklin et al. (2003), asymmetries to the reduction factors are applied. The asymmetries consist of a four percent variation of the eyewall region reduction factors and a 17 percent variation of the outer and far field reduction factors with the maximum being on the left of TC motion. The resulting two-dimensional wind analysis would produce 1-minute sustained winds valid for 10-meter marine exposure in the region where aircraft reconnaissance is typically available (0-200km) with sufficient detail to resolve the radii of maximum winds and the wind radii. The maximum winds are still difficult to estimate as operational 30Hz data is used and there is a fundamental mismatch between surface SFMR winds and flight-level winds reduced to the surface, and at this time no attempt is made to determine the slant angle between flight-level winds and surface observations. This inner core is almost completely determined by aircraft input (lower figure provides aircraft coverage information) and the outer regions of the storm are determined by blending aircraft observations with the multi-platform tropical cyclone surface wind analysis (MTCSWA).

References:

Franklin, J. L., M. L. Black, and K. Valde, 2003: GPS dropwindsonde wind profiles in hurricanes and their operational implications. Wea. Forecasting, 18, 3244.

Knaff, J.A., S.P. Longmore, R.T. DeMaria, and D.A. Molenar, 2015: Improved tropical-cyclone flight-level wind estimates using routine infrared satellite reconnaissance. J. Appl. Meteor. Climat., 54:2, 463-478. doi: http://dx.doi.org/10.1175/JAMC-D-14-0112.1

Zhang, J.A., and E.W. Uhlhorn, 2012: Hurricane sea surface inflow angle and an observation-based parametric model. Mon. Wea. Rev., 140, 3587-3605. doi:10.1175/MWR-D-11-00339.1

[Aric Dunn]

umm if I were the NHC given it is under a building upper high.. low shear plenty of time over water scenario in the gulf.. ..

get those planes flying.. and put hurricane watches up ( just incase and despite the models we all know how this goes) .. especially looking at the convective patter this morning..

[Hurricane Mike]

umm if I were the NHC given it is under a building upper high.. low shear plenty of time over water scenario in the gulf.. ..

get those planes flying.. and put hurricane watches up ( just incase and despite the models we all know how this goes) .. especially looking at the convective patter this morning..

Yeah, I'm bullish on this one. I think it makes a run at hurricane before Texas.

[Chemmers]

Does anyone think the gfs and ecmwf intensity models will be way off from what the are predicting now

[Aric Dunn]

HMON brings it to 91kts at the 850 MB level.. and if it is anything like the HWRF those always translate to the surface.

[Aric Dunn]

Does anyone think the gfs and ecmwf intensity models will be way off from what the are predicting now

Yes.

[catskillfire51]

I thought there was supposed to be a recon mission this morning?

[Shell Mound]

 https://twitter.com/AndyHazelton/status/1286260142040850437



 https://twitter.com/webberweather/status/1286252086372573184



 https://twitter.com/TropicalTracker/status/1286265314720780297



 https://twitter.com/JackSillin/status/1286265420450803717

[Aric Dunn]

This buoy is just outside the convection to the west. pressure is already 1009 mb winds are 20 mph currently.

sourrouding surface obs have background pressures of 1011 to 1013.

mean the center under the middle of the convection is likely 1005mb or lower..

[wxman57]

It went right over the central Gulf buoy. Winds below 20 kts at the buoy. Closer to 15 kts. Ob just NW of center has NE at 15 kts. Center appears to be on west side of convection. Visible satellite will help. Recon would help, too.

[Nimbus]

Wind flip at buoy 42001 with a pressure of about 1008 mb's so at least its moving at the surface.
The high pressure dome means less likelyhood of dry undercutting shear from inland.
Also may mean a slower landfall with with big QPF changes needed.
Winds are only like 20-30 knots atm but Sunday morning?

[Aric Dunn]

Wind flip at buoy 42001 with a pressure of about 1008 mb's so at least its moving at the surface.
The high pressure dome means less likelyhood of dry undercutting shear from inland.
Also may mean a slower landfall with with big QPF changes needed.
Winds are only like 20-30 knots atm but Sunday morning?

Yeah HMON and HWRF have it slowing down a good deal as it approaches the coast.

[wxman57]

Nearly visible imagery now. Center is on the west side of convection. Wind all around center about 15 kts.

[Jr0d]

Looking much better this morning. Surprised the winds have not picked up given some of the squalls when it was an invest produced tropical storm conditions.

[Aric Dunn]

just roughly following some of the curved low level cloudlines.

center is about right there with some fresh towers building up around it.