ATL: FRANKLIN - Remnants - Discussion

[Alyono]

HWRF comes in dramatically weaker. Meanwhile, HMON comes in quite a bit stronger. GFS based guidance is going to likely struggle big time this year due to the model "upgrade"

[Alyono]

I see the GFS issue. It is trying to increase the shear significantly in the Bay of Campeche. Below is the SHIPS output. Of course, it has the shear doubling during the next few hours when it is decreasing, so GFS likely has no clue in the world. Waiting for the EC to get a real forecast

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 35 38 41 44 49 57 66 76 78 69 63 65 67
V (KT) LAND 35 38 41 44 49 34 38 49 51 42 31 28 27
V (KT) LGEM 35 38 40 43 46 33 36 44 50 50 35 DIS DIS
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP N/A N/A

SHEAR (KT) 7 14 16 7 5 7 4 14 19 17 7 N/A N/A
SHEAR ADJ (KT) 0 -3 -3 -1 -2 -2 -1 -3 -3 0 8 N/A N/A
SHEAR DIR 253 258 270 281 216 313 80 358 336 8 26 N/A N/A
SST (C) 29.1 29.4 29.7 29.8 29.7 29.7 29.7 29.8 29.4 29.0 29.1 N/A N/A

[wxmann_91]

HWRF comes in dramatically weaker. Meanwhile, HMON comes in quite a bit stronger. GFS based guidance is going to likely struggle big time this year due to the model "upgrade"

The GFS is complete crap TC-strength wise but I'd like to see the Euro before completely discounting the trend. The GFS is still decent with upper-air features and I wouldn't be surprised if the sprawling upper ridge to Franklin's NW induces some northerly shear to keep Franklin from RI'ing in the GOM.

[latitude_20]

Hoping you can see this. This was our view on the beach today, looking east over the Caribbean before we have to batten down the hatches.

[Digital-TC-Chaser]

[Alyono]

EC down to 998-997mb at Yucatan landfall

[Alyono]

ASCAT just passed over Franklin. It is a wave according to ASCAT, with the greatest turning down at 16N

Models have not initialized too far south

[Alyono]

EC has 987mb around the time of final landfall. Weaker than its previous run

[Digital-TC-Chaser]

EC 00z Intensify's in the BOC when the the TC is a better environment with high cape and -neg 8 lift values unstable.

[Aric Dunn]

ASCAT just passed over Franklin. It is a wave according to ASCAT, with the greatest turning down at 16N

Models have not initialized too far south

I have it at 16.71°N 83.52° W

The 18z models initialized it well SE and east. 00z seem about right.. at least reasonable. At this point its close enough.

ASCAT showing an open wave not surprising given the southern portion and any major west winds would be over land.

[Hammy]

ASCAT just passed over Franklin. It is a wave according to ASCAT, with the greatest turning down at 16N

Models have not initialized too far south

I have it at 16.71°N 83.52° W

The 18z models initialized it well SE and east. 00z seem about right.. at least reasonable. At this point its close enough.

ASCAT showing an open wave not surprising given the southern portion and any major west winds would be over land.

Given the curvature it looks like it was still open at the time it was upgraded, but the winds to the south were light and it's pretty clear that the low cloud motion offshore is west to east. Convection is continuing to build, and outflow is expanding further west as well. This could be quite a bit stronger tomorrow when the plane gets there.

[Aric Dunn]

ASCAT just passed over Franklin. It is a wave according to ASCAT, with the greatest turning down at 16N

Models have not initialized too far south

I have it at 16.71°N 83.52° W

The 18z models initialized it well SE and east. 00z seem about right.. at least reasonable. At this point its close enough.




ASCAT showing an open wave not surprising given the southern portion and any major west winds would be over land.

Given the curvature it looks like it was still open at the time it was upgraded, but the winds to the south were light and it's pretty clear that the low cloud motion offshore is west to east. Convection is continuing to build, and outflow is expanding further west as well. This could be quite a bit stronger tomorrow when the plane gets there.

doubful on the open wave. it may not have been expansive in terms of the west winds there was more than enough data to support a closed circ prior to sunset. we also know how localized those west winds can be countless times recon will find the west winds while surface and ascat data wont.

But yeah, its current trends are leaning towards a much more organized system and stronger before YP. I would wager recon finds 50 to 60 by the time they get there. hurricane before YP is not out the question,

[Sciencerocks]

[Aric Dunn]

Hurricane Watch issued.. definately not surprised given the rate of orginizatoin that is happening.

I was thinking recon finds 50 to 60 mph .. but could be hgher.

[Sciencerocks]

000
WTNT42 KNHC 070849
TCDAT2

Tropical Storm Franklin Discussion Number 3
NWS National Hurricane Center Miami FL AL072017
500 AM EDT Mon Aug 07 2017

Deep convection associated with Franklin has been steadily
increasing in both coverage and vertical depth since the previous
advisory. Wind data from a late-arriving 0231Z ASCAT-A pass suggest
that Franklin might not have had a closed surface circulation at
that time. However, the new GOES-16 nighttime microphysics imagery
clearly shows low clouds moving from west to east on the south side
of the alleged center, which is suggestive of a closed low-level
circulation. The intensity has been nudged upward to 40 kt based on
sustained winds of 39 kt measured at 4-meters elevation from NOAA
buoy 42057 located about 110 nmi east of the center.

The initial motion estimate is 300/12 kt. The latest NHC model
guidance remains in excellent agreement that Franklin will continue
to move west-northwestward along the south side of a deep-layer
ridge during the next 48 hours or so, making landfall along the
east coast of the Yucatan peninsula in 18-24 hours. After the
cyclone crosses over Yucatan and moves into the Bay of Campeche by
Wednesday, a more westward motion is expected thereafter as the
ridge currently situated over northern Mexico and the southwestern
U.S. builds southward. The track model guidance is tightly clustered
around the previous forecast track, so the new forecast track is
just an extension of the previous one and lies down the middle of
the guidance envelope.

Upper-level outflow continues to expand in the western semicircle,
and a pronounced poleward outflow channel has developed in the
northern semicircle, which is being aided by a large upper-level low
located north of Puerto Rico. Although UW-CIMSS wind analyses
indicate that modest westerly mid-level shear is still affecting the
cyclone, that hindrance is forecast to abate in another 6 h or so.
Both the GFS and ECMWF models are forecasting the deep-layer and
mid-level shear to decrease to near zero in the 12-24 h period,
suggesting that Franklin could undergo a period of rapid
intensification right up until landfall occurs. Unfortunately, the
official intensity forecast does not directly reflect that possible
intensification trend due to the 24-h position being inland over
Yucatan with weakening occuring at that time due to land
interaction. Franklin is likely to reach a peak intensity of about
60 kt or so prior to landfall, and for that reason the government of
Mexico has issued a Hurricane Watch. The cyclone will weaken some as
it moves over the Yucatan, but re-strengthening is expected after
Franklin emerges over the very warm waters of the Bay of Campeche in
the 48-72 h period. The NHC intensity forecast remains close to the
higher SHIPS guidance at 24 hours, and is near the IVCN and HCCA
consensus models after that time.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 17.1N 84.2W 40 KT 45 MPH
12H 07/1800Z 18.0N 85.8W 50 KT 60 MPH
24H 08/0600Z 19.0N 88.0W 55 KT 65 MPH...INLAND
36H 08/1800Z 19.9N 90.2W 40 KT 45 MPH...INLAND
48H 09/0600Z 20.4N 92.3W 45 KT 50 MPH...OVER WATER
72H 10/0600Z 21.0N 96.4W 55 KT 65 MPH
96H 11/0600Z 21.1N 100.5W 25 KT 30 MPH...INLAND
120H 12/0600Z...DISSIPATED

$$
Forecaster Stewart

[Aric Dunn]

Very good discussion ....AS Suspected ASCAT likely had some issues with the westerly flow being so near land.

[Aric Dunn]

Looking closely at the convective pattern.. There are some signs of early banding and a long curved band wrapping around the center. like Stewart mentioned some RI maybe occuring or about to happen.

[Aric Dunn]

Also starting to come into radar range.

[Aric Dunn]

Also here is a good composite radar loop. its becoming organized quite rapidily.
http://barbadosweather.org/Composite/ki ... site=Sabre

sheesh maybe approaching hurricane strength by the time recon gets there at this rate..
and another view

[GCANE]

Looking at TPW and the other levels, it appears the vort is located primarily above the boundary layer to about 500mb.
So, Franklin may make it across the Yucatan relatively unscathed.
BOC may get it cranking.