ATL: ARTHUR - Post-Tropical

[wxman57]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

There will also be a butt-load of shear (technical met term) north of the OB if the center tracks that way. Could see some low-end TS winds across OB Monday. Big low developing inland next week will have more of an impact north of the OB.

[Aric Dunn]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

dont jump to quick on that..

they all initialized this down by miami and west palm. it is currently about 12 + hours faster than Euro..

SC/NC border to hatteras or offshore are still very much in play.

[chaser1]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

I think it's premature to assume that Arthur will have no measurable impact to the U.S. coastline. Timing and track forecast will be better tuned once a better defined COC is determined. A measurable impact could occur without a direct landfall.

[ScottNAtlanta]

How many years has there been an Atlantic "A" storm before the EPAC?

[Shell Mound]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

I think it's premature to assume that Arthur will have no measurable impact to the U.S. coastline. Timing and track forecast will be better tuned once a better defined COC is determined. A measurable impact could occur without a direct landfall.

As wxman57 mentioned, any “measurable impact” would more probably be attributable to the developing extratropical system rather than Arthur itself.

[plasticup]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

n = 1

[GCANE]

Looks like recon packed it up and heading back for a beer.

[Shell Mound]

Despite recent “underperformance,” the ECMWF still correlates far better (92.2%) with the H5 pattern than the GFS (90.1%) and Canadian (89.2%).
 https://twitter.com/VBryan_wx/status/1260554840931008513

[GCANE]

[chaser1]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

I think it's premature to assume that Arthur will have no measurable impact to the U.S. coastline. Timing and track forecast will be better tuned once a better defined COC is determined. A measurable impact could occur without a direct landfall.

As wxman57 mentioned, any “measurable impact” would more probably be attributable to the developing extratropical system rather than Arthur itself.

Incorrect. Wxman made a reference to potential upper level shear as Arthur were to reach the OB latitude. He also made a reference to a developing CONUS low that could potentially impact the OB with strong winds sometime during the week. I think the timing of either is a bit early to assume exactly how strong Arthur might get prior to reaching that latitude and too early to guess when it will begin to transition into an extra-tropical low. Besides, a transitioning tropical to extra-tropical low could just as well deepen and would certainly result in an expanding wind-field.

[GCANE]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 16th day of the month at 17:42Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF97-5303
Mission Purpose: Investigate first suspect area (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 13 ( See all messages of this type for this mission. )

A. Time of Center Fix: 16th day of the month at 17:12:10Z
B. Center Fix Coordinates: 27.98N 78.75W
B. Center Fix Location: 115 statute miles (185 km) to the E (95°) from Melbourne, FL, USA.
C. Minimum Height at Standard Level: Not Available
D. Minimum Sea Level Pressure: 1008mb (29.77 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: 34kts (39.1mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 10 nautical miles (12 statute miles) to the ENE (62°) of center fix at 17:08:30Z
J. Maximum Flight Level Wind Inbound: From 54° at 30kts (From the NE at 34.5mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 12 nautical miles (14 statute miles) to the NNW (336°) of center fix at 16:59:30Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 33kts (38.0mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 7 nautical miles to the W (276°) of center fix at 17:14:30Z
N. Maximum Flight Level Wind Outbound: From 338° at 12kts (From the NNW at 13.8mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 7 nautical miles to the W (276°) of center fix at 17:14:30Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 22°C (72°F) at a pressure alt. of 187m (614ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 23°C (73°F) at a pressure alt. of 192m (630ft)
R. Dewpoint Temp & Sea Surface Temp: Not Available
S. Fix Determined By: Penetration, Wind, Pressure and Temperature
S. Fix Level: 1,500 feet
T. Navigational Fix Accuracy: 0.02 nautical miles
T. Meteorological Accuracy: 6 nautical miles

Remarks Section:

Maximum Flight Level Wind: 30kts (~ 34.5mph) which was observed 12 nautical miles (14 statute miles) to the NNW (336°) from the flight level center at 16:59:30Z
Sea Level Pressure Extrapolation From: Below 1500 feet

[OuterBanker]

While this is certainly going to become TS Arthur, it is highly unlikely to deliver any measurable impacts to the Carolinas or Mid-Atlantic states. The most reliable of the dynamically based models—the UKMET, the EC suite, and the consensus models—show Arthur curving eastward well to the east of the Outer Banks. Only the GFS-based guidance takes this system into the U.S. Recall that the GFS-based guidance falsely forecast Joaquin (2015) to reiterate Sandy (2012) and strike the Mid-Atlantic, while the UKMET and EC consistently and correctly showed a track offshore, well to the east and southeast.

Better check the 06z Euro. Now only 20 miles east of hatteras. Also at 995mb as against 1003 from gfs.

[Aric Dunn]

I think it's premature to assume that Arthur will have no measurable impact to the U.S. coastline. Timing and track forecast will be better tuned once a better defined COC is determined. A measurable impact could occur without a direct landfall.

As wxman57 mentioned, any “measurable impact” would more probably be attributable to the developing extratropical system rather than Arthur itself.

Incorrect. Wxman made a reference to potential upper level shear as Arthur were to reach the OB latitude. He also made a reference to a developing CONUS low that could potentially impact the OB with strong winds sometime during the week. I think the timing of either is a bit early to assume exactly how strong Arthur might get prior to reaching that latitude and too early to guess when it will begin to transition into an extra-tropical low. Besides, a transitioning tropical to extra-tropical low could just as well deepen and would certainly result in an expanding wind-field.

agreed..

that and the system is 12 hours faster than the previous runs of the euro and UK met.

next couple runs should be interesting.

[chaser1]

https://i.imgur.com/zQexH7H.png

Nice graphic. Battling vort centers. This will eventually resolve itself but perhaps one more reason why NHC is not too quick on pulling the 'Arthur switch". Still, i'd say it seems generally reasonable for this to be upgraded to a T.D.

[NDG]

Despite recent “underperformance,” the ECMWF still correlates far better (92.2%) with the H5 pattern than the GFS (90.1%) and Canadian (89.2%).
https://twitter.com/VBryan_wx/status/1260554840931008513

The Euro has definitely not performed too well the last few weeks, I count at least 4 times that it has under performed the GFS, they say the lack of data collected from commercial flights.

[wxman57]

I think that the faster it tracks, the more likely it turns NE after passing the OB. Less time for the digging trof to the west to make it "pull a Sandy". 18Z NHC outlook issued - advisories may be started later today as a TD or STD.

[drezee]

NHC says no thank you. It is Saturday and no threat. We are short staffed and do no want to write full advisories. I cannot recall two vortex messages on a tropical wave...one yes

Data from the Air Force Hurricane Hunters and satellite images
indicate that the low pressure system located just off the coast of
east-central Florida has become better defined today. In addition,
the associated showers and thunderstorms continue to gradually
organize. If these trends continues, advisories will likely be
initiated on this system as a tropical or subtropical depression
later today

[Aric Dunn]

Looks like it went a little too far north too fast..

ran back into some of that mid level shear.

[wxman57]

12Z EC takes it about 100-120nm east of the OB Monday then out to sea.

[Dylan]

 https://twitter.com/dylanfedericowx/status/1261722514977435649