09L Advisories

...Humberto now extratropical, racing towards the United Kingdom...


Advisory 8


1-minute sustained wind: 85 knots; 100 mph; 155 km/hEstimated minimum pressure: 965 mbCurrent position: 39.2N 58.4W

Discussion

No scientific discussion was written for this advisory. This advisory is based off of ATCF input.

Forecaster ID

MCK

Advisory Archive

Below is an archive of previous advisories for 09L..

...Humberto raking Bermuda while turning extratropical...


Advisory 7A

03Z/August 19


1-minute sustained wind: 110 knots; 125 mph; 205 km/hEstimated minimum pressure: 951 mbCurrent position: 33.9N 64.0W

Discussion

The purpose of this update is to discuss new recon data, as well as retrospective data from the Bermuda landfall. Reconnaissance data found a peak SFMR of 113 knots with a peak flight-level wind of 122 knots in the RMW. A peak gust from Bermuda, which was somewhere in the outer portion of the eyewall, was around 115 knots, which adjusts to 92 knots based on the standard gust-to-sustained wind ratio. Readjustments based on the Schloemer Equation with the newer dropsonde data suggests that peak winds during Humberto's closest pass to Bermuda was likely 115 knots, based on the fact that Humberto's wind field has expanded despite the pressure being steady. Based primarily on these trends, Humberto is estimated as having winds of 110 knots at this time.

Forecaster ID

MCK

Advisory 7


1-minute sustained wind: 95 knots; 110 mph; 175 km/hEstimated minimum pressure: 951 mbCurrent position: 33.2N 65.0W

Discussion

Humberto is currently moving northeast, just past the island of Bermuda. Recent satellite images, as well as weather station data as far west as New Jersey, are suggesting that Humberto's wind field is expanding in accordance with typical extratropical transition processes. Microwave data is depicting a rain-shield appearance that is more typical of nor'easters, and model synthesis of Humberto is suggesting that it is now connecting directly with a trough. The last piece of Bermuda radar data suggests that the eyewall had opened up, and most rainfall is beginning to migrate towards the poleward section of the cyclone.
The latest pass by a reconnaissance mission was at 1438z, in which flight-level winds of 120 knots was recorded, with a peak SFMR of 101 knots. Averaging these values after adjustments results in a 105 knot estimate for that time. There were reports of gusts of 104 miles per hour (90 knots) on Bermuda. Based on this as well as the trend in satellite appearance, Humberto is being estimated as a 95-knot hurricane. Do note that the pressure is expected to remain mostly constant, or even deepen, which will likely result in an expansion of the wind field despite the peak winds decreasing.

Forecaster ID

MCK

...Humberto now a major hurricane...


Advisory 6


1-minute sustained wind: 100 knots; 115 mph; 185 km/hEstimated minimum pressure: 951 mbCurrent position: 31.2N 71.6W

Discussion

Humberto continues to show signs of increasing orgnanization and strengthening convection, with a ring of sub-70C cloud tops now mostly encircling the eye completely. Reconnaissance data has found SFMRs of 100 knots, with flight-level winds of 105 knots in the flight-level in the northwest eyewall. At this intensity, SFMRs are still deemed as mostly accurate, so that will be the value used for this advisory.
It should be noted that the windfield is significantly larger. Effects such as gale-force winds and heavy surf are more likely to affect the United States, even if Humberto is forecast to continue moving further east.

Forecaster ID

MCK

...Humberto strengthens into a hurricane...


Advisory 5


1-minute sustained wind: 65 knots; 75 mph; 120 km/hEstimated minimum pressure: 967 mbCurrent position: 30.2N 75.4W

Discussion

Humberto now has a fairly clearly-defined eye feature surrounded by modest cloud tops, with a much-expanded windfield evident on reconnaissance data. This windfield is mostly as a result of an ongoing eyewall replacement cycle, evident on microwave as well as on the reconnaissance data. Flight-level winds have peaked at around 75 knots (reducing to 68 knots), with SFMRs peaking at 65 knots. A dropsonde found winds of 70 knots in the lowest 150 gpm, which reduces to around 60 knots. Based on this data, Humberto is now a minimal hurricane.
It should be noted that the windfield is significantly larger. Effects such as gale-force winds and heavy surf are more likely to affect the United States, even if Humberto is forecast to continue moving further east.

Forecaster ID

MCK

...Humberto almost a hurricane...


Advisory 4


1-minute sustained wind: 60 knots; 70 mph; 110 km/hEstimated minimum pressure: 988 mbCurrent position: 29.1N 77.9W

Discussion

Humberto continues to organize, now displaying quite flaring convection in a curveband pattern with a 100% banding around the center. With Dvorak IR adjustments, this suggests T4/65 knots, which is fairly in line with the reconnaissance data, which has found flight-level winds of 70 knots, and SFMRs peaking at 54 knots. Averaging all of this data creates an intensity estimate of 60 knots, just shy of hurricane-strength.
Most models currently suggest that Humberto will move eastward rapidly in response to a trough encroaching from the west. As such, Humberto will likely not be a danger to the East Coast, though it will likely give adverse effects to Bermuda.

Forecaster ID

MCK

...Tropical depression strengthening a bit...

Probabilities

INIT 00Z/SEP15 27.6N 77.3W 45KT 50MPH12HR 12Z/SEP15 28.6N 77.8W 55KT 65MPH24HR 00Z/SEP16 29.7N 77.7W 65KT 75MPH36HR 12Z/SEP16 30.6N 76.9W 70KT 80MPH48HR 00Z/SEP17 31.2N 75.4W 70KT 80MPH72HR 00Z/SEP18 31.8N 75.2W 85KT 100MPH96HR 00Z/SEP19 32.8N 70.7W 90KT 105MPH120H 00Z/SEP20 34.1N 65.1W 85KT 100MPH

Advisory 3


1-minute sustained wind: 45 knots; 50 mph; 85 km/hEstimated minimum pressure: 1003 mbCurrent position: 27.6N 77.3W

Public Advisory

09L (Humberto) is currently moving northwest at 6 knots, or 7 miles per hour, with a measured minimum pressure of 1003 millibars and a maximum sustained wind of 45 knots, or 50 miles per hour. 09L is expected to continue northwest until about 48 hours from now, in which it will turn eastward towards Bermuda. Chances for direct impacts to the Southeast are decreasing based on latest model trends.
This is the last full advisory for Humberto based on the lessening chance of impacts on the United States. Status updates will be posted here on the TCD website.

Scientific Discussion

Humberto's structure shows increasing signs of organization, with the banding feature becoming more pronounced with some stronger convection. Recon aircraft found a 50 knot SFMR, though there was a 45 knot SFMR adjacent to it that was suspect, thus it is not particularly being used for this advisory, and thus I am holding the intensity at 45 knots.
The track forecast reasoning has not changed much since yesterday, thus I will only discuss the philosophy behind the intensity forecast. The slow movement from FH24-48 should limit strengthening as a result of cold-water upwelling, though with the predicted strength combined with the position over the Gulf Stream, this is not expected to be a significant inhibitor. Beyond FH48, Humberto will intensify as it enters a favorable area with a boost in upper-level divergence, and extratropical transition is expected to take place somewhere after forecast hour 96 or 120. The forecast rides near the upper edge of the model intensity guidance, and exceeds it on a few locations.

Forecaster ID

MCK

...Tropical depression strengthening a bit...

Probabilities

INIT 00Z/SEP14 25.6N 74.8W 30KT 35MPH12HR 12Z/SEP14 26.6N 76.0W 35KT 40MPH24HR 00Z/SEP15 27.7N 77.1W 40KT 45MPH36HR 12Z/SEP15 28.9N 78.4W 45KT 50MPH48HR 00Z/SEP16 29.0N 78.2W 50KT 60MPH72HR 00Z/SEP17 31.8N 75.2W 65KT 75MPH96HR 00Z/SEP18 32.8N 70.7W 75KT 85MPH120H 00Z/SEP19 34.1N 65.1W 80KT 90MPH

Advisory 2


1-minute sustained wind: 30 knots; 35 mph; 55 km/hEstimated minimum pressure: 1008 mbCurrent position: 25.6N 74.8W

Public Advisory

09L is currently moving northwest at 7 knots, or 8 miles per hour, with a measured minimum pressure of 1008 millibars and a maximum sustained wind of 30 knots, or 35 miles per hour. 09L is expected to continue northwest until about 48 hours from now, in which it will turn eastward towards Bermuda. There is the chance of tropical-storm force winds making it to a few coastlines in the Southeast.

Scientific Discussion

A recon plane has investigated 09L for the past few hours, with a 4/10 banding pattern that suggests T2.0, or 30 knots. This is fully in line with SFMR data measuring 30 knots. A dropsonde has recorded 1008 mb, and given the storm's fairly weak circulation, this is the value being used for the advisory.
Currently, 09L is not in an ideal location for strengthening due to moderate shear. However, within the next 24 hours, shear will abate enough to allow strengthening. The HMON, CTCX, and HWRF models are suggesting a peak of at least 90 knots beyond the short-term, while global models are remaining conservative with the intensity predictions. The track forecast mostly follows the consensus, in which a weakness in the ridge steers the system towards the northwest, before a trough picks up the storm and drags it towards the east.

Forecaster ID

MCK

...Tropical wave organizing...

Probabilities

Chance of tropical cyclone formation within 24 hours: 70%Chance of tropical cyclone formation within 48 hours: 80%Chance of tropical cyclone formation within 72 hours: 95%

Advisory 1


1-minute sustained wind: 25 knots; 30 mph; 45 km/hEstimated minimum pressure: 1008 mbCurrent position: 23.7N 74.8W

Discussion

The National Hurricane Center has classified a new potential tropical cyclone as PTC 09, currently a tropical wave that is stationary over the southeastern Bahamas. TCD analysis suggests that tropical cyclogenesis is likely in the next 48 hours.
Currently model guidance suggests that 09L will move towards Florida, potentially making landfall there. However, the center is very ill-defined, and is not clear enough for TCD to initiate full advisories.
If tropical cyclogenesis completes, GWES-TCD will begin issuing full advisories.
Chance of tropical cyclone formation within 48 hours: 80%

Forecaster ID

MCK