Thunder44's Helene 8am Thurs Forecast: Turns North/Weakens

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products

8am Mon Forecast: Helene Now a Major Hurricane

Discussion:

As of the 5am Advisory, the NHC placed the center of Hurricane Helene at 22.3 N 49.6W and now moving to the NNW at 7mph. Maximum sustained winds have increased to 105kts and the minimum pressure is at 958mb.

Helene is now a major Cat 3 hurricane. It winds increased to 100kts last night and has continued to intensify to 105kts early this morning. The storm is getting good outflow from all quadrants, except the SW Quad, and it upper-level winds and sea surface temps, appear favorable for some additional strenghtening for the next 36hrs or so. I will now forecast a peak intensity of 120kts by 36hrs, making this a Cat 4 hurricane. Afterwards, upper-level winds will become less favorable for strenghtening and it will be moving over slightly cooler waters in 4 or 5 days. I expect gradual weakening up to 96hrs, then perhaps some fluctuations in intensity afterwards.

The intensity forecast also assumes that Helene follows my current forecast track, which is still remains very uncertain this morning. The storm took an unexpected movement to the NNW overnight and it forced me to adjust my track little further north the first 72hrs. This movement should be temporary, and it should resume a NW movement later this morning, then turn WNW this afternoon as the ridge builds to the north of the storm. After 72hrs there still remains much disagreement amongst the models on where Helen will go. The GFS shifted much farther east overnight, and now turns the storm slowly north and moves it SE of Bermuda by 5 days. the 0z ECMWF still turns the storm north but it’s little further west and slower, while the other models showed little change. However, only the UKMET and NOGAPS show going further south and west Bermuda, and this is a little less likely now with Helene gaining some latitude this morning. Still they can’t be discarded as they may have a better handle on the subtropical ridge building further west, then the GFS and the other models often do not.

Nevertheless the forecast track will be remain much further north of the models and it will be a little to the left GFS and ECMWF and also the global model consensus. I expect Helene to the NNW after 72hrs, and by 120hrs to slow down it’s forward speed to less than 5mph.

Forecast Points and Intensity:

Initial 22.3N 49.6W 105kts
12hrs 23.1N 50.8W 110kts
24hrs 23.4N 53.5W 115kts
36hrs 23.4N 53.5W 120kts
48hrs 23.7N 54.8W 110kts
72hrs 24.5N 57.4W 110kts
96hrs 27.5N 59.5W 100kts
120hrs 30.5N 60.5W 100kts

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products

8pm Forecast: Forecast to Recurve

Discussion:

As of the 5am Advisory, the NHC placed the center of Hurricane Helene at currently at 23.9N 51.W and is moving to the WNW at 8kts. Maximum sustained winds are at 115mph and the minimum central pressure is 960mb.

A NOAA Research plane investigating Helene today found the storm to be weaker then earlier estimates of 105kts to 110kts. I don’t know if there was some weakening today or if satellite estimates were too high, but Helene has had a healthy appearance on satellite imagery today and upper-level winds are still favorable for addition strenghtening. It appears late this evening that storm is getting stronger on satellite imagery, as the eye has been shrinking and cloud tops have cooled over the eyewall. I still forecast Helene to peak at Cat 4 strength during the next 24 hours, but I lowered the intensity slightly to 115kts (135mph). Afterwards the storm should gradually weaken as upper-level shear increases from a large trough in the Western Atlantic and then eventually moves over cooler waters.

The good news this afternoon is that the global models have come into much better agreement and all now forecast Helene to recurve out into the North Atlantic by 5 days. Over the next 36hrs, Helene is expected to move westward, as the ridge builds back north of the system. Afterwards, a large-deep layer trough will start to erode this ridge, and force to gradually turn north than NE. All models now track keep the system east of 60W, with the NOGAPS being the closest at turning the storm north around 59W. The models also move the storm much faster then previous runs. My forecast track has been shifted to the right and is faster, but will be slower and to the left of most of the model guidance and the CONU and resemble the NOGAPS solution for now. Not because I favor that solution, but I don’t shift too far west yet, in case the models shift back west again tonight. However, at this time, it looks unlikely that Helene will come very close to Bermuda in the 3 to 5 days and even more unlikely to be a threat to the US Mainland.

I will have another forecast out tomorrow morning.

Forecast Points and Intensity:

Initial 23.9N 51.1W 100kt
12hrs 24.5N 53.0W 110kt
24hrs 24.6N 55.0W 115kt
36hrs 25.3N 56.8W 105kt
48hrs 27.3N 57.8W 100kt
72hrs 30.0N 59.0W 90kt
96hrs 34.0N 59.0W 80kt
120hrs 40.5N 55.0W 65kt

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products

8am Tues Forecast: Helene Going Out to Sea

Discussion:

As of the 5am Advisory, the NHC placed the center of Hurricane Helene currently at 24.4.N 52.1W and is moving to the WNW at 7kts. Maximum sustained winds remain at 100kts and mininimum central pressure is at 960mb.

The models are still in good agreement this morning on a recurvative out to sea by 5 days. The CMC and it’s ensembles, shifted a little further west with it’s track but all the models and the GFS ensembles still have the storm turning before reaching 60W. A 9z CIMSS layer-mean analysis this morning shows a weakness in ridge between 56W and 59W, being caused by a upper-level trough over the Western Atlantic. Therefore I am more confident of a sharper recurvature this morning and my forecast track will be shift farther to right to be closer the latest CONU and NHC tracks. Helene should move to the W or WNW for the next day or so, than turn north and than NE and out into North-Central Atlantic within five days, well east of Bermuda.

Helene had an elongated north to south appearance and apparently did not intensify overnight. She has about another 24hrs to intensify, before upper-level wind shear increases. Satellite imagery this morning shows that she has a more circular appearance again. So I still expect her to intensify to a Cat 4 hurricane with winds of 115kts (135mph). After 24 hours she would gradually weaken through through 48hrs, then some flucations in intensity could occur until 96hrs, than weakening at faster rate, as she moves over cooler waters. The intensity forecast is close to the latest SHIPS forecast, except somewhat higher through 36hrs.


Forecast Points and Intensity:


Initial 24.4N 52.1W 100kts
12hrs 24.8N 54.0W 110kts
24hrs 25.4N 55.2W 115kts
36hrs 26.6N 53.6W 115kts
48hrs 28.5N 57.0W 100kts
72hrs 33.5N 54.0W 100kts
96hrs 38.0N 51.5W 85kts
120hrs 44.0N 41.5W 65kts

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products

8pm Forecast: Helene Not Strenghtening

As of 5pm Advisory today, the HPC placed the center of Hurricane Helene currently at 24.6N 54.1W and is moving toward the WNW at 8kts. Maximum sustained winds have decreased to 95kts and the minimum central pressure is at 956mb.

Hurricane Helene is now a Category 2 storm. She has looked more impressive on satellite imagery than what a NOAA research plane found the last couple days. Today found the storm to be have winds closer 95kts, but they also found a lower pressure at 956mb. My guess is that Helene is near her peak intensity and has had flucations in intensity. But we will probably never truly know her peak intensity since the plane is not there 24/7 and surface obs are scarce in that part of the Atlantic.

That being said Helene is looking better tonight than earlier. I’ve said that before but the plane always seems to find a weaker system. So given that I think Helene has 12hrs or so to strengthen, until upper-level winds become a somewhat less favorable for strenghtening. In that time, she can become a Cat 3 hurricane again, but I will no longer forecast a Cat 4 intensity, since Helene doesn’t seem to want to intensity much. After 36hrs, Helene will begin to weaken at a faster rate, as she moves over first cooler than colder waters in the open waters of the North Atlantic. By 120hrs, she is expected to become extratropical.

Helene has made some wobbles today to the west and SW and the forecast track has been adjusted for this for the first 24hrs. Otherwise the forecast reasoning has not changed here. All the models remain consistent in recurving Helene before 60W and quickly out into open waters of North Atlantic and I see no reason to doubt them. Helene should begin her north turn tomorrow and should remain far enough from Bermuda to not impact them with anything other than high surf and swells. The forecast track has remains close to the CONU and close to the NHC track as well.

I will have another forecast out tomorrow morning.

Forecast Points and Intensity:

Initial 24.6N 54.1W 95kt
12hrs 26.0N 55.5W 105kt
24hrs 27.7N 56.5W 105kt
36hrs 31.8N 55.0W 105kt
48hrs 36.9N 52.2W 85kt
72hhrs 40.8N 47.2W 75kt
96hrs 44.0N 41.2W 65kt
120hrs 48.0N 32.5W 65kt...Extratropical

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products.

8am Wed Forecast: Helene Turns NW

As of the 5am Advisory, the NHC placed the center of Hurricane Helene at 25.3N 55.4W is now moving to the NW at 8kts. Maximum sustained are at 95kts and the pressure is at 958mb.

Helene has turned NW west this morning, as expected. And she turn north than NE the next couple days. The models still remain in agreement for recurvative before 60W. The synoptic reasoning for this track has already been discussed in previous discussions and no longer needs to be repeated as long Helene remains on forecast. There are no changes to the forecast track expect to the forecast point real times. The forecast track remains close to the latest CONU and the NHC tracks.

Helene has not strengthened over and on the latest satellite images it appears to have weakened as the eye has become cloud filled and there is some erosion of the convection on the southwest side. So it may be going under an eyewall replacement cycle. Which may mean a intensification phase could start later today. However it’s difficult to forecast how long these cycles will last, if there was on actually occurring here. I don’t expect much strengthening, due to increasing shear, and there will probably be flucations in intensity, but the forecast will assume strenghten today and will increase in intensity of 105kts through 36hrs. Then weakening will be shown as Helene it races off into cooler waters of the North Atlantic. Helene is expected become extratropical at the end of the forecast period. The forecast intensity after 36hrs follows the 6z SHIPS closely.

I will have another forecast out sometime this evening.

Forecast Points and Intensity:

Initial 25.3N 55.4W 95kts
12hrs 27.0W 56.6W 105kts
24hrs 29.1N 56.5W 105kts
36hrs 31.8N 55.0W 105kts
48hrs 36.9N 52.2W 95kts
72hrs 44.1N 41.2W 85kts
96hrs 48.6N 31.2W 70kts
120hrs 51.4N 22.0W 65kts...Extratropical

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products.

8pm Wed Forecast: Helene Weaker and No Threat to Land

As of the 5pm Advisory today, the NHC placed the center of Hurricane Helene currently at 26.6N 57.1W and is moving to the NW at 8kts. Maximum sustained winds are at 90kts and the pressure is at 960mb.

Helene did not strengthen today and maybe a little weaker, than currently estimated. The eye has not been seen on visible or infrared satellite images since last night, although the storm has excellent outflow on all quadrants. A NOAA Research plane investigating the storm today found a higher pressure of 960mb and the eyewall to be poorly defined and with a large windfield. This all leads me to believe that Helene is having trouble organzining it’s inner core. Therefore, there will probably only be no significant change in strength before the upper and mid-level shear increases again in about 24hrs or so. The intensity forecast maintains the current intensity through 24hrs and then shows weakening through 72hrs. By 96hrs, Helene will be moving over much colder waters and become a large and powerful extratropical storm over the North Central Atlantic.

The models are still in agreement in recurvature and are now more clustered for a north turn later tonight with Helene, near 57.5W and racing out to sea. The forecast track has been adjusted further to the left, but still takes it well away from Bermuda, the US East Coast, and the Canadian Maritimes. However, Helene will likely create rough surf, rip currents, and large sea swells in all these area shorelines through this weekend.

I will have another forecast out sometime tomorrow morning.

Forecast Points and Intensity:

Initial 26.6N 57.1 W 90kt
12hrs 28.5W 57.4W 90kt
24hrs 31.0N 56.2W 90kt
36hrs 37.1N 53.1W 80kt
48hrs 44.1N 45.0W 70kt
72hrs 48.7N 37.4W 60kt...Becoming Extratropical
96hrs 52.6N 28.3W 60kt...Extratropical

[Thunder44]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products.

8am Thursday Forecast: Helene Turns North and Weakens

As of the 5am Advisory today, the NHC placed the center of Hurricane Helene currently at 28.4N 56.8W and is moving to the north at 11kts. Maximum sustained winds have decreased to 80kts and the pressure is at 964mb.

Helene has finally made her turn north as expected and it is actually moving a little east of due north at 10 degrees. She should make a further turn to the NNE later day and then start racing off to the NE tomorrow and into the North Central Atlantic, in 4 or 5 days. The models remain in agreement of recurvature but the consensus is slower and further east. Therefore the track as has been adjusted further to the right and is slower than the previous forecast. This track is very close to the 6z CONU and the 5am NHC track and will continue to be no threat to land.

Helene has weakened overnight and is now a strong Cat 1 hurricane. The system appears to be entraining some dry air and mid-level shear has increased. The convection has diminished to a smaller area of deeper convection around the center and the system might be trying to organize an inner core. Since the upper-level outflow remains excellent in all quadrants and storm will still be moving over warm SSTs, it is possible the storm could strengthen a little today, however, given this storm’s history of not strenghtening with favorable conditions aloft, I expect little change in strength over the next 36hrs, before environmental conditions become increasingly unfavorable for a tropical cyclone. The large deep-layer trough over the West Atlantic should induce extratropical transition by 72hrs and Helene could become a large and powerful non-tropical storm in the North Central Atlantic by 5 days, as suggested by many of the global models. I've added a 120hr position. The intensity forecast is close to the 6z SHIPS guidance.

Since Helene will be going to sea the next five days and should be no threat to land, this will be my last forecast for this storm. Please refer to NHC products for future information.

Forecast Points and Intensity:

Initial 28.4N 56.8W 80kt
12hrs 31.1N 55.8W 80kt
24hrs 34.0N 55.0W 80kt
36hrs 36.0N 52.5W 80kt
48hrs 40.0N 47.0W 75kt
72hrs 45.0N 37.0W 65kt...Becoming Extratropical
96hrs 49.5N 27.0W 60kt...Extratropical
120hrs 55.0N 19.0W 55kt...Extratropical