ATL: HELENE - Models

[DunedinDave]

The faster the storm goes, the further east it gets. That's what seems to be the trend with these models.

[chris_fit]

12z EPS different view

[Gums]

Salute!

Well, Belly, the storm could be a "Michael" and veer east AND get stronger!

Looks like Cedar Key in for another one, huh?

And keep in mind that the forward speed "helps" the surge, so looks like a higher surge than we have seen last coupla storms in that area at landfall - from St George island to Crystal River. Nevertheless, the big bend area is where we see the least damage and human loss. The folks there have had a lotta practice last 5 years with recovery and surviving. I pray for them.

Gums sends...

[Pipelines182]

Levi does a good job explaining what the half a.. models are doing. It assumes a stacked system which where it is now would explode in development. Reality is the system is not stacked, so the assumption is wrong. Unless it stacks quickly, then probably still too strong. We will see. With today's models could we have predicted a Wilma like intensification?

Thanks since I didn't get a chance to watch it. Definitely 2 camps of model intensity. All the globals except GFS are around 970's. GFS landfalls at 950. And the Hurricane Models as well as NAM 12km are substantially lower. While the actual NAM intensity needs to be ignored, look for compression in the spread of intensity over the next few series of runs. Not sure which way it's going to go, but I think we could see 950's or 960's as the low pressure consensus unless the globals stay locked in that 970-972 range.

The hurricane models are typically the best on intensity when compared to the globals, especially the euro.

[Steve]

Levi does a good job explaining what the half a.. models are doing. It assumes a stacked system which where it is now would explode in development. Reality is the system is not stacked, so the assumption is wrong. Unless it stacks quickly, then probably still too strong. We will see. With today's models could we have predicted a Wilma like intensification?

Thanks since I didn't get a chance to watch it. Definitely 2 camps of model intensity. All the globals except GFS are around 970's. GFS landfalls at 950. And the Hurricane Models as well as NAM 12km are substantially lower. While the actual NAM intensity needs to be ignored, look for compression in the spread of intensity over the next few series of runs. Not sure which way it's going to go, but I think we could see 950's or 960's as the low pressure consensus unless the globals stay locked in that 970-972 range.

The hurricane models are typically the best on intensity when compared to the globals, especially the euro.

Someone posted the verifications last season during one of the events and I think I recall the HWRF being best overall at least for a couple of years at some distance out (3 days? 4 days?). This is within 4 days, but I'm willing to bet we don't get down as low as what they're suggesting. I feel like when they first start running them they tend to dive the pressure too low. But then everything sort of comes into agreement within a few millibars except for the extreme outliers. Hard to know what's going to happen here. I'm tentative on it because I don't know where the core is going to stack. I'm pretty sure we're going to get a pull to the NW toward the Yucatan Channel then a bit of a east of due north movement from there to landfall. Seems like 940's would probably be my floor and a landfall between Bay County and Citrus with a tighter window of Gulf to Taylor.

[Pipelines182]

Thanks since I didn't get a chance to watch it. Definitely 2 camps of model intensity. All the globals except GFS are around 970's. GFS landfalls at 950. And the Hurricane Models as well as NAM 12km are substantially lower. While the actual NAM intensity needs to be ignored, look for compression in the spread of intensity over the next few series of runs. Not sure which way it's going to go, but I think we could see 950's or 960's as the low pressure consensus unless the globals stay locked in that 970-972 range.

The hurricane models are typically the best on intensity when compared to the globals, especially the euro.

Someone posted the verifications last season during one of the events and I think I recall the HWRF being best overall at least for a couple of years at some distance out (3 days? 4 days?). This is within 4 days, but I'm willing to bet we don't get down as low as what they're suggesting. I feel like when they first start running them they tend to dive the pressure too low. But then everything sort of comes into agreement within a few millibars except for the extreme outliers. Hard to know what's going to happen here. I'm tentative on it because I don't know where the core is going to stack. I'm pretty sure we're going to get a pull to the NW toward the Yucatan Channel then a bit of a east of due north movement from there to landfall. Seems like 940's would probably be my floor and a landfall between Bay County and Citrus with a tighter window of Gulf to Taylor.

IIRC the GFS has some skill on intensity but the Euro had almost none, I never look to the Euro for intensity. I thought the HWRF had a bit of a tendency to over do storms but man, the HAFS is putting it to shame with their sub 900 mb forecasts lol I thought it was supposed to be the new model with higher accuracy that's going to replace the HWRF, seems to still need work I guess.

[kevin]

A bit late since I had some meetings (life & work always seems to get busier when hurricanes arrive), but here is an overview of the 12z hurricane models and a blend. Blended winds are a bit low for the pressure mainly due to the HWRF run which has very low winds for its 935 mb pressure. Some previous HWRF & HMON runs also showed this disbalance so there might be some truth to it, but at the moment HWRF is the main one still showing it to this degree. In terms of pressure this is the strongest blend so far with a peak of 913 mbar just before landfall. Normally such a pressure would translate to a low-end cat 5, but due to HWRF it blends to a high-end cat 4. Catastrophic either way.

HWRF
PEAK: 930 mb @ 72 hrs | 98 kt @ 57 hrs
hr / pressure (mb) / wind (kt)
00 / 1005 / 35 - TS
06 / 1001 / 51
12 / 999 / 43
18 / 998 / 51
24 / 993 / 51
30 / 987 / 51
36 / 980 / 58
42 / 970 / 59
48 / 957 / 78 - C1
54 / 945 / 91
60 / 935 / 91 - C2
66 / 934 / 87
72 / 930 / 96 - landfall
78 / 940 / 64

HMON
PEAK: 918 mb @ 84 hrs | 124 kt @ 75 hrs
hr / pressure (mb) / wind (kt)
00 / 1003 / 27
06 / 1001 / 37 - TS
12 / 1001 / 35
18 / 997 / 44
24 / 994 / 46
30 / 984 / 60
36 / 981 / 58
42 / 973 / 63
48 / 964 / 80 - C1
54 / 959 / 87 - C2
60 / 953 / 76
66 / 941 / 104 - C3
72 / 933 / 121 - C4
78 / 925 / 122
84 / 918 / 120 - landfall
90 / 956 / 62

HAFS-A
PEAK: 899 mb @ 75 hrs | 162 kt @ 75 hrs
hr / pressure (mb) / wind (kt)
00 / 1003 / 31 - TD
06 / 1000 / 43 - TS
12 / 998 / 45
18 / 991 / 57
24 / 987 / 51
30 / 983 / 57
36 / 979 / 59
42 / 972 / 65 - C1
48 / 954 / 105 - C3
54 / 943 / 110
60 / 925 / 134 - C4
66 / 907 / 146 - C5
72 / 899 / 155
78 / 900 / 159 - landfall
84 / 922 / 81

HAFS-B
PEAK: 888 mb @ 72 hrs | 159 kt @ 69 hrs
hr / pressure (mb) / wind (kt)
00 / 1004 / 30 - TD
06 / 998 / 46 - TS
12 / 1000 / 45
18 / 990 / 56
24 / 988 / 49
30 / 985 / 55
36 / 978 / 55
42 / 963 / 77 - C1
48 / 948 / 95 - C2
54 / 941 / 92
60 / 924 / 124 - C4
66 / 903 / 157 - C5
72 / 888 / 155
78 / 901 / 134 - landfall
84 / 920 / 102

Blend
PEAK: 913 mb @ 72 hrs | 132 kt @ 72 hrs
hr / pressure (mb) / wind (kt)
00 / 1004 / 31 - TD
06 / 1000 / 44 - TS
12 / 1000 / 42
18 / 994 / 52
24 / 991 / 49
30 / 985 / 56
36 / 980 / 58
42 / 970 / 66 - C1
48 / 956 / 90 - C2
54 / 947 / 95
60 / 934 / 106 - C3
66 / 921 / 124 - C4
72 / 913 / 132
78 / 917 / 120 - landfall
84 / 932 / 87

[chaser1]

The hurricane models are typically the best on intensity when compared to the globals, especially the euro.

Someone posted the verifications last season during one of the events and I think I recall the HWRF being best overall at least for a couple of years at some distance out (3 days? 4 days?). This is within 4 days, but I'm willing to bet we don't get down as low as what they're suggesting. I feel like when they first start running them they tend to dive the pressure too low. But then everything sort of comes into agreement within a few millibars except for the extreme outliers. Hard to know what's going to happen here. I'm tentative on it because I don't know where the core is going to stack. I'm pretty sure we're going to get a pull to the NW toward the Yucatan Channel then a bit of a east of due north movement from there to landfall. Seems like 940's would probably be my floor and a landfall between Bay County and Citrus with a tighter window of Gulf to Taylor.

IIRC the GFS has some skill on intensity but the Euro had almost none, I never look to the Euro for intensity. I thought the HWRF had a bit of a tendency to over do storms but man, the HAFS is putting it to shame with their sub 900 mb forecasts lol I thought it was supposed to be the new model with higher accuracy that's going to replace the HWRF, seems to still need work I guess.

My thoughts on the topic all around. Once a viable disturbance (not a model-can LOL), GFS does seem pretty solid in the 3-5 day range.

[Steve]

Thanks kevin. I’d be surprised if it got down to the 930’s or lower but you never know.

[Jr0d]

I really hope weather stations over the CONUS are launching extra weather balloons for better data on the trough that is digging down and to help the models get a better idea when and where the cutoff ULL will form.

I have been closely watching the mesoscale models in hopes of guessing this better as I think it is a strength of them. Of course they have a weakness in terms of predicting tropical storm's track and intensity.

I noticed the NAM(currently running now) had the cutoff low over Arkansas with a slight retrograde motion, while the FV3 had it further north and east with no retrograde, but does not go as far out with the forecast, this results in 97L being significantly further east on the FV3 runs.

[Powellrm]

Thanks since I didn't get a chance to watch it. Definitely 2 camps of model intensity. All the globals except GFS are around 970's. GFS landfalls at 950. And the Hurricane Models as well as NAM 12km are substantially lower. While the actual NAM intensity needs to be ignored, look for compression in the spread of intensity over the next few series of runs. Not sure which way it's going to go, but I think we could see 950's or 960's as the low pressure consensus unless the globals stay locked in that 970-972 range.

The hurricane models are typically the best on intensity when compared to the globals, especially the euro.

Someone posted the verifications last season during one of the events and I think I recall the HWRF being best overall at least for a couple of years at some distance out (3 days? 4 days?). This is within 4 days, but I'm willing to bet we don't get down as low as what they're suggesting. I feel like when they first start running them they tend to dive the pressure too low. But then everything sort of comes into agreement within a few millibars except for the extreme outliers. Hard to know what's going to happen here. I'm tentative on it because I don't know where the core is going to stack. I'm pretty sure we're going to get a pull to the NW toward the Yucatan Channel then a bit of a east of due north movement from there to landfall. Seems like 940's would probably be my floor and a landfall between Bay County and Citrus with a tighter window of Gulf to Taylor.

Really well said, my thoughts exactly. Those models tend to really put out some low numbers early on, not uncommon to see some numbers that are far too bullish. Needs to be a formed system closer to landfall to put too much stock into those. And agreed, something in the 940s could be a more realistic outcome. The data is just data and still worth discussion.

But the crazy low numbers to also reflect my concern with this setup from the get go. It just has the setup to really maximize its potential strength. Not many impediments to strengthening with its short time over very favorable conditions. It may not reach those really low numbers, but it wouldn’t be shocking to see this storm exceed expectations.

[Steve]

I really hope weather stations over the CONUS are launching extra weather balloons for better data on the trough that is digging down and to help the models get a better idea when and where the cutoff ULL will form.

I have been closely watching the mesoscale models in hopes of guessing this better as I think it is a strength of them. Of course they have a weakness in terms of predicting tropical storm's track and intensity.

I noticed the NAM(currently running now) had the cutoff low over Arkansas with a slight retrograde motion, while the FV3 had it further north and east with no retrograde, but does not go as far out with the forecast, this results in 97L being significantly further east on the FV3 runs.

Solution has been gradually moving east with almost each model. We started off with an plains cut off then arkansas and now NAM 3km is mid mississippi valley centered at point where AR/MO/KY/TN/IL. Storm is too far out of range for the NAM 12km but it is much weaker (995mb vs. 972 at 12z). Still got some run to go on TT.

[Torgo]

I really hope weather stations over the CONUS are launching extra weather balloons for better data on the trough that is digging down and to help the models get a better idea when and where the cutoff ULL will form.

I have been closely watching the mesoscale models in hopes of guessing this better as I think it is a strength of them. Of course they have a weakness in terms of predicting tropical storm's track and intensity.

I noticed the NAM(currently running now) had the cutoff low over Arkansas with a slight retrograde motion, while the FV3 had it further north and east with no retrograde, but does not go as far out with the forecast, this results in 97L being significantly further east on the FV3 runs.

Solution has been gradually moving east with almost each model. We started off with an plains cut off then arkansas and now NAM 3km is mid mississippi valley centered at point where AR/MO/KY/TN/IL. Storm is too far out of range for the NAM 12km but it is much weaker (995mb vs. 972 at 12z). Still got some run to go on TT.

It's much weaker because it took quite a lengthy trip to the Yucatan.

[tolakram]

Globals based on what's available from TT right now.



Euro 12Z

[tolakram]

Hurricane model roundup. Please beware that while anything is possible the super low pressure shown by these is rarely accurate prior to storm formation.

[DunedinDave]

18z ICON with a shift east. Hard to tell but it appears landfall north of Pasco county. Hard to tell. Looks like between Spring Hill and Crystal River.

[WaveBreaking]

Will the recon data be assimilated into the 18z suite of hurricane models, or will it be the 00z suite instead?

[Blown Away]

18z Icon… Decent shift S to just N of Tampa…

[ronjon]

18z ICON with a shift east. Hard to tell but it appears landfall north of Pasco county. Hard to tell. Looks like between Spring Hill and Crystal River.

Yikes not liking this one bit. ICON has been a pretty good forecast model this year picking up early trends.

[SouthFLTropics]

18z ICON with a shift east. Hard to tell but it appears landfall north of Pasco county. Hard to tell. Looks like between Spring Hill and Crystal River.

That’s a significant shift East. Not as noticeable at landfall as it is once it gets into Georgia.


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