ATL: KIRK - Models

[WaveBreaking]

Like the ensemble from Kirk it's beautiful...
https://i.imgur.com/CD9JP43.png

https://i.imgur.com/qw6ZUmW.png

Possible Lee repeat (without the mid-level shear that stopped it from being a top-10 storm)?

[cycloneye]

 https://x.com/NbergWX/status/1840914893299728587

[cycloneye]

[kevin]

Another potentially strong hurricane? It's time for the hurricane model blend. Here is the 00z blend of HWRF/HMON/HAFS-A/HAFS-B. First the peak intensities of all the individual models.

HWRF 00z = 939mb/121kt
HMON 00z = 938mb/117kt
HAFS-A 00z = 947mb/97kt
HAFS-B 00z = 923mb/128kt

And now for the blend. The current blend shows Kirk intensifying into a hurricane in about 16 hours, becoming a MH roughly 2.5 days from now and remaining one at least until ~120 hours. I also added an ACE metric based on the rounded blend wind speed at 6-hour intervals.

Blend
PEAK: 938 mb @ 96 hrs | 108 kt @ 96 hrs
ACE (0 - 126 hrs) = 18.5
hr / pressure (mb) / wind (kt)
00 / 996 / 50
06 / 992 / 61
12 / 989 / 58
18 / 984 / 61
24 / 980 / 71
30 / 975 / 74
36 / 973 / 78
42 / 969 / 79
48 / 968 / 81
54 / 961 / 87
60 / 960 / 89
66 / 953 / 98
72 / 949 / 107
78 / 946 / 106
84 / 944 / 107
90 / 940 / 107
96 / 938 / 108
102 / 939 / 101
108 / 941 / 103
114 / 942 / 100
120 / 943 / 102
126 / 946 / 94

While I haven't posted the previous blends, I've already been keeping track of Kirk since yesterday's 00z runs so here are all the blend peak intensities so far:
00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)

[kevin]

06z hurricane model intensity blend. Slightly weaker than 00z. It's mainly being brought down by a very weak HAFS-A run which doesn't bring Kirk to cat 2 strength until +84 hours when the other models all show a MH. The peaks for individual models below.

HWRF 06z = 938mb/119kt
HMON 06z = 946mb/107kt
HAFS-A 06z = 951mb/100kt
HAFS-B 06z = 927mb/121kt

The blend shows Kirk being a MH for 2 days and peaking as a mid-range cat 3, before slowly going further north and weakening.

Blend
PEAK: 943 mb @ 96 hrs | 105 kt @ 96 hrs
ACE (0 - 126 hrs) = 17.2
hr / pressure (mb) / wind (kt)
00 / 996 / 53
06 / 994 / 52
12 / 991 / 54
18 / 987 / 57
24 / 981 / 64
30 / 979 / 68 - C1
36 / 974 / 76
42 / 971 / 82
48 / 965 / 82
54 / 965 / 88 - C2
60 / 959 / 95
66 / 956 / 95
72 / 951 / 96 - C3
78 / 950 / 97
84 / 945 / 101
90 / 944 / 104
96 / 943 / 105
102 / 947 / 103
108 / 946 / 105
114 / 949 / 98
120 / 952 / 95
126 / 953 / 87

-- All blends so far --
00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)

[cycloneye]

[kevin]

I didn't have time for 12z & 18z blends, but here's today's 00z hurricane model intensity blend. Of the ones I've made it's the strongest so far in terms of wind speed.

HWRF 06z = 939mb/116kt
HMON 06z = 943mb/113kt
HAFS-A 06z = 937mb/110kt
HAFS-B 06z = 927mb/133kt

The blend shows Kirk becoming a MH in roughly 15 hours and remaining one for 3 - 4 days (peaking as a high-end cat 3 or low-end cat 4) before weakening in wind speed (while maintaining a low pressure) as it gets pulled north. Kirk alone would get this year's ACE above 100.

Blend
PEAK: 939 mb @ 78 hrs | 112 kt @ 72 hrs
ACE (0 - 126 hrs) = 22.0
hr / pressure (mb) / wind (kt)
00 / 984 / 67
06 / 978 / 69
12 / 972 / 87 - C2
18 / 964 / 91
24 / 962 / 98 - C3
30 / 958 / 97
36 / 956 / 101
42 / 952 / 109
48 / 950 / 108
54 / 946 / 110
60 / 945 / 111
66 / 940 / 111
72 / 940 / 112
78 / 939 / 108
84 / 942 / 109
90 / 942 / 110
96 / 944 / 106
102 / 947 / 95
108 / 950 / 86
114 / 950 / 84
120 / 949 / 82
126 / 945 / 75

-- All blends so far --
00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)
00z, 02/10 = 939mb/112kt (22.0 ACE)

[kevin]

06z, Oct 1, hurricane model blend

--- Model peak intensity ---
HWRF = 942mb/112kt
HMON 940mb/117kt
HAFS-A= 939mb/114kt
HAFS-B = 931mb/125kt

--- Hurricane model blend ---

The blend forecasts Kirk to become a category 2 hurricane in 5 hours (+12) and a major hurricane in the 6 - 12 hours afterwards. As of tomorrow this period of explosive intensification will make room for gradual intensification with possible EWRCs and a peak as a high-end category 3 or low-end category 4 hurricane. After +90, Kirk is expected to encounter higher shear and weaken as it goes further north and slowly undergoes extra-tropical transition. Due to this transition Kirk's pressure is expected to remain quite low despite the relatively weak winds.

Blend
PEAK: 942 mb @ 72 hrs | 112 kt @ 60 hrs
ACE (0 - 126 hrs) = 21.6
hr / pressure (mb) / wind (kt)
00 / 981 / 69
06 / 977 / 76
12 / 977 / 88 - C2
18 / 963 / 97 - C3
24 / 959 / 97
30 / 959 / 101
36 / 952 / 105
42 / 952 / 108
48 / 949 / 108
54 / 947 / 108
60 / 943 / 112
66 / 942 / 109
72 / 942 / 105
78 / 945 / 111
84 / 944 / 109
90 / 945 / 107
96 / 949 / 91
102 / 951 / 86
108 / 953 / 80
114 / 951 / 78
120 / 945 / 80
126 / 943 / 75

--- Previous blend analyses ---

00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)
00z, 02/10 = 939mb/112kt (22.0 ACE)
06z, 02/10 = 942mb/112kt (21.6 ACE)

[kevin]

12z, Oct 1, hurricane model blend

--- Model peak intensity ---
HWRF = 943mb/113kt
HMON 939mb/118kt
HAFS-A= 943mb/123kt
HAFS-B = 930mb/128kt

--- Hurricane model blend ---

The blend has Kirk as a minimal category 2 hurricane around this point in time (+6). In about 10 hours Kirk is forecast to reach MH status. The latest blend is more aggressive with subsequent intensification than previous blends and, like the NHC, explicitly shows a category 4 peak for the first time. After about 60 hours Kirk is expected to slowly weaken though it is expected to remain a large hurricane until it becomes extra-tropical near the end or beyond the forecast period. For the next 36 hours the standard deviation in the wind speed between the models remains relatively small at roughly +/- 5 kt. However, interestingly this uncertainty increases to roughly +/- 12 kt in the 48 - 72 hr period before decreasing again afterwards. This indicates a larger uncertainty regarding Kirk's peak intensity which will most likely occur within the 48 - 72 hr period. As such both a lower peak intensity near 100 kt or a higher peak intensity in the range of 130 kt should be considered as a realistic possibility. It is expected that Kirk and TD13 together will bring the Atlantic's ACE from 81 to 110 over the next 5 days.

Blend
PEAK: 941 mb @ 54 hrs | 116 kt @ 48 hrs
ACE (0 - 126 hrs) = 22.3
hr / pressure (mb) / wind (kt)
00 / 978 / 76
06 / 971 / 86 - C2
12 / 964 / 95
18 / 959 / 98 - C3
24 / 957 / 103
30 / 952 / 107
36 / 951 / 111
42 / 947 / 112
48 / 944 / 116 - C4
54 / 941 / 116
60 / 942 / 110
66 / 943 / 108
72 / 946 / 105
78 / 943 / 105
84 / 945 / 107
90 / 949 / 93
96 / 951 / 86
102 / 952 / 79
108 / 951 / 80
114 / 942 / 77
120 / 946 / 83
126 / 947 / 82

--- Previous blend analyses ---

00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)
00z, 02/10 = 939mb/112kt (22.0 ACE)
06z, 02/10 = 942mb/112kt (21.6 ACE)
12z, 02/10 = 941mb/116kt (22.3 ACE)

[kevin]

00z, Oct 3, hurricane model blend

--- Model peak intensity ---
HWRF = 930mb/117kt
HMON = 941mb/117kt
HAFS-A = 939mb/125kt
HAFS-B = 930mb/131kt

--- Hurricane model blend ---

Kirk has intensified faster than nearly all guidance and models showed just 12 hours ago. Kirk's initial intensity is set at 111 kt. After some initial struggles trying to mix out dry air in the last few hours, the blend shows Kirk rapidly intensifying into a category 4 hurricane roughly 10 - 12 hours from now. However, it should be noted that the uncertainty regarding Kirk's intensity is larger than normal even regarding short-term intensity. Kirk is expected to remain a large category 4 hurricane for a little over 2 days. Afterwards, wind shear is expected to increase and slowly weaken Kirk as it accelerates northward. Models strongly disagree how much this will affect Kirk's wind speed, with some models showing a TS near the end of the forecast period while others still show a strong hurricane or even a major hurricane. Either way, Kirk is expected to rake in a lot of ACE over the coming days. Kirk's forecast peak intensity is 118 kt, but due to the large uncertainty, values of 110 - 130 kt are realistic. Furthermore, due to Kirk defying all guidance over the last 12 hours even intensities above this range should be taken into consideration.

Blend
PEAK: 941 mb @ 42 hrs | 118 kt @ 42 hrs
ACE (0 - 126 hrs) = 23.7
hr / pressure (mb) / wind (kt)
00 / 952 / 111
06 / 947 / 105
12 / 947 / 112
18 / 943 / 115 - C4
24 / 945 / 115
30 / 942 / 113
36 / 944 / 115
42 / 941 / 118
48 / 941 / 116
54 / 943 / 114
60 / 945 / 114
66 / 944 / 113
72 / 944 / 108
78 / 944 / 97
84 / 950 / 86
90 / 948 / 87
96 / 947 / 81
102 / 943 / 80
108 / 942 / 83
114 / 942 / 85
120 / 945 / 78
126 / 944 / 70

--- Previous blend analyses ---

00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)
00z, 02/10 = 939mb/112kt (22.0 ACE)
06z, 02/10 = 942mb/112kt (21.6 ACE)
12z, 02/10 = 941mb/116kt (22.3 ACE)
00z, 03/10 = 941mb/118kt (23.7 ACE)

[kevin]

Since Kirk is near or at peak intensity at the moment the models become less important than the actual imagery/measurements. So I'll stop with the blends, but as a short summary here are the peak intensities of the 12z hurricane models.

HWRF = 935mb/121kt
HMON = 944mb/124kt
HAFS-A = 934mb/126kt
HAFS-B = 930mb/132kt

[Travorum]

As Kirk has surpassed model estimates and is seemingly post its (potentially only first) peak, here are the peak intensities from the 18z hurricane models and the forecast times they occur.

HWRF = 939mb/122kt (+9hrs|03z Fri 10/04)
HMON = 944mb/126kt (+9hrs|03z Fri 10/04)
HAFS-A = 938mb/132kt (+27hrs|21z Fri 10/04)* **
HAFS-B = 934mb/132kt (+27hrs|21z Fri 10/04)

* HAFS-A has min pressure at 936mb (+12hrs|06z Fri 10/04)
** HAFS-A also has 131kt at (+42hrs|12z Sat 10/05)

---

TLDR: Of the 18z hurricane models, HWRF and HMON say Kirk is peaking about now, both HAFS models say Kirk will level off/undergo ERC tonight then reach a secondary maximum peak tomorrow afternoon.

[Travorum]

Peak intensities and times on 06z hurricane models:

HWRF = 933mb/128kt (+3hrs|09z Fri 10/04)
HMON = 937mb/130kt (+3hrs|09z Fri 10/04)
HAFS-A = 932mb/130kt (+27hrs|09z Sat 10/05)*
HAFS-B = 925mb/140kt (+21hrs|03z Sat 10/05)**

* HAFS-A has min pressure of 925mb (+3hrs|09z Fri 10/04)
** HAFS-B has min pressure of 918mb (+3hrs|09z Fri 10/05)

The trend continues with the hurricane models, with HWRF and HMON insisting Kirk has peaked while both HAFS continue to predict a second peak overnight tonight. HAFS-B continues to be the most bullish, modelling Category 5 winds (barely) tonight and keeping Kirk above 130kts more often than below it until Sunday. HAFS-A predicts a comeback to a strong Category 4 that is able to persist into tomorrow night. The one thing all models are in agreement about is that Kirk's pressure has reached its absolute minimum as of a few hours ago.

[kevin]

Now that we can safely say that Kirk has passed its peak intensity, here's how the blends have performed compared to reality.

00z, 30/09 = 934mb/110kt (15.7 ACE)
06z, 30/09 = 942mb/107kt (12.9 ACE)
12z, 30/09 = 941mb/108kt (16.6 ACE)
18z, 30/09 = 941mb/106kt (17.8 ACE)
00z, 01/10 = 938mb/108kt (18.5 ACE)
06z, 01/10 = 943mb/105kt (17.2 ACE)
00z, 02/10 = 939mb/112kt (22.0 ACE)
06z, 02/10 = 942mb/112kt (21.6 ACE)
12z, 02/10 = 941mb/116kt (22.3 ACE)
00z, 03/10 = 941mb/118kt (23.7 ACE)
Reality = 934mb/125kt

As you can see the hurricane blends slightly underestimated Kirk's maximum wind speeds by 7 - 19 kt depending on the blend. They did trend towards the 110 - 120 kt range in the last 2 days before peak intensity was reached. The lowest pressure has been within 10 mb of the actual lowest pressure since the first blend more than 4 days out.