ATL: ERIN - Tropical Storm - Discussion

[cycloneye]

8 AM=90/90. TD or TS at 11 AM?

Eastern Tropical Atlantic (AL97):
Shower and thunderstorm activity has persisted and continues to
show signs of organization with a well-defined area of low pressure
located just to the west of the Cabo Verde Islands. If these
structural trends continue, the system is likely to become a
tropical depression or storm, possibly as soon as later this
morning. Locally heavy rainfall and gusty winds are expected to
continue today across portions of the Cabo Verde Islands, and
interests there should monitor the progress of this system.
Regardless of development over the next couple of days, the system
is expected to continue moving westward to west-northwestward at 15
to 20 mph across the eastern and central tropical Atlantic.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 7 days...high...90 percent.

[Jr0d]

8 AM=90/90.

Maybe a TD at 11am. I noticed the NHC likes to go in 10% increments when a storm is not an immediate threat.

Convection appears to waning the moment however. Also still going wnw not west or wsw. If this continues then the chances of a CONUS hit will continue to go down.

[NDG]

 https://x.com/NDGMETCHEF/status/1954879087199080714

[wxman57]

https://i.imgur.com/lymGUl1.png

With that wind barb and the low resolution, I'd go 35 kt for the initial intensity. If this was 24 hours ago, I'd classify it as TS Erin now to get the warnings out. But with the storm leaving the islands, there may be a bit of time to wait. If this trend continues, I'd start advisories early tomorrow (EDT), which I believe is 8 am CVT if 0900Z.

So far this summer, the Azores-Bermuda High has been much weaker than normal. The Subtropical Atlantic is dominated by lower pressure. This results in lower trade wind speeds and an easy avenue for developing storms to recurve east of the Caribbean, as I expect this one to do. I think it'll pass by Bermuda by next Tuesday as a major hurricane. Too early to determine if it might impact the northeast U.S.

[Nuno]

Surprised this still hasnt been upgraded

[cycloneye]

Moving west now per 12z Best Track. I would not be surprised if the famous NHC banner is up in less than one hour from this post.

AL, 97, 2025081112, , BEST, 0, 173N, 273W, 30, 1006, LO

[KirbyDude25]

Looks like the 12Z Best Track has been updated. We have Erin

AL, 05, 2025081112, , BEST, 0, 173N, 273W, 40, 1004, TS, 34, NEQ, 20, 0, 0, 30, 1010, 160, 20, 0, 0, L, 0, , 0, 0, ERIN, M, 0, , 0, 0, 0, 0, genesis-num, 016, TRANSITIONED, alA72025 to al052025,

[Hurricane2022]

Unfortunately, Cape Verde has reported damages and 5 deaths from the newly-upgraded Tropical Storm ERIN.
 https://x.com/dtudo1poucocv/status/1954862958984540427

[cycloneye]

Is Official TS ERIN at 11 AM

 https://x.com/NHC_Atlantic/status/1954908302325744076

[HurricaneBelle]

 https://x.com/NHC_Atlantic/status/1954908302325744076

[eastcoastFL]

Moving west now per 12z Best Track. I would not be surprised if the famous NHC banner is up in less than one hour from this post.

AL, 97, 2025081112, , BEST, 0, 173N, 273W, 30, 1006, LO

https://i.imgur.com/B7txVQ9.png

It's up now.

NHC WILL BEGIN ADVISORIES ON TS ERIN AT 11AM EST

[TampaWxLurker]

So if they're jumping straight to TS Erin at 11am, its safe to say they could have started initiating advisories for a tropical depression or PTC at least 12+ hours ago, yes? I mean it was affecting the Cabo Verde Islands.

[Hurricane2022]

OUTLOOK VALID 16/1200Z 21.5N 60.0W
MAX WIND 100 KT...GUSTS 120 KT.
50 KT... 70NE 50SE 40SW 50NW.
34 KT...140NE 130SE 80SW 120NW.

[Hurricane2022]

Tropical Storm Erin Discussion Number 1
NWS National Hurricane Center Miami FL AL052025
200 PM CVT Mon Aug 11 2025

The system we have been monitoring that moved across the Cabo Verde
Islands over the past 6-12 h (Invest 97L) has maintained a small,
but persistent area of deep convection. This activity prompted an
earlier TAFB subjective Dvorak fix of T2.5/35 kt suggesting the
convection is now sufficently organized to be classified as a
tropical cyclone. We also received scatterometer data at 1107 UTC
with a peak wind retrieval of 39 kt embedded in this convection,
with an ambiguity analysis suggesting the circulation is also
well defined, albeit still somewhat elongated on the eastern edge.
The combination of all this data suggests that a tropical storm has
formed, and NHC is initiating advisories on Tropical Storm Erin with
a current intensity of 40 kt.

Erin is moving quickly off to the west, with the motion estimated at
275/17 kt. Over the next few days, this motion should continue with
possibly some slight south-of-due-west motion. Erin's motion is
primarily influenced by an east-to-west oriented mid-level ridge
draped across the subtropical Atlantic basin. By the end of the
forecast period, this ridge may start to become more oriented to the
northeast of Erin, inducing a more poleward motion by 120 h. The
initial NHC track forecast elects to stick fairly close to the HFIP
corrected consensus approach (HCCA), which is a touch on the south
side of the overall track guidance envelope. It should be noted that
spread in the track guidance, especially the ensembles, begins to
increase markedly at the end of the forecast period.

The intensity forecast in the short-term is a little tricky. The
earlier scatterometer data indicate the system has a small
circulation which could be prone to rapid intensity changes, either
up or down. While vertical wind shear over the system is forecast to
be low, between 5-10 kt over the next 72 hours, sea-surface
temperatures are more marginal, around 26-27C, with a decent amount
of dry mid-level air along the path of the tropical storm. The first
NHC intensity forecast will thus only forecast slow intensification
in the short-term, assuming the marginal SSTs and lack of mid-level
moisture will keep the small vortex in check. After 48 h, however,
the SSTs start to gradually increase and should allow the local
environment of Erin to moisten up. Thus, the rate of intensification
will likely increase in the second half of the forecast period. The
NHC intensity forecast is a little on the high side of the guidance
in the short-term, partially due to the initial intensity, but is in
line with the HCCA intensity aid. By 120 h, the hurricane-regional
models (e.g., HWRF/HAFS), and statistical-dynamical aids
(EC-SHIPS/LGEM) show Erin becoming a major hurricane, and that will
be explicitly forecast at the end of the period.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 17.4N 28.0W 40 KT 45 MPH
12H 12/0000Z 17.5N 31.2W 45 KT 50 MPH
24H 12/1200Z 17.4N 35.1W 50 KT 60 MPH
36H 13/0000Z 17.1N 38.7W 55 KT 65 MPH
48H 13/1200Z 17.1N 41.7W 60 KT 70 MPH
60H 14/0000Z 17.4N 45.0W 70 KT 80 MPH
72H 14/1200Z 18.0N 48.4W 80 KT 90 MPH
96H 15/1200Z 19.6N 54.0W 90 KT 105 MPH
120H 16/1200Z 21.5N 60.0W 100 KT 115 MPH

$$
Forecaster Papin

[aspen]

:double:

OUTLOOK VALID 16/1200Z 21.5N 60.0W
MAX WIND 100 KT...GUSTS 120 KT.
50 KT... 70NE 50SE 40SW 50NW.
34 KT...140NE 130SE 80SW 120NW.

A little more aggressive than I thought they’d go for. I was expecting maybe 90 kt max due to this being the first advisory, and the slower rate of intensification over the next 2-3 days.

It’s been a long time since we had a long-tracking MDR hurricane form east of 30W before September. I think the last was Florence in 2018, and before that Irma in 2017. Both were after August 20th, much later than Erin. Wonder if this means the MDR will be a lot more favorable than expected this year (the precip plots from earlier in the summer looked pretty inactive), or if this is just a fluke.

[kevin]

Time to bring the list back once again. Here's a list of the most aggressive first advisories based on NHC advisories since 1998 (of which the 1998 - 2002 advisories only went to +72 hrs). Erin is one of only 6 TCs to get a first advisory with a 100+ kt forecast point. At the end of the name I have added the verified peak intensity in kt for each storm.

120 kt
2023 - Lee (145)

105 kt
2024 - Kirk (130)
2023 - Nigel (85)

100 kt
2025 - Erin (-)
2021 - Sam (135)
2010 - Tomas (85)

95 kt
2024 - Milton (155)
2024 - Helene (120)
2024 - Ernesto (85)
2022 - Ian (140)
2021 - Ida (130)
2020 - Iota (135)
2019 - Lorenzo (140)
2012 - Isaac (70)
2010 - Danielle (115)
2005 - Philippe (70)
2004 - Karl (110)

90 kt
2024 - Beryl (145)
2021 - Larry (110)
2017 - Jose (135)
2016 - Matthew (145)
2009 - Bill (115)
2007 - Dean (150)

85 kt
2020 - Delta (120)
2015 - Danny (110)
2014 - Gonzalo (125)
2011 - Katia (120)
2010 - Igor (135)
2010 - Earl (125)
2006 - Helene (105)
2005 - Wilma (160)

80 kt
2024 - Leslie (90)
2022 - Danielle (75)
2020 - Teddy (120)
2019 - Jerry (90)
2017 - Maria (150)
2017 - Irma (155)
2016 - Gaston (105)
2012 - Leslie (70)
2005 - Rita (155)
2004 - Earl (45)
1999 - Emily (45)

[cycloneye]

 https://x.com/philklotzbach/status/1954923193015369746

[cycloneye]

Kevin, that is a vey interesting archieve that you have about those first strong advisories at peak intensity. Keep it up for years to come.

[cycloneye]

Good analysis from Levi Cowan.

@TropicalTidbits
Tropical Storm #Erin has formed in the far eastern Atlantic, expected to track generally westward and intensify over the next 5 days. Intensification is likely to be slow at first due to Erin moving over currently cool sea surface temperatures, followed by strengthening into a hurricane once Erin tracks farther west over warmer waters later this week.

Computer models are in good agreement that Erin will likely pass north of the Leeward Islands of the eastern Caribbean this weekend, though the region should monitor the forecast for any southward shifts this week.

It is too early to be confident in Erin's long-term future beyond this weekend. Current indications favor an ultimate turn northward over the western Atlantic, avoiding North America, but this portion of Erin's track is not yet certain. We are now in the peak of the hurricane season, so it is wise to have a hurricane plan ready to activate in case Erin or any other storm comes your way.


 https://x.com/TropicalTidbits/status/1954925227198316794

[Beef Stew]

A recurve is definitely the most likely outcome here, but I won't feel reaching that conclusion for at least a few more days. Mid-August climo suggests that, while still less likely than a recurve, the sub-seasonal risk for a US east coast landfall from an MDR storm remains comparatively elevated. Until Erin completes her forecasted WSW motion and we have a better idea of the position and strength of the ridge over the North Atlantic, we won't be able to say where this storm ends up definitively. The synoptic pattern surrounding Florence was also favoring a recurve... until the building ridge turned out to be far stronger than originally modeled.

And even if the likely recurve does happen, I think it's important to remember that recurve ≠ fish storm. An impact to Bermuda or Atlantic Canada are both well within the range of realistic outcomes.