{ "number": 735, "headline": "September 15, 2025 Monday Evening Hurricane Season Update", "standfirst": "NHC 90% high chance of developing tropical wave", "desk": "tropics", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-09-15", "published": "2025-09-15T23:00:57.888000Z", "updated": null, "access": "free", "body_html": "
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Good Evening!

Invest 92L is underway in the central Main Development Region (MDR) and it is firing off sustained convection over a broad area. NHC has increased the likelihood of TS development to 90% \u2014 and this time, we mean it!

The Atlantic basin looks \u201chealthier\u201d this evening with more thunderstorm activity helping to moisten the atmosphere and increase instability.

Atlantic Infrared Satellite Snapshot

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Where will Invest 92L \u2014> T.S. Gabrielle go? On a NW course from the lower latitude of the MDR (12\u00b0N) to almost 30\u00b0N in 7-days. Note the HCCA consensus (answer key) is on the west/left side of the guidance envelope. Once the system reaches 25\u00b0N it will slow down to a crawl and then probably turn abruptly to the right/ENE out-to-sea.

ATCF Spaghetti | Invest 92L

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Atlantic Basin Outlook | 2 PM ET Update | 90% HIGH

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2025 Hurricane Season [Day 107]. My FORECAST for this year is (still) 14 named storms, 7 hurricanes, and 3 major hurricanes (near average)

2025 Season to Date: 6 named storms, 1 hurricanes, and 1 majors | ACE = 40 ACE of Erin: 32.2 (140-knots maximum wind)

ECMWF 12-Days Integrated Vapor Transport | 12z cycle

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The wave train continues WNW until the parade comes to a halt \u2014 the tropical waves jumble up, and then quickly exit stage right out to sea \u2014> \u201cfish mixer\u201d \u2026 note how Gabrielle absorbs or drags a tropical wave to the NE \u2026 but another is allowed to continue westward into the Lesser Antilles in the longer-range.

Maximum intensity looks to be high end Category 4 or even Category 5 in 9-days (931 mb) \u2014 Day 9:

Gabrielle | Major Hurricane closest approach to the Lower 48

ECMWF 12z | Precipitable Water Next 8-days

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Mario and Narda decay over the cooler waters of the Pacific off Baja California to the west. Gabrielle enters the picture as a potential Major Hurricane by this time next week.

We will need to monitor the troughs/ridges over North America for steering currents to keep any approaching hurricanes from reaching the United States.

ECMWF 12z | Cyclonic Vorticity Next 12-days

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3 distinct systems including Gabrielle, a tropical wave a few days behind it that gets gobbled up, and then another trailing at lower-latitude in the MDR to near the Lesser Antilles in 12-days.

HAFS Intensity of Invest 92L through 5-days \u2014 near hurricane intensity but large circulation

Atlantic Satellite Imagery | Water Vapor | Mid-level Loop

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The upper-level low (yellow spinner) to the NNW of the tropical wave doesn\u2019t seem to be affecting it much \u2026 and it may be oriented such that it orbits/rotates harmlessly to the SW and decays. The current circulation at mid-levels may be helping to ventilate Invest 92L \u2014 upper-level diffluence.

SST and SST Anomaly | ECMWF 12:00 UTC Forecast

Very warm water on the path of our next hurricane \u2014 Atlantic \u201cwarm pool\u201d

NOAA Tropical Surface Analysis | 12z

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Atlantic Tropical Waves = 3 including the 90% NHC (Invest 92L)

Eastern Atlantic and Africa Infrared Satellite

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At least 4 more tropical waves lined up in a parade \u2014 African Easterly Wave train

Ensemble Spaghetti

Ensemble spaghetti \u2014 from 51-members of the ECMWF full-physics and A.I. trained systems. Note, there is only one reality \u2014 and while there are potentially hundreds of forecasted scenarios in the coming days, we will only have 1 or 2 actual hurricanes. The tracks are meant to show uncertainty in location and intensity to trained forecasters.

ECMWF EPS 12z Ensemble | Active Cyclone Tracks Through 5-days

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ECMWF EPS 12z Ensemble | Active Cyclone Tracks Through 7-days

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ECMWF EPS 12z Ensemble | Active Cyclone Tracks Through 10-days

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ECMWF EPS 12z Ensemble | Active Cyclone Tracks Through 15-days

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AIFS-ENS Comparison at 12z | Active Tracks at Day 5

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The A.I. trained system is weaker in the Atlantic with tracks than the full-physics

AIFS-ENS Comparison at 12z | Active Tracks at Day 10

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AIFS-ENS Comparison at 12z | Active Tracks at Day 15

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AIFS-ENS 12z | 15-day Loop of Active Cyclones

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Busy Atlantic during the next 2-weeks with potential for 1-3 named tropical systems

Eastern Pacific Tropical Update | Tropical Storm Mario

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Mario almost became a hurricane, but will now decay quickly over cooler waters.

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Mario is up to 55-knots this evening \u2014 but has 12-18 hours before losing all convection and steam over < 26\u00b0C ocean temperatures

55-knot tropical storm Mario

Next storm is Narda in a few days but may not intensity much beyond a minimal TS.

Western Pacific Typhoon Season Update

It\u2019s been busy with numbered systems \u2014 22 of them, but almost all of them have been quite weak and short-lived. That should change soon with potential for a Super Typhoon to develop east of the Philippines.

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Two Invests 98W and 99W may likely become Typhoons with the eastern storm very intense \u2014 and potentially a Super Typhoon in 7-8 days near Philippines heading westward

Integrated Vapor Transport | Next 10-days

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ECMWF 12z | 9-days Snapshot | UV850 | IVT

Maps sourced from weathermodels.com designed and innovated by yours truly! Please subscribe there for real-time access to the newest maps, charts from all of the weather models including ECMWF.

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Invest 92L is underway in the central Main Development Region (MDR) and it is firing off sustained convection over a broad area. NHC has increased the likelihood of TS development to 90% \u2014 and this time, we mean it!

The Atlantic basin looks \u201chealthier\u201d this evening with more thunderstorm activity helping to moisten the atmosphere and increase instability.

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