{ "number": 731, "headline": "September 11, 2025 Thursday Evening Update", "standfirst": "NHC yellow hatchling up to 30% for Eastern MDR 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": "2025-09-12", "published": "2025-09-12T01:15:26.202000Z", "updated": null, "access": "free", "body_html": "
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Good Evening! Update to move the maps and models forward.

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Lower 48 Precipitable Water Forecast | Next 6-days

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Tropical Storm Marco enters the frame in a few days and may become a hurricane prior to moving over cooler waters off Baja California Sur.

Scattered showers in the mountain west + easterly flow across Florida peninsula for next several days. A plume of moisture that appears to originate from the Atlantic cruises through the Gulf and heads northward through the Plains \u2014 part of a highly amplified pattern: troughs on either side of a strong Canadian blocking ridge. The ridge is gobbling up the moisture and helping to sustain itself from the latent heat release.

Large Scale View of Integrated Vapor Transport Next 10-days

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A lot going on \u2014 but not seeing much in the way of extreme weather in our neighborhood \u2014 typical for mid-September as long as the hurricanes stay away.

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Weather | Fronts this Evening

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RTMA Temperatures and Anomaly | 8:00 PM ET

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Lower 48 is above normal +1.0\u00b0F

Low Temperatures Friday Morning

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High Temperatures Friday

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Hot across the Plains into mid-Mississippi River Valley \u2026 76 million at least 90\u00b0F

Rainfall Next 72-hours | NWS NDFD

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7-Day Precipitation from NOAA WPC

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North America Upper Level Height Anomaly | AIFS 18z | Next 10-days

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Canadian blocking ridge finally breaks down toward Days 8-10 with more \u201cpolar vortex\u201d influence from the Arctic. Troughs and cut-offs dominate the Lower 48 under the ridge until then.

ECMWF EPS 12z | 7-day Temperature Anomaly | Week 1 (Sept 11-17)

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ECMWF EPS 12z | 7-day Temperature Anomaly | Week 2 (Sept 18-24)

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Atlantic Hurricane Season

2025 Hurricane Season [Day 103]. 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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Traffic jam in the MDR from the ECMWF 12z flagship model with 3 candidate tropical waves all squished together by Day 12. Just one scenario of 51 members, but suggests an uptick in TS/H activity next week!

ECMWF 18z | Precipitable Water Next 6-days

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A tropical wave emerging off coast of Africa in the next 24-hours has a 30% chance of development \u2014 and another emerges in 4-5 days behind it.

ECMWF 18z | Vorticity 6-day Forecast

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By Tuesday, a circulation makes it to 45\u00b0W and will likely develop in a day or two after that \u2026 30% chance from NHC, but we won\u2019t count our chickens before they hatch!

Atlantic Basin Outlook | 8 PM ET Update

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30% chance of development for a tropical wave that will emerge off Africa over next 24-hours.

Atlantic Satellite Imagery | Infrared

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Strong convection with wave just coming off Africa.

Water Vapor | Mid-level

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And a nice blob of tropical moisture to work with \u2026 not a yellow moat of negative dry air and descent

SST and SST Anomaly | ECMWF 12z analysis

NOAA Tropical Surface Analysis | 18z

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Atlantic Tropical Waves = 4 with one along 15\u00b0W (over Africa) with strong convection

Eastern Atlantic and Africa Infrared Satellite

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

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I\u2019d say a 50/50 signal from EPS through Day 7

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

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Majority of members feature a hurricane. Another wave on its heels develops right off the coast of Africa.

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

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Many major hurricane possibilities \u2014 over the central Atlantic (September 26th)

AIFS-ENS Comparison at 12Z | Active Tracks at Day 8

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AIFS ENS remains very excited about this tropical wave \u2014 high chance > 90%

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

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A more active Atlantic basin for sure, but thankfully everything looks to be recurving or staying away off the U.S. mainland.

Eastern Pacific Tropical Update | TD 13E

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To become Marco by tomorrow afternoon

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ATCF Spaghetti | TD 13E \u2014> Marco

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HWRF 18z \u2014 Marco nears hurricane strength at peak

ECMWF 18z shows 1000 mb | Not very impressive \u2014 not sure why!

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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Tropical Storm Marco enters the frame in a few days and may become a hurricane prior to moving over cooler waters off Baja California Sur.

Scattered showers in the mountain west + easterly flow across Florida peninsula for next several days. A plume of moisture that appears to originate from the Atlantic cruises through the Gulf and heads northward through the Plains \u2014 part of a highly amplified pattern: troughs on either side of a strong Canadian blocking ridge. The ridge is gobbling up the moisture and helping to sustain itself from the latent heat release.

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