{ "number": 727, "headline": "September 8, 2025 Monday Evening Update", "standfirst": "Day 100 of Hurricane Season remains quiet for next week, at least", "desk": "tropics", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-09-09", "published": "2025-09-09T01:48:35.700000Z", "updated": null, "access": "free", "body_html": "
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Monday Evening Weather Update

  1. The Atlantic basin is a disorganized mess of troughs and scattered convection.

  2. Hurricane Kiko has further weakened to Category 1 on a WNW course well away from the Hawaii Islands. Tropical Storm Marco is coming in 3-days along the coast of Mexico.

Weather Trader is a reader supported newsletter by Dr. Ryan Maue. To receive new posts and support my research and work, consider becoming a free or paid subscriber.

Weather | Fronts this Evening

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Smoke from a California wildfire is reaching into Nevada and southern Idaho. However Canadian wildfire smoke is spreading across the northern Plains and MIdwest but southerly flow is mostly keeping it bottled up.

Smoke Analysis | 8 PM ET

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Smoke Forecast | 9 AM ET Tuesday

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Satellite Image | Monday Evening

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Severe storms ongoing in Oklahoma and Texas panhandles this evening

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

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A strong and persistent blocking ridge builds across Canada over the next 7-10 days for a much warmer pattern across the Lower 48. Hard to get any Arctic air to flood southward. However, unsettled weather will result from several cut-off troughs that necessarily have to go around the ridge + wave breaking.

Day 10 Temperature Anomaly + Height Anomaly

ECMWF EPS 12z | 7-day Temperature Anomaly | Week 1 (Sept 8-14)

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ECMWF EPS 12z | 7-day Temperature Anomaly | Week 2 (Sept 15-21)

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RTMA Temperatures and Anomaly | 8:30 PM ET

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Lower 48 is -2.5\u00b0F below normal

HRRR Radar Simulation Next 48-Hours

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Heavy rain along the frontal boundary in Florida + showers in the Great Lakes through Tuesday

Rainfall Next 48-hours | NWS NDFD

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Showers return to the Pacific Northwest including 1-inch or more along the coast in Oregon

Low Temperatures Tuesday

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High Temperatures Tuesday

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Very comfortable across much of the Lower 48 with only 28 million at/above 90\u00b0F.

7-Day Precipitation from NOAA WPC

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Atlantic Hurricane Season Day 100

2025 Hurricane Season [Day 100]. My FORECAST for this year is 14 named storms, 7 hurricanes, and 3 major hurricanes (near average) BUT that might be generous

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

I\u2019d like to highlight this post by Scott Yuknis on LinkedIn \u2014 a valuable resource for weather and climate analysis by professionals.

He diagnoses the rather inactive Atlantic hurricane season as being a consequence of colder SSTs in the North Atlantic due to the \u201cNorth Atlantic Warm Hole\u201d \u2026 leading to the subtropical ridge pushed farther south into the vicinity of the MDR. This allows Saharan Dust Layers, dry air from the Azores, and subtropics to infiltrate the tropics and increase wind shear and stability.

His thinking makes sense, of course! The impact of this weather regime on African Easterly Waves seems to be deleterious especially with the monsoon trough and ITCZ nudged southward while waves come off Africa at higher latitude (20\u00b0N) crossing cooler waters. It\u2019s all connected!

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ECMWF 12-Days Integrated Vapor Transport | 12z cycle

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Flagship model simulation for next 10-days \u2014 low chance for \u201csomething\u201d is STILL a wave that emerges next weekend.

VERY quiet \u2014 dormant Atlantic \u2014> ghost town! I think we\u2019ll need to dial back the seasonal forecasts a little bit mainly because we\u2019ll sail through the peak of the season with NOTHING.

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Let\u2019s look at another tropical wave in the 12-13 day range \u2014 more robust. However, that\u2019s way down the road \u2014 but we can use this model scenario to remind folks that Atlantic hurricane season is NOT over, just taking a little break.

ECMWF 18z | Precipitable Water Next 6-days

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A tropical wave by this weekend coming off Africa is next shot at a tropical system.

Atlantic Basin Outlook | 8 PM ET Update

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Ghost town!

Atlantic Satellite Imagery | Water Vapor

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The wave formerly known as Invest 91L continues to generate convection NE of the Caribbean. We\u2019ve lost some of the yellow dry blob coverage.

Infrared Imagery | Loop

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NOAA Tropical Surface Analysis | 18z

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Atlantic Tropical Waves = 3 generating moderate convection + remnants of Invest 91L

ECMWF SST and Anomaly | Atlantic

NASA Dust 5-day Forecast

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An early September dust plume helped to wipe out Invest 91L creating a dry and stable environment ahead of the tropical wave \u2014 and another one is on its heels. The dust is the symptom or proxy of the Saharan Air Layers (SAL) coming off Africa at about 20\u00b0N and ruining the chances of tropical storm formation.

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

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Tiny chance of a development (5%)

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

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A handful of members with tropical waves that develop \u2014 at most 20% \u2014 no change from yesterday\u2019s 12z cycle.

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

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Additional members \u201ccatch fire\u201d with tropical waves into major hurricanes \u2014 again in the 20% to 30% range, which is near climatology into third week of September.

Interesting to see the systems in the Gulf of Mexico again popping up \u2014 likely out of the Central American Gyre. GFS has been hinting at this for the last day in its model cycles.

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

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

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

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Plenty of options \u2014 but, as we saw with Invest 91L \u2014 don\u2019t count your chickens before they hatch.

Eastern Pacific Tropical Update| Hurricane Kiko

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Hurricane Kiko is asymmetric due to wind shear out of the SW but maintains hurricane force winds in the Northeast Quadrant.

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Kiko will weaken to a Tropical Storm but could linger for the next 4-5 days \u2014 no threat to Hawaii.

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70% chance of next system \u2014 Marco

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In 3-days we can expect Marco, and it should become a hurricane on a track paralleling the coast but no direct impacts.

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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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The Atlantic basin is a disorganized mess of troughs and scattered convection.

Hurricane Kiko has further weakened to Category 1 on a WNW course well away from the Hawaii Islands. Tropical Storm Marco is coming in 3-days along the coast of Mexico.

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