{ "number": 724, "headline": "September 4, 2025 Thursday Evening Update", "standfirst": "Invest 91L up to 90% chance of becoming Gabrielle in coming days", "desk": "notebook", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-09-05", "published": "2025-09-05T01:12:30.342000Z", "updated": null, "access": "free", "body_html": "
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2025 Atlantic Hurricane Season [Day 96]. My FORECAST for this year is 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)

Thursday Evening Tropical Update

  1. Invest 91L in central MDR at 90% chance of development but not in a hurry with marginal background environment (dry air)

  2. Hurricane Kiko remains Category 4 but has entered another eyewall replacement cycle. The storm should skirt just north of the Big Island of Hawaii over cooler water.

  3. Tropical Storm Lorena decoupled and fell apart. The moisture went into Mexico while the low-level circulation remains behind.

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

Good Evening \u2014 another update as we watch the Cowboys at Eagles underway in Philadelphia \u2014 exciting game so far.

Invest 91L has a nice curved band of thunderstorms (convection) but it a very small system compared to Erin earlier in August, which was a sprawling monster circulation.

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We may have a tropical depression in the next 24-hours if this curved band can remain coherent and initiate the \u201cheat engine\u201d

RTMA Temperatures and Anomaly | 8:15 AM ET

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Cool / chilly air across the Midwest and Great Lakes. Lower 48 is -3.4\u00b0F below normal.

Low Temperatures Friday

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5% of the Lower 48 is under 40\u00b0F but only 0.1% below freezing.

High Temperatures Friday

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Hot across Texas again \u2014 and 90s into Nashville and Atlanta and perhaps as far north as Washington D.C.

7-Day Precipitation from NOAA WPC

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Atlantic Basin | ECMWF 18z | Precipitable Water Next 6-days

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90% chance of development of the tropical wave becoming Tropical Storm Gabrielle in the next 3-4 days, most likely on a much LOWER latitude course \u2014 almost due westward for 6-7 days, and then it could jump northward.

Atlantic Basin | ECMWF 18z | Vorticity Next 6-days

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Due westward course during the next 6 days \u2014 scenario with ECMWF 18z but VERY slow \u2014 up to 7-days to reach the Islands.

ECMWF 12-Days Integrated Vapor Transport | 12z cycle

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This is just one model scenario \u2014 but the ECMWF flagship model solution. Note that Gabrielle is wiped out by Hispaniola and has significant trouble organizing thereafter. Two more tropical waves invade the MDR.

Atlantic Basin Outlook | 8 PM ET Update

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Invest 91L ATCF Spaghetti through 7-days

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HAFS at Day 5: poorly organized but probably TS

GFS 18z Happy Hour Solution

near Major Hurricane in 7-days into the Lesser Antilles

Then at Day 12 \u2026 major hurricane east of the Bahamas with \u201cHumberto\u201d next up in central MDR

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Way out at Day 15 \u2014 Gabrielle curves northward out to sea \u2014 while Humberto drifts westward.

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Atlantic Satellite Imagery | Water Vapor

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Huge dry spot in the water vapor over the central Atlantic tropics and subtropics with Invest 91L right on the eastern edge of the huge yellow/orange dry spot (color enhanced water vapor imagery) \u2014 but it is a small vortex/circulation so the dry air may be effectively walled off.

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NOAA Tropical Surface Analysis | 18z

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Atlantic Tropical Waves = 2 including wave in monsoon trough in Central MDR (90%)

ECMWF 12z SST and Anomaly

ECMWF EPS 12z Ensemble | Active Cyclone Tracks Through 8-days

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Gabrielle could be a hurricane threat to the NE Caribbean

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

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

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And, we can\u2019t discount yet some impacts to the Bahamas and East Coast of the U.S. but that\u2019s over the horizon.

We\u2019re seeing ancillary development of a hurricane in the Gulf of Mexico. Low chance but worth watching.

ECMWF AIFS Ensemble 12z

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Eastern Pacific Tropical Update| Kiko and Lorena

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Kiko at Category 4 but now undergoing another eyewall replacement cycle.

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Track by NHC is just north of Big Island of Hawaii but much weaker as a tropical storm due to cooler water.

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ATCF guidance is clustered right over the Hawaii Island chain.

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HAFS-A and HAFS-B (18z) for Kiko at Day 5

Could be surprising intensity \u2014 maybe a weak hurricane that remains resilient to the cooler SSTs.

Tropical Storm Lorena fell apart.

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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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Invest 91L in central MDR at 90% chance of development but not in a hurry with marginal background environment (dry air)

Hurricane Kiko remains Category 4 but has entered another eyewall replacement cycle. The storm should skirt just north of the Big Island of Hawaii over cooler water.

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