{ "number": 751, "headline": "September 29, 2025 Monday Weather Update", "standfirst": "Humberto and Imelda will encounter a powerful early fall upper-level trough", "desk": "notebook", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-09-30", "published": "2025-09-30T01:20:53.947000Z", "updated": null, "access": "free", "body_html": "
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2025 Hurricane Season [Day 121]. My FORECAST for this year is (still) 14 named storms, 7 hurricanes, and 3 major hurricanes (near average)

2025 Season to Date: 9 Named Storms, 3 Hurricanes, and 3 Majors | ACE = 80

Good Evening! This is post 751 in this newsletter\u2019s brief history (~2 years). I\u2019m shifting back to full time USA weather coverage as winter is fast approaching, and that means snow and cold.

Mid-Level Water Vapor Loop

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Impressive upper-level outflow from Imelda as a trough digs through the Southeast \u2014 dry as a bone underneath the yellow + orange colors.

Medium and Range | AIFS 18z | 10-days Height Anomaly

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We can thank this powerful Canadian trough for obliterating Humberto \u2014 and just enough of a connection with Imelda to keep it from affecting the U.S. East Coast. A ridge then sweeps eastward across the U.S. = warm conditions into mid-October.

We really lucked out on this \u201ctwin hurricane\u201d system \u2014 saved by a strong dip in the Canadian Arctic jet stream.

Not much going on weather-wise this week across the Lower 48 except late summer like warmth into October!

High Temperatures Next 9-days

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

Precipitable Water Next 6-days

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Precipitation Type Next 6-days

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Snowfall Next 10-days

Plenty of snowfall already in the Arctic including Alaska \u2014 and some in the Rockies across Wyoming and Colorado.

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Global 10-day Snowfall

Siberia snowfall quite healthy with widespread winter weather already.

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Tuesday Low Temperatures

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Tuesday High Temperatures

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Warmth | High Temperature Anomaly Next 5-days

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NOAA WPC 7-Day Precipitation

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Atlantic Basin Outlook | 8 PM ET Update

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Thankfully Imelda will not be a threat to the U.S. East Coast but could bring hurricane conditions to Bermuda.

Evening Water Vapor Satellite Loop | mid-level

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Wind shear is starting to impinge upon the circulation of Humberto \u2014 and it should steadily weaken until becoming post-tropical on Wednesday.

To the west of Imelda, another trough is digging through Florida and wrapping around the storm. Imelda is more asymmetric but the inner-core seems to be shielded from the worst of the mid-level dry air and upper-level wind shear \u2014> so we should see Imelda become a hurricane on Tuesday and come close to \u201cmajor status\u201d before turning rapidly ENE out-to-sea.

NHC Track for Tropical Storm Humberto | 942 mb | 140 mph Winds

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Hurricane Humberto IR Satellite

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Wind shear is eroding the western semi-circle of the storm and the eyewall is opening \u2026 signaling a potential rapid weakening. Good news is that Humberto will go north and around Bermuda.

Tropical Storm Imelda | NHC Forecast Cone

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Winds are nearing hurricane intensity with Imelda \u2014 and NHC has a maximum forecast of 85-knots by Wednesday (Category 2).

However, the satellite loop looks messy \u2014 with the curved band of convection becoming less organized. Hostile environment for a developing tropical storm \u2014 for now.

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ECMWF Next 10-Days Integrated Vapor Transport | 12z cycle

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Humberto and Imelda both out-to-sea and gone by the end of the week.

Two more named storms in the next 10-days likely in the Eastern Pacific: Octave and Priscilla \u2014 with the latter developing close to the Mexico coast \u2014 and could be quite intense.

Need to watch a tropical wave coming across the MDR over the next 5 to 10-days and arriving near the Lesser Antilles.

ECMWF 18z Precipitable Water | Next 6-days | Humberto and Imelda

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ECMWF 18z Relative Vorticity | Next 6-days | Humberto and Imelda.

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Cool loops of precipitable water as the two hurricanes interact \u2014 and form a twin cyclone systems that eventually breaks apart as Humberto becomes weaker during extratropical transition. Imelda will probably linger for a while longer \u2014 but will eventually head away as a post-tropical storm.

SST Analysis and Anomaly

Forecast in 15-days | ECMWF 12z

Just in two weeks, the 26\u00b0C isotherm begins rapidly eroding southward near 30\u00b0N latitude as Northern Hemisphere Fall continues.

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NOAA Tropical Surface Analysis | 18z

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Atlantic Tropical Waves = 2 but neither flagged as development potential by NHC

Eastern Pacific | Invest 98E \u2014 90% chance of development

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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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Impressive upper-level outflow from Imelda as a trough digs through the Southeast \u2014 dry as a bone underneath the yellow + orange colors.

We can thank this powerful Canadian trough for obliterating Humberto \u2014 and just enough of a connection with Imelda to keep it from affecting the U.S. East Coast. A ridge then sweeps eastward across the U.S. = warm conditions into mid-October.

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