{ "number": 404, "headline": "Oct 2, 2024 Wednesday Tropical Update", "standfirst": "Model support for Gulf of Mexico tropical system remains limited", "desk": "tropics", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2024-10-02", "published": "2024-10-02T15:03:00.263000Z", "updated": null, "access": "free", "body_html": "
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Enormous rainfall amounts fell over the past 7-days across the Southeast U.S. and Ohio River Valley into the Middle Atlantic. All told, well over 40 Trillion gallons of rain fell from combination of a Predecessor Rain Event (PRE) associated with a cut-off low or deep-layer trough + Hurricane Helene.

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Rainfall Analysis Last 7-Days

Looking at the past 30-days compared to normal (%) the extreme rainfall across the Southeast shows up with values 2-7x September climatology.

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Rainfall [% of normal] Last 30-days

Actual Rainfall (not anomaly) is incredible for the past 30-days

Total USA: 135 Trillion gallons

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Actual Rainfall (analysis) last 30-days

AP Coverage of Total Rainfall

I spoke to Seth Borenstein at the Associated Press about the meteorology behind the PRE + Helene\u2019s extreme rainfall. The article puts the enormous totals into context including Dallas Cowboys Stadium and Olympic Swimming Pool metrics.

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Nice description of the methodology using the NWS rainfall analysis.

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Headlines for Wednesday

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  1. Hurricane Kirk likely to become a major hurricane in next 2-days. The next wave behind Kirk will also develop into a potentially Cat 4 Hurricane Leslie on a similar track as Kirk.

  2. Gulf of Mexico gyre remains at 40% chance of development into a tropical cyclone. Model support remains limited but ensembles do show a large, broad circulation with lower pressure in 7-days mainly drenching Florida.

  3. Typhon Krathon to landfall Taiwan at Category 2 intensity in the next 12-18 hours. Heavy rain is the primary threat with Taiwan\u2019s topography.

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ECMWF 00z Integrated Vapor Transport (IVT) shows the massive size of Hurricane Kirk as it recurves north with potential to slam into United Kingdom in 9 to 10-days as a very powerful post-tropical storm. Leslie follows a bit further to the west on a similar recurving track. There could be some upwelling from Kirk that holds Leslie back, similar to how Krathon is weakening near Taiwan.

The complicated Central America gyre evolves into a large circulation encompassing the entire Gulf of Mexico but lacking a singular or dominant low-pressure center.

Confusion about Eastern Pacific storm activity including TD 11E (Kristy) maybe merging with Invest 97E and limiting the development of Lane.

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Atlantic GeoColor Satellite

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Hurricane Kirk is putting on a show in the central Atlantic with excellent outflow and banding. Kirk is \u201cvery large\u201d size and will only get bigger as it gains latitude.

Wave behind Kirk will likely become Leslie [13L] in the next 24-hours.

NHC 7-Day Outlook

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We\u2019re still at 40% with the large Gulf of Mexico gyre through 7-days. Good bet that Leslie will develop, however. NHC upgrades it to TD 13 at 11 AM

Hurricane Kirk

Water Vapor Imagery

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Kirk is very large and has a well-defined inner-core surrounded by sprawling spiral bands.

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ECMWF HRES does have a post-tropical Kirk threat to Ireland and the UK in 8-10 days.

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IVT shows an atmospheric river directed into Spain, Portugal and France from the low-pressure of post-Hurricane Kirk +8-days

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Heavy rainfall is the primary threat along with gusty winds. Nothing they haven\u2019t experienced in previous autumns being at the tail end of the North Atlantic hurricane track corridor.

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Tropical moisture with PWAT > 2\u201d will stream into Europe.

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Interesting non-tropical \u2014> tropical development possible NW of Kirk in the next 48-hours according to GFS 06z. No impact to land.

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The 3 systems are nicely lined up from NW to SE.

Leslie at 981 mb in 48-hours show rapid intensification is possible way out there.

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Gulf of Mexico Model Forecasts at Day 7

Quick round-up of global models (00z) for the Gulf of Mexico. The Canadian model is the only one of the 4 that develops a strong TS/H1.

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GFS 00z +7 Days
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ECMWF 00z + 7 Days
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Germany ICON 00z + 7 Days
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Env Canada GEM 00z + 7 Days

Typhoon Krathon [20W]

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Krathon has weakened to 100-knots under the effects of wind shear and upwelled / cooler SST due to wave mixing.

JTWC Forecast Track

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Forecast track still shows landfall along SW coast of Taiwan at 90-knots (Category 2) with extreme rainfall amounts due to the terrain of the island.

Eastern Pacific IR Satellite

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A small swirl has been designated TD 11E \u2014> Kristy by Wednesday.

Another area that was expected to become Hurricane Lane may now not develop as it merges with 11E (Kristy). Thus, the chance of development has been significantly knocked down.

Eastern Pacific 7-Day Outlook

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TD 11E \u2014> Kristy

ECMWF 00z Tropical Cyclone Tracks

Day 4: October 6 00z

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Some hints of development in the Gulf of Mexico at Day 4

Day 7: October 8

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About 50/50 chance of development in the Gulf of Mexico with most members in the 990s suggestive of a large, disorganized tropical storm (at worst) with heavy rain as the primary threat.

Day 10: October 11

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Blend of Models | 10 Days Total Precipitation

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Not seeing much in the way of rainfall across much of the Lower 48 west of the Mississippi, while Florida and the immediate Gulf Coast are drenched.

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Enormous rainfall amounts fell over the past 7-days across the Southeast U.S. and Ohio River Valley into the Middle Atlantic. All told, well over 40 Trillion gallons of rain fell from combination of a Predecessor Rain Event (PRE) associated with a cut-off low or deep-layer trough + Hurricane Helene.

Looking at the past 30-days compared to normal (%) the extreme rainfall across the Southeast shows up with values 2-7x September climatology.

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