GaWx

Jeff Piotrowski:

Before Melissa, the lowest SLP on record in Jamaica was 958 mb (1951’s Charlie) followed by 960 mb (Gilbert 1988).

ACE will likely exceed 122.5 by 18Z today.

I received 0.20” since last night bringing me to 2.75” MTD, which is only modestly below normal.

Today’s Euro Weeklies run mean has an even weaker SPV with only 8 of the 42 days’ mean stronger than normal, and it even includes 15% of members with a very early major SSW, by far the most yet of any run this season! Note that the progged mean Thanksgiving through Dec 11th of 2025 SPV is only ~20 vs normal of 31, which would be the weakest for that period since 2019-20: Compare the above to the prog at the same time last year: 40 of the 42 days’ mean stronger than normal along with ZERO members with a major SSW: Note that the mean Thanksgiving through Dec 12th of 2024 was up at ~37 (it verified to be way up at ~45) Now compare to the prog from the same time two years ago: 30 of the 42 days’ mean stronger than normal with only 2% with a major SSW: Note that the mean Thanksgiving through Dec 9th of 2023 was ~31 (it verified to be ~34): In summary, this post shows that the 100 member Euro Weeklies mean is suggesting a mainly weak SPV in late Nov and early Dec, which would compare to a very strong SPV for the same time in 2024 and a slightly stronger than normal SPV in 2023. Even if we assume that the 2025 prog is biased modestly too negative, a bias adjustment would still be progged pretty weak (~25) and would be way below 2024’s actual of 45 and significantly below 2023’s actual of 34. @mitchnick@snowman19

This epic modeling failure would be amazingly great news. Do you think this is a realistic possibility? Keep moving west!

The IOD will almost certainly still rebound sharply by winter as it did in those other 3 cases since 2010 as we’ve been in a +IOD regime in recent years and IOD almost always bottoms by this time of year:

1995-2005 did average ~160. But outside of those years, 10 seasons (1991-4, 2006-7, 2009, and 2013-5) were <80. If I were classifying what’s hyperactive, I’d add some years that were <175 during a much lower avg recorded ACE era such as 1886’s 166, 1899’s 151, 1906’s 162, 1916’s 144, 1932’s 170, and 1955’s 158. Even 1880’s 131 should be considered imho as it was way higher than all preceding years other than 1878 back to 1851.

2025 ACE: Through Sept 16th: 39 Sept 17th+: 74 and rising rapidly. The full season to date ACE is progged to get above the 1991-2020 full season avg of 122 by tonight and then go well above that within the next few days. This very active late season ACE has been the pattern especially in recent La Nina seasons. There have been 4 MH with 3 of them occurring since Sept 22!

That’s the nature of a solid +PNA as you know, especially without an accompanying -EPO. There has been a pretty strong +EPO in recent days. Often the coldest anomalies on average tend to be further SE with it often above normal in much of Canada. As the Euro Weeklies show, I also expect a warmup after the next 2 weeks. But, in the meantime, as mentioned the E 1/4 of the US is overall progged to have its coldest 10/27-11/9 since 2012 with coldest anomalies centered southern Mid-Atlantic states and SE US. Per the EW, a warmup follows but mainly to near normal rather than AN with only week 4 AN and it only slightly AN.

There are 3 Atlantic basin hurricanes on record on this date or later that were cat 5 and they had these lowest pressures/highest sustained winds: -Mitch of 1998: Oct 26-28; 905 mb/180 mph; but landfall was way down at 80 mph on Honduras. The extreme rainfall though was what made it so deadly. -Hattie of 1961: Oct 31; 914 mb/165 mph; it weakened slightly at landfall in Belize to 915 mb/150 mph (cat 4) -Cuba hurricane of 1932: Nov 5-8; 915 mb/175 mph; but it weakened some before hitting land as it was 150/cat 4 on landfall The latest on record cat 5 landfall was on Cuba on Oct 19 (in 1924) near its peak intensity of 165 mph. So, IF this were to hit Jamaica as a cat 5, it would become the latest on record to make landfall anywhere by 9 days.

This is very sad and terrifying to see knowing that Jamaica is in the crosshairs of this monster. Hopefully something unexpected will change things at least a little bit for the better before landfall. Any weakening would be quite welcome obviously.

It isn’t just upwelling that cools the waters at or near where a hurricane crosses: it also cools due to the conservation of energy (potential energy from warm water transitions to kinetic (wind) energy of the storm/heat engine), cooling from raindrops (I assume this factor is relatively minor), and cooling from cloudcover blocking the sun: Hurricanes cool the ocean by acting like "heat engines" that transfer heat from the ocean surface to the atmosphere through evaporation. Cooling is also caused by upwelling of cold water from below due to the suction effect of the low-pressure center of the storm. Additional cooling may come from cold water from raindrops that remain on the ocean surface for a time. Cloud cover may also play a role in cooling the ocean by shielding the ocean surface from direct sunlight before and slightly after the storm passage. All these effects can combine to produce a dramatic drop in sea surface temperature over a large area in just a few days. https://earthobservatory.nasa.gov/images/6223/passing-of-hurricanes-cools-entire-gulf#:~:text=Hurricanes cool the ocean by,pressure center of the storm

BULLETIN Hurricane Melissa Intermediate Advisory Number 22A NWS National Hurricane Center Miami FL AL132025 800 PM EDT Sun Oct 26 2025 ...LIFE-THREATENING AND CATASTROPHIC FLASH FLOODING AND LANDSLIDES EXPECTED IN PORTIONS OF JAMAICA AND SOUTHERN HISPANIOLA THROUGH MIDWEEK WITH HURRICANE FORCE WINDS LIKELY TO BEGIN TOMORROW... SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION ---------------------------------------------- LOCATION...16.4N 77.3W ABOUT 115 MI...185 KM SSW OF KINGSTON JAMAICA ABOUT 295 MI...475 KM SSW OF GUANTANAMO CUBA MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H PRESENT MOVEMENT...W OR 270 DEGREES AT 5 MPH...7 KM/H MINIMUM CENTRAL PRESSURE...933 MB...27.55 INCHES

Today’s Euro Weeklies out 6 weeks for E US: - Coldest 1st 2 weeks of any run for that period (10/27-11/9) thanks to a combo of an impressive +PNA and impressive ascending -NAO, which should it verify closely would be coldest for E US overall since the similarly chilly Oct 27-Nov 9 in 2012. For those curious, that period in 2012 actually had a mean near opposite weak -PNA as well as a similarly strong -NAO and weak -AO. It had a +EPO like we have now. It had for the MJO a moderate 2, mod 3, and ended with weak 4/5. - No long period of mild in sight with weeks 3, 5, and 6 NN and week 4 only barely AN

Today’s Euro Weeklies out 6 weeks for E US: - Coldest 1st 2 weeks of any run (see below) for that period thanks to a combo of an impressive +PNA and impressive ascending -NAO, which should it verify closely would be coldest for E US overall since the similarly chilly 2012 for Oct 27-Nov 9. For those curious, that period in 2012 actually had a mean near opposite weak -PNA as well as a similarly strong -NAO and weak -AO. Edit: it had a +EPO like we have now. It had for MJO moderate 2, mod 3, and ended with weak 4/5. - No long period of mild in sight with weeks 3, 5, and 6 NN and week 4 only barely AN Week 1 (Oct 27-Nov 2): Week 2 (Nov 3-9):

WTNT43 KNHC 262100 TCDAT3 Hurricane Melissa Discussion Number 22 NWS National Hurricane Center Miami FL AL132025 500 PM EDT Sun Oct 26 2025 After an earlier pause in intensification, this afternoon's Air Force Reserve reconnaissance mission has found Melissa intensifying again. The minimum pressure has fallen 12 mb from this morning NOAA-P3 mission, with the last dropsonde indicating a minimum pressure of 941 mb, and the plane reported a shrinking eyewall down to 6 n mi in diameter. In addition to the low pressure, the satellite presentation of Melissa remains very impressive, with 1-minute visible satellite images from a GOES-19 meso-sector showing a very clear eye with a stadium effect. The eye temperature on water vapor imagery has continued to warm, while the thick ring of eyewall cloud tops remains between -75 to -80 C around the eye. The presentation of Melissa on radar reflectivity from Kingston, Jamaica has also improved, though there still appear to be hints of a moat forming around the inner eyewall, though without an obvious secondary eyewall formation yet. Subjective Dvorak CI-numbers from both SAB and TAFB were T7.0/140 kt, with objective satellite estimates between 132-143 kt. However, Melissa's peak winds from the last couple of recon missions have been lagging the satellite-based estimates. The last fix had peak 700 mb flight level winds of only 129 kt, but a dropsonde launched in the north eyewall also reported a 500 m layer average of 142 kt, with an earlier dropsonde in the NE eyewall with a surface wind gust of 131 kt. This data is enough to raise the maximum sustained winds of 125 kt, and given the satellite presentation, this could be conservative. Melissa continues to move slowly westward, estimated at 270/4 kt. The hurricane has been moving a little faster to the west today, and this motion will likely continue for another 12-18 hours while the narrow mid-level ridge to the north remains in place. Soon, a short-wave trough will be moving into the SE United States, and this feature should create a weakness that Melissa will turn sharply northeast into, as it gradually accelerates. The track guidance has shifted a little westward again this cycle, and the NHC track forecast was nudged a little west again, but still shows landfall on Tuesday morning along the south coast of Jamaica. There remain some timing differences thereafter, but a second landfall is anticipated along the southeastern Cuba coast by Tuesday night or early Wednesday morning. As Melissa then accelerates into the southwestern Atlantic, it will move through the Bahamas and potentially approach Bermuda by the day 4-5 time frame, with a reinforcing trough helping to kick it farther out to sea. The latest NHC track forecast is a little west in the first 24-60 h, but falls back near the previous forecast track thereafter. The track is roughly a blend of the reliable HFIP Corrected Consensus Approach (HCCA) and Google Deep Mind ensemble mean (GDMI). Now that Melissa is intensifying again, it seems more clear that the earlier pause in intensification was a temporary oscillation, and the hurricane now appears poised to intensify more in the short-term. The latest NHC intensity forecast shows a little more intensification in 12 h, but continues to show a peak intensity of 140 kt, which is supported by HAFS-B which shows landfall of Melissa as a catastrophic Category 5 hurricane. The Google DeepMind ensemble members also continue to indicate this peak, with now 48/50 members reaching this lofty intensity. However, inner-core processes like ERCs could occur at any time, and the current small eye of Melissa likely suggests an ERC could begin in the next 24 hours or so, though it is very difficult to predict these occurrences with much skill. After landfall in Jamaica, Melissa will likely weaken some due to the interaction with that Island's high terrain, but it is still expected to be a major hurricane when crossing the Cuba coastline on Tuesday night. After emerging into the southwestern Atlantic Ocean, increasing vertical wind shear should continue gradual weakening through the end of the forecast, with the possibility that Melissa could start extratropical transition by day 5. The NHC intensity forecast continues to be on the high side of the guidance, but falls closer to the HCCA and IVCN aids towards the end of the forecast period. ———— Monday. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 16.4N 77.2W 125 KT 145 MPH 12H 27/0600Z 16.4N 77.7W 135 KT 155 MPH 24H 27/1800Z 16.6N 78.2W 140 KT 160 MPH 36H 28/0600Z 17.2N 78.2W 140 KT 160 MPH 48H 28/1800Z 18.4N 77.5W 115 KT 130 MPH...INLAND OVER JAMAICA 60H 29/0600Z 20.0N 76.1W 105 KT 120 MPH...ON THE SE CUBA COAST 72H 29/1800Z 22.1N 74.4W 90 KT 105 MPH...OVER WATER 96H 30/1800Z 28.0N 69.5W 80 KT 90 MPH 120H 31/1800Z 37.0N 60.0W 70 KT 80 MPH $$ Forecaster Papin

WTNT33 KNHC 262055 TCPAT3 BULLETIN Hurricane Melissa Advisory Number 22 NWS National Hurricane Center Miami FL AL132025 500 PM EDT Sun Oct 26 2025 ...HURRICANE MELISSA RESUMES INTENSIFYING... ...LIFE-THREATENING AND CATASTROPHIC FLASH FLOODING AND LANDSLIDES EXPECTED IN PORTIONS OF JAMAICA AND SOUTHERN HISPANIOLA THROUGH MIDWEEK WITH HURRICANE FORCE WINDS LIKELY TO BEGIN TOMORROW... SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...16.4N 77.2W ABOUT 115 MI...185 KM SSW OF KINGSTON JAMAICA ABOUT 295 MI...470 KM SSW OF GUANTANAMO CUBA MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H PRESENT MOVEMENT...W OR 270 DEGREES AT 5 MPH...7 KM/H MINIMUM CENTRAL PRESSURE...941 MB...27.79 INCHES

Today’s Euro Weeklies 10 mb zonal wind update fwiw:

60 knot increase from 5AM EDT Saturday’s 60 knots to 5AM today’s 120 knots!

Yeah, it was first at 10:54AM. All of it was later vs average release time.

That wasn’t released til 10:56 AM EDT. That’s very late for the 11AM. And discussion still wasn’t out yet. It wasn’t released til 10:59AM!

There was only 39 ACE through Sept 16th. There has been 67 ACE Sept 17th through 12Z today with likely 20+ more to come from Melissa, alone. This heavy late season vs earlier has been more common in recent years, especially during La Niña.