The 2023 Atlantic hurricane season officially began last Thursday, with Tropical Storm Arlene forming right as the season started (it was actually not the first classifiable system of the season, as an unnamed subtropical storm developed in January). As we get closer to the peak of the season, usually the upcoming hurricane season becomes easier to forecast. However, 2023 is shaping up to be quite unusual, and is quite possibly the most challenging June forecast I’ve had to write. With a developing El Niño in the equatorial Pacific, it would normally be an easy below-average forecast to near-average at most, due to the increased vertical shear over the tropical Atlantic and Caribbean usually associated with the phenomenon. Our current forecast calls for a near-average season due to the competing factors, but uncertainty is much higher than normal for a forecast this late in the year.

Atlantic Sea Surface Temperatures

Currently, the sea surface temperature anomaly pattern in the Atlantic basin resembles that of the multi-decade active era that began in 1995. In fact, the deep tropical Atlantic and eastern subtropical Atlantic is much warmer than normal, and the Atlantic sea surface temperature anomaly profile is starting to look like the classical +AMO (Atlantic Multidecadal Oscillation) pattern. According to Dr. Philip Klotzbach, the May sea surface temperatures in the eastern Atlantic were more than 3 standard deviations above the mean, which is likely to strongly enhance Atlantic hurricane activity. Climate models, such as the CFS, CanSIPS, and ECMWF, predict this anomalous warmth to persist through the peak of the hurricane season. Such a sea surface temperature anomaly pattern is most commonly associated with extremely active Atlantic hurricane seasons. Normally, during an El Niño, enhanced tropical Atlantic trade winds result in the tropical Atlantic being cooler than normal, but that does not seem to be the case this year. Overall, I think that the Atlantic sea surface temperature anomaly pattern will be a significant enhancing factor for the 2023 hurricane season.

El-Niño Southern Oscillation (ENSO)

An El Niño event is developing over the equatorial Pacific. The latest weekly Nino 3.4 sea surface temperature anomaly value was +0.8C, indicating that the Climate Prediction Center (CPC) should declare the onset of El Niño shortly. The Nino 1+2 region is already much warmer than normal, with a weekly sea surface temperature anomaly of +2.3C. The equatorial Pacific subsurface is also much warmer than normal, which is another typical precursor sign of El Niño development. The 90-day averaged Southern Oscillation Index was approximately -7.5, which suggests that the atmosphere is beginning to respond to the development of El Niño. There is now high confidence that El Niño will be in place during the Atlantic hurricane season – which would normally suggest a quiet season. In their May forecast, the CPC gave a 93% chance of El Niño conditions for August-September-October (ASO), and I’d expect these probabilities to be raised even further this week. This event is extremely likely to become the strongest El Nino event since the 2014-16 Super El Niño, and will likely be in moderate to strong territory by October. The Caribbean Sea is the region of the Atlantic typically most affected by El Niño, and it is likely that the region will be suppressed for hurricane development this year. However, over the eastern tropical Atlantic and the subtropical Atlantic, El Niño suppressive effects tend to be less adverse, so it is likely that we’ll see some tropical cyclones take advantage of more favorable conditions in the rest of the basin. It should be stressed that El Niño does not mean the season is “canceled” or that coastal land areas are safe this hurricane season – it only takes one storm to have a significant impact!

West African Monsoon (WAM) / Precipitation

In recent years, a fairly strong West African Monsoon (WAM) has led to increased precipitation and precipitable water over the Sahel region of western Africa where tropical waves originate. It appears like that will be the case again this season, as precipitable water was above normal in nearly all of western Africa during April and May. This is usually a sign of an oncoming strong WAM during the season.

In addition to Africa precipitable water being above normal, model guidance suggests that there are elevated chances of above-normal precipitation over Africa and the Atlantic Main Development Region (MDR) for the August-September-October period. The May NMME suite shows this, with also elevated chances of below-normal precipitation over the Caribbean Sea – a typical feature of El Niño. It should be stressed, however, that precipitation anomaly models are not a good indicator of tropical cyclone tracks. I expect the West African Monsoon to be a slight to moderate enhancing factor for the 2023 Atlantic hurricane season.

Cyclonic Fury’s June 2023 Atlantic hurricane season forecast

• 13-16 named storms (1991-2020 average: 14.4)
• 5-7 hurricanes (1991-2020 average: 7.2)
• 2-4 major (Category 3+) hurricanes (1991-2020 average: 3.2)
• Accumulated Cyclone Energy 100 (+/- 25) (1991-2020 average: ~122)

Cyclonic Fury also gives the following probabilities of activity.

• Hyperactive season: 10% (Accumulated Cyclone Energy (ACE) of 160 or greater) – This is an unlikely scenario, but could occur if the El Niño remains weak but the anomalously warm tropical Atlantic completely counteracts ENSO.
• Above normal season: 25% (Accumulated Cyclone Energy (ACE) of 126-159) – This could occur if the Atlantic is generally favorable due to the strong WAM and favorable sea surface temperature pattern, but the El Niño does keep activity less active than normal in the Caribbean Sea.
• Near normal season: 35% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria) – This is the most likely scenario. In this scenario, the El Niño does significantly limit activity in the Caribbean Sea, but the rest of the basin is fairly favorable.
• Below normal season: 30% (Accumulated Cyclone Energy (ACE) of 73 or less) – This scenario will likely occur if the El Niño suppressive shear is more of a factor than anticipated. If the El Niño is strong enough, it could significantly limit the effects of the anomalously warm tropical Atlantic, and could shut down the Caribbean Sea almost entirely.

Forecast Verification

This is the first time Cyclonic Fury has issued a June Atlantic hurricane season forecast. From 2017 to 2022, I released a forecast in late May. Our first May Atlantic hurricane season forecast was released in 2017, predicting 13 named storms, 6 hurricanes and 3 major hurricanes (excluding Tropical Storm Arlene). This forecast fell well short of the actual activity, which was 17 named storms, 10 hurricanes, and 6 major hurricanes. In May 2018, Cyclonic Fury began to use ranges as I do now, predicting 10-14 named storms, 4-7 hurricanes, 2-3 major hurricanes, and an ACE index of 90 +/- 25 units. This forecast, just like expert groups in 2018, fell well short of the actual activity of 15 named storms, 8 hurricanes, 2 major hurricanes and an ACE index of 130 units. In May 2019, Cyclonic Fury predicted 11-15 named storms, 5-8 hurricanes, and 1-3 major hurricanes, with an ACE index of 105 +/- 40 units. Atlantic hurricane activity verified higher than my forecast, as 18 named storms, 6 hurricanes, and 3 major hurricanes formed, with an ACE index of 130 units. However, I did correctly suggest that El Niño persisting was not a guarantee, while NOAA expected it to persist in May 2019. In May 2020, I correctly predicted an above-average to hyperactive season, predicting 15-19 named storms, 7-10 hurricanes and 3-5 major hurricanes. Once again, Atlantic hurricane activity verified higher than my forecast, with 30 named storms forming, 14 hurricanes and 7 major hurricanes. In May 2021, my May forecast verified very well, as I predicted 15-20 named storms (actual: 21), 7-10 hurricanes (actual: 7), 3-5 major hurricanes (actual: 4), and an ACE index of 140 units (actual: 145.7). In May 2022, my May forecast was much higher than the expected activity, as I predicted 16-21 named storms (actual: 14), 7-11 hurricanes (actual: 8), 3-6 major hurricanes (actual: 2) and an ACE index of 150 units (actual: 95).

It should be stressed that, at this extended range, it is too early to predict which areas will be the most at risk for hurricanes this season, but it only takes one hurricane to have a significant impact.