Spring 2026 Hong Kong climatology
Neutral ENSO transition · late La Niña retreat · MJO & Amihan interplay
Assessment for March–May 2026 · Issued: February 2026
ENSO phase Neutral (ENSO‑neutral) established by late Feb/March 2026 after a weak La Nina retreated with local weather prominent approaching summer that will warm.
HKO outlook Temperature: normal to above‑normal · Rainfall: normal to below‑normal [citation:1]
Background Equatorial West Pacific SST warming (Feb 2026 observation) with weather resembling the Normal Nuetral ENSO phase changes.
1. Convection factors
- SST gradient: South China Sea warms faster than equatorial Pacific (neutral phase), enhancing local instability.
- Late La Nina inertia: suppressed Walker cell over western Pacific slowly relaxes → gradual increase in subtropical convection.
- Coastal convergence: weak prefrontal squall lines possible from mid‑March onward.
CAPE anomaly (Spring 2026 vs 1991–2020)
↑ Slightly enhanced convection by late spring (neutral ENSO + warming SCS)
2. MJO pulse (early spring)
- Monitor MJO status next 8 weeks arrival in Maritime Continent area may influence HK weather accordingly.
- Likely outcome: one or two active rainfall windows (10–15 days) with possible thunderstorm outbreaks around mid‑March (only forecasted might be possible).
- After pulse: drier regime as MJO moves into phases 6‑7 (suppressed convection over South China).
Phase 4/5: +rain
Phase 6/7: drier
Typical MJO influence under neutral ENSO [based on historical composites]
3. Amihan → spring monsoon
- Amihan (NE monsoon): gradually weakens in March, but late surges possible until early April.
- Transition (April–May): increasing southerly / southwesterly flow, onset of pre‑monsoon troughs.
- Result: humid, showery by early May, but neutral ENSO delays organised monsoon rain by ~1‑2 weeks?
NE (Mar)
S (Apr)
SW (May)
4. Neutral ENSO local effects
With ENSO neutral established after the late La Nina retreat [citation:1], synoptic variability becomes more dependent on regional drivers:
- Diurnal cycle plays bigger role — sea breeze convergence triggers afternoon showers by late April.
- Mid‑latitude troughs more efficient in drawing moisture from the south.
- South China Sea SST near 27–28°C by May supports localized heavy convection despite neutral background.
5. Spring parameters outlook
23-26°C mean temp
Mar–May, near to above normal [citation:1]
Mar–May, near to above normal [citation:1]
75-85% RH
increasing from dry Mar (70%) to humid May (85%)
increasing from dry Mar (70%) to humid May (85%)
~5840gpm 500mb height
mid‑spring, weak subtropical ridge
mid‑spring, weak subtropical ridge
27.5°C SST (May)
around HK waters, maritime fair
around HK waters, maritime fair
Maritime: Sea state slight to moderate, visibility reduces in April‑May haze or sea fog.
500mb geopotential height & wind – Spring 2026 composite (neutral analogue)
mid‑level flow: westerly 15‑25kt
🌊 Wave height 0.5–1.2m
🌡️ Sea surface 22°C (Mar) → 27°C (May)
🌀 Tropical potential low early season
500mb winds: Weak troughing near 120°E during transition, favouring shortwaves – neutral ENSO typical [citation:1][citation:2]
Assessment based on HKO seasonal forecast (Feb–Apr 2026) [citation:1][citation:2] and ENSO neutral progression. The forecast for March–May 2026 will be updated in early March [citation:1]. MJO influences are probabilistic; 500mb pattern reflects multi‑model consensus.
Charts are illustrative schematics. Data reference: Hong Kong Observatory, Tokyo Climate Center, NCEP.
Published: 23 February 2026
🌐 ENSO state: neutral (NOAA OISST weekly + HKO assessment Dec 2025 near‑normal) [citation:1]