Major Tropical Cyclone Heading to Port Hedland Mid-week

Headline: Big warm-up and snowmelt ahead!

Fig. 1-2: NOAA 5-day significant river flood forecast (left) and current weather watch, warning, and advisory areas emphasizing snowmelt/flood risk areas.

Discussion: River flood warnings stretch across the Midwest, much of the Mississippi River, and Mid-south U.S. plus parts of East Texas (Fig. 1). Stronger flood risk in central Arkansas while adding parts of South and North Dakota to the list are likely early this week (Fig. 2). Parts of the Carolinas to Georgia also have river flood risk early this week. Snowmelt due to warm weather over the next few days leads to a large area of flood risk from the Great Basin to the northern Continental Divide States and eastward to the far northwest Great Plains plus the Upper Midwest. Currently, snow cover remains in the 10-20 in. range across eastern North Dakota and northeast Wisconsin with most of the Dakotas and Minnesota continuing snow cover (Fig. 3). Significant flooding caused by snow melt is likely in the eastern Dakotas and California/Great Basin April 15-21 (Fig. 4). Plenty of short-term warmth this week from the Southwest to North-central and Northeast States.

In the medium-range, the GFS ENS is utilized which indicates the short-term cool regime in the Southeast States expands into the East while Interior West warmth will linger, and the North-central States cool off in the 6-10-day period (Fig. 5). In the 11-15-day period, models vary widely. The GFS ENS

Fig. 3: Daily snow cover analysis for the U.S. for late April 8, 2023.

Fig. 4: NOAA indicates where flooding due to snow melt is likely for mid-April.

Fig. 5-6: The GFS ENS medium-range temperature anomaly forecast.

In the medium-range, the GFS ENS is utilized which indicates the warmth convenes on the Northeast U.S. in the 6-10-day period while lingering Interior West (Fig. 5). The Central U.S. turns cooler. In the 11-15-day period, the Southeast and East U.S. are cooler while more snow melt is ahead for the Great Basin and vicinity (Fig. 6). The U.S. gas population weight HDD forecast maintains below normal late season heating demand although the Apr. 21-27 forecast trend is toward normal (Fig. 7). The CDD projections remain low, in the 7-15 range for each week through April.

Fig. 7: U.S. gas population weight HDD forecast for the weeks in April utilizing all models, their consensus and comparison with 24 hours ago and normal.

In Australia, a tropical cyclone is forecast to develop the next 2-3 days and become a category-4 major tropical cyclone turning into Port Hedland midweek (Fig. 8).

Fig. 8: The 5-day forecast for Tropical Storm 18 is indicated.