Wednesday’s Tropical Update

1. Atlantic Basin: NHC tropical weather outlook has a 10% chance of development for area of rain in northern Gulf from disturbance yet to cross Florida.

2. Eastern Pacific Basin: Chance for 1-2 systems in the next 7-10 days

3. Western Pacific Basin: Busy basin with Tropical Storm Francisco (10W), newly formed TD 11W, and Invest 98W. The latter will likely become a strong typhoon.

Looking into August, the 10-15 day period is beginning to light up on the ensemble model systems for storm / hurricane development in the western Atlantic off the U.S. East Coast.

Current Satellite Imagery

The showers and storms moving through the northern Gulf are well out ahead of the main area of interest still to the east on the Atlantic side of NE Florida.

The model depictions do not show much at all — just a band of weak vorticity associated with a trough and the countervailing flow of the very strong Bermuda high.

This is similar to the non-development of Invest 93L, which did help focus high-moisture content across the Lower Mississippi River Valley and Southeast over the past several days. This is a repeat weather pattern.

Large Basin view of Simulated Water Vapor | ECMWF 00z

Nothing has developed in the Main Development Region (MDR) of the Atlantic for a bunch of reasons:

It’s early in the season so even into the end of July, tropical waves coming off Africa are not likely to develop even with warm ocean temperatures. Also, the influence of Saharan Air Layers and dust to the north of the waves = stable and dry => suppression of convection. You can also see from the orange and light brown colors on the simulated water vapor imagery that middle latitude air is being shunted into the tropics from wave breaking and troughs — with help from the SAL.

The dry, dusty and stable (warm) air near the surface and in the boundary layer puts a lid on convective development.

The large-scale or basin scale environment is unfavorable for tropical storm formation with anomalously high pressure and sinking air. Note, the Eastern Pacific is also dead after a fast start = hemispheric tropical basin dead period.

However, into August, there may be a change in the sub-seasonal signals to more favorable as the Eastern Pacific gets going in 7-10 days meaning the Atlantic could follow in 10-14 days. The AIFS-Ensembles from ECMWF do show more action albeit low chance into August.

Integrated Vapor Transport Next 10-days | Atlantic Basin

Features: tropical wave off Africa moving steadily westward to Lesser Antilles in 1-week, but no development

Sunday: tropical wave emerges into Atlanta but opens within a few days. Again, not seeing development. There may be a short-lived surface circulation that shows up on visible satellite, but lack of convection won’t sustain it.

Thank you to readers continuing into this Hurricane Season. My goal is to keep you informed about ongoing extreme weather events inside and outside of the tropics, but also a week (hopefully) heads up on what’s coming. I’ll be using a variety of weather modeling output, some of it may be unfamiliar, but it’s state-of-the-art and industry leading standard.

Atlantic Basin Outlook

10% chance of development into weekend across the Northern Gulf.

Eastern Atlantic Satellite Image

Dust and dry air to the north of the weak tropical wave and the overall ITCZ/monsoon trough.

NASA GEOS-5 | 00z DUST Aerosol Optical Depth (AOD) | 10-d Forecast

Tropical waves will need to deal with continued dust plumes into August. I thought the intensity would wane significantly in the coming 1-2 weeks, but this model delivers a major plume on August 1st off Africa.

Atlantic Ocean Surface Temperatures (SST) | Anomaly

Ocean temperatures plenty warm from African coast to the Lesser Antilles with 28°C corridor or warm pool extending into the western Atlantic around Bermuda. However, the anomaly (which doesn’t do anything) remains near-normal or slightly below in the Main Development Region (MDR) from Caribbean to Africa.

Tropical Atlantic Satellite Imagery

A bit more convection in the eastern MDR with a tropical wave — more so that we’ve seen in previous weeks.

ECMWF Precipitable Water Next 6-days

My favorite parameter … fun to see the various interacting features in the atmosphere. The tropical Atlantic is not a friendly place for tropical storm formation during the next 6-days. The tropics are being infiltrated with dry, stable air from the subtropics in addition to dust and Saharan Air Layers. There are plenty of tropical waves but none can sustain convection and organize in the face of unfavorable background conditions.

ECMWF 00z depiction of Vorticity | Next 6-days

The ribbon of vorticity in the northern Gulf does not develop. Not seeing anything in the MDR or elsewhere through July 29th.

NOAA Tropical Surface Analysis | 06z

Atlantic Tropical Waves = 3 but not developing. The disturbance in the Gulf is associated with a trough.

Medium range ensemble model outlook

These are 51-realizations of the same model with different initial conditions. Each ensemble gets equal ~2% weight in a mean calculation.

ECMWF Ensembles 00z | Next 15-days

We do have hurricanes in the ensembles (EPS 00z) with 5/51 showing a powerful system in the western Atlantic. However, that is only 10%, so not a strong signal. We will monitor closely.

Compare with AIFS Ensembles | Next 10-days

Next 15-days

The 10-15 day period lights up with the AIFS-ENS v1 showing many systems. This is a more coherent signal that deserves attention.

Eastern Pacific Tropical Update

A couple weak systems could become TD or TS out near Hawaii in 7-days. Also, another system south of Mexico should develop with better chance at a hurricane.

AIFS-Ensembles through 5-days

Weak lows in the far southern tropics along the ITCZ

Day 10 Active Tracks

Better chance of significant storm off Mexico going to die over cooler waters.

Western Pacific Tropical Update

Busy / wild Western Pacific with multiple systems underway. Invest 98W will become the most impressive — the further east / detached from the main monsoon trough. Inside that mess, 10W and 11W are underway.

Tropical Storm 10W (Francisco)

Forecast to head WNW but weaken as a minimal TS.

Tropical Storm 11W

Could become a typhoon as it loops near Luzon

Invest 98W

Models bullish in this system near Guam becoming more a powerful typhoon.

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