Tropical Storm Isaias

Tropical Storm Isaias is packing 35-kt (40-mph) winds, moving ENE at 7 kt (8 mph). Moves inland over the Alabama coast Sat.

At 400 AM CDT (0900 UTC), the center of Tropical Storm Isaias was located near latitude 22.0 North, longitude 94.1 West. Isaias is moving toward the east-northeast near 8 mph (13 km/h). A continued east-northeastward motion is expected today, followed by a turn toward the northeast and north on Thursday and Friday. On the forecast track, Isaias is expected to pass to the north of the Yucatan Peninsula on Thursday and approach the U.S. northern Gulf Coast on Friday. Maximum sustained winds have increased to near 40 mph (65 km/h) with higher gusts. Rapid strengthening is forecast over the next day or two, and Isaias is expected to become a hurricane by Thursday. Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1004 mb (29.65 inches).— National Hurricane Center · public advisory 3

This is the Atlantic · 20°N–42°N, 96°W–83°W. Isaias’s forecast track is the dotted spine — the labelled dots mark its position each day. Every cell is shaded by how many hours it spends inside Isaias’s gale-force (≥34 kt · 39 mph) wind across the whole forecast, the damaging core counted double.

Read it two ways at once. Colour is the total — the hours of gale-force wind a place piles up. A slow storm writes its danger in duration, not in any single gust, so the longer the wind sits over a place, the deeper its colour. Opacity is confidence — solid where the official probability of that wind is high, faint where it is only a chance. So a deep, solid cell is a place the wind will work for a long time and likely will; a pale, faint one is a brief, uncertain brush at the edge of the cone.