HURRICANE ANDREW TIMELINE – 5 DAYS UNTIL LANDFALL + A Gulf system to watch

At 5:00 PM on Wednesday, August 19, 1992 – thirty years ago today - Tropical Storm Andrew's winds were estimated at 50 mph – the same as the day before. The official National Hurricane Center forecast showed steady movement in the general direction of Florida or the Southeast, but in South Florida, we weren't worried. For more than 25 years, storms had always turned north or stayed offshore. The center of Andrew was 1,400 miles from Miami.

A large upper-level low spinning to the north was keeping Andrew from developing by preventing the thunderstorms from wrapping around the center. They were all in a blob on the east side of the circulation.

In the Technical Discussion that was part of the Wednesday afternoon advisory, National Hurricane Center forecaster Hal Gerrish discussed the possibility that a high-pressure system might strengthen to the north of Andrew after about three days. It was just speculation at that point, but that possibility figured into my thinking later in the week. The stronger the high, the more likely Andrew would make landfall somewhere in Florida.

Since there was a remote possibility that Andrew might affect the state, I decided to premiere a new cone-like graphic to talk about the uncertainty in the track forecast. I had been working on new ways to communicate hurricane information for the past year, and this was the first chance to use the new graphic.

Over the winter of 1991/92, I contacted retired National Hurricane Center-modeling guru Charlie Neumann about my idea of showing what the average NHC forecast errors were in the 24, 48, and 72-hour forecasts. Forecasts only went out three days at that time. I made a dashed arc on the map at each forecast time representing those average errors. The arcs were wider with each successive day representing the increasing uncertainty as forecasts were made for days further in the future.

Four years later, those arcs eventually morphed into a cone graphic like we use today. TV weather-graphics software finally allowed us to draw an outline and fill it in when an upgraded graphics system became available in 1995. We drew the forecast cone by hand for eight years beginning in 1996 until the graphics software caught up and finally plotted the data from the National Hurricane Center automatically.

The cone-like arcs that Wednesday in 1992 showed that Andrew would turn north and head north if it stayed on the right side of the quasi-cone’s set of possibilities. On the other hand, if it tracked on the left side of the arcs, the storm could come toward South Florida.

I premiered the new graphic on the news that Wednesday afternoon and evening. Even though the arcs showed the possibility of a problem in South Florida, it looked remote. In Miami, we weren’t concerned. The vast majority of the track possibilities at that point showed Andrew going somewhere else.

In reality, Hurricane Andrew was only 4 1/2 days from landfall less that 20 miles from downtown Miami with 165 mph winds.

IN 1992, A disturbance that has tracked across the Atlantic and Central America is moving into the extreme southwestern Gulf of Mexico known as the Bay of Campeche. If a cluster of thunderstorms persist over the warm Gulf water, it might have a chance to briefly organize.

The National Hurricane Center is now giving it a medium chance of developing into at least a tropical depression today or tomorrow. By late tomorrow it is forecast to move inland into Mexico or South Texas.

There is a corridor with a supportive environment for the system to organize and strengthen a little, though it’s narrow. The Mexican mainland is on the left, and hostile upper winds are on the right. We’ll see if it threads the needle.

In any case, the main effect is likely to be a moisture surge bringing heavy rain to the affected areas when it comes ashore.

The tropical Atlantic continues to be covered by a combination of Saharan dust and dry air from the north. A moist passage is developing south of the dry zone, so disturbances that move off Africa have a bit of a runway, but dry air is so close by that, so far, nothing has been able to develop.

The macro factors all appear quite favorable for systems to develop. The upper-level winds are generally conducive, and the ocean water is quite warm. The MJO – the Madden-Julian Oscillation – is a broad pulse that travels around the earth alternately encouraging and discouraging storm development. It is in a mode that would normally support tropical activity in the Atlantic.

The fly in the beeswax would seem to be the dry air. Though sometimes there are smaller-scale issues that discourage tropical development that aren’t obvious.

The long-range computer models show some effort at activity around the end of next week, but they have shown that before. Let’s see. For now… enjoy.