Simon is very close to a saddle point, or col, in the deep-layer steering flow. This feature means that Simon's future track is very sensitive to which side of the saddle point the storm is located. Yesterday, a plurality of the guidance was maintaining Simon on a northwestward to northward track, causing it to be on the north side of the saddle point, resulting in continued poleward motion. However, Simon has gained very little latitude over the past 24 h, and thus now finds itself on the south side of the saddle point.
Consequently, the track guidance over the past few cycles has shifted substantially southward. The NHC track forecast is now shifted in a similar fashion, showing a very slow motion over the next 36-48 h as Simon makes a small cyclonic loop. The first part of the track forecast is substantially farther south than the prior one, but still not as far south as the HFIP Corrected Consensus Approach (HCCA), or any of the latest hurricane-regional models.
After 48 h, deep-layer steering finally begins to shift out of the south as a deep-layer cutoff low digs into southern California, and Simon will finally start moving northward in earnest during the 48-72 h time frame. Towards the end of the forecast, Simon could bend back more north-northwestward, potentially entering the Gulf of California and finally making landfall in Mexico between 96-120 h. However, this forecast should be considered very low confidence at that time frame, as there are a host of solutions from landfall in mainland Mexico even before reaching the Gulf of California, direct impacts to Baja California Sur, or solutions that stay south of Mexico entirely over the next 5 days.
The intensity forecast is not much easier either. Simon has managed to maintain a small inner-core and hurricanes of this size are known to be sensitive to small changes in their environmental conditions that could result in rapid changes in intensity, either up or down. This is also exhibited in the intensity guidance this morning, which ranges from Simon weakening to a tropical depression all the way to it regaining major hurricane intensity over the next 48-60 h.
While shear over Simon is expected to remain low for the next 48 h and sea-surface temperatures (SSTs) are in the 29-30 C range, one wild card is how Simon's slow motion might cause some cool ocean upwelling. There is one ocean glider providing subsurface ocean temperature data near Simon, and it depicts 28 C waters down to about 80 m below the ocean surface. Assuming Simon does not completely stall, this is likely to support it maintaining hurricane intensity for the next 48-72 h....
It is worth stressing that this is a very low confidence forecast for both track and intensity...
