Most models have the remnant moisture of Hurricane Laura moving into our area on Saturday. It currently appears that the storm’s energy and moisture will become incorporated into a non-tropical low pressure system moving through to our north. A cold front moves through Saturday evening.
At this stage of things, there’s little agreement where the maximum dynamics, moisture and precipitation will fall.
The GFS model, along with the statistical ensemble version, the GEFS, have the maximum precipitation falling in New England—
The NAM-NEST has a very different scenario, with much higher amounts falling closer to home—
Most models agree that rain starts Saturday morning and becomes heavier during the afternoon. It’s likely that the NAM-NEST is over-forecasting the rain here and we’ll likely get only 0.5 to 1.5 inches of rain.
The latest information about Hurricane Laura shows it to be a major and dangerous hurricane. The latest US Navy COAMPS tropical model has it as a category 5 storm at landfall. The National Hurricane Center is always your best bet for information.
Latest satellite imagery is impressive—
Where does all this moisture and energy end up? The COAMPS continues to suggest it moves just south of our area on Saturday.
The latest GEFS (Global Ensemble Forecast) shows the remnants as a increase in “precipitable water”, referred to as PWAT. Here’s the PWAT forecast for Saturday at 1 PM—
There’s much uncertainty with the position of this moisture when it gets to the mid-Atlantic area on Saturday. The above is the soon-to-be released GEFS model, showing the PWAT maxima.
The current operational GEFS model, the GFS model and new pre-release version of the GFS model all have different timing and positions for the remnants of Laura.
This is not surprising… hurricane tracks and intensity are difficult to forecast; once a hurricane transitions to an extra-tropical system, it seems to get even more complicated to forecast.
I expect the forecasts for the next few days to become very changeable. I call it the “tropical storm effect”. Even yesterday’s model forecast bust, I believe, was due to the “tropical storm effect”.
The “tropical storm effect” is a total creation of my own and it is NOT at all science-based. Over the many years of weather forecasting as a hobby, it’s been my strong impression that local model forecasts are more unreliable when there’s a strong tropical storm or hurricane in the picture. Does it cause a discontinuity in the mathematical models? Only the numerical weather scientists can answer that.
I leave the forecast of hurricanes and tropical storms to the many experts and scientists at the National Hurricane Center and the Center for Tropical Prediction.
That said, I like to chime in when these storms may affect the Philadelphia area.
The experimental Navy COAMPS tropical model has been my go-to, one-stop-shop for hurricane tracks and intensity forecasts. Overly-simplistic, but it works for me.
The COAMPS has been predicting a category 4-5 hurricane for the past 18 hours. Most interesting is the post-tropical storm track, which takes it just south of our area. The circulation may remain intact enough to redevelop into a tropical structure storm when it hits the Delmarva coast. Just a possibility, but worth watching.
Right now, the main bolus of tropical moisture looks to affect us on Saturday. Stay tuned.