Below are plots of the Global Ensemble Forecast System’s (GEFS) latest forecast for a point at 32N, 65W (Bermuda is roughly 32.3N, 64.8W). More on GEFS here. This model output is at 1º latitude/longitude spatial resolution and 6 hour temporal resolution out to 384 hours. The ensemble systems is re-run every 6 hours with an updated analysis.
I have included the model output out to 168 hours with the 21 members in grey lines, and the ensemble mean as a black line. The ensemble mean values are the numbers either along the top, or the bottom of the plot. Bias corrected model output is used for all but the precipitation accumulation and wind gust plots. Plots are generated using R scripts. These products are generated using data from the NOAA Operational Model Archive Distribution System (NOMADS).
Winds are officially measured as 10 m above ground level in knots. The 925mb and 850mb pressure levels roughly correspond to 750 and 1500 m above sea level. Winds at these levels can be used to get a better sense of potential peak 10 m wind gusts. The y-axis is categorized in the following way >20 kts strong, >34 kts gale force, >48 kts storm force, >64 kts hurricane force.
Pressure, more specifically, changes in pressure can help identify the approach or departure of storm systems. Large scale unsettled weather is typically associated with low pressure, while quiescent weather is typically associated with high pressure. Falling pressures with time can indicate the approach of a frontal system, trough or even tropical cyclone.
Temperature outputs from the GEFS are not representative of morning to afternoon temperature changes associated with the typical diurnal cycle of afternoon solar heating and overnight cooling. This is because the 1º spatial resolution is too coarse to well represent the island as an area of land, so the model treats these coordinates as ocean. The general trends in temperature (eg. associated with the passage of frontal systems) can, however, be identified.
These are not forecasts, they are purely model output from one ensemble system and do not have invaluable human-added value, or the perspective of other models with different initial conditions or physics. Some models and their ensembles perform better in certain scenarios, and there can be meaningful changes from run to run within the same model. For the latest official observations, forecasts, watches and warnings, see the Bermuda Weather Service.
[Click to enlarge]
Bias Corrected 10 m Wind Speed (knots):
10 m Wind Gusts (knots):
Bias Corrected 925 mb Wind Speed (knots):
Bias Corrected 850mb Wind Speed (knots):
Bias Corrected Mean Sea-Level Pressure (mb):
Total Accumulated Precipitation (inches):
Bias Corrected 2m Temperatures (Fahrenheit):