And then beyond

from Jeff Masters:

Long range forecast for Matthew: a loop-de-loop
Our top two hurricane track models—the GFS and European—continue to show high pressure building in to the north of Matthew this weekend, blocking the hurricane’s forward path. Matthew is expected to loop back towards the south and southwest, potentially reaching The Bahamas by Tuesday. Along the way, though, Matthew may draw close enough to Hurricane Nicole to force the two storms to rotate around a common center—something known as the Fujiwhara effect. This behavior can occur when two storms get within 800 miles of each other. This potential interaction with Nicole on Sunday and Monday makes the 3 - 5 day forecast for Matthew’s track of higher uncertainty than usual-though if anything, it is most likely to reinforce the expected northward track of Nicole and southward track of Matthew. One thing we are confident of: Matthew will be a much weaker storm by Tuesday when it makes its closest approach to the Bahamas. High wind shear of 30 - 50 knots is expected to affect Matthew Sunday through Tuesday, along with very dry air—humidities at mid-levels of the atmosphere are expected to drop to 20% by Monday, which is bound to cause significant weakening of the storm. If Matthew does pass through The Bahamas on Tuesday, it would likely be no stronger than a 35 mph tropical depression.


Figure 4. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Friday, October 7, 2016. The red line is a version of the 00Z Friday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. All of these forecasts show Matthew doing a loop over the waters east of The Bahamas, with three of them showing Matthew moving through The Bahamas. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. The grey crosses along the Gulf Coast are the locations of oil wells, as this forecast tool was designed primarily for use by the oil and gas industry. Image credit: Climate Forecast Applications Network (CFAN).