WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Matthew Stalls and Weakens, but Expected to Head North; Threat to U.S. Increases

By: Jeff Masters 4:02 PM GMT on October 02, 2016

Hurricane Matthew is weaker as it meanders over the central Caribbean south of Haiti, but the mighty Category 4 hurricane is expected to move northwards later today and deliver a punishing blow to the islands of Hispaniola, Cuba, and Jamaica on Monday and Tuesday. An Air Force hurricane hunter aircraft made three passes through the eye of Matthew on Sunday morning, and found that Matthew’s winds had weakened to 140 mph and the central pressure had risen to 947 mb. This weakening may be partially due to the fact Matthew has essentially stalled, allowing the storm to bring up cooler waters from below. In addition, satellite loops on Sunday morning showed that Matthew had wrapped some dry air into its circulation, and this may have contributed to weakening of the storm. Moderate wind shear of 10 - 20 knots is affecting Matthew, and the storm is over warm ocean waters of 28.5°C (83°F) and has plenty of moisture to work with: 75 - 80% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model. The outer spiral bands of Matthew can be seen on Jamaican radar. Matthew will pass within 50 miles of NOAA buoy 42058 late this afternoon. At 9:50 am EDT Sunday, winds at the buoy were 47 mph, gusting to 56 mph, and seas were 23 feet.

Figure 1. Latest satellite image of Matthew.

Two-day track forecast for Matthew
Despite Matthew drifting a bit further westward than expected on Sunday morning, the models are very unified in their two-day track forecasts for Matthew. A large upper-level low pressure system over east-central U.S. will pull Matthew to the north through Tuesday, resulting in a landfall or a near-miss in southwest Haiti on Monday night, followed by a second landfall in eastern Cuba/northwest Haiti on Tuesday morning. Matthew will then continue northwards into the southeastern Bahamas on Tuesday afternoon. In their 11 am EDT Sunday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds to Les Cayes in southwest Haiti (35%) and to Guantanamo Bay, Cuba (31%). Lower odds were given to Kingston, Jamaica (6%) and Port-Au-Prince, Haiti (6%).

Figure 2. View of Matthew’s eye as seen from the Air Force Hurricane Hunters on their Saturday morning flight. Image credit: ARWO Lt Froelich, Air Force hurricane hunters.

Two-day intensity forecast for Matthew
The latest SHIPS model forecast predicts that wind shear will steadily drop during the next two days, becoming very low, less than 5 knots, by Monday afternoon. At the same time, ocean temperatures will warm to 29° C (84°F) and the heat content of the ocean will increase, which ordinarily would argue for re-intensification of Matthew. However, this morning’s observation that dry air was getting wrapped into the circulation may mean that intensification will struggle to occur today and Monday. Furthermore, this morning’s hurricane hunter flight showed evidence of a secondary maximum in winds outside of the eyewall. This may be an indication that Matthew could undergo an eyewall replacement cycle (ERC), where the inner eyewall collapses and is replaced by a larger-diameter eye, with a new eyewall formed from an outer spiral band. This process usually causes a weakening to the storm’s top winds for a day or so. The down side of an ERC is that it spreads out the storm’s hurricane-force winds over a wider area, resulting in severe impacts over a wider area. Our top three intensity models—the HWRF, LGEM, and SHIPS models—were predicting on Sunday morning that Matthew would be at Category 3 or 4 strength at landfall on Monday evening. The SHIPS model gave Matthew a 0% chance of rapid intensification of 30 mph or more by Monday morning. All factors considered, a Category 3 hurricane at landfall Monday night is probably the most likely scenario. It is unknown what role, it any, the unusual blob of heavy thunderstorms that has persisted on Matthew’s east side might play in the future evolution of the storm. If this intense area of thunderstorms remains intact through Monday night, it could result in catastrophic rains for Haiti.

Figure 3. MODIS satellite image of Matthew taken at 2:30 pm EDT October 1, 2016. At the time, Matthew was a Category 4 storm with 150 mph winds. Image credit: NASA.

Longer-range intensity forecast for Matthew
Matthew’s anticipated landfall over Jamaica/Cuba/Haiti on Monday will weaken the storm, due to the high mountains it will interact with. However, it now appears that Matthew will have limited time over land, due to the storm’s expected track mostly over the water areas between Haiti and Cuba. While this is good news for those nations, this would be bad news for The Bahamas. Matthew inner core may be able to survive the land interaction, resulting in a much stronger storm in the Bahamas. The latest 12Z Sunday SHIPS model forecast predicts low to moderate wind shear, a very moist atmosphere and near-record warm ocean temperatures near 30°C (84°F) for Matthew later this week when it is over The Bahamas, so we can expect strengthening. Matthew is likely to be a major Category 3 or stronger hurricane for at least a portion of its trek through The Bahamas. As Matthew moves north of the Bahamas, waters will cool and the shear is likely to increase, resulting in some weakening late this week.

Figure 4. The 70 forecasts from the 00Z Sunday European (ECMWF) model ensemble (top) and GFS model ensemble (bottom) were beginning to converge on a solution for the track of Matthew that would put the storm very close the U.S. East Coast late this week. In their 11 am EDT Sunday Wind Probability Forecast, NHC gave highest 5-day odds of tropical storm-force winds in the U.S. to West Palm Beach and Fort Lauderdale, Florida (24%), with probabilities of 15 - 20% along most of the North Carolina coast.

Longer-range track forecast for Matthew: risk increases to U.S. East Coast
Over the past two days, our two best computer models have been trending towards a more westerly track for Matthew late this week, increasing the odds that Matthew will make a direct hit somewhere along the U.S. East Coast. Sunday’s 00Z European model and 06Z GFS model had Matthew coming very close to or making landfall in North Carolina 6 - 7 days from now. As one can see from the latest set of ensemble model runs (Figure 4), just about any location along the East Coast could potentially see a hurricane landfall this week. Since the hurricane is expected to be moving roughly parallel to the coast, a long stretch of the coast may receive strong winds and heavy rain from Matthew. We do have three decent models predicting a path for Matthew well away for the U.S. coast late in the week, though—the HWRF, Canadian and GFDL—so it is not yet a foregone conclusion that Matthew will impact the U.S. coast.

98L: A potential steering influence on Matthew?
An area of low pressure associated with a tropical wave that (designated Invest 98L by NHC on Sunday morning) is over the central tropical Atlantic several hundred miles east-northeast of the northern Lesser Antilles, and may alter the steering currents for Matthew. Over 50% of the members of the 00Z Sunday European ensemble forecasts predicted that this system would develop into a tropical depression or tropical storm as it heads northwest at about 15 mph early this week; the GFS model showed virtually no development. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 20% and 30%, respectively. If this storm develops significantly, it may exert a steering influence on Matthew that could help pull it out to sea. Satellite loops on Sunday morning showed that 98L had a very limited amount of heavy thunderstorm activity that was poorly organized, thanks to dry air and high wind shear of 25 - 30 knots. The 12Z Sunday SHIPS model forecast predicted wind shear would rise even higher by Tuesday—in excess of 50 knots—so I doubt 98L will be able to develop.

Figure 5. 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 Sunday, October 2, 2016. The red line is a version of the 00Z Sunday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Four out of five of these forecasts showed Matthew hitting the U.S. The high-probability cluster (grey lines) perform best at forecast times of five days and beyond. Image credit: Climate Forecast Applications Network (CFAN).

We’ll be back this afternoon with an update on Matthew. Meteorologist Steve Gregory has also been making regular updates on Matthew,

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.