Here is the latest from the National Hurricane Center….
SUMMARY OF 800 AM EDT…1200 UTC…INFORMATION
LOCATION…15.0N 79.4W
ABOUT 320 MI…550 KM SSE OF GRAND CAYMAN
ABOUT 590 MI…950 KM SE OF THE WESTERN TIP OF CUBA
MAXIMUM SUSTAINED WINDS…50 MPH…85 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 12 MPH…19 KM/H
MINIMUM CENTRAL PRESSURE…1001 MB…29.56 INCHES
BRIEF DISCUSSION
At 800 AM EDT (1200 UTC), the center of Tropical Storm Ian was located near latitude 15.0 North, longitude 79.4 West. Ian is moving toward the west-northwest near 12 mph (19 km/h). A turn toward the
northwest at a similar forward speed is expected later today, followed by a turn toward the north-northwest on Monday and north on Tuesday. On the forecast track, the center of Ian is forecast to
pass well southwest of Jamaica today, and pass near or west of the Cayman Islands early Monday. Ian will then move near or over western Cuba Monday night and early Tuesday and emerge over the southeastern Gulf of Mexico on Tuesday.
Maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Rapid strengthening is forecast to begin later today. Ian is expected to become a hurricane later today or tonight and reach major hurricane strength by late Monday or Monday night before it reaches western Cuba.
Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center.
The estimated minimum central pressure is 1001 mb (29.56 inches) based on NOAA Hurricane Hunter dropsonde data.
KEY IMPACTS
WIND: Hurricane conditions are expected to reach Grand Cayman by early Monday, with tropical storm conditions expected by tonight. Tropical storm conditions are possible in Little Cayman and Cayman
Brac by tonight or early Monday. Hurricane conditions are possible within the hurricane watch area in Cuba by Monday night or early Tuesday, with tropical storm conditions possible by late Monday.
Tropical storm conditions are possible within the tropical storm watch area in Cuba Monday night and Tuesday.
RAINFALL: Tropical Storm Ian is expected to produce the following rainfall:
— Jamaica and the Cayman Islands: 3 to 6 inches, with local maxima up to 8 inches.
— Western Cuba: 4 to 8 inches, with local maxima up to 12 inches.
— Florida Keys to the southern and western Florida Peninsula: 2 to 4 inches, with local maxima up to 6 inches through Wednesday morning.
These rains may produce flash flooding and mudslides in areas of higher terrain, particularly over Jamaica and Cuba. Flash and urban flooding is possible with rainfall across the Florida Keys and the
Florida peninsula through mid week. Additional flooding and rises on area streams and rivers across northern Florida and parts of the Southeast cannot be ruled out, especially in central Florida given already saturated antecedent conditions.
STORM SURGE: Storm surge could raise water levels by as much as 9 to 14 feet above normal tide levels along the coast of western Cuba in areas of onshore winds in the watch area Monday night and early Tuesday.
Storm surge could raise water levels by as much as 2 to 4 feet above normal tide levels along the immediate coast in areas of onshore winds in the Cayman Islands Sunday night into Monday. Localized coastal flooding is possible along the coast of Jamaica in areas of onshore winds on Sunday.
SURF: Swells generated by Ian are affecting Jamaica and will spread to the Cayman Islands later today. Swells will then spread northwestward to the southwestern coast of Cuba and the coasts of Honduras, Belize, and the Yucatan Peninsula of Mexico Monday and Monday night. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
TECHNICAL DISCUSSION
Bands of deep convection have developed primarily over the northern portion of Ian’s circulation overnight, however data from an Air Force Reserve reconnaissance aircraft show that the low- and
mid-level centers of the tropical storm have not yet become in better alignment. The Air Force plane essentially performed a low-level invest-like mission at about 2500 ft and found an east-southeast to west-northwest elongated area of light and variable winds that is located to the southeast of the mid-level center seen in infrared satellite imagery.
Given the time spent searching for the low-level center, the aircraft did not fully sample the northern portion of the circulation where the strongest winds are likely located. Therefore, the initial intensity is held at 45 kt, which is in line with the latest subjective and objective satellite estimates. It should be noted that the advisory position is a compromise between the low- and mid-level centers as it is quite likely that a new low-level center will form closer to the convection and the mid-level center very soon.
Due to the current lack of center definition, the initial motion estimate is a somewhat uncertain 285/10 kt. The track forecast philosophy remains unchanged, with Ian forecast to move around the western periphery of a subtropical ridge located over the western Atlantic. Ian is forecast to turn northwestward later today, passing near or southwest of the Cayman Islands on Monday, and approach western Cuba on Monday night or early Tuesday.
While the models agree on the overall scenario, there are still significant differences regarding the exact track of the storm, especially after 72 hours. Even with the addition of the NOAA G-IV synoptic surveillance dropsonde data and additional upper-air balloon releases across much of the United States, the spread in the guidance has not narrowed from before. The UKMET and ECMWF models continue to hold firm along the eastern side of the guidance and show a track into west-central Florida, while the GFS and HWRF remain one the western side, taking the Ian into the central or western Florida panhandle. The updated NHC track continues to split these differences and remains closest to the TVCA multi-model consensus, and the latest GFS ensemble mean.
The new track is very similar to the previous advisory. With the cross-track spreading remaining between 200-220 n mi at days 4 and 5, it cannot be overstated that significant uncertainty remains in Ian’s long-range prediction. Another NOAA G-IV synoptic surveillance mission is already underway collecting data around the storm which will hopefully reduce some of the model spread.
Ian remains within an environment that appears quite conducive for strengthening. Once the circulation become more vertically coherent, low vertical wind shear conditions and high ocean heat content are expected to allow for rapid intensification while Ian moves over the northwestern Caribbean Sea. The Deterministic to Probabilistic Statistical Rapid Intensification Index (DTOPS) once again calls for a 90 percent chance of rapid strengthening during the following 48- and 72-hour forecast periods.
The NHC intensity forecast calls for rapid intensification to begin later today, and forecasts Ian to be a major hurricane when it nears western Cuba in about 48 hours. The latest official intensity forecast shows a similar peak intensity around 72 h over the southeastern Gulf of Mexico as the previous advisory.
After that time, a significant increase in southwesterly shear is predicted by the global models, and weakening is forecast to occur while Ian approaches the Florida coast. Despite the reduction in
intensity, Ian is likely to have an expanding wind field and will be slowing down by that time, which will have the potential to produce significant wind and storm surge impacts. Users are urged to not focus on specific forecast intensities in the 4- and 5-day forecasts and instead focus on the potential hazards Ian may produce across portions of Florida.
MODEL GUIDANCE
There wasn’t a big change overnight in teh model guidance. It has slowed down the shifting to the west, but now most of the guidance does point toward the Florida panhandle specifically.
Intensity guidance is still pointing toward rapid intensification as it moves through the Gulf and toward the northern Gulf Coast. The official forecast from the NHC agrees, too. This should top out between a Category 3 and Category 4 Hurricane before is starts to weaken as it move toward shore.
The SHIPS Intensity guidance agrees with the above assessment, too.
Since this will be weakening as it makes landfall, it means the wind field could be very, very large as it moves ashore. Tropical Storm force wind is now looking possible as far west as New Orleans and even Jackson just based on the pressure gradient alone. So, if nothing else, when this makes landfall, if you aren’t dealing with the teeth, you’ll see have to handle some of the fur.
THE BOTTOM LINE
