Hurricane Irma Intermediate Advisory Number 20A
NWS National Hurricane Center Miami FL AL112017
800 AM AST Mon Sep 04 2017
…NOAA HURRICANE HUNTER AIRCRAFT FINDS IRMA A LITTLE STRONGER…
SUMMARY OF 800 AM AST…1200 UTC…INFORMATION
ABOUT 610 MI…980 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS…120 MPH…195 KM/H
PRESENT MOVEMENT…WSW OR 255 DEGREES AT 14 MPH…22 KM/H
MINIMUM CENTRAL PRESSURE…947 MB…27.96 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Hurricane Watch is in effect for…
* Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis
* Saba, St. Eustatius, and Sint Maarten
* Saint Martin and Saint Barthelemy
A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours before
the anticipated first occurrence of tropical-storm-force winds,
conditions that make outside preparations difficult or dangerous.
Interests in the remainder of the Leeward Islands, the British and
U.S. Virgin Islands, Puerto Rico, and the Dominican Republic should
monitor the progress of Irma. Additional hurricane and tropical
storm watches and warnings will likely be required for portions of
this area later this morning or this afternoon.
For storm information specific to your area, please monitor products
issued by your national meteorological service.
DISCUSSION AND 48-HOUR OUTLOOK
At 800 AM AST (1200 UTC), the eye of Hurricane Irma was located near
latitude 16.8 North, longitude 52.6 West. Irma is moving toward the
west-southwest near 14 mph (22 km/h). A turn toward the west is
expected later today, followed by a west-northwestward turn late
Tuesday. On the forecast track, the center of Irma will move closer
to the Leeward Islands through Tuesday and then be near the northern
Leeward Islands Tuesday night.
Data from a NOAA Hurricane Hunter aircraft indicate that the
maximum sustained winds have increased to near 120 mph (195 km/h)
with higher gusts. Irma is a category 3 hurricane on the
Saffir-Simpson Hurricane Wind Scale. Additional strengthening is
forecast through Tuesday night.
Hurricane-force winds extend outward up to 30 miles (45 km) from
the center, and tropical-storm-force winds extend outward up to 140
miles (220 km).
The latest minimum central pressure estimated from data received by
the reconnaissance aircraft is 947 mb (27.96 inches).
HAZARDS AFFECTING LAND
WIND: Hurricane conditions are possible within the watch area by
Tuesday night, with tropical storm conditions possible by late
SURF: Swells generated by Irma will begin affecting the northern
Leeward Islands today. These swells are likely to cause life-
threatening surf and rip current conditions. Please consult
products from your local weather office.
Next complete advisory at 1100 AM AST.