Weather Radar — Palm Bay, Florida

Palm Bay is covered by KMLB, the National Weather Service WSR-88D Doppler radar in Melbourne, about 8.5 miles north of the Palm Bay forecast point.

The Weather Service station record for KMLB gives the name Melbourne, the type WSR-88D and the position 28.11305 N, 80.65444 W (NWS radar station record). The Palm Bay point forecast is computed for 27.99 N, 80.66 W (Palm Bay point forecast). The arithmetic: 28.113 minus 27.99 is about 0.12 degrees of latitude, and at roughly 69 miles per degree that is close to 8.5 miles, with almost no east or west offset because the two longitudes differ by about 0.006 degrees (80.66 minus 80.65444). Palm Bay therefore sits just south of the radar, close enough that storms over Malabar Road or Palm Bay Road are sampled at low altitude.

The radar sits close enough to Melbourne International Airport that construction there mattered. The NWS Melbourne office history describes a radar tower raising project completed in January 2013 to mitigate a potential beam blockage to the south and south southeast from new hangar construction at Melbourne International Airport (NWS Melbourne office history). South and south southeast of the airport is the direction of Palm Bay, so that project kept the city in clear view of the lowest radar scan.

The Melbourne WSR-88D has scanned the Palm Bay area since October 1991, when it became the second operational unit of its kind in the United States.

Construction of the Melbourne system began in January 1991, and the office history describes the unit that began operating in October 1991 as the country's second WSR-88D and its first in a sub-tropical, maritime climate. In March 1994 Melbourne became the third NWS office in the nation, and the first east of the Mississippi, to commission the WSR-88D (office history). The station digest repeats the short version: the office has the second operational WSR-88D in the country, dated 10/91 (NWS Melbourne station digest).

Two entries in that history fall close to Palm Bay. In August 1995, Hurricane Erin struck just south of the Melbourne WSR-88D, the side of the radar that faces Palm Bay, and in November 1994 Tropical Storm Gordon spawned a killer tornado at Barefoot Bay south of Melbourne (office history). The history also notes that the Melbourne WSR-88D supports the nation's space program, with the Air Force at Cape Canaveral and Patrick among its dedicated users.

The official KMLB imagery for Palm Bay is on radar.weather.gov and on the NWS Melbourne radar page, both run by the National Weather Service.

The national viewer offers an Enhanced Radar and a Standard Radar (Low-Bandwidth) version, and its station view shows products for one selected radar such as KMLB along with storm based alerts (NWS radar viewer, KMLB). Its Weather for a location view is described as similar to a radar application on a phone that provides radar, current weather, alerts and the forecast for a location, and a Palm Bay address can be bookmarked in that view.

The NWS Melbourne page titled East Central Florida Radar Data lists Local Radar (Enhanced), Local Radar (Standard) and Regional Radar (Standard), plus Melbourne Standard and Melbourne Enhanced imagery and regional Southeast radars (NWS Melbourne radar page). The Palm Bay point forecast page also carries a Radar & Satellite Image link under its additional resources (Palm Bay point forecast).

Radar colors over Palm Bay show reflectivity in dBZ, and NOAA's guide equates 50 dBZ with rain falling at about 1.90 inches per hour and 40 dBZ with about 0.45 inches per hour.

Reflectivity is the amount of energy returned to the radar, and NOAA calls it likely the product most familiar to the general public (NOAA JetStream, reflectivity). The WSR-88D at Melbourne is a pulsed Doppler radar, sending brief pulses rather than a continuous stream (NOAA JetStream, how radar works). NOAA warns that the rates below are hourly rainfall rates only and are not the actual amounts of rain a location receives, so a 50 dBZ cell that crosses Bayside Lakes in ten minutes leaves far less than 1.90 inches.

Shapes matter as much as colors. NOAA describes a hook echo as a good indication that a storm has obtained rotation, a bowing segment as a sign of possible damaging winds, and training echoes, new storms tracking over ground already soaked, as a sign of flash flooding potential (reflectivity guide). On a KMLB loop, training over Palm Bay shows up as cell after cell following the same track across the city.

The velocity product is different. A fixed radar such as KMLB can only measure how fast a target is moving toward or away from the radar itself, which NOAA calls radial velocity, and that is almost always less than the true wind (NOAA JetStream, velocity). Because Palm Bay lies almost due south of the radar, a north or south wind over the city shows up nearly at full strength, while a pure east or west wind over Palm Bay reads close to zero.

Palm Bay's short distance from KMLB keeps the radar beam narrow and low over the city, and the 2012 dual polarization upgrade lets the radar tell rain from hail and debris.

NOAA puts the WSR-88D beam width at around 1 degree and says the beam spreads approximately 1,000 feet for every 10 miles of travel, reaching more than 2 miles wide at 120 miles (NOAA JetStream, radar beams). Applying that rule to the roughly 8.5 miles between the radar and the Palm Bay forecast point gives a beam about 850 feet wide over central Palm Bay. A storm near Lake Okeechobee or Orlando is seen far more coarsely by the same radar.

Dual polarization arrived at Melbourne in January 2012, when upgrades to the Melbourne 88D radar were completed to bring the technology to east central Florida (office history). NOAA explains that during 2012 the national network was upgraded, adding three base products: Differential Reflectivity, Correlation Coefficient and Specific Differential Phase (NOAA JetStream, dual polarization). NOAA calls correlation coefficient likely the most used of the three, and a sharp drop in its values when a tornado lofts debris high enough to be sampled marks a Tornado Debris Signature over a place such as Palm Bay.

Rain totals come from the same data. NOAA describes a one-hour rainfall estimate and a storm total estimate, and says the precipitation products reset after 1 continuous hour of no precipitation echoes (NOAA JetStream, precipitation estimation). For a slow Palm Bay storm, the storm total view is the closest radar answer to how much rain fell across the city, though it remains an estimate rather than a gauge reading.