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POINT FORECAST MATRIX

INTRODUCTION

The National Weather Service Forecast New Orleans/Baton Rouge Area Office is now providing detailed forecasts in a matrix format known as "Point Forecast Matrix" or PFM. The detailed digital forecasts are routinely issued around 430 am and 430 pm local time, with updates issued as needed. The PFM is issued under the NEWPFMLIX header This guide will explain how to read and interpret the new product. This product will be replacing the Area Forecast Matrix or AFM which was issued under the NEWAFMLIX header after 430 AM Friday, December 19, 2003.

The Point Forecast Matrix presents nearly the same information in an identical format as the Area Forecast Matrix.

WHAT IS THE POINT FORECAST MATRIX?

The Point Forecast Matrix displays forecast weather parameters in 3-hour, 6-hour and 12-hour intervals. These intervals, combined with a matrix format, create a detailed forecast of various weather parameters. In the Point Forecast Matrix you will find 3-hourly and 12-hourly forecasts for up to 48 hours into the future. 6-hourly and 12-hourly forecasts are provided between 3 and 7 days into the future. The product is available via all NWS routine distribution channels, and is available on our website at http://www.srh.noaa.gov/lix by selecting the Digital Forecasts link.

HOW TO READ AND INTERPRET THE DETAILED POINT FORECAST MATRIX PRODUCT

An example of the Detailed Point Forecast Matrix product is displayed below. There are several forecast parameters which appear. Some of these values are displayed in 12-hour intervals while others are displayed in 6-hour or 3-hour intervals. At the top is the local time and date that the forecast was issued. In the case illustrated, the forecast was issued on Monday, May 12th, and the time of issuance was 1:05 p.m. Central Daylight Time (CDT). The matrix format is below the time and date, and a forecast timeline is established in 3 hour increments for 48 hours (2 days) into the future. Listed on the far left of this timeline is the local time zone. In this example, CDT is listed, which means the hours in the timeline are in Central Standard Time. Another timeline in "UTC" or Universal Coordinated Time (sometimes called "Z" time or "Zulu", or "GMT" - Greenwich Mean Time) is provided for reference. Whether using UTC or CDT, the hours of the day use the 24-hour clock system, where "00" is "midnight" and "18" is 600 pm. The time lines are organized under a line called "DATE" which lays out the day of the week and the calendar date.

Note that the Point Forecast Matrix product is organized into two blocks of data. The upper matrix includes forecast parameters for the first 48 hours out into the future, while the lower matrix includes data for days 3 through 7 into the future. The lower matrix can be identified by locating a second set of "timelines". The lower matrix is the "extended forecast".

000
FOUS54 KLIX 152142
PFMLIX

POINT FORECAST MATRICES
NATIONAL WEATHER SERVICE NEW ORLEANS, LA
430 PM CST MON DEC 15 2003

MSZ070-161030-
MCCOMB-PIKE MS
31.18N 90.46W
430 PM CST MON DEC 15 2003

DATE                        TUE 12/16/03            WED 12/17/03            THU
UTC 3HRLY    21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12
CST 3HRLY    15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06

MIN/MAX                     52          54          30          52          29
TEMP         64 63 60 56 53 52 53 54 55 53 46 38 32 30 36 46 52 51 45 37 31 29
DEWPT        47 50 54 55 53 52 53 38 40 35 29 26 24 28 29 30 29 27 25 24 24 26
RH           54 62 81 96100100100 54 57 50 51 62 72 92 75 53 41 39 45 59 75 88
WIND DIR      S  S  S  S  S SW  W NW NW NW NW NW NW NW NW NW NW NW NW NW NW NW
WIND SPD     10  9  9  9 10 10 11 14 14 13 13 12  9  6 10 13 12 11 11 11 10  9
CLOUDS       SC SC BK BK BK BK BK BK SC SC SC FW FW FW FW FW FW FW FW FW FW SC
POP 12HR                     0          30           0           0           0
QPF 12HR                     0        0.05           0           0           0
RAIN SHWRS                   C  C  S  S
OBVIS                 PF PF


DATE          12/18/03  FRI 12/19/03  SAT 12/20/03  SUN 12/21/03  MON 12/22/03
UTC 6HRLY    18 00 06   12 18 00 06   12 18 00 06   12 18 00 06   12 18 00
CST 6HRLY    12 18 00   06 12 18 00   06 12 18 00   06 12 18 00   06 12 18

MAX/MIN         58      34    62      44    63      52    60      42    60
TEMP         50 56 42   34 54 61 50   44 58 62 56   52 58 59 48   42 55 59
DEWPT        39 36 40   34 37 40 38   37 37 46 50   49 47 42 42   41 42 MM
PWIND DIR       NW      NW     W      SW    SW      NW    NE       E     E
WIND CHAR       GN      LT    LT      GN    GN      LT    LT      GN    LT
AVG CLOUDS   SC FW FW   FW FW FW SC   SC SC SC FW   FW SC SC SC   SC SC SC
POP 12HR         0       0     0       0     0       0     0       0     5

$$            S  S

FORECAST PARAMETERS

Taken line by line ... the upper matrix ...

1) MN/MX - The forecast maximum or minimum temperature. MN/MX is located near the ending time of each 12 hour period for which it is forecast out to 48 hours. The maximum temperatures are forecast from 6:00 a.m. to 6:00 p.m. Local Time. Minimum temperatures are forecasted from 6:00 p.m. to 6:00 a.m. Local Time, but on occasion the low temperature for the night may occur after 6:00 a.m.

2) TEMP - The expected temperature at a specified time, in degrees Farenheit. The temperature is forecast in 3 hour intervals.

3) DEWPT - The expected dewpoint temperature at a specified time, in degrees Farenheit. The dewpoint temperature is forecast in 3 hour intervals.

4) RH - The relative humidity based on the expected temperature and dewpoint.

5) WIND DIR - The expected direction from which wind should blow at 3 hour intervals. The 8 point compass is used (e.g., W, NW, N. . . etc.) Dashes (- -) represent no wind direction forecast due to a calm wind.

6) WIND SPD - The expected average wind speed in miles per hour, during each three hour time period.

7) CLOUDS - The expected cloud cover during each 3-hour time period. The contractions used and their meanings are as follows:

CL = CLEAR SKIES (0-6% CLOUD COVER)

FW = MOSTLY CLEAR SKIES (7-31% CLOUD COVER)

SC = PARTLY CLOUDY SKIES (32-69% CLOUD COVER)

BK = MOSTLY CLOUDY SKIES (70-94% CLOUD COVER)

OV = CLOUDY SKIES (95-100% CLOUD COVER)

8) POP 12HR - The probability of precipitation is for a 12-hour "daytime" period, or a 12-hour "nighttime" period. This percentage probability is listed toward the ending time of each period for which it applies. In the example, there is a 20% probability of precipitation during the day Sunday. There is an 80% probability of precipitation overnight Sunday night.

9) QPF 12HR - The amount of rainfall expected in each 12-hour period ("daytime"/"nighttime"). The values given are in inches, and may be in ranges. For example: ".01-.10" means between a hundredth and a tenth of an inch during the 12-hour period.

10) SNOW 12HR - The amount of snowfall expected in each 12-hour period ("daytime"/"nighttime"). The values given are in inches.

Additional lines, such as "RAIN", "WIND CHILL", and "MIN CHILL" in the example above, are included in the upper matrix if any of the following are in the forecast for that 48-hour period:

WIND CHILL = "How it feels" based on temperature and wind each 3 hours

MIN CHILL = Lowest wind chill over last 6 hour period

HEAT INDEX = "How it feels" based on temperature and relative humidity each 3 hours

MAX HEAT = Highest heat index over last 6 hour period

RAIN = Precipitation type for each 3 hour period is RAIN

RAIN SHWRS = Precipitation type for each 3 hour period is RAIN SHOWERS

SPRINKLES = Precipitation type for each 3 hour period is SPRINKLES

TSTMS = Precipitation type for each 3 hour period is THUNDERSTORMS

DRIZZLE = Precipitation type for each 3 hour period is DRIZZLE

SNOW = Precipitation type for each 3 hour period is SNOW

SNOW SHWRS = Precipitation type for each 3 hour period is SNOW SHOWERS

FLURRIES = Precipitation type for each 3 hour period is SNOW FLURRIES

SLEET = Precipitation type for each 3 hour period is ICE PELLETS

FRZNG RAIN = Precipitation type for each 3 hour period is FREEZING RAIN

FRZNG DRZL = Precipitation type for each 3 hour period is FREEZING DRIZZLE

EACH PRECIPITATION PARAMETER IS CLASSIFIED AS FOLLOWS...

IS = ISOLATED (10-20% COVERAGE)

S = SLIGHT (10-20% PROBABILITY)

SC = SCATTERED (30-50% COVERAGE)

C = CHANCE (30-50% PROBABILITY)

NM = NUMEROUS (60-70% COVERAGE)

L = LIKELY (60-70% PROBABILITY)

O = OCCASIONAL (80-100% PROBABILITY)

D = DEFINITE (80-100% PROBABILITY)

OBSTRUCTIONS TO VISIBILITY ARE CLASSIFIED AS FOLLOWS...

F = FOG

PF = PATCHY FOG

F+ = DENSE FOG

PF+ = PATCHY DENSE FOG

Taken line by line ... the lower matrix or "Extended" Forecast ... (after the time lines)

1) MN/MX - The forecast maximum or minimum temperature. MN/MX is located near the ending time of each 12 hour period for which it is forecast. The maximum temperatures are forecast from 6:00 a.m. to 6:00 p.m. Local Time. Minimum temperatures are forecasted from 6:00 p.m. to 6:00 a.m. LocalTime, but on occasion the low temperature for the night may occur after 6:00 a.m.

2) TEMP - The expected temperature at the specified time, in degrees Farenheit. The temperature is forecast in 6 hour intervals.

3) DEWPT - The expected dewpoint temperature at the specified time, in degrees Farenheit. The dewpoint temperature is forecast in 6 hour intervals.

4) PWIND DIR - Primary wind direction for each 12 hour period

5) WIND CHAR - Wind characteristic for each 12 hour period, where

LT = LIGHT (< 8 MPH)

GN = GENTLE (8-14 MPH)

BZ = BREEZY (15-22 MPH)

WY = WINDY (23-30 MPH)

VW = VERY WINDY (31-39 MPH)

SD = STRONG (>40 MPH)

HF = HURRICANE (>=74 MPH)

6) AVG CLOUDS - Average cloud cover for each 12 hour period, where

CL = CLEAR SKIES (0-6% CLOUD COVER)

FW = MOSTLY CLEAR SKIES (7-31% CLOUD COVER)

SC = PARTLY CLOUDY SKIES (32-69% CLOUD COVER)

BK = MOSTLY CLOUDY SKIES (70-94% CLOUD COVER)

OV = CLOUDY SKIES (95-100% CLOUD COVER)

7) POP 12HR - The probability of precipitation is for a 12-hour "daytime" period, or a 12-hour "nighttime" period. This percentage probability is listed toward the ending time of each period for which it applies.

Additional lines, such as "RAIN", in the example above, are included in the lower matrix if any of the following are in the forecast in the extended period:

WIND CHILL = "How it feels" based on temperature and wind each 3 hours

MIN CHILL = Lowest wind chill over last 6 hour period

HEAT INDEX = "How it feels" based on temperature and relative humidity each 3 hours

MAX HEAT = Highest heat index over last 6 hour period

RAIN = Precipitation type for each 6 hour period is RAIN

RAIN SHWRS = Precipitation type for each 6 hour period is RAIN SHOWERS

SPRINKLES = Precipitation type for each 6 hour period is SPRINKLES

TSTMS = Precipitation type for each 6 hour period is THUNDERSTORMS

DRIZZLE = Precipitation type for each 6 hour period is DRIZZLE

SNOW = Precipitation type for each 6 hour period is SNOW

SNOW SHWRS = Precipitation type for each 6 hour period is SNOW SHOWERS

FLURRIES = Precipitation type for each 6 hour period is SNOW FLURRIES

SLEET = Precipitation type for each 6 hour period is ICE PELLETS

FRZNG RAIN = Precipitation type for each 6 hour period is FREEZING RAIN

FRZNG DRZL = Precipitation type for each 6 hour period is FREEZING DRIZZLE