Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 5-7. HPC Surface Analysis Chart Wind Plotting Model
5.1.2.3.6 Ceiling Ceiling is plotted in hundreds of feet above ground level.
5.1.2.3.7 Visibility Surface visibility is plotted in whole statute miles.
5.1.2.3.8 Pressure Sea-level pressure is plotted in tenths of millibars (mb), with the first two digits (generally 10 or
9) omitted. For reference, 1013 mb is equivalent to 29.92 inches of mercury. Below are some sample conversions between plotted and complete sea-level pressure values:
410: 1041.0 mb 103: 1010.3 mb 987: 998.7 mb 872: 987.2 mb
5.1.2.3.9 Pressure Trend The pressure trend has two components, a number and a symbol, to indicate how the sea level pressure has changed during the past three hours. The number provides the 3-hour change in tenths of millibars while the symbol provides a graphic illustration of how this change occurred.
Figure 5-8 contains the meanings of the pressure trend symbols:
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-6
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) Continuously falling Continuously rising Falling, then steady Rising, then steady Falling before a lesser rise Falling before a greater rise Rising before a greater fall Rising before a lesser fall Steady Figure 5-8. HPC Surface Analysis Chart Pressure Trends
5.1.2.3.10 Sky Cover The approximate amount of sky cover can be determined by the circle at the center of the station plot. The amount the circle is filled reflects the amount of sky covered by clouds. Figure 5-9 contains the common cloud cover depictions:
Clear catered cloud approximately 25% cloud cover (apply cinately 50% cloud cover) (apstYxinoely 75% cloud cover) Overcast Sky Obscured Sky Cover Missing Figure 5-9. HPC Surface Analysis Chart Sky Cover Symbols
5.1.2.3.11 Water Temperature Water temperature is plotted in whole degrees Fahrenheit.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-7
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.1.2.3.12 Swell Information Swell direction, period, and height are represented in the surface observations by a 6-digit code.
The first two digits represent the swell direction, the middle digits describe the swell period (in seconds), and the last two digits are the swell's height (in half meters).
090703 09 - The swell direction is from 90 degrees (i.e. it is coming from due east).
07 - The period of the swell is 7 seconds.
03 - The height of the swell is 3 half meters.
271006 27 - The swell direction is from 270 degrees (due west).
10 - The period is 10 seconds.
06 - The height of the swell is 6 half meters.
5.1.2.3.13 Wave Information Period and height of waves are represented by a 5-digit code. The first digit is always 1. The second and third digits describe the wave period (in seconds), and the final two digits give the wave height (in half meters).
10603 1 - A group identifier. The first digit will always be 1.
06 - The wave period is 6 seconds.
03 - The wave height is 3 half meters.
10515 1 - The group identifier again.
05 - The wave period is 5 seconds.
15 - Wave height is 15 half meters.
In some charts by the OPC, only the wave height (in feet) is plotted.
5.1.2.4 Analyses Isobars, pressure systems, and fronts are the most common analyses depicted on surface analysis charts.
5.1.2.4.1 Isobars An isobar is a line of equal or constant pressure commonly used in the analysis of pressure patterns.
On a Surface Analysis Chart, isobars are solid lines usually spaced at intervals of 4 millibars (mb). Each isobar is labeled. For example, 1032 signifies 1,032.0 mb and 992 signify 992.0 mb.
METAR/SPECI (Section 2.1) reports pressure in hectopascals. However, one millibar is equivalent to one hectopascal, so no conversion is required.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-8
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.1.2.4.2 Pressure Systems On a Surface Analysis Chart, a High (H) is a maximum of atmospheric pressure, while a Low (L) is a minimum of atmospheric pressure. Central pressure is the atmospheric pressure located at the center of a High or Low. In general, the central pressure is the highest pressure in the center of a High and the lowest pressure at the center of a Low. The central pressure is denoted near each pressure center.
A trough or an elongated area of low atmospheric pressure is denoted by dashed lines and identified with the word TROF. A ridge or an elongated area of high atmospheric pressure is denoted by saw-toothed symbols. Ridges are rarely denoted on charts produced by the HPC.
Tropical storms, hurricanes, and typhoons (See Figure 5-2) are low-pressure systems with their names and central pressures denoted.
5.1.2.4.3 Fronts The analysis shows positions and types of fronts by the symbols in Figure 5-2. The symbols on the front indicate the type of front and point in the direction toward which the front is moving.
Two short lines across a front indicate a change in front type.
Figure 5-10. HPC Surface Analysis Chart – North America Example
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-9
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 5-11. HPC Surface Analysis Chart - Contiguous U.S. Example
Figure 5-12. HPC Surface Analysis Chart - Northeast U.S. Example
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-10
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 5-13. HPC Surface Analysis Chart for Aviation Interests – Contiguous U.S. Example
Figure 5-14. HPC Surface Analysis Chart for Aviation Interests – South central U.S. Example
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-11
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.1.3 OPC and WFO Honolulu Surface Analysis Charts The Ocean Prediction Center (OPC) in Camp Spring, Maryland is responsible for the Atlantic and Pacific Oceans north of 30°N latitude. The charts are found at:
• http://www.opc.ncep.noaa.gov/ The Weather Forecast Office in Honolulu, Hawaii (WFO HNL) is responsible for the tropical Pacific Ocean, south of 30°N latitude and west of 160°E longitude. The charts are found at:
• http://www.prh.noaa.gov/hnl/pages/analyses.php
5.1.3.1 Issuance The Ocean Prediction Center (OPC) produces surface analysis charts for the Atlantic and Pacific Oceans north of 30°N latitude four times daily (Table 5-2). The Weather Forecast Office in Honolulu, Hawaii (WFO HNL) issues surface analysis charts for the tropical Pacific Ocean, south of 30°N latitude and west of 160°E longitude four times daily. Surface analysis charts for the North Pacific are jointly issued by both offices.
Table 5-2. OPC and WFO Honolulu Surface Analysis Charts Issuance Schedule UTC 00 06 12 18
5.1.3.2 Analysis Symbols Figure 5-15 shows analysis symbols used on OPC and WFO HNL surface analysis charts.
H 30 • MODERATE ICING TEXT ABBREVIATIONS:
1024 24HR HIGH PRES MOVMI O HEAVY ICING AND PRES IN MBS STORM = 48-63 KT GALE = 34-47 KT HIGH PRES CENTER WIND BARBS: HURCN => 64 KT WITH PRES IN MBS = 5 кТ KI = KNOTS, G = GUSTS 99 HR = HOUR 10 KT MBS = MILLIBARS LOW PRES 996 CENTER AND PRES 24HR LOW PRES MOVMT IN MBS EFF = 20 КТ - 15 KT HURCN = HURRICANE PRES = PRESSURE DSIPT = DISSIPATED WITH PRES IN MBS = 25 KT SINRY = STATIONARY = 35 KT WKNG = WEAKENING COLD FRONT = 50 кТ RPDLY = RAPIDLY FRMG = FORMING = 60 KT MOVG = MOVING WARM FRONT ALL • = 65 KT AlL = 75 KT SINRY FRONT L = 100 KT OCCLUDED FRONT LAL =110 KT COMB = COMBINING DCRS = DECREASING RIDGE LIL = 120 KT INCR = INCREASING INTSFYG = INTENSIFYING ) HURCN TROF • HURCN SOUTHERN HEMISPHERE PSN = POSITION Q TRPCL STORM I TROPICAL DEPRESSION < TROPICAL DISTURBANCE Figure 5-15. OPC and WFO HNL Surface Analysis Chart Symbols AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-12
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 5-16. WFO HNL Surface Analysis Chart – North Pacific Example
5.1.3.3 Wave Information Period and height of waves are represented by a 5-digit code. The first digit is always 1. The second and third digits describe the wave period (in seconds), and the final two digits give the wave height (in half meters). Below are two examples:
10603 1 - A group identifier. The first digit will always be 1.
06 - The wave period is 6 seconds.
03 - The wave height is 3 half meters.
10515 1 - The group identifier again.
05 - The wave period is 5 seconds.
15 - Wave height is 15 half meters.
In certain charts by the OPC, only the wave height (in feet) is plotted.
5.1.3.4 Analyses Isobars, pressure systems, and fronts are the most common analyses depicted on the surface analysis charts.
5.1.3.4.1 Isobars An isobar is a line of equal or constant pressure commonly used to analyze pressure patterns.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-13
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) On a Surface Analysis Chart, isobars are solid lines usually spaced at intervals of 4 millibars (mb). Each isobar is labeled. For example, 1032 signifies 1,032.0 mb and 992 signify 992.0 mb.
METAR/SPECI (Section 2.1) reports pressure in hectopascals. However, one millibar is equivalent to one hectopascal, so no conversion is required.
5.1.3.4.2 Pressure Systems On a Surface Analysis Chart, a High (H) is a maximum of atmospheric pressure, while a Low (L) is a minimum of atmospheric pressure. Central pressure is the atmospheric pressure at the center of a High or Low -- the highest pressure in a High and the lowest pressure in a Low. The central pressure is denoted near each pressure center. Tropical storms, hurricanes, and typhoons (See Figure 5-15) are low-pressure systems with their names and central pressures denoted.
A trough or an elongated area of low atmospheric pressure is denoted by dashed lines and identified with the word TROF. A ridge or an elongated area of high atmospheric pressure is denoted with saw-toothed symbols. Ridges are rarely denoted on charts produced by the HPC.
5.1.3.4.3 Fronts The analysis shows positions and types of fronts by the symbols in Figure 5-15. The symbols on the front indicate the type of front and point in the direction toward which the front is moving.
Two short lines across a front indicate a change in front type.
5.1.4 TPC Surface Analysis Charts The Tropical Prediction Center (TPC) in Miami, Florida is responsible for the tropical regions of the western hemisphere south of 30oN latitude and east of 160oE longitude. The surface analysis chart is located at:
• http://www.nhc.noaa.gov/marine_forecasts.shtml
5.1.4.1 Issuance The Tropical Prediction Center (TPC) issues Surface Analysis Charts for tropical regions of the western hemisphere south of 30oN latitude and east of 160oE longitude four times a day (Table 5-3).
Table 5-3. TPC Surface Analysis Charts Issuance Schedule Valid Time (UTC) 00 06 12 18
5.1.4.2 Analysis Symbols Figure 5-17 shows analysis symbols used on TPC surface analysis charts.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-14
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) H1024 CENTER OF HIGH PRES
ITH PRES IN MILLIBARS TRPCL × 999 WITH PRES IN MILLIBARS TRPCL DEPRESSION CENTER OF LOW PRES STORM (IS) L 10 KI 5 KT COLD FRONT • HURRICANE (HRON) L L 15 KT 20 KT Ш 25 КТ WARM FRONT P CONVECTION We- 35 KT
GALE OR TRPCL STORM STATIONARY FRONT TRPCL - 50 KT STORM WAVE Ale 74 KT HRCN
OCCLUDED FRONT TEXT ABBREVIATIONS M 105 KT DRY LN KT KNOTS 24 HR HIGH PRES
FT FEET MOVEMENT
SQUALL LN NM NAUTICAL MILES
GI GUSTS
TROF LN HRCN - HURRICANE TRPCI- TROPICAL 24 HR LOW PRES
PRES - PRESSURE MOVEMENT
RIDGE AXIS TROF - TROUGH LINE
MOV MOVING
STNR - STATIONARY Figure 5-17. TPC Surface Analysis Chart Symbols SON 04 1026 1826-21 STHRY 3ON 20 TROF 1016 20 08 12
21.4N 11. IPC PSN *120KT 994 OITEZ- N 35. 34 0900 T MOYE 1955КГ 6 5k 5N los .
16 14025 . 130W 120W . 110W. 100W . 90W. SOW 16 10y 16 GOH 50W 3OW 20W 20;4!
06Z TROPICAL SURFACE ANALYSIS 2004 TROPICAL PREDICTION CENTER ISSUED: 17 SCALLOP LINES MIAMI, THUNDERSTORMS: COLLABORATING CENTERS: TAFB ANALYST: FORMOSA TPC OPC НРС HF0 Figure 5-18. TPC Tropical Surface Analysis Chart Example
5.1.4.2.1 Wind Wind is plotted in increments of 5 knots (kts). The wind direction is in "true" degrees and is depicted by a stem (line) pointed in the direction from which the wind is blowing. The wind speed is determined by adding up the value of the flags (50 kts), lines (10 kts), and half-lines (5 kts), each of which has the following individual values:
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-15
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
A single circle over the station with no wind symbol indicates a calm wind.
Figure 5-19 shows some sample wind symbols:
Figure 5-19: TPC Surface Analysis Chart Wind Plotting Model
5.1.4.3 Analyses Isobars, pressure systems, and fronts are the most common analyses depicted on the surface analysis charts.
5.1.4.3.1 Isobars An isobar is a line of equal or constant pressure commonly used to analyze pressure patterns.
On a Surface Analysis Chart, isobars are solid lines usually spaced at intervals of 4 millibars (mb). Each isobar is labeled. For example, 1032 signifies 1,032.0 mb and 992 signify 992.0 mb.
METAR/SPECI (Section 2.1) reports pressure in hectopascals. However, one millibar is equivalent to one hectopascal, so no conversion is required.
5.1.4.3.2 Pressure Systems On a Surface Analysis Chart, a High (H) is a maximum of atmospheric pressure, while a Low (L) is a minimum of atmospheric pressure. Central pressure is the atmospheric pressure at the center of a High or Low -- the highest pressure in a High and the lowest pressure in a Low. The central pressure is denoted near each pressure center. Tropical storms, hurricanes, and AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-16
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) typhoons (See Figure 5-17) are low-pressure systems with their names and central pressures denoted.
A trough or an elongated area of low atmospheric pressure is denoted by dashed lines and identified with the word TROF. A ridge or an elongated area of high atmospheric pressure is denoted by saw-toothed symbols. Ridges are rarely denoted on charts produced by the TPC.
5.1.4.3.3 Fronts The analysis shows positions and types of fronts by the symbols in Figure 5-17. The symbols on the front indicate the type of front and point in the direction toward which the front is moving.
Two short lines across a front indicate a change in front type.
5.1.5 Unified Surface Analysis Chart The Unified Surface Analysis Chart is a composite of all the surface analysis charts produced by HPC, OPC, TPC and WFO Honolulu. It contains an analysis of isobars, pressure systems and fronts.
5.1.5.1 Issuance The chart is issued four times daily by the OPC (see Table 5-4).
Table 5-4. Unified Surface Analysis Chart Issuance Schedule Valid Time (UTC) 00 06 12 18
Figure 5-20. Unified Surface Analysis Chart Example
5.1.5.2 Analysis Symbols Figure 5-21 shows analysis symbols used on the Unified Surface Analysis charts.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-17