Surface ChartInterpretation

John Bravender, Aviation Program Manager

National Weather Service – Honolulu, HI

john.bravender@noaa.gov(808) 973-5282

Outline

• Overview of charts– Analysis

• MSLP – northern hemisphere• Streamlines – tropics

– Forecast

• Description of features and symbols

Unified Surface Analysis

• Collaborative product between NOAA offices:– HFO: WFO Honolulu– OPC: Ocean Prediction Center (Camp Springs, MD)– HPC: Hydrologic Prediction Center (Camp Springs, MD)– TPC: Tropical Prediction Center (Miami, FL)

Unified Surface Analysis

• Collaborative product covers the northern hemisphere:– Western boundary: 130°E– Eastern boundary: 30°E

Streamline Analysis

• Streamlines show wind flow• Useful to define surface features in the

tropics where MSLP analysis is difficult– Pressures do not change as much as at higher

latitudes

• HFO streamline analysis covers area from:– 30°N to 30°S– 110°E to 130°W

Forecast Charts

• Contain same features as analysis charts

• Valid at +24h, +48h, and +72h• HFO forecast charts cover area from:

– 50°N to 30°S– 110°E to 130°W

Transmission Frequency

• Surface Analysis Charts– Issued every 6 hours (usually around

H+3:30)• e.g., 1200 UTC chart issued around 1530 UTC

• Forecast Charts– Issued every 12 hours (usually by H+06:00)

• e.g., 01/1200 UTC charts issued around 01/1800 UTC

• valid at 02/1200 UTC, 03/1200 UTC, and 04/1200 UTC

Features

• Symbols• Fronts• Troughs/Ridges• Winds

SymbolsSurface Pressure Chart Streamline Chart

High Pressure

Low Pressure

Anticyclonic Rotation

Cyclonic Rotation

Central pressure: 1032mb

Central pressure: 997mb

Northern Hemisphere: Clockwise

Southern Hemisphere: Counter-clockwise

Southern Hemisphere: Clockwise

Northern Hemisphere: Counter-clockwise

Tropical Cyclone Symbols

Northern Hemisphere:

Hurricane Tropical Storm

Tropical Cyclone Symbols

Northern Hemisphere:

Southern Hemisphere:

Hurricane Tropical Storm

Tropical StormHurricane

Tropical Cyclone Text

• Tropical cyclone text box will include:– Name and intensity (hurricane, tropical storm, etc)– Position– Movement– Max wind

Fronts

• Pips point in the direction of movement

Occluded

WarmCol

dStationary

Weakening Fronts

• Dashed lines indicate a weakening/dissipating front

Occluded

WarmCol

dStationary

Other Features

Trough

RidgeInter-Tropical Convergence Zone

(ITCZ)

Shear Line

Wind Barbs

• Barbs indicate wind speed:– Half barb: 5 knots– Full barb: 10 knots– Flag: 50 knots

5 kt

10 kt

15 kt

20 kt

50 kt

65 kt

25 kt – Southern Hemisphere

Wind Barbs

• Angle indicates wind direction:– Line points in direction the wind is blowing to– Angle references direction the wind is blowing from

South wind180°

East-northeast wind070°