Forecasters Guide - (IMD), Pune

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S.No. Category/ Meteorological Offices issuing Weather Forecasting Details of Service (d) Forecast for July rainfall over the country as a whole issued by the end of June/ first of week of July. User Interest Govt. Officials Public and Media. (e) Forecast for northeast monsoon season (October- December) rainfall over Southern Peninsula issued in the first week of October. Govt. officials (f) Forecast for rabi season (October to March) rainfall over Northw est India issued in the first week of October. (g) Forecast for winter season (January – March) precipitation issued in the first w eek of January. 7
CHAPTER I INTRODUCTION 1.1 Seasons & associated Weather Phenomena As per <strong>IMD</strong>’s criteria, a calendar year is divided into 4 distinct seasons, viz. Winter (Cold Weather Season) Pre-monsoon (Hot Weather Season) Southw est monsoon (Rainy Season) Post-monsoon (NE monsoon Season) January, February March, April, May June, July, August, September October, November, December During w inter season, NW India, especially Jammu & Kashmir and Punjab receive significant amount of rainfall due to w estern disturbances. Also, the southeast peninsula receives rainfall, mainly due to easterly w aves. Cold w ave conditions manifest over various parts of the country, especially, over the northern and central regions. Also, w idespread Fog occurs over major parts of the country. The rainfall during the Hot Weather Season is essentially due to mesoscale systems like thunderstorms and hailstorms. Also dust storms occur over NW India. The activity of these meso-scale systems is often regulated by w estern disturbances. The important synoptic scale system, which causes damage during this season, is the tropical cyclones, which in most cases, originate in the latitude belt of 10ºN to 15ºN over the oceanic regions and often re-curves tow ards Myanmar coast. Also, heat w ave conditions develop over major parts of the country during the mid-season, w hich often persist until the monsoon advances over the region. India receives the major part of its annual rainfall during the SW Monsoon season. The main components of southw est monsoon over India are Mascarene HIGH, Somali low level jet, Heat Low , Tibetan anticyclone and Tropical easterly jet. The location and intensity of these components govern the strength and spatial distribution of rainfall over India. Also, the semi-permanent feature of southw est monsoon viz. monsoon trough w ith embedded vortices control the rainfall activity. The major w eather systems contributing to the rainfall during the season are: Monsoon lows & Depressions, Off shore trough and vortices and Mid tropospheric cyclonic circulations. During Post monsoon season, cyclonic storms, forming over the Bay of Bengal as well as over the Arabian Sea, w hich move inland and the easterly w aves which move westwards across the peninsula are the important rain producing systems. In the earlier part of October, the storms originate in the latitude belt to the north of 15 o N, travel north or northeastw ards and cause w idespread and heavy rainfall in West Bengal and Assam. Later during the season, they mostly form in the latitude belt 10 o N to 15 o N and strike Tamil Nadu and Andhra Pradesh coasts and produce heavy rainfall along their tracks. Tamil Nadu also receives rainfall during this season due to cyclonic w ind shear in northeasterly w inds. 1.2 General Objectives of the forecasting services Weather plays an important role in almost all aspects of the life on earth. Hence, its accurate and timely forecasting has got w ide implications ranging from increasing the Agricultural Production to reducing the damage to life and property. Currently, forecasting services are rendered to farmers, fishermen, shipping, air navigation etc., apart from the general public. The main objective is to forewarn people so 8
Page 4 and 5: FORECASTERS’ GUIDE CONTENTS Page
Page 6 and 7: 3.2.4 RELEVANT PORTIONS OF THE RECO
Page 8 and 9: DEFINITIONS Pressure: The pressure
Page 10 and 11: FORECASTING ORGANISATION (NON-AVIAT
Page 12 and 13: S.No. Category/ Meteorological Offi
Page 16 and 17: as to reduce the death and damage f
Page 18 and 19: pressure tendency and pressure anom
Page 20 and 21: CHAPTER 3 TERMINOLOGIES IN WEATHER
Page 22 and 23: CHAPTER 5 IMPORTANT PROCEDURES DURI
Page 24 and 25: of Bengal. However, the additional
Page 26 and 27: terrestrial links are disrupted. Th
Page 28 and 29: (3) Police W/T Any action required
Page 30 and 31: Action taken by w arnees The action
Page 32 and 33: Special observations from surface o
Page 34 and 35: Other Registers Though the above th
Page 36 and 37: Coastal Station : Name Surface Wind
Page 38 and 39: Annexure I FORMAT OF CYCLONE WARNIN
Page 40 and 41: CHPATER 7 LOCAL FORECAST A detailed
Page 42 and 43: MAP SHOWING THE 36 METEOROLOGICAL S
Page 44 and 45: 2.2 CHANGES IN SHIPS’ AND UPPER A
Page 46: 2.4 ANALYSIS OF UPPER AIR CHARTS. F
Page 52 and 53: 2.7 W3 CHARTS DDGM (WF) UOI No.W-39
Page 54 and 55: 3. TERMINOLOGY: 3.1 RAI NFAL L 3.1.
Page 56 and 57: 3.1.3 INTRODUCTION OF EXTREM ELY HE
Page 58 and 59: 3.1.5 TERMINOLOGY OF RAINFALL DISTR
Page 60 and 61: 1.5 When a station satisfies both t
Page 62 and 63: Wind-chill equivalent temperature (
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3.2.3 DESCRIBING NORMAL TEMPERATURE
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3.2.5 DESCRIPTION OF 24 HRS TEMPERA
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3.3.2 DESCRIPTION OF PRESSURE GRADI
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3.4. NOMENCLATURE FOR DIFFERENT PAR
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4. WEATHER FORECASTS, BULLETINS AND
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4.2 SECOND FARMER’S WEATHER BULLE
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4.4. ISSUE OF WEEKLY WEATHER MAPS.
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4.6. COMPACTNESS OF WEATHER BULLETI
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2.1 Free supply of the RDWR of the
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5. MONSOON PROCEDURES 5.1 ONSET/ WI
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II Further advance of monsoon over
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Normal for these stations Average n
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5.2.3 SUBDUED MONSOON ACTIVITY FORE
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5.2.5 HIGH TEMPERATURE EPOCHS WHICH
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5.3 CRITERIA FOR DECLARING ONSET OF
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6. PROCEDURES DURING THE CYCLONE PE
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6.2. CRUCIAL OBSERVATIONS RESPONSIB
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6.4 PRE CYCLONE PROCEDURES Forecast
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6.5 WARNINGS FOR STRONG WINDS EXPEC
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Date and Time of Issue …………
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CYCLONE WARNING: 4. Format of Cyclo
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NOTES : a] In the bulletins for gen
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6.7 UNIFORMITY IN MAINTAINING THE I
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6.9 INSTRUCTIONS FOR RMCS / MCS FOR
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public is interested to know about
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4. Wind : For indicating forecast w
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“Mainly clear skies; Maximum temp
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HEAT INDEX °F (°C) RELATIVE HUMID
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Verification of Local Forecast The
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STAGES OF VERIFICATION OF FORECASTS
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2.4 Expression of confidence Foreca
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11.3 Marks allotted to various elem
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1..3.1.2 Height of tops 4 (i) Less
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2.3 Upper air temperatures 3 Same a
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-6 to -8 -3 to -4 Appreciably fall
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RULES OF V ERIFICA TION OF FORECAST
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8.2 LOCAL FORECAST VERIFICATION FOR
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Format for Local Forecast issued at
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8.4 REVISED FORECAST VERIFICATION M
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DETERMINISTIC FORECAST Annexure I (
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VERIFICATION OF SPATIAL DISTRIBUTIO
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Forecasters Guide - (IMD), Pune

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